Transparent failover and restore?
gblock at ctoforaday.com
Tue Dec 21 06:57:33 PST 2004
On 20 Dec 2004, at 21:08, Richard 'toast' Russo wrote:
> Memcached clients* will rehash the key if the server the key gets
> hashed to is offline. When you take one machine offline you'll lose
> 1/5th of your cache, and when you bring it back, you'll again lose
> 1/5th of your cache as the keys originally asigned to the that server
> migrate back (when the clients notice the server is back).
> You could make the connection timeouts more agressive to reduce the
> cost of the client finding dead servers.
...or implement what I originally discussed, in the client, which
pushed updates to 2 servers instead of 1, where the second server is
the server it would have chosen next if the first one were to be marked
as "down"; when server 1 isn't down, servers 1 and 2 get updates; when
1 goes down, 2 gets results; when 1 comes back up, query 1 and 2, and
push the missing update into 1.
This *could* be done very, very painlessly, and it would eliminate the
whole problem instantly.
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