Re: Controlling a Perl Daemon with Signals

[sk]

You are saying the script is not terminating right after the interrupt is issued?

I took your code and added a sub that i can test and also changed your TERM to INT so it is easy for me to test

#!/usr/bin/perl -w

use constant MAX_ITERATIONS => 1000000;
use constant MAX_TIME => 600;

use warnings;
use strict;

my $start_time = time;
my $iterations = 0;
my $exit_requested = 0;
my $handling_request = 0;

sub sig_handler {
    $exit_requested = 1;
    print "Caught interrupt\n";
#   exit(0) if !$handling_request;
}

sub handle_request {
    print ("hi: $iterations\n") if $iterations % 10000 == 0;
}

$SIG{INT} = \&sig_handler;

# init();

while (!$exit_requested && $iterations <= MAX_ITERATIONS && (time - $s
+tart_time) < MAX_TIME) {
    $handling_request = 1;
    handle_request();
    $iterations++;
    $handling_request = 0;
}

print ("Exit value: Iteration = $iterations exit_req = $exit_requested
+\n");

Output Here when I run the script and hit ^C while it is running I get this output

hi: 0
hi: 10000
hi: 20000
hi: 30000
hi: 40000
hi: 50000
hi: 60000
hi: 70000
hi: 80000
hi: 90000
hi: 100000
hi: 110000
hi: 120000
hi: 130000
Caught interrupt
Exit value: Iteration = 133660 exit_req = 1

Seems to suggest that it picked the interrupt and terminated the loop at that point.

Is this the behavior you want and you don't see that? Are you sure you are sending TERM signals?

-SK

[eastcoastcoder]

Right - I'm not getting that behaviour.

I am sure I'm sending term (kill -TERM <pid>)

Another fact: When I do kill -TERM, instead of exiting, the program seems to freeze, except that memory usage climbs indefintely - so it must be in some time of endless loop!

[sk]

I modified the code to handle TERM signal and sent TERM from command prompt. It caught correctly and gave me expected results.

I am guessing this not a web-based prog, if so I am not well-versed to explain why you it is not working for you.

Regarding the jch341277's reply on TERM signal, I am not sure whether it is applicable to your case. For example, If the program was entering the condition in the  while block, it should execute just one more time and quit as you do not modify  $exit_requested inside the while block. Other cases should terminate next time the while condition is evaluated

Can you try the sample program which prints "hi" and see if the same problem occurs. If it does it is very strange as it works just fine for me and I don't see any mistakes in your code.

However if the above sample code works but not your original code then you might have to check your  handle_request() sub.

-SK

[jch341277]

sk - I agree, it depends on what handle_request actually does. I just figured that it doesn't deal with the interruption gracefully; mainly because on my first attempt to run the code my handle_request looked like this:


sub handle_request {
   sleep 13;
   return 1;
}

Which looked like it was doing what the OP is having trouble with.