joefk commented on issue #6347: PIP 57: Improve Zookeeper Session Timeout 
Handling
URL: https://github.com/apache/pulsar/pull/6347#issuecomment-588254298
 
 
   @sijie @mateo @codelipenghui 
   1)This is a very high risk fix. This should have been written up as a PIP 
and discussed.  I think an issue and PR is not the right approach to make this 
change. Specifically i would like to see it spelled  out, how the broker ceases 
topic activity,  in the window between expiry of timeout and recreation of the 
session. Especially there should  be a verifiable assertion that write ordering 
on a topic is not broken by this change.
   
   2)For backward compatibility, there should be  an option to completely turn 
this off ( retries = 0), and it be the default. 
   
   3)The desirable outcome of this change ..."Theoretically, the mechanism can 
guarantee that the ownership of most bundles will not change during the session 
timeout. "  ..seems possible only in situations where bundle/topic ownership 
changes are slow.  This change will benefit a particular use where topic 
activity is slow. This change is not desirable for fast responsive systems, 
where if a broker is unresponsive ( long JVM GC pause etc), the desired 
behaviour is for the broker to shutdown, so that a quick failover of the bundle 
is triggered by the next lookup.  
   
   4)The other issues mentioned  (JVM GC, ZookeeperCacheLoader etc) are 
problems that need addressing, but this fix is not the solution to them. 

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