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Groups > comp.lang.java.programmer > #10428

Re: java.io.File

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Mark wrote:
> Lew wrote:
>> Mark wrote:
>>> Can a java.io.File object use a OS file descriptor?  I am trying to
>>> find the source of a fd leak in a[n] application.
>>
>> At some point, depending on the operations performed by the 'File' instance, 
>> there may be a file descriptor involved, and then the 'File' instance certainly
>> does use it, at least indirectly via JVM system calls that proxy to OS system
>> calls.
>>
>> From a Java perspective you should look for unclosed I/O streams/channels and 
>> packratted 'File' instances rather than file descriptors.
> 
> I've done a code inspection and the streams are all explicitly closed.
> There are a number of File objects used and I notice that File does
> not have a close() method so we have to rely on GC.

If there were a 'close()' method, as there is with streams, it would have nothing to do with GC.  'close()' is for resources (such as file handles).  GC is for heap memory.  I only suggested checking for packratted 'File' instances as a foolish guess.  Now that I think about it, it is highly unlikely that unclaimed instances would have anything to do with your issue.

>> Of course I'm shooting in the dark since you've said absolutely nothing about
>> your application, much less provided an http://sscce.org/.
> 
> I know.  It would be difficult to produce an example since I cannot
> reproduce the problem myself - it happens in production only and I
> don't have any access there.
> 
> I get the exception:
> java.io.IOException: Cannot run program "/path/to/script":
> java.io.IOException: error=24, Too many open files

Do you have any reason to believe it's your program that holds those files?

> The script is called via ProcessBuilder object and I don't see any
> obvious problems there.

Or subtle ones either, I guess.

An irreproducible problem involving disparate runtime environments (inside and outside the JVM), executing black-box code on an undisclosed platform, yielding an error message possibly originated by an entity outside the JVM with no data forthcoming - is that the issue with which you request assistance?

Note:  the preceding paragraph implies a path forward, in that a problem statement illuminates prospective solutions.  In case you missed it, the path forward is for you to gain visibility into that plethora of unknowns, or sadly report to your client, as we do to you, that with nothing to go on you have nothing to offer.

Visibility involves things like logging.  You do use logging, don't you?

As an extra benefit, the experience of using logs to diagnose a production issue will provide an object lesson into how useless most programmers are at designing logging, and give you insight into proper logging practices.

-- 
Lew

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Thread

java.io.File Mark <i@dontgetlotsofspamanymore.net> - 2011-12-02 09:35 +0000
  Re: java.io.File Lew <lewbloch@gmail.com> - 2011-12-02 07:25 -0800
    Re: java.io.File Mark <i@dontgetlotsofspamanymore.net> - 2011-12-02 15:55 +0000
      Re: java.io.File Lew <lewbloch@gmail.com> - 2011-12-02 08:17 -0800
        Re: java.io.File Mark <i@dontgetlotsofspamanymore.net> - 2011-12-02 16:31 +0000
          Re: java.io.File markspace <-@.> - 2011-12-02 08:53 -0800
          Re: java.io.File Lew <lewbloch@gmail.com> - 2011-12-02 14:02 -0800
            Re: java.io.File Arne Vajhøj <arne@vajhoej.dk> - 2011-12-02 17:12 -0500
              Re: java.io.File Lew <lewbloch@gmail.com> - 2011-12-02 14:16 -0800
                Re: java.io.File Arne Vajhøj <arne@vajhoej.dk> - 2011-12-02 18:42 -0500
                Re: java.io.File Lars Enderin <lars.enderin@telia.com> - 2011-12-03 01:06 +0100
                Re: java.io.File Jukka Lahtinen <jtfjdehf@hotmail.com.invalid> - 2011-12-07 15:51 +0200
            Re: java.io.File Mark <i@dontgetlotsofspamanymore.net> - 2011-12-05 15:14 +0000
              Re: java.io.File markspace <-@.> - 2011-12-05 07:49 -0800
                Re: java.io.File Mark <i@dontgetlotsofspamanymore.net> - 2011-12-05 16:28 +0000
              Re: java.io.File Lew <lewbloch@gmail.com> - 2011-12-05 15:25 -0800
                Re: java.io.File Mark <i@dontgetlotsofspamanymore.net> - 2011-12-06 10:29 +0000
          Re: java.io.File Arne Vajhøj <arne@vajhoej.dk> - 2011-12-02 17:08 -0500
      Re: java.io.File Roedy Green <see_website@mindprod.com.invalid> - 2011-12-03 00:57 -0800
    Re: java.io.File Mayeul <mayeul.marguet@free.fr> - 2011-12-02 17:33 +0100
      Re: java.io.File Lew <lewbloch@gmail.com> - 2011-12-02 14:07 -0800
        Re: java.io.File Mayeul <mayeul.marguet@free.fr> - 2011-12-06 15:52 +0100
          Re: java.io.File Lew <lewbloch@gmail.com> - 2011-12-06 09:23 -0800

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