Varnish is a robust caching web service used by many high profile and high traffic websites. Acquia uses Varnish to help end users retrieve web sites faster and to help keep the load down on your servers. Once a page is in the cache performance will be fast, but what if you need to make a quick content adjustment? Now that the cached content is no longer up to date and needs to be cleaned, how can you keep your cache fresh?
What we did for our Drupal site is setup Cache Expiration with Purge modules to connect to our Varnish nodes and keep all our pages up to date. Most module like Varnish and Purge will integrate some page cleaning, but these modules don’t work for cleaning Views or Panels caches. What Cache Expiration offers is a more configurable options to act on and utilize the Workflow module to update our Views. With this extra control we were more comfortable to extend our Caching time beyond what Drupal allows to you select from the pull down to 7 days. With a quick config line change in sites.php we can setup the cache time
$conf['page_cache_maximum_age'] = 84600*7;
Now that we have our pages setting the cache header to 7 days, we need to setup one of the many different Purge options that Cache Expiration offers. After install Cache Expiration go to admin/config/system/expire and select External Expiration as we are wanting to connect to our external cache server. If you are going to use Acquia Purge or Varnish uncheck “Include Base URL in Expires”. The only sections I really needed to worry about were Node Expiration and Menu Links Expiration as we don’t use Comments and our User pages are not their Drupal user account pages. For files we use Apache to send file type headers for how long the cache server can hold onto those and all of the file uploads will append _[0-9] to the file name. For Node Expiration we set all three actions Insert, Update, Delete to trigger a page cache purge. Depending on your setup you might be fine with the basic Front Page and Node Page being purged but I wanted to do something al little different and did Custom with these two URLS
http://[site:url-brief]/node/[node:nid] http://[node:url:brief]
The next setting that we setup was the Menu Links Expiration section. Again all actions are checked. For menu Depth, it really depends on your menu structure and what menus you have content on that will be updated more frequently, for us Main Menu with depth of 1 was all I needed.
Definition of what Menu Depth is from the maintainer:
The goal is to easily arrange for a high visibility menu to be consistent and current on all the pages the menu links to. So, if you are using a menu block with a depth of 2, you can configure this plugin to clear the URLs linked to by said menu block.
Now that we have all our nodes setup to purge when content is change as well as our menus its time to move on to our Views. The way we setup our rules to purge our Views is One rule per View, so for Feature Story we have one rule that will purge the Home page and our All Stories page.
Create a new Rule and use two events as the trigger, After Saving New content and After Updating Existing Content now with these events we filtered them by a specific content type so that way the rule will only fire for this specific pice of content, for this example I will use Feature Story as the content type. We didn’t need any conditions so that was left as None. Finally down to the part that matters, the Actions. Add a new action Clear URL(s) from the Page Cache. As soon as you select this action the page will update and present you with a text box to enter in your different URL(S) you wish to purge. To continue with the Feature Story example, our site only had one URL that needed to be purge
http://[site:url-brief]/feature-story
Save and that’s it. Any time someone updates a Feature Story on your site, the Node Page and the View’s page will now be wiped from the Cache server and the next request to those pages will now cache the newest content.
For the home page I have a special rule to purge it from the cache anytime anything is updated on the site, you might want to make modifications to this to suite your needs.
Modules:
Cache Expiration: https://www.drupal.org/project/expire
Purge: https://www.drupal.org/project/purge
Workflow: https://www.drupal.org/project/workflow
Varnish: https://www.drupal.org/project/varnish
Acquia Purge: https://www.drupal.org/project/acquia_purge