WWW::Curl pause conflict

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

Im trying to understand why the following code wont run correctly, when Im using pause instead of sleep and WWW::Curl. This code will loop two times only and it will get stuck no matter how long I will wait. This happens in Linux, FreeBSD. Stuck here means, it does not continue the loop, seems stuck in pause ... Same construct, alarm,pause works fine if I dont use WWW::Curl, for other types of work.

use strict;
use warnings;
use WWW::Curl::Easy;
use POSIX qw(pause);
use Time::HiRes qw(time alarm setitimer sleep ITIMER_REAL);
use Getopt::Std;

###  Process command line args
usage() if defined $ARGV[0] and $ARGV[0] eq "--help";
getopts('hvV') or usage();

# process [interval [count]],
my ( $interval, $loop_max );
if ( defined $ARGV[0] ) {
    $interval = $ARGV[0];
    $loop_max = defined $ARGV[1] ? $ARGV[1] : 2**32;
    usage() if $interval == 0;
}
else {
    $interval = 1;
    $loop_max = 1;
}

###  Variables
my $loop = 0;              # current loop number


# how often do we trigger (seconds)?
my $first_interval = $interval;

# signal handler is empty
$SIG{ALRM} = sub { };

# first value is the initial wait, second is the wait thereafter
setitimer( ITIMER_REAL, $first_interval, $interval );

my $http = WWW::Curl::Easy->new();
if (&WWW::Curl::Easy::version() !~ /ssl|nss/i) {
    die "No SSL support";
}


# Get the results


while (1) {

my $url = "http://kronometrix.org/";
$http->setopt(CURLOPT_URL, $url);
my $retcode = $http->perform();

## Get the results
my $response =  $http->getinfo(CURLINFO_HTTP_CODE);

if ($retcode == 0) { 
    print "Ok, Status: $response\n"; 
} else { print "Error, Status: $response\n"; }

    ### Check for end
    last if ++$loop == $loop_max;

    ### Interval
    pause;
    # sleep $interval; 

}
[download]

and if I replace pause with sleep this works fine. Im using this alarms with timers to trigger certain actions at specific time intervals.

Anyone any ideas why WWW::Curl breaks down on pause or am I using this wrong ?. Many thanks for help.

Comment on WWW::Curl pause conflict Download Code

Replies are listed 'Best First'.
Re: WWW::Curl pause conflict by Anonymous Monk on Sep 20, 2015 at 23:47 UTC
From reading pause, you shouldn't be using pause, you should be using sleep	[reply]
Re^2: WWW::Curl pause conflict by krmx (Novice) on Sep 21, 2015 at 06:38 UTC
Additional: I was wrong - using sleep instead of pause does not work. there is no difference whatsoever between: `while (1) { my $url = "http://kronometrix.org/"; $http->setopt(CURLOPT_URL, $url); my $retcode = $http->perform(); ## Get the results my $response = $http->getinfo(CURLINFO_HTTP_CODE); if ($retcode == 0) { print "Ok, Status: $response\n"; } else { print "Error, Status: $response\n"; } ### Check for end last if ++$loop == $loop_max; ### Interval pause; }` [download] and `while (1) { my $url = "http://kronometrix.org/"; $http->setopt(CURLOPT_URL, $url); my $retcode = $http->perform(); ## Get the results my $response = $http->getinfo(CURLINFO_HTTP_CODE); if ($retcode == 0) { print "Ok, Status: $response\n"; } else { print "Error, Status: $response\n"; } ### Check for end last if ++$loop == $loop_max; ### Interval sleep; }` [download] The code gets stuck after 2 run samples. Always 2 . not sure why. It seems to me something between WWW::Culr (libcurl) and perl regarding alarms and timers.	[reply] [d/l] [select]
Re^3: WWW::Curl pause conflict by Anonymous Monk on Sep 21, 2015 at 07:00 UTC
Hmm , try turning off safe signals, see Perl::Unsafe::Signals Also try turning on cpan curl timeout , site:metacpan.org curl timeout , site:cpan.org curl timeout , -> https://metacpan.org/pod/WWW::Curl::Simple#connection_timeout-connection_timeout_ms/ https://metacpan.org/source/ANDREMAR/WWW-Curl-Simple-0.100191/lib/WWW/Curl/Simple.pm Read more... (1217 Bytes) http://search.cpan.org/grep?cpanid=SZBALINT&release=WWW-Curl-4.17&string=time&i=1&n=1&C=0 `t/01basic.t 20:ok(! $curl->setopt(CURLOPT_TIMEOUT, 30), "Setting CURLOPT_TIMEOUT") +;` [download]	[reply] [d/l] [select]
Re^4: WWW::Curl pause conflict by krmx (Novice) on Sep 21, 2015 at 07:17 UTC
Re^2: WWW::Curl pause conflict by krmx (Novice) on Sep 21, 2015 at 05:06 UTC
I understand that it is not safe to use sleep and a timer at the same time within Perl code. My sample uses POSIX timers and alarm. https://www.febo.com/pages/perl_alarm_code/ At the same time: this code works fine for other types of work, like here: https://github.com/kronometrix/recording/blob/master/bin/linux/cpurec	[reply]
Re^3: WWW::Curl pause conflict by Anonymous Monk on Sep 21, 2015 at 06:52 UTC
https://metacpan.org/pod/Time::HiRes#setitimer-which-floating_seconds-interval_floating_seconds says Use of interval timers may interfere with alarm(), sleep(), and usleep(). In standard-speak the "interaction is unspecified", which means that anything may happen: it may work, it may not.	[reply]
Re: WWW::Curl pause conflict by Anonymous Monk on Sep 21, 2015 at 18:46 UTC
Maybe the handle goes away somehow when you pause. What if you obtained www::curl each time in the loop?	[reply]