Benjamin Jaton created LOG4J2-1197:
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Summary: Improve RollingFileAppender to avoid having stale log
events in the buffer
Key: LOG4J2-1197
URL: https://issues.apache.org/jira/browse/LOG4J2-1197
Project: Log4j 2
Issue Type: Improvement
Reporter: Benjamin Jaton
With bufferedIO=true the buffer contains log events that I want to see, but the
buffer is only flushed to disk when it is full (which is not frequent enough).
Typical scenario is when the server is not in production, so almost no traffic
except for the request manually triggered by the operator, usually in order to
debug something.
>From Remko:
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If you use AsyncAppender or Async Loggers, the buffer will be flushed when the
queue is empty. This results in efficient IO (lumping together IO operations
where possible), but at the same time your log file always reflects the most
recent message.
For synchronous buffered logging, I can see how a smarter flushing mechanism
would be useful.
Question is, what would trigger the check (whether the buffer needs to be
flushed)?
Easiest is to check with each log event, but if no new event arrives you still
end up with a stale buffer. Better than nothing, but not great.
An alternative is to check periodically from a background thread and flush if
the buffer is non-empty. This probably gives the best results but is fairly
complex to implement.
(...)
Now, with Async Appenders/Loggers, we can use what Martin Thompson calls "smart
batching
<http://mechanical-sympathy.blogspot.jp/2011/10/smart-batching.html>": when the
background thread processes a log event, it checks if the queue is now empty
(no further log events are in the pipeline to be processed) and if it is, it
will also call Appender.flush() in addition to the above.
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Note 1: The FlumeAppender uses a maxDelayMillis to address this.
Note 2: Could all synchronous appenders benefit from this improvement?
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