Apache + Mongrel Cluster Caching (cross server)

Rails
1

Has anyone here successfully setup a system to take advantage of rails
page/action caching when using a mongrel cluster that spans multiple
servers? If so, could you shed some light on how you handled expiring
cache across multiple mongrel servers (physically different machines)?

2

I’m working on this now. I have two approaches:

  1. (Implemented) - If you control the URLs, put the timestamp of the
    resource in the URL linking to it. eg url_for(:product =>
    product, :timestamp => product.modified_at.to_i)

  2. Instead of using page caching, have Apache cache, use mod_cache.
    Then, set the expires header very short - Apache will ask Rails for
    the resource. But don’t return it if it’s still okay - see
    Client HTTP Caching in Rails - igvita.com

(I have the headers in #2 working but have not turned on mod_cache
yet)
Let me know how your experience goes.

3

Action caching can be configured to use a shared fragment store - DRb
or Memcache fragment stores are supplied. Expiry from any server will
expiry the action for all servers, and, with Memcache, the store can
be distributed over a set of servers for redundancy.

Page caching will need some form of sharing of the cache directory
across machines - NFS would be the obvious choice, but I don’t know
how reliable this is, or how Rails or Apache behave when there are
network problems.

4

On 3/21/07, S. Robert J. [email protected] wrote:

  1. (Implemented) - If you control the URLs, put the timestamp of the
    resource in the URL linking to it. eg url_for(:product =>
    product, :timestamp => product.modified_at.to_i)
  1. Instead of using page caching, have Apache cache, use mod_cache.
    Then, set the expires header very short - Apache will ask Rails for
    the resource. But don’t return it if it’s still okay - see
    Client HTTP Caching in Rails - igvita.com
  1. Use a SAN.

J.

5

I have it implemented and working for a long time using NFS mounts for
the public directory. But you don’t really need NFS specifically.
Anything you can mount and share across servers will work.

Bye,

Guy.

On 3/21/07, Justin [email protected] wrote:

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