Smarty

[rascal]

Hello,

I use smarty for our homepage. We have may hits and now we need one more webserver for managing the heavy load. Now I have a question about the caching feature (I use it almost everywhere).
For example, in our forum application I generate cache. I have to delete it when there is a new post. How can I delete the cache of both machines at once? I've already thought about a extended Smarty class, in which I override the clear_cache* methods. My question is: Have you already done something like that and how do you solve this problem? Is there an elegant way to do this?

Thanks for your answers and regards from switzerland,
Pascal

[mohrt]

You could keep your cache files on a shared network drive, that would be the most painless.

[boots]

[mohrt]

We have NFS v3 with a 30 sec file cache enabled and have had very good success with Smarty cache files in this setup, they are virtually local files.

[boots]

Sorry, I didn't mean that it isn't workable, but I don't think it is exceptionally scalable. Of course, my bias may be based on the fact that I don't do it that way.

YMMV

[mohrt]

In our case the advantages of maintaining one source of cache files outweighed the network latency involved (which is mostly eliminated by the NFS cache anyways.)

[rascal]

@mohrt: Because we have a second machine with a picture server, we already have some experiences with nfs. We store there the user pics, and on this server also runs a httpd which distributes only pictures. This is maybe a good idea to do this.

@boots: I think it is also a good idea to let each server manage it's own cache. What do you mean with "writing a memcached wrapper for the smarty cache"?

[boots]

I meant using the following items:
http://www.danga.com/memcached/
http://pecl.php.net/package/memcache
http://smarty.php.net/manual/en/section.template.cache.handler.func.php

After some consideration I wonder if I am making things too hard

[rascal]

@boots: I read several articles about memcached after your post. This is a very clever solution I think. Do you have an idea, how to store cache groups in memcache, because it would be fine if I could delete groups.. I think, this could be a problem when writing the cache handler function.

[boots]

Hi rascal. You might get some insights from this code http://www.phpinsider.com/smarty-forum/viewtopic.php?t=1507 (particluarly andre's solution) which implements a smarty cache handler using eaccelerator (was turck mmcache).

Although not a distributed solution, it is otherwise quite similar to using memcached and faces many of the same issues. To handle the cache groups, it stores an index directly in the caching engine as a plain item. The cache wrapper manages the index based on the items it enters or removes from the cache.

Let us know how you fare

[rascal]

Since May, we are doing the whole thing with a nfs volume, but this is not a very good solution for us..
Now I had the time to analyse the code from the eAccelerator cachehandler. I think, it's impossible to port this piece of code to a memcached based cache handler. memcached doesn't support locking - so there is a problem of race conditions.. one thread can read the keys and analyse them to update the list, while the other thread updates the list while the other thread is still analyzing...

Do you have any other ideas, how I could solve this problem? I can't believe, that we are alone with our problem :-/

[luxurylink]

[boots]

I wonder if anyone has yet created a cachehandler for Pear's SharedMemory package (which is now at the completed proposal stage: http://pear.php.net/pepr/pepr-proposal-show.php?id=294 ) This package is really just a consistent front-end API with pluggable backend support for various caching services. Also, more backends are already supported than listed in the proposal -- for example, I had requested the author to add support for sharedance and he promptly did.

If no one has, I may tackle this one.

[luxurylink]

[luxurylink]