Fwd: Tomcat6 port keeps locking up??

Kaya Saman kayasaman at gmail.com
Fri Sep 17 09:15:58 UTC 2010

Thanks a lot Jeremy for the response!!

On 17/09/2010 11:56, Jeremy Chadwick wrote:
> [...]
> You should probably spend a bit of time in a debugger (specifically a
> Java debugger) figuring out if your code is spinning or not.  Debugging
> anything under Tomcat/Java is a PITA, and I say that from experience.
> I would advocate you open up a bug/report with the Apache folks and
> provide them this information, especially if the only thing you're
> seeing problems with is Tomcat (and not other software).
> For example -- at my workplace we run Solaris 10, with Tomcat heavily
> used for different purposes (mainly a translation layer between HTTP and
> Cisco ICR protocols).  For years we saw a problem where a Tomcat thread
> would take up 100% CPU (ex. on a 4-core machine, 25% CPU) when a Cisco
> PG would disconnect/reconnect repetitively (common during network
> problems).  The problem turned out to be two fold: a bug in Tomcat, and
> some improper code on our part, resulted in Tomcat spinning.  We did not
> open up a SunSolve case because there wouldn't have been a point to it.

Hmm... it's the Xwiki application I'm using which works fine on the 
OpenSolaris homesite although running a different OS and proper 
programmers there with the experience to deal with such things!!

I'll try though and see what happens.

>> Otherwise I will have to start looking at migrating this service
>> away from BSD and much more costlier option of Nexenta based on
>> OpenSolaris, but hogs RAM as uses ZFS natively meaning min 4GB
>> unlike my FreeBSD build with ZFS and UFS2 using 4GB for that many
>> processes and 7 jails!
> I don't think you understand how Solaris's VM behaves with ZFS.  It
> behaves very differently than FreeBSD.  On Solaris/OpenSolaris with ZFS,
> you'll see the ARC taking up as much memory as possible -- but unlike
> FreeBSD (AFAIK), when a userland or kernel application requires more
> memory, the Solaris kernel dynamically releases portions of the ARC.
> We use ZFS on Solaris 10 exclusively at my day job (thousands of x86
> servers).  When we moved to ZFS, we had to adjust our system memory
> monitors to take into consideration ARC usage.
> What I'm trying to say: on Solaris with ZFS, don't let "I don't see any
> free memory in top or prstat" equate to "there isn't any free memory
> available for applications".  Solaris handles this situation very,
> *very* well; we have never seen any userland applications get starved
> for memory as a result of using ZFS on all of our machines.

Thanks for explaining!! :-)

Actually with everyone claiming that OpenSolaris/Solaris needs min. 4GB 
memory to run a basic system it kinda confuses me a little. Also since I 
am currently in a job where I can only use MS products there's no one to 
ask either, even though my personal projects are all UNIX based. It's 
just hard sometimes to work alone on EVERYTHING which is often how I'm 
left... anyhow!!

I'll look into this situation and see if it is possible to migrate over 
to Nexenta using Glassfish and MySQL instead of the Postgresql and 
Tomcat6 setup I have currently.

Best regards,


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