{"id":267279,"date":"2023-08-16T17:49:06","date_gmt":"2023-08-16T17:49:06","guid":{"rendered":"https:\/\/www.webscale.com\/?page_id=267279"},"modified":"2023-10-12T07:04:47","modified_gmt":"2023-10-12T12:04:47","slug":"varnish-cache","status":"publish","type":"page","link":"https:\/\/www.webscale.com\/varnish-cache\/","title":{"rendered":"Varnish Cache"},"content":{"rendered":"<p>[et_pb_section fb_built=&#8221;1&#8243; module_id=&#8221;top&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;b8b8d61a-a82d-40ed-8e84-5794fa50a2fb&#8221; background_color=&#8221;#F9F9F9&#8243; background_enable_image=&#8221;off&#8221; background_position=&#8221;bottom_center&#8221; locked=&#8221;off&#8221; global_colors_info=&#8221;{}&#8221;][et_pb_row use_custom_gutter=&#8221;on&#8221; make_equal=&#8221;on&#8221; custom_padding_last_edited=&#8221;on|phone&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;default&#8221; min_height=&#8221;280px&#8221; custom_padding=&#8221;||||false|false&#8221; custom_padding_tablet=&#8221;45px||45px||true|false&#8221; custom_padding_phone=&#8221;45px||45px||false|false&#8221; custom_css_main_element=&#8221;margin: auto;&#8221; global_colors_info=&#8221;{}&#8221; custom_css_main_element_last_edited=&#8221;off|phone&#8221; custom_css_main_element_phone=&#8221;padding: 45px 0px !important;||margin: auto;&#8221;][et_pb_column type=&#8221;4_4&#8243; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;9ee36b17-ef9b-4cd1-9b7c-33b20dfd565a&#8221; custom_padding_phone=&#8221;||30px||false|false&#8221; custom_css_main_element=&#8221;margin:auto;&#8221; pac_dcm_carousel_specific_module_num=&#8221;0&#8243; global_colors_info=&#8221;{}&#8221; custom_css_main_element_last_edited=&#8221;off|phone&#8221; custom_css_main_element_tablet=&#8221;margin:auto;&#8221; custom_css_main_element_phone=&#8221;||padding: 4vw 0vw;&#8221;][et_pb_text module_class=&#8221;grd-org-pnk&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; text_text_color=&#8221;#231F20&#8243; text_font_size=&#8221;20px&#8221; header_font=&#8221;|600|||||||&#8221; header_text_align=&#8221;center&#8221; header_text_color=&#8221;#FF6700&#8243; text_orientation=&#8221;center&#8221; background_layout=&#8221;dark&#8221; custom_margin=&#8221;||0px||false|false&#8221; custom_padding_tablet=&#8221;&#8221; custom_padding_phone=&#8221;60px||||false|false&#8221; custom_padding_last_edited=&#8221;on|phone&#8221; custom_css_main_element=&#8221;margin: auto;&#8221; global_colors_info=&#8221;{}&#8221;]<\/p>\n<h1>Varnish Cache<\/h1>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;sub-title&#8221; module_class=&#8221;sub-title&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; text_text_color=&#8221;#231F20&#8243; text_font_size=&#8221;20px&#8221; header_font=&#8221;|600|||||||&#8221; header_text_align=&#8221;center&#8221; header_text_color=&#8221;#FF6700&#8243; text_orientation=&#8221;center&#8221; background_layout=&#8221;dark&#8221; custom_padding_phone=&#8221;30px||||false|false&#8221; custom_padding_last_edited=&#8221;off|desktop&#8221; custom_css_main_element=&#8221;margin: auto;&#8221; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p>A quick reference guide for all things Varnish!<\/p>\n<p>[\/et_pb_text][et_pb_image src=&#8221;https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Banners-Varnish-Pillar-page.png&#8221; title_text=&#8221;Banners Varnish Pillar Page&#8221; align=&#8221;center&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;409b6e2c-1e19-445a-9288-17262126632b&#8221; max_width=&#8221;800px&#8221; module_alignment=&#8221;center&#8221; custom_padding_tablet=&#8221;&#8221; custom_padding_phone=&#8221;||60px||false|false&#8221; custom_padding_last_edited=&#8221;on|phone&#8221; global_colors_info=&#8221;{}&#8221;][\/et_pb_image][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=&#8221;1&#8243; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;71c26c89-a3e8-47e6-bef4-1cd5c9b1225a&#8221; global_colors_info=&#8221;{}&#8221;][et_pb_row column_structure=&#8221;1_4,3_4&#8243; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;default&#8221; custom_margin=&#8221;0px||||false|false&#8221; custom_padding=&#8221;0px||||false|false&#8221; global_colors_info=&#8221;{}&#8221;][et_pb_column type=&#8221;1_4&#8243; module_id=&#8221;left-col&#8221; disabled_on=&#8221;on|on|off&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;f8b983f5-d82f-45cf-9337-b9f8c424771a&#8221; pac_dcm_carousel_specific_module_num=&#8221;0&#8243; global_colors_info=&#8221;{}&#8221;][et_pb_text ul_type=&#8221;none&#8221; disabled_on=&#8221;off|off|off&#8221; module_id=&#8221;table-of-cont&#8221; module_class=&#8221;li-content&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; link_font=&#8221;||||||||&#8221; link_text_color=&#8221;#919191&#8243; background_enable_color=&#8221;off&#8221; width=&#8221;280px&#8221; max_width=&#8221;280px&#8221; module_alignment=&#8221;left&#8221; max_height=&#8221;400px&#8221; custom_padding=&#8221;90px|25px|25px|25px|false|true&#8221; sticky_position=&#8221;top&#8221; sticky_limit_top=&#8221;section&#8221; sticky_limit_bottom=&#8221;section&#8221; link_font_last_edited=&#8221;off|desktop&#8221; sticky_position_tablet=&#8221;top&#8221; sticky_position_phone=&#8221;none&#8221; sticky_position_last_edited=&#8221;off|desktop&#8221; custom_css_main_element=&#8221;margin-top: 60px;&#8221; border_color_all=&#8221;#eaeaea&#8221; global_colors_info=&#8221;{}&#8221; link_text_color__hover_enabled=&#8221;on|hover&#8221; link_text_color__hover=&#8221;#FF6700&#8243;]<\/p>\n<ul>\n<li class=\"intro\"><a href=\"#getting-started\">Getting Started with Varnish Cache<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#understanding-vcl\">Understanding VCL<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#caching-strategies-with-varnish\">Caching Strategies with Varnish<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#extending-varnish-cache-capabilities\">Extending Varnish Cache capabilities<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#securing-varnish-cache\">Securing Varnish Cache<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#load-balancing-high-availability\">Load Balancing and High Availability<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#varnish-cache-SSL-TLS\">Varnish Cache and SSL\/TLS<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#monitoring-metrics\">Monitoring and Metrics<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#cache-invalidation\">Cache Invalidation<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#ecommerce-websites\">Ecommerce Websites<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#what-content-to-cache\">What Content to Cache<\/a><\/li>\n<li class=\"why-merchant\"><a href=\"#integrating-CDN\">Integrating with a CDN<\/a><\/li>\n<\/ul>\n<p>[\/et_pb_text][\/et_pb_column][et_pb_column type=&#8221;3_4&#8243; module_id=&#8221;right-col&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;f8b983f5-d82f-45cf-9337-b9f8c424771a&#8221; pac_dcm_carousel_specific_module_num=&#8221;0&#8243; global_colors_info=&#8221;{}&#8221;][et_pb_code _builder_version=&#8221;4.20.4&#8243; _module_preset=&#8221;default&#8221; min_height=&#8221;20px&#8221; global_colors_info=&#8221;{}&#8221;]<script><!-- [et_pb_line_break_holder] -->   jQuery(document).ready(function( $ ){ <!-- [et_pb_line_break_holder] -->    if ($(window).width() > 1200) {<!-- [et_pb_line_break_holder] -->\t$('#right-cont').appendTo('#right-col');<!-- [et_pb_line_break_holder] -->    }<!-- [et_pb_line_break_holder] -->      \/\/ Attach click event handler to elements matching the selector<!-- [et_pb_line_break_holder] -->   $('#table-of-cont li a').on('click', function(e) {<!-- [et_pb_line_break_holder] -->        \/\/ Remove the active class from all the <\/p>\n<li> elements<!-- [et_pb_line_break_holder] -->        $('#table-of-cont li').removeClass('active');<!-- [et_pb_line_break_holder] --><!-- [et_pb_line_break_holder] -->        \/\/ Add the active class to the parent \n<li> of the clicked <a><!-- [et_pb_line_break_holder] -->        $(this).parent('li').addClass('active');<!-- [et_pb_line_break_holder] -->     });<!-- [et_pb_line_break_holder] --> $(window).scroll(function() {<!-- [et_pb_line_break_holder] -->        var height = $(window).scrollTop();<!-- [et_pb_line_break_holder] -->\t\t\/\/var width = $( window ).width() \/ 2;<!-- [et_pb_line_break_holder] -->       console.log(height);<!-- [et_pb_line_break_holder] -->   <!-- [et_pb_line_break_holder] -->   var bottom = $(document).height() - $(window).height() - $(window).scrollTop() + 750;<!-- [et_pb_line_break_holder] -->     \/\/ console.log(bottom);<!-- [et_pb_line_break_holder] -->   <!-- [et_pb_line_break_holder] --> if ($(document).scrollTop() < '5987') { $('#table-of-cont').css('top','60px'); }<!-- [et_pb_line_break_holder] -->  if ($(document).scrollTop() >= '5987'){ $('#table-of-cont').css('top','-160px'); }<!-- [et_pb_line_break_holder] -->});<!-- [et_pb_line_break_holder] -->  <!-- [et_pb_line_break_holder] -->   });<!-- [et_pb_line_break_holder] --><\/script>[\/et_pb_code][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=&#8221;1&#8243; custom_padding_last_edited=&#8221;off|phone&#8221; module_id=&#8221;right-cont&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;b8b8d61a-a82d-40ed-8e84-5794fa50a2fb&#8221; background_enable_color=&#8221;off&#8221; locked=&#8221;off&#8221; global_colors_info=&#8221;{}&#8221;][et_pb_row use_custom_gutter=&#8221;on&#8221; make_equal=&#8221;on&#8221; custom_padding_last_edited=&#8221;off|desktop&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;default&#8221; module_alignment=&#8221;center&#8221; custom_margin=&#8221;0px||||false|false&#8221; custom_padding=&#8221;0px||||false|false&#8221; custom_padding_tablet=&#8221;|15px||15px|false|true&#8221; custom_padding_phone=&#8221;|15px||15px|false|true&#8221; global_colors_info=&#8221;{}&#8221;][et_pb_column type=&#8221;4_4&#8243; module_class=&#8221;toc&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;f8b983f5-d82f-45cf-9337-b9f8c424771a&#8221; custom_css_main_element=&#8221;width: 100% !important;&#8221; pac_dcm_carousel_specific_module_num=&#8221;0&#8243; global_colors_info=&#8221;{}&#8221;][et_pb_text admin_label=&#8221;Getting Started with Varnish Cache&#8221; module_id=&#8221;getting-started&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.2&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; text_font=&#8221;|800|||||||&#8221; text_font_size=&#8221;50px&#8221; text_line_height=&#8221;1.2em&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221; max_width_tablet=&#8221;100%&#8221; max_width_phone=&#8221;100%&#8221; max_width_last_edited=&#8221;off|desktop&#8221; module_alignment=&#8221;center&#8221; custom_margin=&#8221;||||false|false&#8221; custom_padding=&#8221;60px||||false|false&#8221; custom_padding_tablet=&#8221;&#8221; custom_padding_phone=&#8221;0px||||false|false&#8221; custom_padding_last_edited=&#8221;on|phone&#8221; hover_enabled=&#8221;0&#8243; text_font_size_tablet=&#8221;32px&#8221; text_font_size_phone=&#8221;32px&#8221; text_font_size_last_edited=&#8221;on|tablet&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; sticky_enabled=&#8221;0&#8243; header_2_text_align=&#8221;center&#8221;]<br \/>\n<h2><strong>Getting Started<\/strong> with Varnish Cache<\/h2>\n<p><em>An introduction to Varnish Cache, its benefits, and how to install and configure it.<\/em><\/p>\n<p>[\/et_pb_text][et_pb_text _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p>Varnish Cache is a powerful open-source HTTP accelerator (reverse proxy for caching HTTP) designed to significantly improve website performance and reduce server load by caching and serving frequently accessed content. It acts as an intermediary between the client and the backend web server, efficiently storing copies of web pages and assets like images, CSS, and JavaScript in its high-speed memory.