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From "Pid *" <...@pidster.com>
Subject Re: Tomcat recycling
Date Mon, 21 Nov 2011 18:52:51 GMT
On 21 Nov 2011, at 13:24, "Jan Vávra" <vavra@602.cz> wrote:

>
>>> Hello,
>>> is there any way how to tell tomcat: Recycle after X minutes OR Y requests like
it is eg. on the IIS server?
>> IIS can reboot itself after N requests?
>> That's awesome. What could possibly go wrong?
>
> Yes, IIS can do recycling
> See eg. at http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/1652e79e-21f9-4e89-bc4b-c13f894a0cfe.mspx?mfr=true
> It is a quite easy to setup it in the configuration.
>
>
>>
>> I might file an enhancement request for Tomcat...
> If you have already done it, can I vote it for?
>
>
>>
>>
>>> If I add my own script containing "/etc/init.d/tomcat restart"  to the crontab
I loose the user sessions and users have to relogin.
>> Yes... because you restarted the server!
> As Chris Schultz wrote it is possible to persist sessions over tomcat restarts. I chagned
my session objects to be serializable and It works.
>
>>
>>> I experience some problems with OutOfMemory error.
>> Wouldn't it be better to understand and fix the OOM, rather than just
>> rebooting the server frequently?
>
> Yes, it is allways better to solve the cause than the consequence of a problem. But not
allways man can have enough time or means to solve it. When an error occurs at production
it is better to setup some kind of recovery (eg. recycling) and than solve it at pre-production
/ devel environment. You can use a third party lib with an error.
>
> Particulary in my case, my app consists of a one single cycle where I download a CRL,
parse it using BouncyCastle lib and retrieve serial numbers of revoked certificates. So the
problem can rather in third party lib than in my small piece of code. I've tried to profile
memory consuption but have not found out nothing. Maybe I had had not enough memory for java
virtual machine. I've set it from 128 MB to 512 MB and the problem have not occured yet.
>
>>
>>
>>> On tomcat I run a periodic thread that downloads CRLs and I suspect this of memory
leaks.
>> Why? Can't you fix that?
>
> If we forget the OOM exception, I was forced to make a ShutDownHook. I use spring quartz
scheduler and my job can run quite a long time. So I had to add some notification to stop
job correctly. Tomcat was complainting about possible memory leaks when ending quartz job-worker
threads when I was stopping app for redeploy my app.

Yes, Tomcat is helping you by warning you about a potential problem.
The last time I looked at Quartz the shutdown process didn't actually
wait for threads to finish before returning.

I had a little success with Thread.yield() but I suspect that it would
not be effective for multiple jobs or a longer process.


> In a single process model (crontab) I could afford to kill -9 the process and I could
rely on transactionality in the database which I'm using.

I'm not sure how that relates to this discussion.


> At the end I'd like to make a little comparision. Recently I've used .NET + native calls
of dlls, php + custom made php modules (native dlls), jsp+java. .NET and php have possibilities
for some kind of recoveries.

I'm not sure what that means.


> It's almost imposible to crash Apache like a whole (control + x worker processes). So
.NET and php seems me they're more stable than tomcat because they have some possibilites.

I completely disagree. You're comparing two languages with an
application server, for a start.


> I haven't studied recovery options in other java app. servers, but I'd really appriciate
something in Tomcat.

I think the harm this function would do would outweigh any perceived benefits.

If you want to reboot Tomcat periodically employ cron and the service wrapper.


p


> Jan
>
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