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From "Remko Popma (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LOG4J2-163) Create asynchronous Logger for low-latency logging
Date Thu, 07 Feb 2013 07:45:13 GMT

    [ https://issues.apache.org/jira/browse/LOG4J2-163?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13573279#comment-13573279

Remko Popma commented on LOG4J2-163:

About the "slight loss" of performance: if it is just a couple of additional method calls,
I doubt there will be any impact.
I am more concerned about the current Logger.log implementation:
configurationMonitor.checkConfiguration() call may access the file system (1 or 2 calls to
file.lastModified(), potentially reloading the config file) so I would like to ensure that
this happens in the I/O thread.

About parent delegation, I'm trying to understand what you mean. I think there are 4 additivity=true
delegation scenarios:
1. sync child -> async parent
2. async child -> sync parent
3. sync child -> sync parent
4. async child-> async parent

In 1 and 3, the call to log(LogEvent) would be in the application thread.
In 2 and 4, the call to log(LogEvent) would be in the I/O thread.

What is it you are trying to achieve?
If the child is the sync audit logger, and the parent is the async debug logger, you want
the call to auditChild.callAppenders to be synchronously (in the application thread) and the
call to debugParent.callAppenders to be asynchronously (in the I/O thread)?

> Create asynchronous Logger for low-latency logging
> --------------------------------------------------
>                 Key: LOG4J2-163
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-163
>             Project: Log4j 2
>          Issue Type: Improvement
>    Affects Versions: 2.0-beta4
>            Reporter: Remko Popma
>         Attachments: FastLog4j-v2-for-beta4.zip, FastLog4j-v3-for-beta4.zip
> One of the main considerations for selecting a logging library is performance, specifically,
how long it takes for a call to Logger.log to return. (See the comments of LOG4J-151 for a
discussion of latency versus application throughput and logging throughput.)
> I believe it is possible to improve this performance by an order of magnitude by having
an asynchronous Logger implementation that hands off the work to a separate thread as early
as possible. The disk I/O would be done in this separate thread. 
> AsynchAppender is not a good match for these requirements, as with that approach (a)
the logging call still needs to flow down the hierarchy to the appender, doing synchronization
and creating objects at various points on the way, and (b) when serializing the LogEvent,
the getSource() method is always called, which is expensive.

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