[Tilecache] Memcached (or Memcachedb )

christopher.schmidt at nokia.com christopher.schmidt at nokia.com
Fri Nov 12 06:54:12 EST 2010


On Nov 12, 2010, at 4:58 AM, ext Sebastian E. Ovide wrote:

> Hi All,
> 
> I am planning to deploy tilecache in a cluster of 2 or 4 machines and just wondering what could be the best way of sharing the cache among the servers (so that the WMS server wont create the same tiles for each tilecache server).
> 
> I was thinking on an alternative of a NFS.... such as memcachedb (persistence memcache) and just wondering how tilecache works with it. Say for example that I have 4 servers with
> 
> [cache]
> type=Memcached
> servers=server1,server2,server3,server4
> 
> how does tilecache queries for a single tile ? does it query to the 4 memcached servers before quering the WMS server ?

Step 1: Learn how memcache works.
Step 2: Figure out how tilecache works with memcache.

More seriously, the entire point of memcache is that the cache
is sharded across all of your available machines. The memcache
client will 'hash' the key it's given, look up the server it 
should be on, then ask only that server for the item. So the
answer to your question is no, it won't, because it always knows
where the item should be; it asks that server, then goes to the 
WMS. 

Note that for many cases, using memcache vs. local disk for tiles
will be several times slower, though in reality, that doesn't
matter much cause you can still fill even the biggest pipe with 
tiles either way.

-- Chris

> thanks
> 
> -- 
> Sebastian E. Ovide
> 
> 
> 
> 
> <ATT00001..txt>



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