cheshirecat has asked for the wisdom of the Perl Monks concerning the following question:

Hi all,

I'm having major problems with LWP and timeouts.
As it stands, my cgi script is making a request of a 3rd party site which occasionally takes more than 10 seconds to fufill.
What I want to do is cancel the request if it takes longer than 3 seconds (it usually completes in this time but sometimes not).
Here's a code snippet, any comments welcome

my $timeout = 3
 my $timedout = 0;
 my $oops = 0;
 my $error;
 my $stime;
 my $etime;
 eval  {
         local $SIG{ALRM} = sub { die "timeout\n" }; # die out of eval
+ statement not entire program
         alarm $timeout;
         $stime = time; # make a note of the time now
     $result = $ua->request($req); # make request of website
     $etime = time; # make a note of the time now
         alarm 0;
        };
  if ($@)
  {
  if ($@ eq "timeout\n") { $timedout = 1; }
   if ($@ and $@ ne "timeout\n") { $oops = 1; } # if there was an erro
+r in the eval and it wasn't the alarm
 }
 
 $error = $timedout || $oops;
 my $dtime = $etime - $stime; # figure out the time taken for the requ
+est
 
 if (!$error)
 {
  open(TEST,">/var/tmp/t4.txt");
  print TEST "http result\n";
# here I get told that the request took 10 seconds and my time out is 
+3 seconds
  print TEST $result->status_line." : $dtime secs taken, timeout = $ti
+meout\n";
 
  # print TEST "ok\n";
  close(TEST);
 }
 else
 {
  open(TEST,">/var/tmp/t4.txt");
  if ($oops) 
    { print TEST "oops error occurred: $@\n"; }
  else
    { print TEST "timeout\n";} 
  close(TEST);   
 }

[download]
Cheers Cheshire Cat

Replies are listed 'Best First'.
Re: Problems trying to timeout LWP requests
by rob_au (Abbot) on Feb 06, 2002 at 12:25 UTC
    There's a much easier way to do this - You can set the timeout for the connection by calling the timeout method on your LWP::UserAgent object.

    For example:

    my $ua = LWP::UserAgent->new;
$ua->timeout(3); # Sets a three-second timeout

    [download]

    By default, this timeout method is set to 180 seconds (3 minutes) - This is described in the LWP documentation. Additionally, the use_alarm method can be used to set/get a value indicating whether to use alarm when implementing timeouts - This is useful if you make use of alarm elsewhere in your applications.

     

    perl -e 's&&rob@cowsnet.com.au&&&split/[@.]/&&s&.com.&_&&&print'

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        The request is working and the host is responding okay but for purposes of testing the timeout I have chosen a value sufficiently low that the request should be cancelled anyway.

        I have looked at the results of Super Search and I believe this is a common question to which nobody has been able to give a satisfactory answer.

        I have now emailed Gisle Aas to see if he can throw any light on the question.

        Cheers

        Cheshire Cat

[reply]
      I've tried using $ua->timeout(3); and it does not work for me,
      this was why I was trying the alarm method.

      As for use_alarm, see the code below from UserAgent.pm

      # depreciated
sub use_eval   { shift->_elem('use_eval',  @_); }
sub use_alarm
{
    Carp::carp("LWP::UserAgent->use_alarm(BOOL) is a no-op")
    if @_ > 1 && $^W;
    "";
}

      [download]

      It appears that the documentation is out of date as this method is now depreciated.

      Cheers

      Cheshire Cat

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Re: Problems trying to timeout LWP requests
by cheshirecat (Sexton) on Feb 06, 2002 at 12:18 UTC
    Hi again, Forgot to say, running on Solaris with LWP 5.63 Cheers Cheshire Cat
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