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From "Erik Steffl (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-6884) Add LOG.isDebugEnabled() guard for each LOG.debug("...")
Date Thu, 12 Aug 2010 23:48:17 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12898007#action_12898007
] 

Erik Steffl commented on HADOOP-6884:
-------------------------------------

Re https://issues.apache.org/jira/browse/HADOOP-6884?focusedCommentId=12897536&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12897536

Me too however then there's no way to automatically or at least semi-automatically check for
the cases where the optimisation would be helpful.

If all debug() logging calls have isDebugEnabled() guard it's easy to check the whole codebase
in few minutes (I have a simple script that only produces few false positives that need to
be eyeballed). If the guard is used in minority of cases where it's actually useful then verification
whether it's used everywhere where it's needed is very expensive.

Possibly better solutions but I don't think they are realistic in short/medium term:

  - use scala and lazy values (arguments for debug() are not constructed unless used)

  - use extensive profiling and see where debug() calls matter (this could be part of automatic
builds/tests)

> Add LOG.isDebugEnabled() guard for each LOG.debug("...")
> --------------------------------------------------------
>
>                 Key: HADOOP-6884
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6884
>             Project: Hadoop Common
>          Issue Type: Improvement
>    Affects Versions: 0.22.0
>            Reporter: Erik Steffl
>            Assignee: Erik Steffl
>             Fix For: 0.22.0
>
>         Attachments: HADOOP-6884-0.22-1.patch, HADOOP-6884-0.22.patch
>
>
> Each LOG.debug("...") should be executed only if LOG.isDebugEnabled() is true, in some
cases it's expensive to construct the string that is being printed to log. It's much easier
to always use LOG.isDebugEnabled() because it's easier to check (rather than in each case
reason whether it's necessary or not).

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