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From artnaseef <>
Subject Re: Failover and non-persistent messages
Date Tue, 28 Jan 2014 20:17:49 GMT
1.  I have some doubt here.  Since non-persistent messages are not written to
disk, failing over to the passive broker should lose any messages still in
the broker's memory.  Does the test use a slow consumer to make sure there
is a backlog of messages on the broker at the time of failover?  Note the
producer, via the failover transport, should resend any message for which it
did not receive the broker's response (I want to say it will, but the logic
there is beyond my understanding).

BTW - are the Topic subscriptions in the test durable?  It shouldn't matter,
but I'm curious.

2.  Not sure on performance.  One thing I do know - if there are a lot of
messages in the persistent store, KahaDB can get extremely slow at startup -
for some reason, it seems to read through the entire store of messages at
broker startup.  We've seen 20 minutes waiting to read through about 10gb of
store, and longer with larger DBs.  I believe LevelDB is supposed to be
better in that regard.

3. If the lock-check-delay is set too low, delays in network traffic can
trigger dual active brokers - a very, very bad scenario as they will trash
the kahadb and step all over each others messages there.  Even 10 seconds
could be too short in some situations.

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