Handling failovers (rewrite)
dustin at spy.net
Wed Jul 4 16:48:09 UTC 2007
[I responded to this off-list because I somehow received a copy in
my inbox that didn't include the list]
On Jul 4, 2007, at 2:15 , a. wrote:
> Isn't it true that a memcached server more likely "goes down"
> becaouse its machine has been restarted, or the process crashed?
> So usually you'll end up with an empty server which does not have
> stale data.
The scenario we were discussing here was a server going down
(causing all requests to go to another server), coming back (writes
causing updates to the server that isn't primary), and then going
down again (causing stale reads).
It's not the server that went down, but the next server in the
list whose freshness is a concern.
Losing connectivity to a node does cause a failure mode where the
secondary was updated, and then the primary comes back with stale
data. Sending a flush on reconnect would prevent that from being a
problem, but could wreak havoc on your primary data store when a
client has a network instability.
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