Re: spontaneous redeployment of a webapp

On 10/12/2025 21:58, Linus Kamb wrote:
> Mark,
> 
> Thanks very much for your response.
> 
> The disk is local, not shared.

So given the statement "... the disk from which all the tomcats run ..." 
does this mean we are talking about multiple Tomcat instances running on 
a single physical machine? Or something else?

Are any files shared between the instances?

How is the web application deployed? WAR file that Tomcat then expands?

I want to make sure I understand the architecture before I spend too 
much time thinking about what might be going on.

> Could the fact that there was no space left on the disk be treated as
> being unavailable?

Seems unlikely. Tomcat has a list of files it checks for each webapp and 
looks to see if the modification time has changed.

> And why only the one webapp?  Perhaps because it was the one attempting to
> write to the disk?

Again, seems unlikely.

Might some external process changed the last modification time on any 
files? A back-up process maybe? Those times should not be sensitive to 
clock / time zone changes but I'd check if there were any changes of 
that nature just in case.

Mark


> 
> - Linus
> 
> On Wed, Dec 10, 2025 at 1:07 PM Mark Thomas <[email protected]> wrote:
> 
>> On 10/12/2025 18:52, Linus Kamb wrote:
>>> All,
>>>
>>> Context:
>>> We have several public facing tomcats (all behind a firewall, no fronting
>>> Apache.)  They are mostly 10.1.44, but there is one 8.5.100.  There is a
>>> mix of webapps on all of them, but they all have one particular webapp in
>>> common.  That webapp often uses a fair amount of memory.  (Not sure if
>> that
>>> is relevant here.)
>>>
>>> Situation:
>>> The night before last *all* of the instances of that particular common
>>> webapp were undeployed and redeployed in the middle of the night. (3 at
>>> ~1am, 1 at ~2am, and 2 at ~2:30.)  There was no apparent nefarious
>> network
>>> traffic, and in several cases, no network access to the tomcats at all
>> for
>>> hours in either direction.  And the timestamps of the war files and
>> web.xml
>>> files had not (or do not appear to have) changed.
>>>
>>> One possibly significant detail is that around that time, the disk from
>>> which all the tomcats run was on the edge (and occasionally over that
>> edge)
>>> of running out of space.  For instance, in some cases where it didn't
>>> already exist, tomcat reported it was unable to create the
>>> catalina.2025-12-09.txt log file as there was no space on the device,
>> which
>>> it was presumably trying to create to log the undeployment and
>> redeployment
>>> of the webapp.  (It was logged there in other tomcats where the file
>>> already existed.)
>>>
>>> There were no OutOfMemoryErrors thrown by any of the tomcats, and none of
>>> the tomcats themselves were shut down and restarted.  Just all the
>>> instances of that one webapp in all the tomcats reloaded.
>>>
>>> Any ideas what might have happened?  Have you ever seen anything like
>>> this?   Can Tomcat spontaneously redeploy specific webapps unprompted?
>>
>> Is there some form of shared disk arrangement between multiple machines
>> here? Is the web application on the shared disk?
>>
>> If the shared disk goes off-line for any reason and auto-deployment is
>> enabled, Tomcat will undeploy the web application and redeploy it when
>> the shared disk returns.
>>
>> Mark
>>
>>
>>
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>