# Distributed caching techniques?

**URL:** <https://www.ruby-forum.com/t/distributed-caching-techniques/69092>\
**Category:** Rails\
**Created:** [September 18, 2006, 5:22pm UTC](https://www.ruby-forum.com/t/distributed-caching-techniques/69092 "2006-09-18T17:22:21Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![elliterate](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/9de053/32.png) [@elliterate](https://www.ruby-forum.com/u/elliterate)\
**Post date:** [September 18, 2006, 5:22pm UTC](https://www.ruby-forum.com/t/distributed-caching-techniques/69092/1 "2006-09-18T17:22:21Z")

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Hi,

I need to cache various things at server startup (parsed CSS selectors,  
parsed Liquid template objects, Liquid drop object registry etc…) and  
I’d  
like a single cache location, instead of a cache on each web node. A  
dedicated memcached node looks like a good idea but I’m worried that the  
cost of marshaling my objects on each cache get will out-weight the  
speed  
advantages gained by using the cache in the first place.

Does anyone have any tips on what to do in this situation?

Cheers  
Ian.

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**Author:** ![elliterate](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/9de053/32.png) [@elliterate](https://www.ruby-forum.com/u/elliterate)\
**Post date:** [September 18, 2006, 5:44pm UTC](https://www.ruby-forum.com/t/distributed-caching-techniques/69092/2 "2006-09-18T17:44:26Z")

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On Sep 18, 2006, at 8:11 AM, Ian L. wrote:

> A dedicated memcached node looks like a good idea but I’m worried  
> that the cost of marshaling my objects on each cache get will out-  
> weight the speed advantages gained by using the cache in the first  
> place.
> 
> Does anyone have any tips on what to do in this situation?

Yes.

Test your assumptions about speed. Memcached is easy enough to setup  
and experiment with.

Also: remember that memcached is not persistent and if you want to  
cache things at startup which hang around indefinitely, you’re using  
it wrong. What’s so bad about keeping a local copy of the cache if  
it’s never going to change and consistent across all nodes?

–  
Chris W.

> **[err.the\_blog](http://errtheblog.com)**
>
> Err the Blog: Ruby and Rails from the front.

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<div class="post-metadata">

**Author:** ![elliterate](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/9de053/32.png) [@elliterate](https://www.ruby-forum.com/u/elliterate)\
**Post date:** [September 18, 2006, 6:44pm UTC](https://www.ruby-forum.com/t/distributed-caching-techniques/69092/3 "2006-09-18T18:44:35Z")

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Ah, I didn’t know memcached wasn’t persistent. Having a cache per node  
isn’t  
a big problem, it’s just that i’ll need a mechanism in place to ensure  
the  
caches don’t get out of sync. Once I start clustering Mongrel, I’m going  
to  
need something that I can use to share objects among each ruby process.

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**Author:** ![elliterate](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/9de053/32.png) [@elliterate](https://www.ruby-forum.com/u/elliterate)\
**Post date:** [September 18, 2006, 11:59pm UTC](https://www.ruby-forum.com/t/distributed-caching-techniques/69092/4 "2006-09-18T23:59:16Z")

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OK, Drb is what I was looking for. A few wrapper script here and there  
and I  
can use my objects as if they were local.

For anyone doing this, remember to include DRbUndumped into any classes  
your  
server will return instances of, you’ll be unable to transparently  
access  
the remote methods otherwise.