Webapp killing entire Tomcat process

[Jerry Malcolm <te...@malcolms.com>]

I am running TC 8.0.24.  It's been stable ever since I installed it.  I 
have been making changes/enhancements to a web app that has been in 
production for many years.  I have now encountered a situation when I 
request a certain page, the entire Tomcat process dies.  Literally, the 
Windows service is stopped.  There are no errors in any of the Tomcat 
log files.  It's like I went to the task manager and killed the process 
from there.  Fortunately it's on a development machine.  But I've got to 
figure this out before I put it on a production machine.

I have been developing web apps for over 15 years.  I've obviously had 
lots of bugs in my code over the years.  But I've never encountered a 
situation where a coding problem caused the entire web app server to 
die.  I'm am pretty much certain that it's something I'm doing in my 
code to cause it.  But in my opinion, no matter what happens in the 
code, TC shouldn't completely die, correct?  So it looks like my bad 
code has possibly exposed a vulnerability in TC. it's very frustrating 
and just about impossible to debug when every time I call the page that 
has the problem, I then have to wait 3-4 minutes after restarting the TC 
service for it to come back up before I can do anything again.  I'm 
pretty much relegated to table-top visual debug of the code and hope I 
accidentally see what's wrong.  Difficult process at best.  I feel like 
I'm shooting blind.

I guess my question is, do you have any suggestions for anything my code 
might do that could kill the process?  At least it might give me a start 
at what to look for.

Thanks.

Jerry

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Re: Webapp killing entire Tomcat process

[Christopher Schultz <ch...@christopherschultz.net>]

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Chuck,

On 8/30/15 8:52 PM, Caldarale, Charles R wrote:
>> From: Jerry Malcolm [mailto:techstuff@malcolms.com] Subject:
>> Webapp killing entire Tomcat process
> 
>> But in my opinion, no matter what happens in the code, TC
>> shouldn't completely die, correct?
> 
> Nope, it's all one process, and any thread can take it out.
> Running with a security manager reduces the chance, but doesn't
> preclude it.  Simple silliness such as calling System.exit() will
> also stop everything.
> 
>> I guess my question is, do you have any suggestions for anything
>> my code might do that could kill the process?  At least it might
>> give me a start at what to look for.
> 
> The first step is to stop running Tomcat as a service, and instead
> start it from a command prompt using the startup.bat script.  You
> can also attach a debugger this way and watch what's going on, set
> breakpoints, etc.

+1

Having access to stdout/stderr is very helpful. I'm not sure what the
Windows service runner does with those streams, but you ought to find
them and look at the history.

If it's not a System.exit() (which would be very susprising to find in
a web application's code), it's more likely to be something like a JVM
bug or some native component (like tcnative) crashing the JVM.

Even OOME doesn't kill the JVM... it just likely lobotomizes the
application that's currently running within it.

- -chris
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RE: Webapp killing entire Tomcat process

["Caldarale, Charles R" <Ch...@unisys.com>]

> From: Jerry Malcolm [mailto:techstuff@malcolms.com] 
> Subject: Webapp killing entire Tomcat process

> But in my opinion, no matter what happens in the code, TC shouldn't 
> completely die, correct?

Nope, it's all one process, and any thread can take it out.  Running with a security manager reduces the chance, but doesn't preclude it.  Simple silliness such as calling System.exit() will also stop everything.

> I guess my question is, do you have any suggestions for anything my code
> might do that could kill the process?  At least it might give me a start 
> at what to look for.

The first step is to stop running Tomcat as a service, and instead start it from a command prompt using the startup.bat script.  You can also attach a debugger this way and watch what's going on, set breakpoints, etc.

 - Chuck


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