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Posted to log4j-dev@logging.apache.org by Gary Gregory <ga...@gmail.com> on 2017/02/05 22:20:18 UTC
Re: Making copies of LogEvent to avoid no-GC problems
On Thu, Jan 26, 2017 at 2:45 PM, Remko Popma <re...@gmail.com> wrote:
> Yes, makes sense to me.
> Remko
>
I have a patch attached here:
https://issues.apache.org/jira/browse/LOG4J2-1807
But I'd like to be able to build on Windows before committing it...
Gary
>
> Sent from my iPhone
>
> On Jan 27, 2017, at 3:32, Gary Gregory <ga...@gmail.com> wrote:
>
> Hi All:
>
> Just like in our SMTP appender, I have a custom Appender which needs to
> track LogEvents. To do this without falling prey to all of our no-GC epic
> cleverness, the SMTP appender does this:
>
> public void add(LogEvent event) {
> if (event instanceof Log4jLogEvent && event.getMessage()
> instanceof ReusableMessage) {
> ((Log4jLogEvent) event).makeMessageImmutable();
> } else if (event instanceof MutableLogEvent) {
> event = ((MutableLogEvent) event).createMemento();
> }
> buffer.add(event);
> }
>
> The code in my Appender is functionally identical, I just use a different
> buffer type.
>
> This kind of Appender code is impossible to write correctly first IMO.
>
> My first implementation was just:
>
> public void add(LogEvent event) {
> buffer.add(event);
> }
>
> After a bug hunt by a colleague of mine, I thought the fix for our use
> case was 'simple':
>
> public void add(LogEvent event) {
> buffer.add(event instanceof MutableLogEvent ? ((MutableLogEvent)
> event).createMemento() : event);
> }
>
> But that was not complete!
>
> Our Appender now does the same thing the SMTP Appender does.
>
> Should we allow LogEvent to express this more cleanly? Maybe:
>
> public void add(LogEvent event) {
> buffer.add(event.asImmutableLogEvent());
> }
>
> Where MutableLogEvent.asImmutableLogEvent() just calls createMemento()
> and LogEvent changes its internal state by calling makeMessageImmutable()
> and returns 'this' since creating a new LogEvent is not needed.
>
> Thoughts?
>
> Gary
>
> --
> E-Mail: garydgregory@gmail.com | ggregory@apache.org
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--
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