sharding with varnish: generating director identifier from an integer
Enno van Amerongen
enno at tty.nl
Thu Nov 15 17:21:35 CET 2012
From: Per Buer [mailto:perbu at varnish-software.com]
On Thu, Nov 15, 2012 at 3:52 PM, Enno van Amerongen <enno at tty.nl> wrote:
My coworkers and I are working on a sharding VMOD and we got to the point
it's actually working (woohoo!).
Now, our implementation is pretty straightforward:
- get id from url
- do a "id mod n" to pick correct shard ( = director)
- set req.backend = shardN
Any particular reason you didn't use the client director? This is more or less exactly what it does.
You would set client.identity to the ID you pick and Varnish will use a hash algorithm to consistently pick a backend from the backends in the director.
yes, we didn't use it because we also need to be able to determine which backend should receive which images. We aren't only sharding the requests, but also the storage.
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