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Varnish-Basic.png\" width=\"804\" height=\"239\" alt=\"\" class=\"wp-image-268979 aligncenter size-full\" \/><\/p>\n<p>The primary benefit of Varnish Cache lies in its ability to dramatically speed up website response times, leading to a better user experience. By serving cached content directly from memory, Varnish reduces the need for repeated processing of dynamic content on the backend, resulting in faster page loads and reduced server resource utilization.<\/p>\n<p>To install Varnish Cache, you\u2019ll need to ensure your server meets the system requirements and has necessary dependencies like GCC and the PCRE library. Once ready, the installation process involves using package managers like YUM or APT to download and install the software. Alternatively, you can compile Varnish from source code for more customization options.<\/p>\n<p>After installation, configuration is key to getting the best out of Varnish Cache. It involves setting up a Varnish Configuration Language (VCL) file, which defines how Varnish should handle incoming requests and what to cache. Careful consideration should be given to handling cookies, cache invalidation strategies, and the caching of personalized content.<\/p>\n<p>When properly installed and configured, Varnish Cache can significantly improve website performance, reduce server load, and handle sudden traffic spikes more efficiently. As a result, businesses can enjoy better user retention, improved search engine rankings, and increased overall customer satisfaction. Varnish Cache has become an essential tool for websites dealing with high traffic volumes, making it an invaluable asset for developers seeking to optimize web performance.<\/p>\n<p>The biggest advantages of Varnish Cache are its speed and flexibility. It can speed up content delivery by 300-1000x, and thanks to the flexibility of Varnish Configuration Language (VCL), it can be configured to act as a load balancer, and block IP addresses. This combination of speed and configurability has led to Varnish Cache growing in popularity over Nginx, another reverse proxy used for caching that has been around longer.<\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Understanding VCL (Varnish Configuration Language)&#8221; module_id=&#8221;understanding-vcl&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221;]<\/p>\n<h2><strong>Understanding VCL<\/strong> (Varnish Configuration Language)<\/h2>\n<p><em>A deep dive into Varnish&#8217;s powerful configuration language, including examples of common use cases and best practices for writing efficient VCL code.<\/em><\/p>\n<p>[\/et_pb_text][et_pb_text _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p>Understanding Varnish Configuration Language (VCL) is essential for harnessing the full potential of Varnish Cache. VCL is a domain-specific language used to define how Varnish handles incoming HTTP requests and decides what content to cache. It consists of various subroutines that are executed during different stages of request processing.<\/p>\n<p><span style=\"color: #000000;\"><strong>Here&#8217;s some sample code to give you an idea of what VCL looks like:<\/strong><\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Understanding-VCL-e1692206820103.png\" width=\"1416\" height=\"597\" alt=\"\" class=\"wp-image-268861 aligncenter size-full\" \/><\/p>\n<p>One of the key subroutines is &#8220;vcl_recv,&#8221; which is responsible for processing incoming requests before they are fetched from the backend. This subroutine allows developers to make decisions based on request headers, cookies, or client IP addresses. Another crucial subroutine is &#8220;vcl_fetch,&#8221; executed after fetching content from the backend but before storing it in the cache. Here, developers can manipulate the fetched content or define cache policies.<\/p>\n<p>A common use case for VCL is cache control based on HTTP headers. Developers can use the &#8220;vcl_recv&#8221; subroutine to inspect headers like &#8220;Cache-Control&#8221; and decide whether to cache the content or pass it to the backend for fresh data. Additionally, VCL enables edge-side includes (ESI), where dynamic and static content can be assembled in real-time, optimizing cache efficiency.<\/p>\n<p>Writing efficient VCL code involves several best practices. Minimizing conditional statements, using &#8220;return&#8221; to stop further processing when appropriate, and leveraging the built-in &#8220;std&#8221; library for common tasks are some key practices. Properly handling cache invalidation, especially for dynamic content, is crucial to avoid stale data issues.<\/p>\n<p>Mastering VCL and its subroutines empowers developers to finely control Varnish Cache&#8217;s behavior, leading to optimal cache performance and improved website responsiveness. Efficient VCL code not only ensures better caching decisions but also contributes to overall web server resource optimization.<\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Caching Strategies with Varnish&#8221; module_id=&#8221;caching-strategies-with-varnish&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221;]<\/p>\n<h2><strong>Caching Strategies<\/strong> with Varnish<\/h2>\n<p><em>Explore various caching strategies, such as edge-side includes (ESI), cache purging, and cache invalidation techniques to optimize content delivery and improve performance.<\/em><\/p>\n<p>[\/et_pb_text][et_pb_text module_class=&#8221;bold-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p>Varnish Cache offers a range of caching strategies that can significantly optimize content delivery and enhance website performance. Three key strategies include Edge-Side Includes (ESI), Cache Purging, and Cache Invalidation techniques.<\/p>\n<p><b>Edge-Side Includes (ESI)<\/b><span style=\"font-weight: 400;\"> is a powerful strategy that allows developers to split web pages into multiple fragments or components. These fragments can be cached separately, and when a request is made, Varnish can dynamically assemble the page by combining the cached fragments with real-time, non-cacheable content from the origin server. ESI is particularly useful for websites with dynamic and personalized elements, as it enables efficient caching of static components while ensuring the freshness of personalized content.<\/span><\/p>\n<p><span style=\"color: #000000;\"><strong>ESI tag<\/strong><\/span><\/p>\n<p><i><span style=\"font-weight: 400;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/ESI-tag.png\" width=\"1412\" height=\"156\" alt=\"\" class=\"wp-image-268883 aligncenter size-full\" \/><\/span><\/i><\/p>\n<p><b>Cache Purging<\/b><span style=\"font-weight: 400;\"> is the process of selectively removing specific cached items to update the cache with fresh content. Varnish provides mechanisms to purge individual URLs or specific objects, allowing developers to invalidate specific parts of the cache when content is updated or becomes stale. By strategically purging outdated content, Varnish ensures that users receive the most up-to-date information, striking a balance between cache efficiency and content accuracy.<\/span><\/p>\n<p><span style=\"color: #000000;\"><strong>Purge code<\/strong><\/span><\/p>\n<p><i><span style=\"font-weight: 400;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Purge-code.png\" width=\"1434\" height=\"686\" alt=\"\" class=\"wp-image-268882 aligncenter size-full\" \/><\/span><\/i><\/p>\n<p><b>Cache Invalidation<\/b><span style=\"font-weight: 400;\"> techniques are essential for ensuring that cached content remains relevant. Varnish provides several options, such as time-based expiration, conditional requests with &#8220;If-Modified-Since&#8221; or &#8220;ETag&#8221; headers, and cache invalidation through backend control. These techniques help maintain cache freshness and avoid serving outdated or irrelevant content to users.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">By adopting these caching strategies, developers can leverage Varnish Cache&#8217;s capabilities to optimize content delivery, reduce server load, and provide users with faster and more responsive websites. However, it&#8217;s crucial to strike a balance between aggressive caching for performance benefits and proper cache invalidation strategies to ensure users receive accurate and up-to-date information.<\/span><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Extending Varnish Cache capabilities with VMODs&#8221; module_id=&#8221;extending-varnish-cache-capabilities&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.2&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; hover_enabled=&#8221;0&#8243; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221; sticky_enabled=&#8221;0&#8243;]<\/p>\n<h2><strong>Extending Varnish Cache<\/strong> capabilities with VMODs<\/h2>\n<p><em>Add custom functionality and enhance cache performance with Varnish Modules<\/em><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Text&#8221; module_class=&#8221;bold-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"font-weight: 400;\">Extending Varnish Cache capabilities with VMODs (Varnish Modules) is a powerful way to add custom functionality and enhance cache performance for specific use cases. VMODs are dynamic loadable modules written in C or other supported languages, allowing developers to introduce new functionalities without modifying the Varnish source code.<\/span><\/p>\n<p><span style=\"color: #000000;\"><strong>VCL snippet that features the cookie VMOD<\/strong><\/span><\/p>\n<p><span style=\"font-weight: 400; color: #000000;\"><\/span><i><span style=\"font-weight: 400;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/VCL-snippet-that-features-the-cookie.png\" width=\"1434\" height=\"686\" alt=\"\" class=\"wp-image-268881 aligncenter size-full\" \/><\/span><\/i><\/p>\n<p><span style=\"font-weight: 400;\">With VMODs, developers can extend Varnish to interact with external systems, perform complex data manipulations, or implement custom caching strategies. For example, VMODs can be created to integrate Varnish with specific databases, implement advanced cache invalidation techniques, or add support for specialized authentication methods.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">VMODs enable Varnish to adapt to unique application requirements, improving the overall efficiency and effectiveness of the cache. By encapsulating custom functionalities in VMODs, developers can easily reuse and share these modules across different projects.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The Varnish community actively contributes to the VMOD ecosystem, resulting in a wide range of pre-built modules available for various purposes. These community-contributed VMODs can be readily incorporated into Varnish setups to address common challenges and optimize performance.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Leveraging VMODs extends the power of Varnish Cache, making it a flexible and customizable caching solution for diverse web application scenarios. By tailoring Varnish with VMODs, developers can unleash the full potential of caching while maintaining the ease and efficiency of Varnish&#8217;s configuration and deployment.<\/span><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Securing Varnish Cache and Handling Attacks&#8221; module_id=&#8221;securing-varnish-cache&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221;]<\/p>\n<h2><strong>Securing Varnish Cache<\/strong> and Handling Attacks<\/h2>\n<p><i><span style=\"font-weight: 400;\">How to secure Varnish Cache from DDoS attacks, SQL injections, and brute-force attempts.