On 2014-06-02 13:47, Cor Bosman wrote:
Thanks for the pointer, but it's kind of a hassle as there's no debian
packages for phpredis. We could package it ourselves, but thats just
more stuff to maintain.
Has anyone ever gotten memcached to be truly redundant? I cant seem to
get it so if I bring 1 (of many) memcached down, then bring it back
up, it still works right. Roundcube sees an empty server and assumes
there's no session key.
I believe that this is the way that memcached expects to work.
You provide a list of memcached servers for horizontal scaling rather
than high availability.
Memcache has a replication/fallback system but i cant get it to work.
I am running Roundcube against memcached with the repcached patch.
Node #1:
/opt/repcached/bin/memcached -m 4096 -c 4096 -d -l 192.168.128.31 -x
192.168.128.81
Node #2:
/opt/repcached/bin/memcached -m 4096 -c 4096 -d -l 192.168.128.81 -x
192.168.128.31
Both nodes claim to be the master node through the stats interface (and
indeed a update on either node is mirrored to the other side). If I
restart memcached on one node it fetches the state from the other side
after a short pause.
This does work: only this morning I was able to walk the memcached
session store from one pair of machines
to another pair of machines in the same cluster without any user visible
downtime by:
1) Shutting down one node and moving the IP address used by that node.
2) Pointing Roundcube at the migrated copy after memcached had
resynchronised there
3) Moving the other node in the same fashion
The only problem that I have had is that memcached slowly leaks memory
when replication is enabled: some memory isn't released until one of the
two nodes is restarted. Consequently I do that once a day, in the
middle of the night.
Session timeouts also behave a little differently when memcached is used
rather than the normal database session management. I found that the
compose page hangs rather than giving a error page if someone clicks
"Send" on a page where the session has timed out. We use a four hour
session timeout, which helps.
--
David Carter Email:
[email protected]
University of Cambridge, Phone: (01223) 334502
Information Services, Fax: (01223) 334679
7 J J Thomson Avenue,
Cambridge UK. CB3 0RB
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