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Date: Tue, 17 Aug 2010 12:43:17 -0400 (EDT)
From: "Tsz Wo (Nicholas), SZE (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-6884) Add LOG.isDebugEnabled() guard for
 each LOG.debug("...")
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    [ https://issues.apache.org/jira/browse/HADOOP-6884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12899462#action_12899462 ] 

Tsz Wo (Nicholas), SZE commented on HADOOP-6884:
------------------------------------------------

For aspectj, first of all, we currently don't use aspectj in Hadoop except for testing.  I beg there are people against using aspectj or other byte-code rewriting technique on the non-testing codes since it is hard to debug.

Let's be academic (as what I see in this issue) and ignore the statement above.  I cannot see a simple solution on using aspectj.  Clearly, if we define a point cut per LOG.debug(..), aspectj will works but this is too much of works and, in some cases, we need to change the codes in order to define a point cut.  For the people suggesting aspectj and saying that it is simple, could you please provide a simple example?

I heard one suggestion from Luke yesterday.  He claimed we could use the "around" advice.  However, it seems to me that around does not prevent parameter evaluation.  I have not tested it yet.

> 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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