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From oliverd <>
Subject LeaseDatabaseLocker and parallel masters
Date Wed, 16 Apr 2014 18:18:29 GMT
when using JDBCPersistenceAdapter with LeaseDatabaseLocker the master node
needs to extend the lease for the next interval 

in case, there is a long running GC (longer than the lease extend time) then
the slave will take over and the old master will detect after the GC
completes that it has to step back (and stop)

during testing it takes some time until the old master really stops (can be
up to 20 secs during tests, in case there are many client connections that
stress the node) 
during that time clients connect to both masters until the old master has
stopped transports

I have seen clients getting SQL exceptions due to duplicate keys on insert
to the MSGS table during that time and so I was wondering what is the risk
of getting potential inconsistencies in client state (messages pretend to
have failed) or even the the message store

is there any chance that the message store can get inconsistent in such a
as longer GCs cannot be prevented under all circumstances a message store
inconsistency as a follow up issue would add a certain risk to the
LeaseDatabaseLocker option

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