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From Florian Trimmel <florian.trim...@gmail.com>
Subject Re: Migration from Tomcat 7 to 9 results in more open file descriptors
Date Mon, 03 Jun 2019 06:27:32 GMT
Am Do., 23. Mai 2019 um 17:14 Uhr schrieb Christopher Schultz <
chris@christopherschultz.net>:

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> Florian,
>
> On 5/23/19 06:59, Florian Trimmel wrote:
> > After migrating from Tomact 7 to Tomcat 9.0.20 (running with same
> > Java Version 1.8.0_25) we have a problem with our JSF2 web
> > application on Linux RHEL 7. After some time we get Exceptions like
> > this:
> >
> >
> >
> > java.io.FileNotFoundException:
> > /f4m/tomcat/tomcat_f4mbs/webapps/ACM/WEB-INF/acm-config.xml (Too
> > many open files)
> >
> > at java.io.FileInputStream.open0(Native Method)
> >
> > at java.io.FileInputStream.open(FileInputStream.java:195)
> >
> > at java.io.FileInputStream.<init>(FileInputStream.java:138)
> >
> > at java.io.FileInputStream.<init>(FileInputStream.java:93)
> >
> >
> >
> >
> >
> > After searching around a while, I have found out that there are
> > many open file descriptors to xhtml files
>
> Do you know if your application opens these files, or are they
> (likely) being opened by Tomcat in response to incoming client
> requests for those files?
>
> > [snip]
> >
> > This is not the complete list - there are many more.
> >
> > The number of listed files goes up and down. For me it seems that
> > xhtml (or one of its used components) has an open file descriptor
> > as long as a page is shown in Browser.
>
> ... and when you close the browser, the fd is closed too? Spooky.
>
> > I already know how to increase the maximum number of open file
> > descriptors, what bothers me is that if I deploy the same
> > application on Tomcat 7 again, I can only see open file descriptors
> > for JAR Files, Sockets, but NEVER for xhtml's.
> >
> > Can someone please explain why this happens?
>
> The obvious explanation would be a fd leak within Tomcat but I see no
> data to support that. The "resources" (aka file-reading)
> implementation changed between Tomcat 7 and 9 and if your application
> is being a little lazy about resource-management, this could cause fds
> to be left open now where they were being cleaned-up for you in the past
> .
>
> Improper caching configuration could also leave file descriptors open,
> but multiple fds open to the same file is the exact opposite of
> caching, so the configuration would have to indeed be particularly bad.
>
> Are you able to attach a profiler to the JVM process? If so, try
> launching Tomcat, attaching the profiler, and then making some
> requests. The profiler ought to be able to show you where certain
> objects were allocated and you can track-down where e.g.
> FileInputStream objects are created. If they are being created in
> Tomcat's code without being called from your application (e.g. from
> within DefaultServlet), then something is very wrong.
>
> But at this point, the new resources implementation is fairly mature
> and I wouldn't expect it to leak like this.
>
> - -chris
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>

Christopher,
Thank you for your quick reply
We were able to figure out what was causing the file descriptor leak.

The leak has occured in the JSF2 MyFaces Implementation we are using.
It is described here: https://marc.info/?l=myfaces-dev&m=152536956716792&w=2
The problem was found using this tool:
http://file-leak-detector.kohsuke.org/


Thanks,
Florian

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