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https://issues.apache.org/jira/browse/CASSANDRA-6572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14006555#comment-14006555
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Benedict commented on CASSANDRA-6572:
-------------------------------------
bq. Added a small optimisation, BBs used for creating the data array in
QR#allocate(String) are now recycled where the largest buffer created is
stored, when a bigger one is required it gets allocated and replaces the older
one.
Instead of this, it is better to simply write the data directly to the QQ; you
can wrap the appropriate range in a ByteBuffer and return the ByteBuffer from
the allocate() method (null indicating there wasn't enough room)
# Your QQ recycling code is broken. This should only be performed by the
flushing thread, once we know the flush has finished, or if we fail to swap the
QQ (i.e. if line 85 returns false)
# you should use getAndSet() on line 87, the result being the value pos should
take
# I wouldn't introduce a special interface for AccessibleKeyspace, and I
wouldn't consider batch statements to be magically safe. Batch mutations have a
set of CFs they maintain of their modifications, you can check these for system
keyspaces, and if _any_ are present avoid logging the whole batch. We don't
want to stuff up the system keyspaces somehow on replay. I would suggest
potentially introducing a boolean method to CQLStatement that returns true if
the statement is safe to log; there are a small number of abstract classes that
would need implementations (AuthStmt, CFStmt, ModStmt)
It occurs to me, on top of logging the thread id as Jonathan suggests, we also
need to log the client session id as well, else "use" statements could cause
absolute chaos. This means we may need to log disconnect of client sessions as
well as a special record to permit state cleanup.
> Workload recording / playback
> -----------------------------
>
> Key: CASSANDRA-6572
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6572
> Project: Cassandra
> Issue Type: New Feature
> Components: Core, Tools
> Reporter: Jonathan Ellis
> Assignee: Lyuben Todorov
> Fix For: 2.1.1
>
> Attachments: 6572-trunk.diff
>
>
> "Write sample mode" gets us part way to testing new versions against a real
> world workload, but we need an easy way to test the query side as well.
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