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From artnaseef <>
Subject Re: Problems with ActiveMQ with LevelDB and shared filesystem over NFS4
Date Tue, 02 Dec 2014 18:03:22 GMT
What method is used to simulate the network outage to the NFS server?

If the original master loses network connection to the NFS server, writes
should fail.  Although there could be NFS settings that affect just how it
operates (e.g. sync vs async and timeouts).  It's been a long time since I
tweaked NFS settings and I don't remember well how it operates under the

One thing to keep in mind - lock timeouts have this problem; if the original
holder of the lock returns after the timeout, it tends to lead to a bad
state because the original holder doesn't know it lost the lock.  ActiveMQ's
locking is based on a single lock file to take ownership of the entire
database of files; individual data files (i.e. the files actually holding
the leveldb content) are not locked.

Another thought - this seems like an odd scenario.  The master server is
still on the network, so it can serve clients, and the NFS server is still
on the network and talking to the slave, but the master cannot talk to the
NFS server.

Also, is there redundancy in the master's network setup?  In other words,
are there two network interfaces and two wires from the server to the
network?  Surviving any single-point-of-failure means considering all points
in the system and making sure they are redundant.  A typical H/A setup will
survive any single-point-of-failure without down time (or with minimal
interruption), but does not survive multiple-points-of-failure.

Hope this helps.

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