Hung WWW::Selenium, waiting for the Selenium server response to a 'getNewBrowserSession' command

[joemcmahon]

I have an application which is invoked by a scheduler, i.e., unattended. Attached is a demo version of it, which very reliably reproduces the problem, under the right conditions, detailed below.

It uses:

• Test::WWW::Selenium ver. 1.35
• WWW::Selenium ver. Ver.1.35
• Test::Builder Ver. 0.98
• Test::More Ver. 0.98
• LWP::UserAgent Ver. 6.02
• HTTP::Request Ver. 6.00
• HTTP::Headers Ver. 6.05
• URI::Escape Ver. 3.31
• Time::HiRes qw(sleep) Ver. 1.9725
• Firefox ver. 19.0.2 (attached its "Troubleshooting Information", as copied from Firefox)
• run with perl v5.14.2 built for MSWin32-x64-multi-thread (with 1 registered patch, see perl -V for more detail) Binary build 1402 [295342] provided by ActiveState http://www.ActiveState.com, Built Oct 7 2011 15:19:36
• on a Windows-7 Pro (x64) machine (System info file attached)

After a long time (a day or two) of no use, but definitely, with 100% repeatability, after a boot up, it ALWAYS hangs and times out with a 500 status code.

I traced the point at which it is hung to the very first HTTP request to the Selenium server with the cmd = 'getNewBrowserSession', line 117, of the 'do_command sub. It results from the call to the 'new' method of 'WWW::Selenium' package, via the methods-chain 'start' -> 'get_string' -> 'do_command'. When in the hanging conditions I listed above (i.e., after boot-up, or after long inactivity), the HTTP request remains un-answered. It then times out after the 3 minutes of LWP's User_Agent + the extra wait you added in the 'ua' sub.

Also with 100% repeatability, once I abort both the Selenium server and the Perl client and restart the application, it NEVER hangs(!)

What seems as a work-around the problem is to place a 2 seconds 'sleep' between the system() call that fires up the Selenium server and the "$sel = Test::WWW::Selenium->new()" call.

My guess (educated I hope...) is that the system ($selenium_call_string) returns a bit too soon, before it is really ready to accept commands. That's why It hangs after a boot up. It works the second time around probably because Selenium is still memory resident. And again, it hangs after a long time of Selenium inactivity because it was purged from memory.

Can you verify that?

[joemcmahon]

Here's a demo.

# ------------------------------------------------------------
# A Selenium Perl client script to demonstrate its start-up
# hanging.
# ------------------------------------------------------------
use strict;
use warnings;
use Time::HiRes qw(sleep);
use Test::WWW::Selenium;
use Test::More "no_plan";
use Test::Exception;

my $selenium_dir        = 'D:/Meir/Dropbox/Data_base/Scripts/Selenium';
my $firefox_profile_dir = 'D:/Meir/Dropbox/Data_base/Scripts/Selenium';
my $selenium_jar_file   = 'selenium-server-standalone-2.28.0.jar';

my $sel;
my $selenium_call_string =
  "start cmd /k java -jar $selenium_dir/$selenium_jar_file ".
  "-firefoxProfileTemplate \"$firefox_profile_dir\"";

system ($selenium_call_string) == 0 or die "system call failed: $?\n";

print "Just fired up the Selenium server\n";

$sel = Test::WWW::Selenium->new(
  host        => "localhost",
  port        => 4444,
  browser     => "*firefox",
  browser_url => "http://www.tase.co.il/"
);

#eval {
#  local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required
#  alarm 15;
#  alarm 0;
#};
#if ($@) {
#  die unless $@ eq "alarm\n";   # propagate unexpected errors
#}

#sleep 10;

print "... and now its client\n";

my $url = "http://www.tase.co.il/Eng/general/company/Pages/companyHistoryData.aspx?companyID=000629&subDataType=0&shareID=00629014";

$sel->open_ok($url);
$sel->click_ok("id=history1");
$sel->click_ok("xpath=(//input[\@value='Display Data'])[2]");
$sel->wait_for_page_to_load_ok("60000");
$sel->click_ok("css=td.GreenTextBtn");
$sel->click_ok("link=TSV");
$sel->wait_for_pop_up_ok("_blank", "60000");

END
{
  $sel->shut_down_selenium_server();
}