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Subject: Re: Tomcat 6.0.35 Crashed again
From: Daniel Mikusa <dmikusa@vmware.com>
In-Reply-To: <BAY146-W12AAECD2BCA5CC2A1AFAA1F6C00@phx.gbl>
Date: Thu, 11 Apr 2013 09:52:24 -0400
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Message-Id: <78E6170A-987B-48F8-907A-62EDA317DADA@vmware.com>
References: <BAY146-W12AAECD2BCA5CC2A1AFAA1F6C00@phx.gbl>
To: "Tomcat Users List" <users@tomcat.apache.org>

On Apr 11, 2013, at 1:09 AM, saumil shah wrote:

> Hello All,
> We are using Tomcat 6.0.35 for our production system with 64 bit JVM =
(1.6.33) on Windows 2008 R2 SP1. Our physical memory is 24gb. Load is ~ =
100 concurrent sessions.
> The Tomcat crashed again with OutOfMemoryError: Java heap space error. =
We are using COTS product SAP Business Objects. Upon providing Tomcat =
logs ,
> SAP came with recommendation of increasing the heap size . Our current =
Java params are :
> -Xms512m -Xmx1024m
> -XX:MaxPermSize=3D512m
> SAP's recommendation is to make it ...
> -Xms1024m -Xmx4096m
> We have ample of free memory on the box ...
> 1a. but the question was heap size as Max 4GB , would it cause =
application delay when java GC is due? It's NOT time-sensitive =
application.

A bigger heap will generally take longer to clean, but 4GB is not =
particularly large. =20

If you're concerned about the performance of the garbage collector, I =
would suggest that you enable garbage collection logging.  This adds =
very little overhead, simply logging an entry for every garbage =
collection that occurs.  Each entry will indicate memory before and =
after the GC, plus how much time was spent performing the collection.  =
You can use that to analyze the performance for your application.


> 1b. Also, when putting MAx as 4GB , does it mean JVM will make base =
effort to get 4GB MAX memory for heap , or is that guaranteed? Based on =
my reading, it appeared that only Min, was guaranteed.

The JVM will start at -Xms and, if needed, expand up to -Xmx.


> 1c. Is it then recommended to have Min and Max as 4GB... so that Heap =
doesn't have to resize and 4GB is guaranteed at the time of =
initialization?

It depends.  This can be good because it will prevent a few full GC's as =
the JVM expands from -Xms to -Xmx.  However, it can also waste memory if =
you allocate too much. =20


> 1d. I have Tomcat service installer..... I have provided Min and Max =
heap size values under Tomcat --> Java tab --> Initial Memory Pool and =
Maximum memory pool ...... I am assuming that means Min and Max values =
for Heap.....is this correct?

Yes, I believe so.


> 2. When trying to monitor Tomcat , using JConsole and VisualVM ..... =
do I need to add JMX agent and port ....  in Java tab of Tomcat and then =
restart , or is it possible to Monitor tomcat , without rebooting it ? =
Since, it would not be possible to re-boot tomcat in production for it.

Normally when you run jconsole or jvisualvm on the same machine as your =
Tomcat instance, you can connect without needing any additional =
configuration.  This is a special case because the two processes are =
running on the same machine.  However, I seem to remember needing to =
configure JMX when running Tomcat as a Windows Service.  Perhaps one of =
the Windows guys on this list can clarify.


> 3. Once JConsole and/or VisualVM is setup ... I can look at =
Heap/Permgen , memory , threads etc...... I was wondering how do I see =
memory leaks and what is causing it , using these tools?

Spotting memory leaks is tricky and I'm not sure that what you're =
proposing will be much help.  You could certainly look at the live =
graphs and watch for a trend in memory usage increasing, but if the leak =
is small it would be very hard to spot.

I would suggest that you add -XX:+HeapDumpOnOutOfMemoryError to your JVM =
options.  This will create a heap dump when you encounter an OOME.  You =
can then view that heap dump in jvisualvm or a profiler to see what was =
consuming the memory. =20


> 4. Also, I am seeing that Tomcat is deploying the webapps on start-up =
.... is there anyway to avoid Tomcat to deploy the application on =
start-up....as the applications are already deployed and exploded?
> Example is below :Apr 5, 2013 7:17:27 PM =
org.apache.catalina.startup.HostConfig deployWARINFO: Deploying web =
application archive AnalyticalReporting.war

Tomcat has to deploy your application when it starts or your user's =
won't be able to access it.  This is normal and expected behavior.


> Apr 5, 2013 7:17:28 PM org.apache.catalina.core.StandardContext =
addApplicationListenerINFO: The listener =
"com.sun.faces.config.ConfigureListener" is already configured for this =
context. The duplicate definition has been ignored.

Looks like you might have a duplicate definition in your application's =
web.xml.  You should remove it, but you don't have to.  This is just =
Tomcat telling you that the duplicate was ignored.

Dan


>=20
> As you can tell , I am novice to Tomcat. Please let me know if I =
missed on something.
> Appreciate all your help. 		 	   		 =20


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