Question

To optimize my Perl application I need to work with async HTTP requests, so I can handle other operations once the HTTP response is finish. So I believe my only option is to work with HTTP::Async module. This works fine for simple requests, but I need to catch cookie header from one response and send it with next one, so I need to read headers. My code is:

             ...

             $async->add($request);
             while ($response = $async->wait_for_next_response)
             {
               threads->yield(); yield();
             }
             $cookie = $response->header('Set-Cookie');
             $cookie =~ s/;.*$//;
             $request->header('Cookie' => $cookie);

             ...

but it’s not working, as it ends with an error Can’t call method “header” on an undefined value. Obviously $response is undef. How can I catch headers before $response gets undef?

Answer 1

while ($response = $async->wait_for_next_response)
{
  threads->yield(); yield();
}

Is guaranteed not to finish until $response is false. The only false value wait_for_next_response will return is undef. You need to either extract the cookie inside the loop, or cache the last good response inside the loop.

Something like

my $last_response;
while ($response = $async->wait_for_next_response)
{
  $last_response = $response;
  threads->yield(); yield();
}

should work, although I’m not sure you need the loop at all. It’s hard to tell without a complete program.