Content caching for Cloud Load Balancers

Cloud Load Balancers have content caching capabilities and store
recently-accessed files for web clients to retrieve.

Enable content caching

You can enable content caching through the Cloud Load Balancers
API
or the Cloud Control Panel.

1. Log in to Cloud Control Panel.
2. Click on Networking > Load Balancers.
3. Select a load balancer.
4. In Optional Features, click the pencil icon next to Content Caching.

Benefits of content caching

Content caching improves the web site's performance by temporarily storing data that was recently accessed. The load balancer serves cached requests instead of making another query to the webserver behind it.

This caching results in improved response times for those requests and less load on the webserver.

What kinds of files work well with content caching?

Content caching works well for files that don't change or rarely change. Most images and static content are good candidates for content caching.

You don't want to cache files that change regularly or that the system generates dynamically for different site visitors.

Caching details

Is there a maximum file size that can be cached?

The maximum file size per cached item is 2 MB.

How long is content cached?

The system caches content for up to 10 minutes, depending on the load and amount of traffic handled by
the load balancer host.

If a cached file is requested before expiration, the load balancer retrieves a new copy of the file earlier than usual to prevent the file from being uncached during a period of heavy traffic.

Can I choose how long to cache files?

No, not at this time. You cannot purge a file from the cache manually, but it the system automatically removes it when its cache time expires.

Do nodes share a cache?

No. Each node has its own cache, separate from other load-balanced nodes.

Does cache carry over in a failover situation?

No. If a failover occurs, the load balancer retrieves a fresh copy of a file from the failover host.

File types

What file types are supported for content caching?

The following file extensions are cached:

• .png
• .gif
• .jpg
• .jpeg
• .ico
• .wav
• .mp3
• .flv
• .mpeg
• .js
• .css
• .mp4
• .swf

Can I exclude specific file types?

Yes. You can set the Cache-Control header to no-cache for requests for the file types you don't want cached.

Set this header in Apache® by adding a configuration block similar to the following example:

Note: Replace ico|flv|jpg|jpeg with the desired extensions you want to bypass, making sure to put a | character between them.

<FilesMatch ".(ico|flv|jpg|jpeg" alt="" title="">}}$">
    Header set Cache-Control "no-cache"
</FilesMatch>