[Haskell-cafe] sendfile leaking descriptors on Linux?

[Jeremy Shaw]

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...

- jeremy


On Thu, Feb 4, 2010 at 7:58 PM, Jeremy Shaw <jeremy at n-heptane.com> wrote:

> Well, that's not good.
>
> I wonder how we are supposed to know that the client has disconnected... We
> use withBinaryFile to open the file, so if an uncaught except is being
> thrown then that should close the file handle..
>
> If you look in Network.Socket.SendFile.Linux, you will see that when the C
> sendfile() function returns -1, we throw an exception, unless it is the
> EAGAIN error. So, that should cause us to close the files when an error
> occurs.
>
> There is one possible odd case.. if sendfile returns 0, then we assume
> nothing went wrong and keep trying to resend the data until everything is
> sent. If it keeps returning 0 then we just keep trying even though nothing
> is happening. (Or if we keep getting EAGAIN errors..). But I am not sure
> that either of these cases would actually happen in practice.
>
> Another cause might be if threadWaitWrite is just never returning after the
> client disconnects..
>
> - jeremy
>
>
>
> On Thu, Feb 4, 2010 at 1:43 PM, Bardur Arantsson <spam at scientician.net>wrote:
>
>> Hi all,
>>
>> I've been using the sendfile package off Hackage, but it seems to be
>> leaking file descriptors when using the Linux-native build.
>>
>> What's happening in my specific case is the following:
>>
>>   1) client requests a range of a file
>>   2) server starts sending the range
>>   3) client disconnects before receiving the whole file
>>
>> This happens over and over with the client requesting different ranges of
>> the file (so the client does make progress).
>>
>> If I use the portable build of the sendfile package, everything works fine
>> for hours and hours of this happening.
>>
>> If I use the Linux-native build of the sendfile package, the server
>> will eventually run out of file descriptors. According to "lsof" the files
>> that are being kept open are the data files being sent in 2) above.
>>
>> This is on GHC 6.10.x (Ubuntu).
>>
>> Is anyone else seeing this? Anyone got any idea what's going on?
>>
>> Cheers,
>>
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>>
>
>
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