Henry Robinson created ZOOKEEPER-1473:
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             Summary: Committed proposal log retains triple the memory it needs 
to
                 Key: ZOOKEEPER-1473
                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1473
             Project: ZooKeeper
          Issue Type: Bug
            Reporter: Henry Robinson


ZKDatabase.committedLog retains the past 500 transactions to enable fast 
catch-up. This works great, but it's using triple the memory it needs to by 
retaining three copies of the data part of any transaction.

* The first is in {{committedLog[i].request.request.hb}} - a heap-allocated 
{{ByteBuffer}}.
* The second is in {{committedLog[i].request.txn.data}} - a jute-serialised 
record of the transaction
* The third is in {{committedLog[i].packet.data}} - also jute-serialised, 
seemingly uninitialised data.

This means that a ZK-server could be using 1G of memory more than it should be 
in the worst case. We should use just one copy of the data, even if we really 
have to refer to it 3 times. 


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