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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6572) Workload recording / playback
Date Thu, 01 May 2014 13:56:17 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13986591#comment-13986591
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Benedict commented on CASSANDRA-6572:
-------------------------------------

Some comments on the in progress patch:

* Don't create a string with the header and convert it to bytes - convert the string to bytes
and write a normal byte-encoded header with timestamp + length as a long. This will make encoding
the prepared statement parameters much easier also
* Encapsulate queryQue and logPosition into a single object, and use an atomicinteger for
the position - don't synchronise, just bump the position however much you need, then write
to the owned range. On flush swap the object (use an AtomicReference to track the current
buffer)
* On flush, append directly from the byte buffer, don't copy it. Create a FileOutputStream
and call its appropriate write method with the range that is in use
* On the read path, you're now eagerly reading _all_ files which is likely to blow up the
heap; at least create an Iterator that only reads a whole file at once (preferably read a
chunk of a file at a time, with a BufferedInputStream)
* On replay timing we want to target hitting the same delta from epoch for running the query,
not the delta from the prior query - this should help prevent massive timing drifts
* Query frequency can be an int rather than an Integer to avoid unboxing
* I think it would be nice if we checked the actual CFMetaData for the keyspaces we're modifying
in the CQLStatement, rather than doing a find within the whole string, but it's not too big
a deal
* atomicCounterLock needs to be removed
* As a general rule, never copy array contents with a loop - always use System.arraycopy
* Still need to log the thread + query id as Jonathan mentioned



> 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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