Varnish Cache is an HTTP accelerator. It's designed for content-heavy and dynamic web sites as well as APIs. Varnish focuses exclusively on HTTP, other proxy servers that often support FTP, SMTP as well as other network protocols. Varnish Cache is really fast.
Poul-Henning Kamp and Redpill-Linpro are the creators of Varnish Software. The lead developer and architect are Danish independent consultants, Poul-Henning Kamp is a well-known FreeBSD developer, with management, infrastructure, and additional development originally provided by the Norwegian Linux consulting company Linpro.
Varnish was written in C.
Initial release | First released in September 2015 |
Stable release | Varnish 6.0.7 is released November 06, 2020 |
There are a lot of other web accelerators out there namely
These are primarily origin servers.
*In computer networking, 'upstream server' is a server that provides a service to another server. An upstream server is a server that is located higher in a hierarchy of servers. The highest server in the hierarchy is sometimes known as the origin-server. There’s a term known as, downstream server but this term is rarely ever used.
Varnish Cache ships with monitoring and logging tools are the most used, is the varnish-stat which gives a detailed snapshot of Varnish’s current performance.
It provides access to in-memory statistics such as:
Varnishstat
Running the Varnishstat from the command line returns a continuously updating list of all available metrics. If the 1st flag is added theVarnishstat will exit after printing the list one time. Varnishstat can be used as a standalone tool to spot-check the health of the cache.
This is done for:
Varnishlog
Is a tool that’s used to debug or tune Varnish configuration because it provides detailed information about individual requests.
Varnish data is stored in virtual memory, the task is to decide what is stored in memory and what is paged out to disk to the operating system. This will help avoid the situation where an operating system starts caching the data while it gets moved to disk by the application.
A policy where you can decide on what content you want to serve and from where you want to get the content, and how the request or response should be altered. You can also extend the Varnish Cache with modules ‘VMODs.’
Varnish Cache is a domain-specific language ‘DSL’ which means it’s also used to write hooks that get called at critical points when it handles each request. Decisions are left to the ‘VCL’ code.
VCL will enable one to write policies on how incoming requests should be handled. Making Varnish configurable and adaptable and more than most other HTTP accelerators.
Enables a user to write policies on how these incoming requests should or will be handled:
vcl_hit subroutine will define how Varnish responds to a request or object that's been cached.
cache.org/vmods/howto.html#vmods-re
*Saint mode can also be used when a Magento instance is individually taken offline to perform maintenance or upgrade the task/s without affecting the availability of a Magento site.
Stores>Settings>Configuration>Advanced>Developer>Static Files Settings>Sign Static Files, then set value to = ‘No’
All the Magento instances must be using the 'production mode' setting before Varnish will start and to also clear the cache on each instance.
System>Tools>Cache Management and click Flush Magento Cache.
One can also run the command to clear cache using the SSH/FTP command:
$ bin/Magento cache:flush
To check feature polls, a Magento server needs to determine if it is responding with good timing. It usually responds to fresh content and it will also be regenerated once the 'Time to Live' (TTL) period expires.
1 2 3 4 5 6 7 | .probe = { .url = "/pub/health_check.php"; .timeout = 2s; .interval = 5s; .window = 10; .threshold = 5; } |
It usually responds to fresh content and it will also be regenerated once the 'Time to Live' (TTL) period expires. Varnish always serves expired content if it's not.
A script must return the response in 2 seconds as the script will determine if any of these resources are down, it will return a 500 HTTP error code. Error code will get received in 6 out of 10 attempts, and the backend will be considered unhealthy.
health_check.php script gets located in Magento’s pub directory. If the Magento root directory is the pub, you need to be sure that you change the path of the URL parameter from:
to
You can change the default value in default.vcl file, then you can edit the ‘vcl_hit’ subroutine.
if (obj.ttl + 300s > 0s) {
Magento 2 has a perfect tool to generate a Varnish configuration.
From an in Store>Configuration it could have the following details:
Save the configuration and file varnish. vcl should be generated.
Click one of the export buttons to create a varnish.vcl you can use with Varnish.
If you have Varnish 4. Click Export VCL for Varnish 4.
The figure below shows an example:
*curl -I *yourdomain.com
*Magento 2 Varnish *test on the frontend
To get Varnish’s access log, we’ll use the command:
$ cd public_html varnishncsa
*Magento 2 Varnish test log
After Varnish has tested the work. You can say its installation and configuration as a reverse proxy for the Nginx web server is completed.
Varnish can also be implemented without having to log Magento ‘Admin’ panel by using a ‘command-line’ Magento Interface tool:
$ bin/magento config:set --scope=default --scope-code=0 system/full_page_cache/caching_application 2 |
Once you have recompiled ‘Saint’ mode in general follow these steps:
$ sudo apt-get install libvarnishapi-dev || sudo yum install varnish-libs-devel ./bootstrap # If running from git. ./configure make make check # optional sudo make install |
(*Saint mode doesn’t come as a part of the Varnish package. It is separately versioned in the VMOD that first needs to get downloaded + installed. This as a result needs Varnish to get re-compiled from ‘source mode’.)