<\/span><\/i><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Text&#8221; module_class=&#8221;bold-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"font-weight: 400;\">Securing Varnish Cache against common web application attacks is crucial to protect both the cache infrastructure and the backend servers from potential vulnerabilities. Here are some essential steps to bolster Varnish Cache&#8217;s security:<\/span><\/p>\n<p><b>Rate Limiting and DDoS Protection: <\/b><span style=\"font-weight: 400;\">Implement rate-limiting mechanisms to restrict the number of requests from a single IP address or user agent within a specified timeframe. Utilize DDoS protection solutions and services to detect and mitigate distributed denial-of-service attacks, safeguarding Varnish from being overwhelmed with malicious traffic.<\/span><\/p>\n<p><b>Input Validation and Sanitization: <\/b><span style=\"font-weight: 400;\">Enforce strict input validation and data sanitization practices at the backend to prevent SQL injection attacks. Apply parameterized queries and prepared statements to mitigate the risk of malicious code injection.<\/span><\/p>\n<p><b>HTTP Request Filtering: <\/b><span style=\"font-weight: 400;\">Set up filters to block requests containing suspicious patterns, malicious user-agents, or known attack signatures. Utilize Varnish VCL to inspect and block requests that may pose security risks.<\/span><\/p>\n<p><b>SSL\/TLS Encryption: <\/b><span style=\"font-weight: 400;\">Use SSL\/TLS encryption to secure communications between clients and Varnish Cache. This ensures that sensitive data transmitted through HTTP is encrypted and protected from eavesdropping.<\/span><\/p>\n<p><b>Authentication and Authorization: <\/b><span style=\"font-weight: 400;\">Implement strong authentication mechanisms for Varnish&#8217;s administrative interfaces. Use passwords, IP whitelisting, or other authentication methods to restrict access to authorized personnel only.<\/span><\/p>\n<p><b>Monitoring and Logging: <\/b><span style=\"font-weight: 400;\">Regularly monitor Varnish Cache and backend server logs to identify potential security threats or suspicious activities. Use security information and event management (SIEM) tools to aggregate and analyze log data for early threat detection.<\/span><\/p>\n<p><b>Regular Updates and Patching: <\/b><span style=\"font-weight: 400;\">Keep Varnish Cache and its dependencies up-to-date with the latest security patches and updates. Regularly check for security advisories and apply fixes promptly to mitigate known vulnerabilities.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">By proactively applying these security measures, developers can significantly enhance Varnish Cache&#8217;s resilience against DDoS attacks, SQL injections, and brute-force attempts, ensuring a robust and secure caching infrastructure for their web applications.<\/span><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Load Balancing and High Availability with Varnish&#8221; module_id=&#8221;load-balancing-high-availability&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221;]<\/p>\n<h2><strong>Load Balancing and High Availability<\/strong><b> with Varnish<\/b><\/h2>\n<p><i><span style=\"font-weight: 400;\">Setting up Varnish Cache in a load-balanced and highly available environment to ensure optimal performance and reliability.<\/span><\/i><\/p>\n<p>[\/et_pb_text][et_pb_text module_class=&#8221;bold-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"font-weight: 400;\">Load balancing and high availability are critical for ensuring optimal performance and reliability of Varnish Cache in high-traffic environments. Setting up Varnish in a load-balanced and highly available configuration involves distributing the incoming requests across multiple Varnish Cache instances and ensuring seamless failover in case of any server downtime.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">vmod_directors <\/span><span style=\"font-weight: 400;\">is a load-balancing <\/span><i><span style=\"font-weight: 400;\">VMOD.<\/span><\/i><\/p>\n<p><i> <\/i><\/p>\n<p><strong>In example 1, we initialize the director in vcl_init and choose the round-robin distribution algorithm to balance load across backend1 and backend2. In example 2, we\u2019re going for a random distribution.<\/strong><\/p>\n<p><i><span style=\"font-weight: 400;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Load-Balancing-and-High-Availability.png\" width=\"1442\" height=\"1026\" alt=\"\" class=\"wp-image-268880 aligncenter size-full\" \/><\/span><\/i><\/p>\n<p><i><span style=\"font-weight: 400;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Load-Balancing-and-High-Availability1.png\" width=\"1418\" height=\"1022\" alt=\"\" class=\"wp-image-268879 aligncenter size-full\" \/><\/span><\/i><\/p>\n<p><span style=\"font-weight: 400;\">To achieve load balancing, a load balancer or proxy server, such as HAProxy or Nginx, is typically used. The load balancer sits between the clients and the Varnish Cache instances, distributing incoming requests evenly across the cache servers based on predefined algorithms like round-robin or least connections.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">For high availability, a cluster of Varnish Cache instances is deployed in active-passive or active-active mode. In active-passive mode, one Varnish instance serves traffic while others remain on standby. If the active instance fails, the load balancer automatically redirects traffic to the next available cache server. In active-active mode, all Varnish instances actively handle incoming requests simultaneously, balancing the load across the cluster.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">To ensure synchronization between the cache instances, a shared storage mechanism, like NFS or a distributed cache storage backend, is often employed. This allows all cache instances to share cached objects and maintain consistency across the cluster.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Additionally, implementing health checks helps the load balancer identify the health of individual Varnish instances and automatically remove unhealthy servers from the load balancing pool.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">By setting up Varnish in a load-balanced and highly available environment, developers can achieve improved performance, scalability, and fault tolerance. This configuration ensures that Varnish Cache can handle high traffic volumes efficiently and provides a seamless user experience even in the face of server failures or maintenance events.<\/span><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Varnish Cache and SSL\/TLS&#8221; module_id=&#8221;varnish-cache-SSL-TLS&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221;]<\/p>\n<h2><b>Varnish Cache and <\/b><strong>SSL\/TLS<\/strong><\/h2>\n<p><i><span style=\"font-weight: 400;\">Configuring Varnish to work seamlessly with SSL\/TLS encrypted traffic, including handling certificates and ensuring secure connections.<\/span><\/i><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Text&#8221; module_class=&#8221;bold-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"font-weight: 400;\">Configuring Varnish is essential for ensuring secure and encrypted communication between clients and the cache infrastructure. Here are the steps on how to achieve this:<\/span><\/p>\n<p><b>Obtain SSL\/TLS Certificates:<\/b><span style=\"font-weight: 400;\"> Acquire SSL\/TLS certificates from a trusted Certificate Authority (CA) for your domain. These certificates will be used to encrypt the communication between clients and Varnish.<\/span><\/p>\n<p><b>Install Required Dependencies: <\/b><span style=\"font-weight: 400;\">Ensure that Varnish is compiled with the appropriate SSL\/TLS support. Check for the presence of libraries like OpenSSL during the installation process.<\/span><\/p>\n<p><b>Configure Varnish for SSL: <\/b><span style=\"font-weight: 400;\">Update the Varnish Configuration Language (VCL) to listen on the SSL port (usually 443). This involves specifying the backend server&#8217;s IP address or hostname and the appropriate port number where the encrypted requests will be forwarded.<\/span><\/p>\n<p><b>Enable SSL\/TLS: <\/b><span style=\"font-weight: 400;\">Enable SSL\/TLS termination by configuring Varnish to use the SSL\/TLS certificates obtained. Set up the &#8220;cert&#8221; and &#8220;key&#8221; paths in the VCL to point to the certificates and private key files.<\/span><\/p>\n<p><b>Implement Forward Secrecy: <\/b><span style=\"font-weight: 400;\">To enhance security, enable Forward Secrecy (FS) by configuring Varnish to support modern and secure ciphers. This ensures that even if the private key is compromised in the future, past encrypted communications remain secure.<\/span><\/p>\n<p><b>Configure HSTS Headers:<\/b><span style=\"font-weight: 400;\"> Implement HTTP Strict Transport Security (HSTS) headers in Varnish&#8217;s VCL to instruct clients to access the website only via HTTPS. This prevents potential downgrade attacks.<\/span><\/p>\n<p><b>Use OCSP Stapling: <\/b><span style=\"font-weight: 400;\">Enable Online Certificate Status Protocol (OCSP) stapling to improve the performance and security of certificate validation.<\/span><\/p>\n<p><b>Load Balancing for SSL Offloading: <\/b><span style=\"font-weight: 400;\">If you are using a load balancer for SSL offloading, ensure that the load balancer forwards decrypted requests to Varnish for further caching and processing.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">By following these steps, developers can seamlessly configure Varnish to work with SSL\/TLS encrypted traffic. This enhances the privacy and security of data transmitted over the network and promotes user trust in a web application.<\/span><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Varnish Cache and HTTPS info-box&#8221; module_class=&#8221;info-box&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; header_3_font=&#8221;|700|||||||&#8221; header_3_font_size=&#8221;24px&#8221; global_colors_info=&#8221;{}&#8221;]<\/p>\n<h3 style=\"text-align: center;\">Varnish Cache and HTTPS<\/h3>\n<p><i><span style=\"font-weight: 400;\">One challenge with Varnish Cache is that it is designed to accelerate HTTP, not the secure HTTPS. But increasingly websites are moving towards HTTPS for better protection against attacks. To enforce HTTPS with Varnish Cache developers have to add an SSL\/TLS terminator in front of Varnish Cache to convert HTTPS to HTTP.<\/span><\/i><\/p>\n<p><i><span style=\"font-weight: 400;\">The most popular way to achieve this is by deploying Nginx as the SSL\/TLS terminator. Nginx is a reverse proxy used to cache content like Varnish Cache, but the latter is much faster. Nginx allows HTTPS traffic, and when installed in front of Varnish Cache will perform the HTTPS to HTTP conversion. Developers should also install Nginx behind the Varnish Cache so that requests are converted back to HTTPS before going to the origin.<\/span><\/i><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Monitoring and Metrics for Varnish&#8221; module_id=&#8221;monitoring-metrics&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221;]<\/p>\n<h2><strong>Monitoring and Metrics<\/strong><b> for Varnish<\/b><\/h2>\n<p><i><span style=\"font-weight: 400;\">Tools and techniques for monitoring Varnish Cache&#8217;s performance, cache hit\/miss ratios, backend response times, and other essential metrics.