Niranjan,
On 2/18/21 13:36, Niranjan Rao wrote:
First apologies for non tomcat question. I have seen that there is
enough expertise here to provide hints and hints are what I am looking
for to solve the problem and question is generic enough. I have tried
researching problem to best of my abilities.
It all happens on Ubuntu 20.04 and JDK 15
We have a java program that regularly throws
"java.lang.OutOfMemoryError: Java heap space" exception. Puzzling point
is it happens only on one VM. We have a set of two VMs/boxes spawned
from same AWS image. Machine class/region is exactly same and since they
are from same image, they should be mostly identical except stuff like
host name, ip address etc.
Number of tasks performed by VMs are comparable and not a significant
difference. Yet, one VM never runs of out of memory and other one does.
Sometimes it's as soon as half an hour after restarting the process
while on the other box process is running for days and no issues.
I took memory dumps from both VMs and they look similar. Program is
started with -Xmx1g flag and we have taken regular memory dumps. In many
cases eclipse MAT reports total memory usage was less than 100MB when
program crashed with out of memory exception.
Has anyone seen anything similar to this? Identical bits of code
behaving differently? What else should I be looking for?
What is the load profile of each application/server? You said you aren't
running Tomcat, but is load on each of the applications balanced in any
way similar to how a web-application load-balancer would work?
Sometimes, the answer is simply that one server is doing more work than
the other.
We have two application servers which are "identical" except that only
one of them handles our email queue.
Maybe though the "types" of tasks are the same for each server, one of
them is getting unlucky and is handling a "big" task that fails each time?
Do you have any logging which would indicate which task, ro what kinds
of tasks are failing?
Do you have a stack trace of the OOME? Do you have a bunch of them (from
many separate events)? Do they all look the same?
The AWS images are the same, have you upgraded the OS on either one
after initial launch, or do you always start fresh with the same image
and no "apt-get update" on them. Same JVM and everything on each of them?
If you start with -Xmx1G then you should consider also using -Xms1G. IF
you have a long-running process which you expect may take up 1G of heap
space, go ahead and allocate it all at once instead of wasting time
re-sizing the heap a bunch of times on your way up to 1G.
-chris
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