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From "Daniel Kluesing (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (CASSANDRA-1305) Slow query log
Date Tue, 20 Jul 2010 17:02:55 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1305?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12890323#action_12890323
] 

Daniel Kluesing edited comment on CASSANDRA-1305 at 7/20/10 1:02 PM:
---------------------------------------------------------------------

There are lots of knobs to tune (row cache, key cache, index sample size, bloom filter buckets,
network, disk, heap) Figuring out what to tune under load isn't always obvious. Turning on
debug logging under load has heisenberg effect of shifting bottlenecks around. The attached
patch is a simple slow query logger to log information about what queries that take longer
than some threshold did that took so long. I've found it useful for pinpointing bottlenecks
under load and figuring out which knobs need tweaking. This patch only instruments the get_slice
command and the read path. Incrementing the other commands/paths is straightforward, and I
can update the patch with the write path.


      was (Author: danielkluesing_bk):
    There are lots of knobs to tune (row cache, key cache, index sample size, bloom filter
buckets, network, disk, heap) Figuring out what to tune under load isn't always obvious. Turning
on debug logging under load has heisenberg effect of shifting bottlenecks around. The attached
patch is a simple slow query logger to log information about what queries that take longer
than some threshold did that took so long. I've found it useful for pinpointing bottlenecks
under load and figuring out which knobs need tweaking. This patch only instruments the get_slice
command and the read path. Incrementing the other commands/paths is straightforward, and I
update the patch with the write path.

  
> Slow query log
> --------------
>
>                 Key: CASSANDRA-1305
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1305
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Daniel Kluesing
>            Priority: Minor
>         Attachments: trunk-SlowQueryLog.txt
>
>
> If a query takes a long time, it's nice to know why

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