<\/span><\/i><\/p>\n<p>[\/et_pb_text][et_pb_text module_class=&#8221;bold-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"font-weight: 400;\">Monitoring Varnish Cache&#8217;s performance is crucial to understanding its impact on web application efficiency and user experience. Several tools and techniques can help gather valuable metrics and insights:<\/span><\/p>\n<p><b>Varnishstat: <\/b><span style=\"font-weight: 400;\">Varnish includes its built-in monitoring tool called &#8220;varnishstat.&#8221; It provides real-time statistics on cache hits, misses, backend connections, cache eviction, and more. Command-line access to &#8220;varnishstat&#8221; enables developers to quickly assess cache performance.<\/span><\/p>\n<p><b>Varnishlog: <\/b><span style=\"font-weight: 400;\">Another built-in utility, &#8220;varnishlog,&#8221; offers a detailed log of incoming requests and VCL processing. It helps troubleshoot and analyze VCL configurations, providing visibility into request handling and potential bottlenecks.<\/span><\/p>\n<p><b>Logging and Analytics: <\/b><span style=\"font-weight: 400;\">Collecting Varnish log data and analyzing it through external log management or analytics tools, such as Elasticsearch, Logstash, and Kibana (ELK Stack), allows for in-depth examination of traffic patterns, cache behavior, and response times.<\/span><\/p>\n<p><b>Varnish Dashboard: <\/b><span style=\"font-weight: 400;\">Build custom dashboards using monitoring systems like Grafana or Prometheus to visualize key performance metrics from Varnish Cache in real-time. This provides an intuitive and comprehensive view of cache hit\/miss ratios, backend response times, and other vital statistics.<\/span><\/p>\n<p><span style=\"color: #000000;\"><strong>Prometheus dashboard<\/strong><\/span><\/p>\n<p><i><span style=\"font-weight: 400;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Prometheus-dashboard.png\" width=\"1418\" height=\"1356\" alt=\"\" class=\"wp-image-268878 aligncenter size-full\" \/><\/span><\/i><\/p>\n<p><span style=\"color: #000000;\"><strong>Grafana dashboard<\/strong><\/span><\/p>\n<p><i><span style=\"font-weight: 400;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Grafana-dashboard.png\" width=\"1386\" height=\"986\" alt=\"\" class=\"wp-image-268877 aligncenter size-full\" \/><\/span><\/i><\/p>\n<p><b>Backend Monitoring:<\/b><span style=\"font-weight: 400;\"> Monitor backend server performance to identify potential bottlenecks and assess how Varnish interacts with the origin servers. Monitoring tools like New Relic, Datadog, or Zabbix can help track backend response times and server health.<\/span><\/p>\n<p><b>Caching Effectiveness: <\/b><span style=\"font-weight: 400;\">By measuring cache hit\/miss ratios and cache efficiency, developers can assess how well Varnish serves cached content and identify opportunities for improvement.<\/span><\/p>\n<p><b>Cache Invalidation Auditing: <\/b><span style=\"font-weight: 400;\">Monitor cache invalidation events to ensure that cached content is purged appropriately when necessary, preventing stale or outdated content delivery.<\/span><\/p>\n<p><b>Load Testing: <\/b><span style=\"font-weight: 400;\">Conduct load testing using tools like Apache JMeter or Siege to simulate heavy traffic and measure Varnish Cache&#8217;s performance under stress conditions.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">By employing these monitoring tools and techniques, developers can gain valuable insights into Varnish Cache&#8217;s performance, identify optimization opportunities, and ensure that it effectively improves website performance and user experience.<\/span><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Cache Invalidation Strategies&#8221; module_id=&#8221;cache-invalidation&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221;]<\/p>\n<h2><strong>Cache Invalidation<\/strong><b> Strategies<\/b><\/h2>\n<p><i><span style=\"font-weight: 400;\">Tools and techniques for monitoring Varnish Cache&#8217;s performance, cache hit\/miss ratios, backend response times, and other essential metrics.<\/span><\/i><\/p>\n<p>[\/et_pb_text][et_pb_text module_class=&#8221;bold-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"font-weight: 400;\">Varnish cache invalidation techniques are essential for ensuring that cached content remains up-to-date and accurate without causing unnecessary cache misses. Proper cache invalidation strikes a balance between serving cached content efficiently and promptly reflecting changes made to dynamic resources. Here are some common Varnish cache invalidation techniques:<\/span><\/p>\n<p><b>TTL (Time-to-Live): <\/b><span style=\"font-weight: 400;\">Set a specific time duration, known as the Time-to-Live, for cached objects to remain valid. Once the TTL expires, Varnish automatically considers the content stale and fetches a fresh copy from the backend on the next request. Adjusting the TTL based on the content&#8217;s update frequency can minimize cache misses.<\/span><\/p>\n<p><b>Cache-Control Headers: <\/b><span style=\"font-weight: 400;\">Leverage the Cache-Control header sent by the backend to instruct Varnish on caching behavior. By specifying cache-control directives like &#8220;max-age&#8221; and &#8220;s-maxage,&#8221; developers can control how long Varnish should cache the resource.<\/span><\/p>\n<p><span style=\"color: #000000;\"><strong>Cache-Control header<\/strong><\/span><\/p>\n<p><i><span style=\"font-weight: 400;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Cache-Control-header.png\" width=\"1434\" height=\"554\" alt=\"\" class=\"wp-image-268876 aligncenter size-full\" \/><\/span><\/i><\/p>\n<p><b>Cache Purging: <\/b><span style=\"font-weight: 400;\">Manually or programmatically purge specific cached objects when they are updated. Using Varnish&#8217;s ban or purge functionality, developers can invalidate specific URLs or patterns to remove stale content from the cache.<\/span><\/p>\n<p><b>Conditional Requests: <\/b><span style=\"font-weight: 400;\">Use HTTP conditional requests, such as &#8220;If-Modified-Since&#8221; and &#8220;ETag&#8221; headers, to check if the cached content is still valid before serving it. This minimizes cache misses by serving the cached content only if it&#8217;s still up-to-date.<\/span><\/p>\n<p><b>Grace Mode: <\/b><span style=\"font-weight: 400;\">Employ Varnish&#8217;s grace mode, which allows Varnish to serve stale content while fetching updated data from the backend. This ensures seamless delivery of content while reducing cache misses during backend fetches.<\/span><\/p>\n<p><span style=\"color: #000000;\"><strong>Using Grace Mode in VLC code<\/strong><\/span><\/p>\n<p><span style=\"color: #000000;\"><strong><\/strong><\/span><i><span style=\"font-weight: 400;\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Using-Grace-Mode-in-VLC-code.png\" width=\"1396\" height=\"662\" alt=\"\" class=\"wp-image-268875 aligncenter size-full\" \/><\/span><\/i><\/p>\n<p><b>Edge-Side Includes (ESI): <\/b><span style=\"font-weight: 400;\">Utilize ESI to split web pages into fragments, enabling efficient caching of static components while fetching personalized or dynamic content separately. This way, only the dynamic fragments need to be updated, reducing the impact of cache invalidation on the entire page.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">By implementing Varnish cache invalidation techniques, developers can maintain an effective caching strategy that ensures cached content remains up-to-date while minimizing unnecessary cache misses. This results in improved performance, reduced server load, and an enhanced user experience on the web application.<\/span><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Varnish Cache for Ecommerce Websites&#8221; module_id=&#8221;ecommerce-websites&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221;]<\/p>\n<h2><b>Varnish Cache for<span>\u00a0<\/span><\/b><strong>Ecommerce Websites<\/strong><\/h2>\n<p><i><span style=\"font-weight: 400;\">Leveraging Varnish Cache to optimize the performance of ecommerce sites, including handling dynamic content and personalization.<\/span><\/i><\/p>\n<p>[\/et_pb_text][et_pb_text module_class=&#8221;bold-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"font-weight: 400;\">Leveraging Varnish Cache is highly beneficial for optimizing the performance of ecommerce sites, especially when dealing with dynamic content and personalized user experiences. Here&#8217;s how Varnish Cache can be utilized effectively:<\/span><\/p>\n<p><b>Caching Static Content: <\/b><span style=\"font-weight: 400;\">Varnish can efficiently cache static elements like product images, CSS, and JavaScript, reducing the load on backend servers and speeding up page loads. This ensures that frequently accessed content is served from cache, resulting in faster and more responsive pages.<\/span><\/p>\n<p><b>Edge-Side Includes (ESI):<\/b><span style=\"font-weight: 400;\"> Implement ESI to cache different fragments of ecommerce pages separately. By caching static components while fetching personalized elements separately, Varnish can efficiently assemble personalized pages on-the-fly, combining cached and dynamic content.<\/span><\/p>\n<p><b>Dynamic Content Caching: <\/b><span style=\"font-weight: 400;\">Configure Varnish to cache certain dynamically generated content, like product listings and search results, without compromising on real-time data accuracy. Using an appropriate cache TTL and cache purging techniques, developers can ensure that the cache remains up-to-date with relevant changes.<\/span><\/p>\n<p><b>Session Handling:<\/b><span style=\"font-weight: 400;\"> Employ Varnish to handle user sessions intelligently. By excluding session-specific data from caching or using ESI to cache personalized parts separately, Varnish can provide a personalized experience without serving the wrong content to multiple users.<\/span><\/p>\n<p><b>Cache Invalidation Strategies: <\/b><span style=\"font-weight: 400;\">Develop robust cache invalidation strategies to promptly update cached content when products, prices, or inventory change. Utilize cache purging and conditional requests to ensure cache freshness while avoiding unnecessary backend requests.<\/span><\/p>\n<p><b>Load Balancing:<\/b><span style=\"font-weight: 400;\"> Implement Varnish in a load-balanced and highly available configuration to distribute traffic efficiently and handle sudden spikes in user activity during peak shopping periods.<\/span><\/p>\n<p><b>Ecommerce Analytics:<\/b><span style=\"font-weight: 400;\"> Integrate Varnish with ecommerce analytics tools to gain insights into cache performance, user behavior, and conversion rates. This information can guide further optimizations.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">By leveraging Varnish Cache effectively, ecommerce sites can significantly improve website performance, reduce server load, and deliver a seamless and personalized shopping experience to their users. It enhances the overall user experience, boosts conversion rates, and strengthens customer loyalty, leading to a competitive edge in the ecommerce market.<\/span><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;What Content to Cache with Varnish Cache&#8221; module_id=&#8221;what-content-to-cache&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221;]<\/p>\n<h2><strong>What Content to Cache<\/strong><b> with Varnish Cache<\/b><\/h2>\n<p><i><span style=\"font-weight: 400;\">For achieving optimum web performance, specific types of content should be cached with Varnish.