Unbuffered writes using Twiggy

[Gurunandan Bhat]

Hi, 

I am trying to understand streaming and I wrote this:

use AnyEvent;

my $app = sub {

    return sub {

        

  my $responder = shift;

  my $writer = $responder->([ 

  200, 

  [ 'Content-Type', 'text/plain' ]

  ]);

  $writer->write("Start : ${\scalar(localtime)}\n");

  my $count = 0;

  my $w;

  $w = AE::timer 0, 5, sub {

  my $time = scalar localtime;

  $writer->write("Its now: $time\n");

  if (++$count > 10) {

  $writer->write("Stopping: $time\n");

  $writer->close;

  undef $w;

  }

  };

};

};

and ran it under Twiggy (plackup -s Twiggy). But I find that rather than getting a line after every 5 seconds, I get the entire output after 50. 

What am I doing wrong?

Thank you

[Tatsuhiko Miyagawa]

Works for me with telnet by connection to localhost 5000.

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Tatsuhiko Miyagawa

[Gurunandan Bhat]

Thanks for responding. 

This is strange. I tried telnet localhost 5000, followed by GET / and got no response. But it works fine with "curl http://localhost:5000" - prints out the time every five seconds.

Why might this be?

On Sat, May 4, 2013 at 1:36 PM, Gurunandan Bhat <gb...@pobox.com> wrote:

Thanks for responding. 

This is strange. I tried telnet localhost 5000, followed by GET / and got no response. But it works fine with "curl http://localhost:5000" - prints out the time every five seconds.

Why might this be?

[Tatsuhiko Miyagawa]

You sure you sent two returns instead of one to indicate your request is done?

Otherwise no idea, especially since you didn't provide any information
how to run it, the whole output, versions of perl, etc.

On Sat, May 4, 2013 at 1:07 AM, Gurunandan Bhat

[Gurunandan Bhat]

My apologies. I did send two returns on telnet. Here is what I get:

nandan@knuth:~/Workspace/OdysseyPay$ telnet localhost 5000

Trying 127.0.0.1...

Connected to localhost.

Escape character is '^]'.

HTTP/1.0 400 Bad Request

Content-Type: text/plain

I am running perl-5.16.3 under perlbrew and the latest version of Plack 1.0024 and AnyEvent 7.04.

However running with curl gives me this:

nandan@knuth:~/Workspace/OdysseyPay$ curl http://localhost:5000

Start : Sat May  4 13:34:41 2013

Its now: Sat May  4 13:34:42 2013

Its now: Sat May  4 13:34:47 2013

Its now: Sat May  4 13:34:52 2013

Its now: Sat May  4 13:34:57 2013

Its now: Sat May  4 13:35:02 2013

Its now: Sat May  4 13:35:07 2013

Its now: Sat May  4 13:35:12 2013

Its now: Sat May  4 13:35:17 2013

Its now: Sat May  4 13:35:22 2013

Its now: Sat May  4 13:35:27 2013

Its now: Sat May  4 13:35:32 2013

Stopping: Sat May  4 13:35:32 2013

And the output is correctly buffered every 5 seconds.

[Gurunandan Bhat]

More info that I missed out. My Twiggy is also the latest 0.1021 and my command line is:

nandan@knuth:~/Workspace/OdysseyPay$ plackup -s Twiggy async.psgi 

Twiggy: Accepting connections at http://0.0.0.0:5000/

Thanks for your help....

[Gurunandan Bhat]

My apologies - This works with raw telnet (I was sending the protocol string in lowercase earlier -doh!) as well as with curl. 

But when I access it with a browser (both, Chrome version 27.0.1453.15, Firefox 20.0) - the output seems to be buffered and is sent to my browser only after I call close on the writer. 

Any help would be great.

Thanks

[Lee Aylward]

In my experience, some browsers do buffer streaming responses quite a bit. My hacks have included streaming JSON with padded with spaces so it would hit 1KB for each update. The default Android browser required an even higher size. I'd suggest using WebSockets or Server Sent Events depending on your needs.

--
Lee

[Gurunandan Bhat]

You are right - I padded the output and it works!

Thanks a ton.