[systemd-devel] OT: Which tool to use to restart service if check-script fails

[Reindl Harald]

Am 27.05.2016 um 06:48 schrieb Thomas Güttler:
> OK, I understand that I need different tool to restart a service
> if a check-script fails.
>
> In my case the check script will be custom code. But the restart stuff
> is very general and reusable:
>
>  Step1: Call check-script
>  Step2: If exit 0 (meaning service is working), then wait N seconds, got
> to Step1
>  Step3: Service is not working: Send process the signal TERM_SIGNAL
> (should be configurable)
>  Step4: Wait N seconds until process terminated.
>  Step5: If process did terminate, restart the service. Wait, go to Step1
>  Step6: Process did not terminate: Wait N seconds, Send signal KILL
>  Step7: Wait until OS has cleaned up the service
>  Step8: Restart the service, Wait, got to Step1
>
> I could implement these steps myself, but I am lazy. I guess this
> has already been done several times before.
>
> Any tool recommendation?

that are just a few lines code in any programming language

your logic is way too complex - just SIGTERM and SIGKILL the service and 
a proper configured systemd-unit with "Restart=always" will 
automatically restarted when you shoot the main process in the head

also; if the service was *manually* stopped it will keep stopped because 
the kill-calls won't do anything
_________________________

[root at testserver:~]$ cat /etc/systemd/system/monitor-dbmail-lmtpd.service
[Unit]
Description=monitor dbmail-lmtpd
After=dbmail-lmtpd.service

[Service]
Type=simple
ExecStart=/usr/local/bin/check-dbmail-service.php 24 dbmail-lmtpd
Restart=always
RestartSec=1
TimeoutSec=5
Nice=19
IOSchedulingClass=3
User=dbmail
Group=dbmail
PrivateTmp=yes
PrivateDevices=yes
NoNewPrivileges=yes
CapabilityBoundingSet=CAP_KILL
ReadOnlyDirectories=/etc
ReadOnlyDirectories=/usr 
 

 
 

[Install] 
 

WantedBy=multi-user.target
________________________________________
 
 

[root at testserver:~]$ cat /usr/local/bin/check-dbmail-service.php 
 

#!/usr/bin/php 
 

<?php 
 

  /** make sure we are running as shell-script */
  if(PHP_SAPI != 'cli')
  {
   exit('FORBIDDEN');
  }

  /** verify that port and binary-name are given */
  if(empty($_SERVER['argv'][1]) || empty($_SERVER['argv'][2]))
  {
   exit('USAGE: check-dbmail-service <port> <process-name>' . "\n");
  }

  /** delay monitoring for 30 seconds */
  sleep(30);

  /** service loop */
  while(1 == 1)
  {
   if(!check_service())
   {
    sleep(5);
    if(!check_service())
    {
     passthru('/usr/bin/killall -s SIGTERM ' . 
escapeshellarg($_SERVER['argv'][2]));
     usleep(750000);
     passthru('/usr/bin/killall -s SIGKILL ' . 
escapeshellarg($_SERVER['argv'][2]));
    }
   }
   sleep(30);
  }

  /**
   * check if service is available and responds
   *
   * @access public
   * @return boolean
  */
  function check_service()
  {
   $errno  = 0;
   $errstr = '';
   $fp = @fsockopen('tcp://127.0.0.1', $_SERVER['argv'][1], $errno, 
$errstr, /**$timeout*/5);
   if($fp)
   {
    $response = @fgets($fp, 128);
    @fclose($fp);
    if(!empty($response))
    {
     return true;
    }
    else
    {
     return false;
    }
   }
   else
   {
    return false;
   }
  }
?>



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