<\/span><\/i><\/p>\n<p>[\/et_pb_text][et_pb_text module_class=&#8221;bold-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"font-weight: 400;\">To achieve optimum web performance and ensure a seamless customer experience, Varnish Cache should be strategically utilized to cache specific types of content. The goal is to prioritize caching elements that contribute significantly to page load times and user interactions. Here are some key types of content that should be cached with Varnish:<\/span><\/p>\n<p><b>Static Assets: <\/b><span style=\"font-weight: 400;\">Static resources like images (png, jpg, gif), CSS stylesheets &amp; fonts, and JavaScript libraries should be cached as they rarely change and contribute to the bulk of a webpage&#8217;s size. Caching these assets ensures quicker load times and reduced bandwidth usage.<\/span><\/p>\n<p><b>Full HTML Documents:<\/b><span style=\"font-weight: 400;\"> The real value of Varnish Cache is in caching the HTML document. The HTML document has all the information needed to build a web page, including CSS files, text, and links to images. A slowly loading HTML document delays the time to first byte (TTFB) and start render time (SRT), adversely impacting user experience and SEO.<\/span><\/p>\n<p><b>Frequently Accessed Pages:<\/b><span style=\"font-weight: 400;\"> Frequently accessed pages, like homepages, product listings, and landing pages, should be cached to improve response times and reduce the load on backend servers.<\/span><\/p>\n<p><b>Database Queries: <\/b><span style=\"font-weight: 400;\">Caching the results of complex database queries can help alleviate the load on the database server and expedite response times, especially for content that doesn&#8217;t change frequently.<\/span><\/p>\n<p><b>API Responses: <\/b><span style=\"font-weight: 400;\">Cache responses from third-party APIs to minimize external requests, improve page load times, and ensure more consistent API performance.<\/span><\/p>\n<p><b>Session-agnostic Content: <\/b><span style=\"font-weight: 400;\">Content that doesn&#8217;t rely on user sessions or personalization, such as blog posts or public information pages, can be effectively cached without risking data inconsistency.<\/span><\/p>\n<p><b>Edge-Side Includes (ESI): <\/b><span style=\"font-weight: 400;\">Utilize ESI for personalized content. By caching static components and using ESI to assemble personalized fragments, Varnish can deliver dynamic content while benefiting from cached static elements.<\/span><\/p>\n<p><b>Error Pages: <\/b><span style=\"font-weight: 400;\">Caching custom error pages ensures a smoother experience for users in case of unexpected errors and prevents unnecessary backend requests.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">By focusing on caching these types of content with Varnish, websites can significantly enhance web performance, reduce server load, and provide a seamless and engaging experience for their customers. However, it&#8217;s essential to strike a balance between cache efficiency and serving the most up-to-date content, particularly for dynamic and personalized elements that require careful cache invalidation strategies.<\/span><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;Integrating Varnish Cache with a Content Delivery Network (CDN)&#8221; module_id=&#8221;integrating-CDN&#8221; module_class=&#8221;dual-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; custom_padding=&#8221;60px||||false|false&#8221; global_colors_info=&#8221;{}&#8221; header_text_align=&#8221;center&#8221; header_2_font=&#8221;||||||||&#8221; header_2_text_align=&#8221;center&#8221; header_2_text_color=&#8221;#231F20&#8243; header_2_font_size=&#8221;32px&#8221;]<\/p>\n<h2><b>Integrating Varnish Cache with a <\/b><strong>Content Delivery Network (CDN)<\/strong><\/h2>\n<p><em>Combine Varnish Cache with a CDN to further improve website performance, reduce server load, and enhance global content delivery.<\/em><\/p>\n<p>[\/et_pb_text][et_pb_text module_class=&#8221;bold-org&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"font-weight: 400;\">Integrating Varnish Cache with a Content Delivery Network (CDN) is a powerful strategy to supercharge website performance, reduce server load, and optimize content delivery on a global scale. By combining Varnish&#8217;s edge caching capabilities with a CDN, businesses can enhance their web application&#8217;s responsiveness and provide a seamless experience to users worldwide.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">When Varnish Cache is deployed at the CDN edge nodes, it acts as an additional caching layer. This setup allows static content, such as images, CSS, and JavaScript, to be cached closer to end-users, significantly reducing latency and speeding up page loads. With cached content being served from nearby CDN servers, the origin server&#8217;s load is dramatically reduced, leading to improved server scalability and better handling of traffic spikes.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Moreover, Varnish Cache&#8217;s advanced caching mechanisms, coupled with the CDN&#8217;s distribution network, ensure that content remains available even during sudden surges in demand or server outages. The combination enables seamless failover and high availability, enhancing overall website reliability.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The integration also enhances the CDN&#8217;s performance by reducing the load on its servers, improving cache hit ratios, and minimizing the need for frequent requests to the origin server. This synergy results in a more cost-effective and efficient content delivery process.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The integration of Varnish Cache with a CDN empowers businesses to deliver content faster, provide a superior user experience, and optimize server resources. This powerful combination is especially valuable for global businesses seeking to provide consistent and high-performing web experiences to users across the world.<\/span><\/p>\n<p>[\/et_pb_text][et_pb_text admin_label=&#8221;info-box&#8221; module_class=&#8221;info-box li-content&#8221; _builder_version=&#8221;4.22.0&#8243; _module_preset=&#8221;06a54c5d-f36b-4396-9f69-bc253efbdbc5&#8243; global_colors_info=&#8221;{}&#8221;]<\/p>\n<p><span style=\"font-weight: 400;\">\u00a0<\/span><i><span style=\"font-weight: 400;\">Though Varnish Cache is open source and free to download and install, there are several providers that offer Varnish Cache as a service or hosted versions of Varnish Cache for a fee. Webscale is the <\/span><\/i><a href=\"\/intelligent-cloudops-for-modern-commerce\/\"><i><span style=\"font-weight: 400;\">Intelligent CloudOps Platform<\/span><\/i><\/a><i><span style=\"font-weight: 400;\"> offering <\/span><\/i><i><span style=\"font-weight: 400;\">7 versions of unmodified Varnish Cache up to 5.1.2. <\/span><\/i><i><span style=\"font-weight: 400;\">If you have any questions about Varnish Cache and VCL, <\/span><\/i><a href=\"\/contact-us\/\"><i><span style=\"font-weight: 400;\">contact us<\/span><\/i><\/a><i><span style=\"font-weight: 400;\"> and one of our Varnish Cache experts would be happy to help you.<\/span><\/i><\/p>\n<p>[\/et_pb_text][\/et_pb_column][\/et_pb_row][\/et_pb_section]<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Varnish CacheA quick reference guide for all things Varnish! Getting Started with Varnish Cache Understanding VCL Caching Strategies with Varnish Extending Varnish Cache capabilities Securing Varnish Cache Load Balancing and High Availability Varnish Cache and SSL\/TLS Monitoring and Metrics Cache Invalidation Ecommerce Websites What Content to Cache Integrating with a CDN Getting Started with Varnish [&hellip;]<\/p>\n","protected":false},"author":34,"featured_media":267300,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_et_pb_use_builder":"on","_et_pb_old_content":"","_et_gb_content_width":"","_aioseo_description":"","_aioseo_keywords":"","_aioseo_og_article_section":"","_aioseo_og_article_tags":"","_aioseo_og_description":"","_aioseo_og_title":"","_aioseo_title":"","_aioseo_twitter_description":"","_aioseo_twitter_title":"","_author_photo":"","_doc_url":"field_63c6a84525c8f","_dp_original":"","_et_autogenerated_title":"","_et_body_layout_enabled":"","_et_body_layout_id":"","_et_builder_dynamic_assets_loading_attr_threshold":"13","_et_builder_module_features_cache":[],"_et_builder_version":"VB|Divi|4.22.2","_et_default":"","_et_enabled":"","_et_footer_layout_enabled":"","_et_footer_layout_id":"","_et_header_layout_enabled":"","_et_header_layout_id":"","_et_pb_ab_current_shortcode":"[et_pb_split_track 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var(--org);\n  font-weight: 600;\n}\n.bold-org .et_pb_text_inner b {\n    color: var(--org);\n}\n.dual-org .et_pb_text_inner h2:after {\n    content: \"\";\n    border-bottom: 2px solid var(--org);\n    padding-bottom: 15px;\n    width: 130px;\n    display: block;\n    margin: auto;\n    text-align: center;\n}\n.et-db #et-boc .et-l #table-of-cont.li-content li::marker {\n    content: \"\";\n}\n.et-db #et-boc .et-l #table-of-cont.li-content li:before {\n    content: \"\";\n    display: block;\n    width: 60px !important;\n    border-top: 2px solid #ccc;\n    position: absolute;\n    left: -50px;\n    margin-top: 12px;\n}\n.et-db #et-boc .et-l #table-of-cont.li-content li:hover:before, .et-db #et-boc .et-l #table-of-cont.li-content li.active:before {\n    border-top: 2px solid var(--org);\n}\n.et-db #et-boc .et-l #table-of-cont.li-content li:hover a, .et-db #et-boc .et-l #table-of-cont.li-content li.active a{\n    color: var(--blk)!important;\n    font-weight: bold;\n    font-size: 0.98em;\n}","_et_pb_enable_shortcode_tracking":"","_et_pb_excluded_global_options":"","_et_pb_first_image":"","_et_pb_gutter_width":"2","_et_pb_module_type":"","_et_pb_page_layout":"et_no_sidebar","_et_pb_page_z_index":"","_et_pb_post_hide_nav":"default","_et_pb_row_layout":"","_et_pb_show_page_creation":"off","_et_pb_show_title":"","_et_pb_side_nav":"off","_et_pb_static_css_file":"","_et_pb_truncate_post":"<p><div id=\"top\" class=\"et_pb_section et_pb_section_0 et_pb_with_background et_section_regular\" >\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_row et_pb_row_0 et_pb_equal_columns et_pb_gutters2\">\n\t\t\t\t<div class=\"et_pb_column et_pb_column_4_4 et_pb_column_0  et_pb_css_mix_blend_mode_passthrough et-last-child\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_module et_pb_text et_pb_text_0 grd-org-pnk  et_pb_text_align_center et_pb_bg_layout_dark\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Varnish Cache<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_1 sub-title  et_pb_text_align_center et_pb_bg_layout_dark\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">A quick reference guide for all things Varnish!