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From "Erik Steffl (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1320) Add LOG.isDebugEnabled() guard for each LOG.debug("...")
Date Tue, 27 Jul 2010 21:55:23 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1320?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12892951#action_12892951
] 

Erik Steffl commented on HDFS-1320:
-----------------------------------

Re fast-path optimization: we don't know and JVM optimizations depends on user setup (user
determines which java command line options are used). Optimizations also vary across platforms
and versions.

Just to make sure I did try code like the following:

LOG.debug("debug log" + a.logSomething());

a.logSomething() is always called, even though debug is not enabled (and debug log message
does not get into log).

It's possible that in different runtime it's optimized away somehow but I don't think we can
rely on it.

Do you have any specific thoughts on how it would be optimized away?

> Add LOG.isDebugEnabled() guard for each LOG.debug("...")
> --------------------------------------------------------
>
>                 Key: HDFS-1320
>                 URL: https://issues.apache.org/jira/browse/HDFS-1320
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 0.22.0
>            Reporter: Erik Steffl
>             Fix For: 0.22.0
>
>         Attachments: HDFS-1320-0.22.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 wheather it's neccessary or not).

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