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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-6884) Add LOG.isDebugEnabled() guard for each LOG.debug("...")
Date Tue, 17 Aug 2010 18:09:19 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12899500#action_12899500
] 

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

>The way you'd write this is:
>
>LOG.debug("a={} b={} c={}", a, b, c);

Dong, I have checked the [slf4j Logger API|http://www.slf4j.org/apidocs/org/slf4j/Logger.html]
but does find a method like that.  There is one requiring creating an array, debug(String
format, Object[] argArray).  From [the FAQ link|http://www.slf4j.org/faq.html#logging_performance]
you provided earlier, it also suggests creating an array in this case.  Below is quoted from
the FAQ.
{quote}
If three or more arguments need to be passed, you can make use of the Object[] variant. For
example, you can write:

logger.debug("Value {} was inserted between {} and {}.", new Object[] {newVal, below, above});
{quote}


> 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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