<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_image et_pb_image_0\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<span class=\"et_pb_image_wrap \"><img fetchpriority=\"high\" decoding=\"async\" width=\"1050\" height=\"350\" src=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Banners-Varnish-Pillar-page.png\" alt=\"\" title=\"Banners Varnish Pillar Page\" srcset=\"https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Banners-Varnish-Pillar-page.png 1050w, https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Banners-Varnish-Pillar-page-980x327.png 980w, https:\/\/www.webscale.com\/wp-content\/uploads\/2023\/08\/Banners-Varnish-Pillar-page-480x160.png 480w\" sizes=\"(min-width: 0px) and (max-width: 480px) 480px, (min-width: 481px) and (max-width: 980px) 980px, (min-width: 981px) 1050px, 100vw\" class=\"wp-image-267282\" \/><\/span>\n\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/div><div class=\"et_pb_section et_pb_section_1 et_section_regular\" >\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_row et_pb_row_1\">\n\t\t\t\t<div class=\"et_pb_column et_pb_column_1_4 et_pb_column_1  et_pb_css_mix_blend_mode_passthrough\" id=\"left-col\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div id=\"table-of-cont\" class=\"et_pb_with_border et_pb_module et_pb_text et_pb_text_2 li-content et_pb_sticky_module  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Getting Started with Varnish Cache<br \/>\nUnderstanding VCL<br \/>\nCaching Strategies with Varnish<br \/>\nExtending Varnish Cache capabilities<br \/>\nSecuring Varnish Cache<br \/>\nLoad Balancing and High Availability<br \/>\nVarnish Cache and SSL\/TLS<br \/>\nMonitoring and Metrics<br \/>\nCache Invalidation<br \/>\nEcommerce Websites<br \/>\nWhat Content to Cache<br \/>\nIntegrating with a CDN<\/div>\n\t\t\t<\/div>\n\t\t\t<\/div><div class=\"et_pb_column et_pb_column_3_4 et_pb_column_2  et_pb_css_mix_blend_mode_passthrough et-last-child\" id=\"right-col\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_module et_pb_code et_pb_code_0\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/div><div id=\"right-cont\" class=\"et_pb_section et_pb_section_2 et_section_regular\" >\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_row et_pb_row_2 et_pb_equal_columns et_pb_gutters2\">\n\t\t\t\t<div class=\"et_pb_column et_pb_column_4_4 et_pb_column_3 toc  et_pb_css_mix_blend_mode_passthrough et-last-child\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div id=\"getting-started\" class=\"et_pb_module et_pb_text et_pb_text_3 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Getting Started with Varnish Cache<br \/>\nAn introduction to Varnish Cache, its benefits, and how to install and configure it.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_4  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Varnish Cache is a powerful open-source HTTP accelerator (reverse proxy for caching HTTP) designed to significantly improve website performance and reduce server load by caching and serving frequently accessed content. It acts as an intermediary between the client and the backend web server, efficiently storing copies of web pages and assets like images, CSS, and JavaScript in its high-speed memory.<\/p>\n<p>The primary benefit of Varnish Cache lies in its ability to dramatically speed up website response times, leading to a better user experience. By serving cached content directly from memory, Varnish reduces the need for repeated processing of dynamic content on the backend, resulting in faster page loads and reduced server resource utilization.<br \/>\nTo install Varnish Cache, you\u2019ll need to ensure your server meets the system requirements and has necessary dependencies like GCC and the PCRE library. Once ready, the installation process involves using package managers like YUM or APT to download and install the software. Alternatively, you can compile Varnish from source code for more customization options.<br \/>\nAfter installation, configuration is key to getting the best out of Varnish Cache. It involves setting up a Varnish Configuration Language (VCL) file, which defines how Varnish should handle incoming requests and what to cache. Careful consideration should be given to handling cookies, cache invalidation strategies, and the caching of personalized content.<br \/>\nWhen properly installed and configured, Varnish Cache can significantly improve website performance, reduce server load, and handle sudden traffic spikes more efficiently. As a result, businesses can enjoy better user retention, improved search engine rankings, and increased overall customer satisfaction. Varnish Cache has become an essential tool for websites dealing with high traffic volumes, making it an invaluable asset for developers seeking to optimize web performance.<br \/>\nThe biggest advantages of Varnish Cache are its speed and flexibility. It can speed up content delivery by 300-1000x, and thanks to the flexibility of Varnish Configuration Language (VCL), it can be configured to act as a load balancer, and block IP addresses. This combination of speed and configurability has led to Varnish Cache growing in popularity over Nginx, another reverse proxy used for caching that has been around longer.<\/div>\n\t\t\t<\/div><div id=\"understanding-vcl\" class=\"et_pb_module et_pb_text et_pb_text_5 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Understanding VCL (Varnish Configuration Language)<br \/>\nA deep dive into Varnish&#8217;s powerful configuration language, including examples of common use cases and best practices for writing efficient VCL code.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_6  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Understanding Varnish Configuration Language (VCL) is essential for harnessing the full potential of Varnish Cache. VCL is a domain-specific language used to define how Varnish handles incoming HTTP requests and decides what content to cache. It consists of various subroutines that are executed during different stages of request processing.<br \/>\nHere&#8217;s some sample code to give you an idea of what VCL looks like:<\/p>\n<p>One of the key subroutines is &#8220;vcl_recv,&#8221; which is responsible for processing incoming requests before they are fetched from the backend. This subroutine allows developers to make decisions based on request headers, cookies, or client IP addresses. Another crucial subroutine is &#8220;vcl_fetch,&#8221; executed after fetching content from the backend but before storing it in the cache. Here, developers can manipulate the fetched content or define cache policies.<br \/>\nA common use case for VCL is cache control based on HTTP headers. Developers can use the &#8220;vcl_recv&#8221; subroutine to inspect headers like &#8220;Cache-Control&#8221; and decide whether to cache the content or pass it to the backend for fresh data. Additionally, VCL enables edge-side includes (ESI), where dynamic and static content can be assembled in real-time, optimizing cache efficiency.<br \/>\nWriting efficient VCL code involves several best practices. Minimizing conditional statements, using &#8220;return&#8221; to stop further processing when appropriate, and leveraging the built-in &#8220;std&#8221; library for common tasks are some key practices. Properly handling cache invalidation, especially for dynamic content, is crucial to avoid stale data issues.<br \/>\nMastering VCL and its subroutines empowers developers to finely control Varnish Cache&#8217;s behavior, leading to optimal cache performance and improved website responsiveness. Efficient VCL code not only ensures better caching decisions but also contributes to overall web server resource optimization.<\/div>\n\t\t\t<\/div><div id=\"caching-strategies-with-varnish\" class=\"et_pb_module et_pb_text et_pb_text_7 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Caching Strategies with Varnish<br \/>\nExplore various caching strategies, such as edge-side includes (ESI), cache purging, and cache invalidation techniques to optimize content delivery and improve performance.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_8 bold-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Varnish Cache offers a range of caching strategies that can significantly optimize content delivery and enhance website performance. Three key strategies include Edge-Side Includes (ESI), Cache Purging, and Cache Invalidation techniques.<br \/>\nEdge-Side Includes (ESI) is a powerful strategy that allows developers to split web pages into multiple fragments or components. These fragments can be cached separately, and when a request is made, Varnish can dynamically assemble the page by combining the cached fragments with real-time, non-cacheable content from the origin server. ESI is particularly useful for websites with dynamic and personalized elements, as it enables efficient caching of static components while ensuring the freshness of personalized content.<br \/>\nESI tag<\/p>\n<p>Cache Purging is the process of selectively removing specific cached items to update the cache with fresh content. Varnish provides mechanisms to purge individual URLs or specific objects, allowing developers to invalidate specific parts of the cache when content is updated or becomes stale. By strategically purging outdated content, Varnish ensures that users receive the most up-to-date information, striking a balance between cache efficiency and content accuracy.<br \/>\nPurge code<\/p>\n<p>Cache Invalidation techniques are essential for ensuring that cached content remains relevant. Varnish provides several options, such as time-based expiration, conditional requests with &#8220;If-Modified-Since&#8221; or &#8220;ETag&#8221; headers, and cache invalidation through backend control. These techniques help maintain cache freshness and avoid serving outdated or irrelevant content to users.<br \/>\nBy adopting these caching strategies, developers can leverage Varnish Cache&#8217;s capabilities to optimize content delivery, reduce server load, and provide users with faster and more responsive websites. However, it&#8217;s crucial to strike a balance between aggressive caching for performance benefits and proper cache invalidation strategies to ensure users receive accurate and up-to-date information.<\/div>\n\t\t\t<\/div><div id=\"extending-varnish-cache-capabilities\" class=\"et_pb_module et_pb_text et_pb_text_9 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Extending Varnish Cache capabilities with VMODs<br \/>\nAdd custom functionality and enhance cache performance with Varnish Modules<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_10 bold-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Extending Varnish Cache capabilities with VMODs (Varnish Modules) is a powerful way to add custom functionality and enhance cache performance for specific use cases. VMODs are dynamic loadable modules written in C or other supported languages, allowing developers to introduce new functionalities without modifying the Varnish source code.<br \/>\nVCL snippet that features the cookie VMOD<\/p>\n<p>With VMODs, developers can extend Varnish to interact with external systems, perform complex data manipulations, or implement custom caching strategies. For example, VMODs can be created to integrate Varnish with specific databases, implement advanced cache invalidation techniques, or add support for specialized authentication methods.<br \/>\nVMODs enable Varnish to adapt to unique application requirements, improving the overall efficiency and effectiveness of the cache. By encapsulating custom functionalities in VMODs, developers can easily reuse and share these modules across different projects.<br \/>\nThe Varnish community actively contributes to the VMOD ecosystem, resulting in a wide range of pre-built modules available for various purposes. These community-contributed VMODs can be readily incorporated into Varnish setups to address common challenges and optimize performance.<br \/>\nLeveraging VMODs extends the power of Varnish Cache, making it a flexible and customizable caching solution for diverse web application scenarios. By tailoring Varnish with VMODs, developers can unleash the full potential of caching while maintaining the ease and efficiency of Varnish&#8217;s configuration and deployment.<\/div>\n\t\t\t<\/div><div id=\"securing-varnish-cache\" class=\"et_pb_module et_pb_text et_pb_text_11 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Securing Varnish Cache and Handling Attacks<br \/>\nHow to secure Varnish Cache from DDoS attacks, SQL injections, and brute-force attempts.