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
--
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