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From Anthony Maire <maire.anth...@gmail.com>
Subject Question about several Async Loggers + RandomAccessFIle appenders with immediateFlush = false
Date Fri, 17 Jun 2016 13:11:04 GMT
Hello

As suggested in AsyncLogger javadoc, I made some performance tests on my
application with (Rolling)RandomAccessFile appenders configured with
immediateFlush = false to take advantage of the potential I/O batching, and
the results are very good :)

However I have a question about the flush on end of batch mechanism when
there are several appenders to flush.

*Case one:*

- AsyncLogger L1 has very few messages to log (let's say its a logger which
logs only when a request fails) and has its dedicated RAF appender A1.
- AsyncLogger L2 is very active (let's say its a logger which logs every
request that enters the system), and has its dedicated RAF appender A2

As far as I understand the code, both loggers use the same disruptor
instance. Let's assume that at some time, an event E1 is submitted to the
disruptor by L1, but the background thread doesn't wake up immediately and
another event E2 is submitted by L2, so both events will be part of the
same batch when the background thread wakes up

I'm afraid that the following will happen :
- A1 encode E1 in its buffer, but does not write to the RAF since
event.isEndOfBatch() == false
- Background thread now process E2, it will be encoded in A2 buffer, and
since E2 is a end of batch event, A2 is flushed
However A1 is not flushed and will never be until another event is logged
to it.

*Case Two:*

Same kind of idea with a single AsyncLogger or AsyncAppender, 2 RAF
appender referenced on it, one of them as a filter (or a level that is
higher than the source level). If the end of batch event is filtered out
for an appender, is there a mecanism that will make flush earlier events
that were ine the same batch ?

I try to find something in the code that will prevent this issue to happen,
but I didn't succeed to find one. Since reproducing these cases is not
trivial to test , I would like to have the analysis of someone who knows
the code better than I do :)

Regards,
Anthony

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