Christopher Schultz wrote:
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André,
On 12/12/13, 2:42 AM, André Warnier wrote:
The original issue of the OP was to be notified ASAP when an OOM
occurs. And he indicated that an OOM resulted in a message in the
logs. So, "something" is already catching the OOM exception, to
write this line in the logs.
Right, but he wants to be notified. Most notification strategies are
flawed at best.
On the other hand, there is ample literature available that seems
to indicate that any method for trying to recover from (or even do
something worthwhile after) an OOM is ultimately flawed and
unreliable.
Yes and no. If the OOME was transient (e.g. a single thread ran-away
and filled-up the heap with thread-specific objects), then the heap
can recover then the thread dies (with OOME) and the JVM is likely to
continue without further related errors. On the other hand, you can of
course fill up the heap with objects that will *not* be collected when
the thread is killed, then you're done and bad things will happen like
the GC getting so angry and confused it can't do its job even if the
heap does recover.
Whilst I am in awe of the various solutions proposed so far (and
of their developers), would it, in this case, not be simpler to
pipe the log through a simple filter which catches the OOM log
message and warns the OP accordingly ?
That works, but you need to make sure that pipe stays up and running
all the time. How do you get notified if the pipe goes down? How do
you recover from the pipe going down... do you need to restart Tomcat?
How do you get notified if the notifier for the pipe going down goes
down? It's turtles all the way down.
I love the Pratchett reference, but seriously, I believe that in this case at least there
is less chance for the pipe (or the 10-line script/program that runs on it) to go down,
than for any of the proposed alternative solutions to misfire.
And if it goes down, then Tomcat and the JVM are quite likely to go down alongside it.
What better notification could one hope for ?
(Except if Nagios goes down of course.)
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