[Haskell-cafe] Re: sendfile leaking descriptors on Linux?

[MightyByte]

I've been seeing a steady stream of similar resource vanished messages
for as long as I've been running my happstack app.  This message I get
is this:

<socket: 58>: hClose: resource vanished (Broken pipe)

I run my app from a shell script inside a "while true" loop, so it
automatically gets restarted if it crashes.  This incurs no more than
a few seconds of down time.  Since that is acceptable for my
application, I've never put much effort into investigating the issue.
But I don't think the resource vanished error results in program
termination.  When I have looked into it, I've had similar trouble
reproducing it.  Clients such as wget and firefox don't seem to cause
the problem.  If I remember correctly it only happens with IE.

On Fri, Feb 5, 2010 at 2:56 AM, Bardur Arantsson <spam at scientician.net> wrote:
> Jeremy Shaw wrote:
>>
>> Actually,
>>
>> We should start by testing if native sendfile leaks file descriptors even
>> when the whole file is sent. We have a test suite, but I am not sure if it
>> tests for file handle leaking...
>>
>
> I should have posted this earlier, but the exact message I'm seeing in the
> case where the Bad Client disconnects is this:
>
>   hums: Network.Socket.SendFile.Linux: resource vanished (Broken pipe)
>
> Oddly, I haven't been able to reproduce this using a wget client with a ^C
> during transfer. When I "disconnect" wget with ^C or "pkill wget" or even
> "pkill -9 wget", I get this message:
>
>  hums: Network.Socket.SendFile.Linux: resource vanished (Connection reset by
> peer)
>
> (and no leak, as observed by "lsof | grep hums").
>
> So there appears to be some vital difference between the handling of the two
> cases.
>
> Another observation which may be useful:
>
> Before the sendfile' API change (Handle -> FilePath) in sendfile-0.6.x, my
> code used "withFile" to open the file and to ensure that it was closed. So
> it seems that withBinaryFile *should* also be fine. Unless the "Broken pipe"
> error somehow escapes the scope without causing a "close".
>
> I don't have time to dig more right now, but I'll try to see if I can find
> out more later.
>
> Cheers,
>
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