libmemcached

Looking for docs on how server failure (and recovery) is handled

Asked by TimBunce

I can't seem to find documentation that describes exactly what happens when a server goes down, and how best to handle its graceful recovery.

The documentation for the behaviours seems to assume a certain level of knowledge that I don't have, or at least I'm not sure about. It's a reference manual. I'm looking for a guide.

My question is similar to http://stackoverflow.com/questions/10029432/libmemcached-fail-over-of-a-clusters-node
except that a) I'd like more background information, and b) there's no discussion of handling the recovery of a node.

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TimBunce (tim-bunce) said : 		#1

As an example, the venerable and original Cache::Memcached module (https://metacpan.org/source/DORMANDO/Cache-Memcached-1.30/lib/Cache/Memcached.pm) seems to recalculate the 'buck2sock' mapping (by $socket_cache_generation++;) whenever a socket is marked dead by _dead_sock() being called.

But some of calls to _dead_sock, specifically those from connection setup, also provide a duration ($dead_for) during which the host should be regarded as dead.

So a single communications error on an established socket doesn't remove a server, but does cause a connection drop and reconnect. If that reconnect fails then the server is removed from the buck2sock calculation for a period.

This seems reasonable and is self-repairing. Sadly the docs don't discuss this behaviour at all.

I'm rather surprised I can't find this kind of discussion in the libmemcached docs. Am I missing something?

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MacDeveloper (cbisegni) said : 		#2

Hi the stackoverflow questions was made by me. I have also wrote to libmemcached main developer but i haven't had any answere. Have you found something of usable?

Can you help with this problem?

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