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_12 bold-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Securing Varnish Cache against common web application attacks is crucial to protect both the cache infrastructure and the backend servers from potential vulnerabilities. Here are some essential steps to bolster Varnish Cache&#8217;s security:<br \/>\nRate Limiting and DDoS Protection: Implement rate-limiting mechanisms to restrict the number of requests from a single IP address or user agent within a specified timeframe. Utilize DDoS protection solutions and services to detect and mitigate distributed denial-of-service attacks, safeguarding Varnish from being overwhelmed with malicious traffic.<br \/>\nInput Validation and Sanitization: Enforce strict input validation and data sanitization practices at the backend to prevent SQL injection attacks. Apply parameterized queries and prepared statements to mitigate the risk of malicious code injection.<br \/>\nHTTP Request Filtering: Set up filters to block requests containing suspicious patterns, malicious user-agents, or known attack signatures. Utilize Varnish VCL to inspect and block requests that may pose security risks.<br \/>\nSSL\/TLS Encryption: Use SSL\/TLS encryption to secure communications between clients and Varnish Cache. This ensures that sensitive data transmitted through HTTP is encrypted and protected from eavesdropping.<br \/>\nAuthentication and Authorization: Implement strong authentication mechanisms for Varnish&#8217;s administrative interfaces. Use passwords, IP whitelisting, or other authentication methods to restrict access to authorized personnel only.<br \/>\nMonitoring and Logging: Regularly monitor Varnish Cache and backend server logs to identify potential security threats or suspicious activities. Use security information and event management (SIEM) tools to aggregate and analyze log data for early threat detection.<br \/>\nRegular Updates and Patching: Keep Varnish Cache and its dependencies up-to-date with the latest security patches and updates. Regularly check for security advisories and apply fixes promptly to mitigate known vulnerabilities.<br \/>\nBy proactively applying these security measures, developers can significantly enhance Varnish Cache&#8217;s resilience against DDoS attacks, SQL injections, and brute-force attempts, ensuring a robust and secure caching infrastructure for their web applications.<\/div>\n\t\t\t<\/div><div id=\"load-balancing-high-availability\" class=\"et_pb_module et_pb_text et_pb_text_13 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Load Balancing and High Availability with Varnish<br \/>\nSetting up Varnish Cache in a load-balanced and highly available environment to ensure optimal performance and reliability.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_14 bold-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Load balancing and high availability are critical for ensuring optimal performance and reliability of Varnish Cache in high-traffic environments. Setting up Varnish in a load-balanced and highly available configuration involves distributing the incoming requests across multiple Varnish Cache instances and ensuring seamless failover in case of any server downtime.<br \/>\nvmod_directors is a load-balancing VMOD.<\/p>\n<p>In example 1, we initialize the director in vcl_init and choose the round-robin distribution algorithm to balance load across backend1 and backend2. In example 2, we\u2019re going for a random distribution.<\/p>\n<p>To achieve load balancing, a load balancer or proxy server, such as HAProxy or Nginx, is typically used. The load balancer sits between the clients and the Varnish Cache instances, distributing incoming requests evenly across the cache servers based on predefined algorithms like round-robin or least connections.<br \/>\nFor high availability, a cluster of Varnish Cache instances is deployed in active-passive or active-active mode. In active-passive mode, one Varnish instance serves traffic while others remain on standby. If the active instance fails, the load balancer automatically redirects traffic to the next available cache server. In active-active mode, all Varnish instances actively handle incoming requests simultaneously, balancing the load across the cluster.<br \/>\nTo ensure synchronization between the cache instances, a shared storage mechanism, like NFS or a distributed cache storage backend, is often employed. This allows all cache instances to share cached objects and maintain consistency across the cluster.<br \/>\nAdditionally, implementing health checks helps the load balancer identify the health of individual Varnish instances and automatically remove unhealthy servers from the load balancing pool.<br \/>\nBy setting up Varnish in a load-balanced and highly available environment, developers can achieve improved performance, scalability, and fault tolerance. This configuration ensures that Varnish Cache can handle high traffic volumes efficiently and provides a seamless user experience even in the face of server failures or maintenance events.<\/div>\n\t\t\t<\/div><div id=\"varnish-cache-SSL-TLS\" class=\"et_pb_module et_pb_text et_pb_text_15 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Varnish Cache and SSL\/TLS<br \/>\nConfiguring Varnish to work seamlessly with SSL\/TLS encrypted traffic, including handling certificates and ensuring secure connections.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_16 bold-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Configuring Varnish is essential for ensuring secure and encrypted communication between clients and the cache infrastructure. Here are the steps on how to achieve this:<br \/>\nObtain SSL\/TLS Certificates: Acquire SSL\/TLS certificates from a trusted Certificate Authority (CA) for your domain. These certificates will be used to encrypt the communication between clients and Varnish.<br \/>\nInstall Required Dependencies: Ensure that Varnish is compiled with the appropriate SSL\/TLS support. Check for the presence of libraries like OpenSSL during the installation process.<br \/>\nConfigure Varnish for SSL: Update the Varnish Configuration Language (VCL) to listen on the SSL port (usually 443). This involves specifying the backend server&#8217;s IP address or hostname and the appropriate port number where the encrypted requests will be forwarded.<br \/>\nEnable SSL\/TLS: Enable SSL\/TLS termination by configuring Varnish to use the SSL\/TLS certificates obtained. Set up the &#8220;cert&#8221; and &#8220;key&#8221; paths in the VCL to point to the certificates and private key files.<br \/>\nImplement Forward Secrecy: To enhance security, enable Forward Secrecy (FS) by configuring Varnish to support modern and secure ciphers. This ensures that even if the private key is compromised in the future, past encrypted communications remain secure.<br \/>\nConfigure HSTS Headers: Implement HTTP Strict Transport Security (HSTS) headers in Varnish&#8217;s VCL to instruct clients to access the website only via HTTPS. This prevents potential downgrade attacks.<br \/>\nUse OCSP Stapling: Enable Online Certificate Status Protocol (OCSP) stapling to improve the performance and security of certificate validation.<br \/>\nLoad Balancing for SSL Offloading: If you are using a load balancer for SSL offloading, ensure that the load balancer forwards decrypted requests to Varnish for further caching and processing.<br \/>\nBy following these steps, developers can seamlessly configure Varnish to work with SSL\/TLS encrypted traffic. This enhances the privacy and security of data transmitted over the network and promotes user trust in a web application.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_17 info-box  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Varnish Cache and HTTPS<br \/>\nOne challenge with Varnish Cache is that it is designed to accelerate HTTP, not the secure HTTPS. But increasingly websites are moving towards HTTPS for better protection against attacks. To enforce HTTPS with Varnish Cache developers have to add an SSL\/TLS terminator in front of Varnish Cache to convert HTTPS to HTTP.<br \/>\nThe most popular way to achieve this is by deploying Nginx as the SSL\/TLS terminator. Nginx is a reverse proxy used to cache content like Varnish Cache, but the latter is much faster. Nginx allows HTTPS traffic, and when installed in front of Varnish Cache will perform the HTTPS to HTTP conversion. Developers should also install Nginx behind the Varnish Cache so that requests are converted back to HTTPS before going to the origin.<\/div>\n\t\t\t<\/div><div id=\"monitoring-metrics\" class=\"et_pb_module et_pb_text et_pb_text_18 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Monitoring and Metrics for Varnish<br \/>\nTools and techniques for monitoring Varnish Cache&#8217;s performance, cache hit\/miss ratios, backend response times, and other essential metrics.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_19 bold-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Monitoring Varnish Cache&#8217;s performance is crucial to understanding its impact on web application efficiency and user experience. Several tools and techniques can help gather valuable metrics and insights:<br \/>\nVarnishstat: Varnish includes its built-in monitoring tool called &#8220;varnishstat.&#8221; It provides real-time statistics on cache hits, misses, backend connections, cache eviction, and more. Command-line access to &#8220;varnishstat&#8221; enables developers to quickly assess cache performance.<br \/>\nVarnishlog: Another built-in utility, &#8220;varnishlog,&#8221; offers a detailed log of incoming requests and VCL processing. It helps troubleshoot and analyze VCL configurations, providing visibility into request handling and potential bottlenecks.<br \/>\nLogging and Analytics: Collecting Varnish log data and analyzing it through external log management or analytics tools, such as Elasticsearch, Logstash, and Kibana (ELK Stack), allows for in-depth examination of traffic patterns, cache behavior, and response times.<br \/>\nVarnish Dashboard: Build custom dashboards using monitoring systems like Grafana or Prometheus to visualize key performance metrics from Varnish Cache in real-time. This provides an intuitive and comprehensive view of cache hit\/miss ratios, backend response times, and other vital statistics.<br \/>\nPrometheus dashboard<\/p>\n<p>Grafana dashboard<\/p>\n<p>Backend Monitoring: Monitor backend server performance to identify potential bottlenecks and assess how Varnish interacts with the origin servers. Monitoring tools like New Relic, Datadog, or Zabbix can help track backend response times and server health.<br \/>\nCaching Effectiveness: By measuring cache hit\/miss ratios and cache efficiency, developers can assess how well Varnish serves cached content and identify opportunities for improvement.<br \/>\nCache Invalidation Auditing: Monitor cache invalidation events to ensure that cached content is purged appropriately when necessary, preventing stale or outdated content delivery.<br \/>\nLoad Testing: Conduct load testing using tools like Apache JMeter or Siege to simulate heavy traffic and measure Varnish Cache&#8217;s performance under stress conditions.<br \/>\nBy employing these monitoring tools and techniques, developers can gain valuable insights into Varnish Cache&#8217;s performance, identify optimization opportunities, and ensure that it effectively improves website performance and user experience.<\/div>\n\t\t\t<\/div><div id=\"cache-invalidation\" class=\"et_pb_module et_pb_text et_pb_text_20 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Cache Invalidation Strategies<br \/>\nTools and techniques for monitoring Varnish Cache&#8217;s performance, cache hit\/miss ratios, backend response times, and other essential metrics.