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From Shanti Subramanyam - PAE <Shanti.Subraman...@Sun.COM>
Subject Re: Thumbnail caching proposal
Date Wed, 04 Feb 2009 18:44:12 GMT
Wouldn't it make more sense to shift the caching to an image server that 
directly serves all the files in the filestore ?
This will also reduce the load on the php application significantly. 
 From Will's and Amanda's notes, it appears that they are deploying the 
rails app in this manner - using nginx to serve the files and forwarding 
all other requests to the thins in the back.

Ideally, we would like a distributed filestore - otherwise,sooner or 
later we're going to run into a bottleneck on the image server as well. 
But at least this is a good first step to take.

Comments ?

Shanti

On 01/28/09 09:18 AM, Akara Sucharitakul wrote:
> As we run into filesystem bottlenecks, it makes sense to reduce the 
> filesystem access by caching thumbnail images in memcached. The 
> thumbnails are about 6-7 KB in size. We want to ensure there's a hot set 
> of thumbnails being cached in memcached but not that every image gets 
> cached. So here's my first draft on how to achieve that:
> 
> 1. All thumbnails that are accessed by the client and driver are cached 
> in memcached with a timeout of 90 seconds. Of course, we can still 
> adjust this. Any access to the thumbnails will check the cache at first.
> 
> 2. In order to keep the hot set low, we will modify our tag search query 
> to order by event date with the most recent upcoming events first. As a 
> result, the set of events searched by each tag are more deterministic 
> and will not often change. Since the tag search only shows 10 events per 
> page, the thumbnails for these top ten events for each tag will be held 
> in memcached.
> 
> The mathematical model for this is a little complicated, though. Since 
> we're dealing with non-uniform distribution of tags and a cap of 10 
> upcoming events on top of that. But please let me know whether you agree 
> with this conceptually.
> 
> Thanks,
> -Akara

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