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From "Scott Carey (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-6884) Add LOG.isDebugEnabled() guard for each LOG.debug("...")
Date Fri, 13 Aug 2010 22:57:17 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12898461#action_12898461

Scott Carey commented on HADOOP-6884:

bq. Scott: build time - means we wouldn't be able to enable debug at runtime, that's a significant
restriction compared to current state and limits troubleshooting capabilities.

Thats not what I meant.   I mean that at build time, the source code:
log.debug("hello " + "world" + "!");

can be transformed into:
if (log.isDebugEnabled()) {
  log.debug("hello " + "world" + "!");

The transformation can be at the source code level prior to compilation OR at byte code level
post compilation.
Obviously, that is a longer term option.

Do we have any information about how much improved the performance is with the patch here?

> 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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