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https://issues.apache.org/jira/browse/LOG4J2-2399?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16574035#comment-16574035
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Remko Popma commented on LOG4J2-2399:
-------------------------------------
Supporting async formatting is likely to make the code significantly more
complex.
There needs to be an equally significant performance gain to make it worth it.
Can you give any indication (ideally with a JMH benchmark) of what the expected
performance gains are for this change?
> Reusable Messages do not respect log4j.format.msg.async
> -------------------------------------------------------
>
> Key: LOG4J2-2399
> URL: https://issues.apache.org/jira/browse/LOG4J2-2399
> Project: Log4j 2
> Issue Type: Task
> Components: Core
> Reporter: Carter Kozak
> Assignee: Carter Kozak
> Priority: Major
>
> Setting "log4j.format.msg.async" applies only to messages that do not
> implement ReusableMessage.
> On applications using asynchronous logging with message formatting in the
> background there is a measurable performance cost to using
> ReusableParameterizedMessages instead of ParameterizedMessages due to
> formatting on the application thread
> (MutableLogEvent/RingBufferLogEvent.setMessage).
> I have a custom layout which does not log formatted messages in most cases,
> but the format string and parameter values separately in order to analyze
> values logged over time bucketed by logger name and format string. In this
> case the formatting is unnecessary work. It is possible to implement a custom
> message factory which doesn't format message data, however that would break
> the ability to add a standard pattern layout in addition to the custom
> formatter.
> h2. Proposed Design
> Our reusable events (MutableLogEvent and RingBufferLogEvent) currently
> capture most of the required information, the format string and parameter
> array, but are missing a bit of context for how the original message
> implementation would format that data.
> ReusableMessage implementations may optionally extend
> "MessageContentFormatterProvider"
> {code:java}
> interface MessageContentFormatterProvider {
> MessageContentFormatter getMessageContentFormatter();
> }{code}
> Where MessageContentFormatter takes the form:
> {code:java}
> interface MessageContentFormatter {
> void appendTo(StringBuilder dest, String format, Object[] params, short
> paramCount);
> }{code}
> Reusable log event implementations will be updated to hold a reference to the
> content formatter (instead of formatting to the local event buffer) when
> asynchronous formatting is enabled _and_ the message is an instance of
> MessageContentFormatterProvider.
>
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