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https://issues.apache.org/jira/browse/SAMZA-1655?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Shanthoosh Venkataraman updated SAMZA-1655:
-------------------------------------------
    Description: 
*Problem:*

StreamProcessor skips all events from zookeeper server after zkClient session 
expiration.

*Reason:*

All the zkWatchers(dataChange, childChange handler) in a StreamProcessor are 
instantiated with an inmemory generationId(zkUtils.generationId).

All the zkWatchers cache this generationId passed through the constructor.

This inmemory generationId is incremented whenever the zkClient session 
expiration occurs.

Any event from zookeeper server is dropped if the inmemory generationId is not 
equal to the generationId cached in a zkWatcher.

After the zkClient session expiration in a StreamProcessor, this will result in 
zombie StreamProcessors and will stall message processing.

In worst case, if this happens to the leader StreamProcessor then the whole 
processors group will be stalled.

GenerationId was added to skip stale events going to handlers registered before 
a session expiration.

 

  was:
*Problem:*

StreamProcessor skips all events from zookeeper server after zkClient session 
expiration.

*Reason:*

All the zkWatchers(dataChange, childChange handler) in a StreamProcessor are 
instantiated with an inmemory generationId(zkUtils.generationId).

All the zkWatchers cache this generationId passed through the constructor.

This inmemory generationId is incremented whenever the zkClient session 
expiration occurs.

Any event from zookeeper server is dropped if the inmemory generationId is not 
equal to the generationId cached in a zkWatcher.

After the zkClient session expiration in a StreamProcessor, this will result in 
zombie StreamProcessors and will stall message processing.

In worst case, if this happens to the leader StreamProcessor then the whole 
processors group will be stalled.

**GenerationId was added to skip stale events going to handlers registered 
before a session expiration.

 


> StreamProcessor skips all events from zookeeper server after zkClient session 
> expiration.
> -----------------------------------------------------------------------------------------
>
>                 Key: SAMZA-1655
>                 URL: https://issues.apache.org/jira/browse/SAMZA-1655
>             Project: Samza
>          Issue Type: Bug
>            Reporter: Shanthoosh Venkataraman
>            Assignee: Shanthoosh Venkataraman
>            Priority: Major
>
> *Problem:*
> StreamProcessor skips all events from zookeeper server after zkClient session 
> expiration.
> *Reason:*
> All the zkWatchers(dataChange, childChange handler) in a StreamProcessor are 
> instantiated with an inmemory generationId(zkUtils.generationId).
> All the zkWatchers cache this generationId passed through the constructor.
> This inmemory generationId is incremented whenever the zkClient session 
> expiration occurs.
> Any event from zookeeper server is dropped if the inmemory generationId is 
> not equal to the generationId cached in a zkWatcher.
> After the zkClient session expiration in a StreamProcessor, this will result 
> in zombie StreamProcessors and will stall message processing.
> In worst case, if this happens to the leader StreamProcessor then the whole 
> processors group will be stalled.
> GenerationId was added to skip stale events going to handlers registered 
> before a session expiration.
>  



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