[logback-dev] [JIRA] Commented: (LBCLASSIC-281) Don't evaluate formattedMessage in LoggingEvent constructor

Joern Huxhorn (JIRA) noreply-jira at qos.ch
Thu Feb 16 14:18:26 CET 2012

    [ http://jira.qos.ch/browse/LBCLASSIC-281?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12361#action_12361 ] 

Joern Huxhorn commented on LBCLASSIC-281:

It's rather critical to evaluate/convert the arguments-array to strings during construction of the event/ASAP. (the actual formatting can be performed later)

Otherwise, the objects in the argument array may change between the logging call and the actual processing of the message in an appender.
Another example are LazyInitializationExceptions caused by Hibernate if an object isn't connected to the database session anymore.

Both can be caused by an asynchronous appender implementation.

> Don't evaluate formattedMessage in LoggingEvent constructor
> -----------------------------------------------------------
>                 Key: LBCLASSIC-281
>                 URL: http://jira.qos.ch/browse/LBCLASSIC-281
>             Project: logback-classic
>          Issue Type: Improvement
>    Affects Versions: 0.9.29
>            Reporter: Andrew Brett
>            Assignee: Logback dev list
> Whenever a ch.qos.logback.classic.spi.LoggingEvent is constructed, MessageFormatter.arrayFormat(...) is called, and the formattedMessage member variable assigned. This involves calling toString() on all arguments in argArray, which can be slow, and occurs even if the formattedMessage is not part of any appender layouts.
> For my project's purposes, I have a custom formatter which only outputs an abbreviated string form of certain objects with expensive toString() methods; however, I am still paying the overhead in the toString() calls, since they're made even when getFormattedMessage() is never called. Note that I don't control the source of the objects with expensive toString() methods, nor do I control the source everywhere they're logged, so I can't simply change them directly.
> formattedMessage is already evaluated lazily in getFormattedMessage(), so the only side effect of this change is the introspection of argsArray to look for a Throwable at the end, which is a trivial operation to perform separately.

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