[PJUG Javamail] What causes "Too many open files" in Tomcat

[Aaron Getz]

I have also seen this issue before.  The application was running in Tomcat
and was failing to close JDBC connections to the database.  It, as Jo
mentions is a misleading error.  I would look for code that is failing to
close connections.  In my particular code it was in a loop so I was opening
a lot of connections very quickly and then failing to close any of them.

Aaron

On Tue, Nov 3, 2009 at 5:03 PM, Creyf, Jo <Jo.Creyf at nike.com> wrote:

>  I’ve seen this issue before where an application running in Tomcat was
> not explicitly closing network sockets and was leaving handles in a
> CLOSE_WAIT state.
>
> The application was grabbing a new IP port each time and left previously
> used ports in limbo land.
>
> Note that this was not a Tomcat issue but more of a coding issue.
>
> The issue was resolved by explicitly closing and cleaning up network
> sockets.
>
> The ulimit setting tells the operating system that each running process on
> the machine can have up to that number of handles (file handles and network
> handles).  If the setting is 1024, then the Tomcat process can have up to
> 1024 files and network ports open.  You’ll get the “Too many open files” if
> that number is reached and Tomcat tries to grab another file or network
> handle.
>
>
>
> The too many open files message may be confusing.  I think it should
> actually read “Too many open handles”.
>
> Your stack trace is showing java.net.SocketException, which leads me to
> think that you too may be dealing with some code that is leaving network
> handles open.
>
>
>
> You may want to run lsof and probably grep for “CLOSE_WAIT” or grep for
> your Tomcat’s process id and monitor the output for a while to see what is
> eating up your resources.
>
>
>
> Good luck!
>
> Jo Creyf
>
>
>
>
>
> *From:* javamail-bounces at pjug.org [mailto:javamail-bounces at pjug.org] *On
> Behalf Of *Rob Tanner
> *Sent:* Tuesday, November 03, 2009 4:01 PM
> *To:* Chris Foster
> *Cc:* Portland Java Users Group
> *Subject:* Re: [PJUG Javamail] What causes "Too many open files" in Tomcat
>
>
>
> I thought about that but the problem isn’t system wide.  But thanks because
> you’ve just reminded me that ulimit is shell specific although the default
> of 1024 should certainly be sufficient.  I’ve modified the catalina.sh start
> up script to set ulimit to 4096 (ulimit –n 4096).  That’s definitely
> overkill and if ulimit was the problem, I shouldn’t see that error again.
>  I’ll just need to keep an eye out.
>
> Again thanks,
>
> Rob
>
>
> On 11/3/09 3:25 PM, "Chris Foster" <cjafoster at gmail.com> wrote:
>
> Check your ulimit. Chances are the Linux (or unix) file limit is too low.
>
> - Chris
>
> On Nov 3, 2009, at 2:53 PM, Rob Tanner <rtanner at linfield.edu> wrote:
>
> Hi,
>
> I’m getting messages like these in the catalina.out log:
>
> java.net.SocketException: Too many open files
> java.io.FileNotFoundException: /usr/dict/wordlist.pwd (Too many open files)
> java.io.FileNotFoundException:
> /var/apache/apache-tomcat-5.5.23/webapps/AccountManager/WEB-INF/classes/log4j.properties
> (Too many open files)
> java.net.SocketException: Too many open files
>
>
>
> And, of course, I have to stop and restart Tomcat to get it to work again.
>  This is not a system error; it’s only in Tomcat.  I did some googling and
> found a suggestion with regard to Java arguments when Tomcat starts up.
>
> These are the options I’m starting Tomcat with: '-XX:NewSize=128m
> -XX:MaxNewSize=128m -XX:SurvivorRatio=8 -Xms256m -Xmx512m'
>
> I’ve also gone through the most active apps and made sure that I was not
> leaving any database or LDAP connections open.
>
> Any ideas?
>
> Thanks,
> Rob
>
>
>
> *Rob Tanner
> *JAVA Developer
> Linfield College, McMinnville Oregon
>
>
>
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