Varnish why not cacheable

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If, however, you need to do something more complicated, like removing one out of several cookies, things get difficult. We have to use regular expressions to do the work. Lets use the Varnish Software VS web as an example here. Very simplified the setup VS uses can be described as a Drupal-based backend with a Varnish cache in front.

VS uses some cookies for Google Analytics tracking and similar tools. The cookies are all set and used by Javascript. A somewhat simpler example that can accomplish almost the same functionality can be found below.

A hit-for-miss object see Actions is created. Varnish cares about the max-age parameter and uses it to calculate the TTL for an object. An HTTP 1. Varnish ignores this header. You could easily add support for this header in VCL. If this is not what you want you can unset the header.

Sometimes your backend will misbehave. It might, depending on your setup, be easier to override the TTL in Varnish then to fix your somewhat cumbersome backend. We recommend that you rely as much as you can on the default caching rules. Some sites are accessed via lots of hostnames. You can mitigate this in your web server configuration by setting up redirects or by using the following VCL:. A lot of the response headers tell the client something about the HTTP object being delivered. Clients can request different variants of a HTTP object, based on their preference.

Their preferences might cover stuff like encoding or language. When a backend server issues a Vary: Accept-Language it tells Varnish that its needs to cache a separate version for every different Accept-Language that is coming from the clients.

Just the lack of a whitespace will force Varnish to cache another version. To achieve a high hitrate whilst using Vary is there therefore crucial to normalize the headers the backends varies on. Remember, just a difference in casing can force different cache entries. Some applications or application servers send Vary: User-Agent along with their content.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Why is Varnish not caching? Ask Question. Asked 9 years, 1 month ago. Active 9 years, 1 month ago. Viewed 16k times. Set this to point to your content server. If, after running this code we find that either of these two cookies remains, we will pass as the page cannot be cached. Append a semi-colon to the front of the cookie string. Remove all spaces that appear after semi-colons.

Match the cookies we want to keep, adding the space we removed previously back. Remove all other cookies, identifying them by the fact that they have no space after the preceding semi-colon. Remove all spaces and semi-colons from the beginning and end of the cookie string. Cookie; set req. Read the documentation and be careful changing settings without understanding the implications. Get yourself up to speed by downloading The Varnish Book.

Monitoring this counter will let you know if your cache is starved for storage. If you see an elevated value here, it means your working set does not fit in the configured storage and you will benefit from adding more space.

You can have a look at www. You can even embed images inline in the HTML markup. Varnish 3. This means that there is no longer a need to manually mangle the Accept-Encoding request header in order to cache both compressed and uncompressed versions of responses. Hit-for-pass is not an intuitive concept. Many users fail to understand how it works and may misconfigure Varnish Cache. Varnish Cache will coalesce multiple requests into one backend request.

If that response then does something funny, like doing a Set-Cookie, Varnish Cache will create a hit-for-pass object in order to remember that requests to this URL should not be put on the waiting list and simply sent straight to the backend. Get Started. Varnish is Caching Pages and ignoring "Cache-control: no-cache" header July 6, Opinionated creators.

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