Hmmm. Interesting.
So consider this:
I have a stream of data, which I'm sending to the POE::Wheel::Run process.
At an arbitrary time I can get a signal that the stream has ended, at which
point I want to shutdown the process's STDIN.
If I knew the last bit of data sent was going to be the last bit of data, I
could set a flag as I send it to the POE::Wheel::Run process, and then the
next StdinEvent could call stdin_shutdown. But I don't know which bit of
data is going to be the last.
So when I receive the signal to shutdown STDIN, I don't know if the STDIN
buffer is flushed or not (do I?). I can set a flag, but if it's already
flushed, the StdinEvent will never get called.
It seems I need a way to tell if there's anything pending in the buffer.
Checking $wheel->get_stdin_filter->get_pending() seems like a good bet, but
doesn't seem to be working -- it always seems to return false, even though
if I then call stdin_shutdown the data never arrives at my process.
Any suggestions? Am I missing something?
Thanks,
Dan
On 12/21/04 3:18 PM, "Rocco Caputo" <[EMAIL PROTECTED]> wrote:
> On Mon, Dec 20, 2004 at 10:44:23PM -0800, Dan McCormick wrote:
>>
>> Shouldn't the code below print 1, 2, 3, 4 on separate lines to the file
>> /tmp/test.txt?
>>
>> If I comment out lines 537-538 of POE::Wheel::Run.pm, namely:
>>
>> $poe_kernel->select_pause_write($self->[HANDLE_STDIN])
>> unless ($self->[OCTETS_STDIN]);
>>
>> ... things work as (I) expected. Some cursory debugging suggests POE isn't
>> flushing the buffer when the state returns, as the docs indicate.
>
> They don't quite work the way I expect, but I think you'll agree that
> teh problem's over in shutdown_stdin() (around line 872):
>
> # Shutdown the pipe that leads to the child's STDIN.
> sub shutdown_stdin {
> my $self = shift;
> return unless defined $self->[HANDLE_STDIN];
>
> $poe_kernel->select_write($self->[HANDLE_STDIN], undef);
>
> eval { local $^W = 0; shutdown($self->[HANDLE_STDIN], 1) };
> close $self->[HANDLE_STDIN] if $@;
> }
>
> The problem's fairly obvious. Your test case calls put() to prime the
> STDIN buffer, then it calls shutdown_stdin() to close STDIN.
> Unfortunately, the wheel also stops select_write() for the handle.
> That prevents the buffer from ever being flushed.
>
> The proper thing to do is perhaps to set a shutdown flag if there is
> pending input for the child process, and do the actual shutdown when
> the input has flushed.
>
>> Also, even with the commented-out lines, it looks like I still need the
>> 'doit' and 'shutdown' events to be separate (i.e., combining everything into
>> the _start event doesn't work). Is that behavior intentional?
>
> I think it's creating a race condition where your expected behavior
> occurs. It seems to be working only by coincidence.