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_21 bold-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Varnish cache invalidation techniques are essential for ensuring that cached content remains up-to-date and accurate without causing unnecessary cache misses. Proper cache invalidation strikes a balance between serving cached content efficiently and promptly reflecting changes made to dynamic resources. Here are some common Varnish cache invalidation techniques:<br \/>\nTTL (Time-to-Live): Set a specific time duration, known as the Time-to-Live, for cached objects to remain valid. Once the TTL expires, Varnish automatically considers the content stale and fetches a fresh copy from the backend on the next request. Adjusting the TTL based on the content&#8217;s update frequency can minimize cache misses.<br \/>\nCache-Control Headers: Leverage the Cache-Control header sent by the backend to instruct Varnish on caching behavior. By specifying cache-control directives like &#8220;max-age&#8221; and &#8220;s-maxage,&#8221; developers can control how long Varnish should cache the resource.<br \/>\nCache-Control header<\/p>\n<p>Cache Purging: Manually or programmatically purge specific cached objects when they are updated. Using Varnish&#8217;s ban or purge functionality, developers can invalidate specific URLs or patterns to remove stale content from the cache.<br \/>\nConditional Requests: Use HTTP conditional requests, such as &#8220;If-Modified-Since&#8221; and &#8220;ETag&#8221; headers, to check if the cached content is still valid before serving it. This minimizes cache misses by serving the cached content only if it&#8217;s still up-to-date.<br \/>\nGrace Mode: Employ Varnish&#8217;s grace mode, which allows Varnish to serve stale content while fetching updated data from the backend. This ensures seamless delivery of content while reducing cache misses during backend fetches.<br \/>\nUsing Grace Mode in VLC code<\/p>\n<p>Edge-Side Includes (ESI): Utilize ESI to split web pages into fragments, enabling efficient caching of static components while fetching personalized or dynamic content separately. This way, only the dynamic fragments need to be updated, reducing the impact of cache invalidation on the entire page.<br \/>\nBy implementing Varnish cache invalidation techniques, developers can maintain an effective caching strategy that ensures cached content remains up-to-date while minimizing unnecessary cache misses. This results in improved performance, reduced server load, and an enhanced user experience on the web application.<\/div>\n\t\t\t<\/div><div id=\"ecommerce-websites\" class=\"et_pb_module et_pb_text et_pb_text_22 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Varnish Cache for\u00a0Ecommerce Websites<br \/>\nLeveraging Varnish Cache to optimize the performance of ecommerce sites, including handling dynamic content and personalization.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_23 bold-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Leveraging Varnish Cache is highly beneficial for optimizing the performance of ecommerce sites, especially when dealing with dynamic content and personalized user experiences. Here&#8217;s how Varnish Cache can be utilized effectively:<br \/>\nCaching Static Content: Varnish can efficiently cache static elements like product images, CSS, and JavaScript, reducing the load on backend servers and speeding up page loads. This ensures that frequently accessed content is served from cache, resulting in faster and more responsive pages.<br \/>\nEdge-Side Includes (ESI): Implement ESI to cache different fragments of ecommerce pages separately. By caching static components while fetching personalized elements separately, Varnish can efficiently assemble personalized pages on-the-fly, combining cached and dynamic content.<br \/>\nDynamic Content Caching: Configure Varnish to cache certain dynamically generated content, like product listings and search results, without compromising on real-time data accuracy. Using an appropriate cache TTL and cache purging techniques, developers can ensure that the cache remains up-to-date with relevant changes.<br \/>\nSession Handling: Employ Varnish to handle user sessions intelligently. By excluding session-specific data from caching or using ESI to cache personalized parts separately, Varnish can provide a personalized experience without serving the wrong content to multiple users.<br \/>\nCache Invalidation Strategies: Develop robust cache invalidation strategies to promptly update cached content when products, prices, or inventory change. Utilize cache purging and conditional requests to ensure cache freshness while avoiding unnecessary backend requests.<br \/>\nLoad Balancing: Implement Varnish in a load-balanced and highly available configuration to distribute traffic efficiently and handle sudden spikes in user activity during peak shopping periods.<br \/>\nEcommerce Analytics: Integrate Varnish with ecommerce analytics tools to gain insights into cache performance, user behavior, and conversion rates. This information can guide further optimizations.<br \/>\nBy leveraging Varnish Cache effectively, ecommerce sites can significantly improve website performance, reduce server load, and deliver a seamless and personalized shopping experience to their users. It enhances the overall user experience, boosts conversion rates, and strengthens customer loyalty, leading to a competitive edge in the ecommerce market.<\/div>\n\t\t\t<\/div><div id=\"what-content-to-cache\" class=\"et_pb_module et_pb_text et_pb_text_24 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">What Content to Cache with Varnish Cache<br \/>\nFor achieving optimum web performance, specific types of content should be cached with Varnish.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_25 bold-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">To achieve optimum web performance and ensure a seamless customer experience, Varnish Cache should be strategically utilized to cache specific types of content. The goal is to prioritize caching elements that contribute significantly to page load times and user interactions. Here are some key types of content that should be cached with Varnish:<br \/>\nStatic Assets: Static resources like images (png, jpg, gif), CSS stylesheets &amp; fonts, and JavaScript libraries should be cached as they rarely change and contribute to the bulk of a webpage&#8217;s size. Caching these assets ensures quicker load times and reduced bandwidth usage.<br \/>\nFull HTML Documents: The real value of Varnish Cache is in caching the HTML document. The HTML document has all the information needed to build a web page, including CSS files, text, and links to images. A slowly loading HTML document delays the time to first byte (TTFB) and start render time (SRT), adversely impacting user experience and SEO.<br \/>\nFrequently Accessed Pages: Frequently accessed pages, like homepages, product listings, and landing pages, should be cached to improve response times and reduce the load on backend servers.<br \/>\nDatabase Queries: Caching the results of complex database queries can help alleviate the load on the database server and expedite response times, especially for content that doesn&#8217;t change frequently.<br \/>\nAPI Responses: Cache responses from third-party APIs to minimize external requests, improve page load times, and ensure more consistent API performance.<br \/>\nSession-agnostic Content: Content that doesn&#8217;t rely on user sessions or personalization, such as blog posts or public information pages, can be effectively cached without risking data inconsistency.<br \/>\nEdge-Side Includes (ESI): Utilize ESI for personalized content. By caching static components and using ESI to assemble personalized fragments, Varnish can deliver dynamic content while benefiting from cached static elements.<br \/>\nError Pages: Caching custom error pages ensures a smoother experience for users in case of unexpected errors and prevents unnecessary backend requests.<br \/>\nBy focusing on caching these types of content with Varnish, websites can significantly enhance web performance, reduce server load, and provide a seamless and engaging experience for their customers. However, it&#8217;s essential to strike a balance between cache efficiency and serving the most up-to-date content, particularly for dynamic and personalized elements that require careful cache invalidation strategies.<\/div>\n\t\t\t<\/div><div id=\"integrating-CDN\" class=\"et_pb_module et_pb_text et_pb_text_26 dual-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Integrating Varnish Cache with a Content Delivery Network (CDN)<br \/>\nCombine Varnish Cache with a CDN to further improve website performance, reduce server load, and enhance global content delivery.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_27 bold-org  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">Integrating Varnish Cache with a Content Delivery Network (CDN) is a powerful strategy to supercharge website performance, reduce server load, and optimize content delivery on a global scale. By combining Varnish&#8217;s edge caching capabilities with a CDN, businesses can enhance their web application&#8217;s responsiveness and provide a seamless experience to users worldwide.<br \/>\nWhen Varnish Cache is deployed at the CDN edge nodes, it acts as an additional caching layer. This setup allows static content, such as images, CSS, and JavaScript, to be cached closer to end-users, significantly reducing latency and speeding up page loads. With cached content being served from nearby CDN servers, the origin server&#8217;s load is dramatically reduced, leading to improved server scalability and better handling of traffic spikes.<br \/>\nMoreover, Varnish Cache&#8217;s advanced caching mechanisms, coupled with the CDN&#8217;s distribution network, ensure that content remains available even during sudden surges in demand or server outages. The combination enables seamless failover and high availability, enhancing overall website reliability.<br \/>\nThe integration also enhances the CDN&#8217;s performance by reducing the load on its servers, improving cache hit ratios, and minimizing the need for frequent requests to the origin server. This synergy results in a more cost-effective and efficient content delivery process.<br \/>\nThe integration of Varnish Cache with a CDN empowers businesses to deliver content faster, provide a superior user experience, and optimize server resources. This powerful combination is especially valuable for global businesses seeking to provide consistent and high-performing web experiences to users across the world.<\/div>\n\t\t\t<\/div><div class=\"et_pb_module et_pb_text et_pb_text_28 info-box li-content  et_pb_text_align_left et_pb_bg_layout_light\">\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t<div class=\"et_pb_text_inner\">\u00a0Though Varnish Cache is open source and free to download and install, there are several providers that offer Varnish Cache as a service or hosted versions of Varnish Cache for a fee. Webscale is the Intelligent CloudOps Platform offering 7 versions of unmodified Varnish Cache up to 5.1.2. If you have any questions about Varnish Cache and VCL, contact us and one of our Varnish Cache experts would be happy to help you.<\/div>\n\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t<\/div><\/p>\n","_et_pb_truncate_post_date":"2024-01-23 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