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Infinite Loop - Queue Processing - Running as a Service - Advice needed

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  • Infinite Loop - Queue Processing - Running as a Service - Advice needed

    I have a Scriptcase Blank application that runs a query to get records from a database table. It "processes" these records, then removes them.
    This is my "Queue" of what needs to be done.
    It works perfectly, the problem I have now is I need it to run this check every 5 seconds. I can not create a CRON job for less than 1 minute interval, not to mention that when it calls this blank application it might run for more than 1 minute and I don't want two instances of it running.

    I have googled solutions but not really found a good solution as it pertains to Scriptcase.
    PHP code that checks if the current script is running by its name does not work since all Scriptcase applications are called "index.php".

    I need an always running script, like an infinite loop... I tried doing a SC_redir at the end of my application redirecting back to itself with a 5 second SLEEP command... this works perfectly, but eventually dies... and I need it to run forever.

    Can anyone offer a suggestion on how to achieve this?

    Thank you for any suggestions!

  • #2
    Just an update on this... my application of type "Blank" works perfectly from the browser but if I call it directly from the command line ex: php Myapp.php it just returns CSS code to me and the PHP of the onExecute event does not appear to run.
    So my first step might be re-writing this application to not use Scriptcase specific macros and getting it to run from the command line. Then I can tackle getting only one instance of it running at a time.


    • #3
      I will report back if this works.... First thing, I did not have to rewrite my application... instead I am using wget in the cron job to call it on a scheduled basis, this runs it like its from a browser instead of from the command interpreter.

      Now to get it to run only one time and not any more than one time I am doing this:

      PHP Code:
      // In OnExecute of type "Blank" Application
      $running exec("ps -aux | grep QueueProcessor|grep -v grep|wc -l");

      $running<=2){ // while loop
      $running exec("ps -aux | grep QueueProcessor|grep -v grep|wc -l");

      /* All my code goes here */

      To explain whats happening here... I am calling this application via a Cron job where I am setting the output file for the wget to be a name "QueueProcessor.txt".

      My CronJob runs this command:
       wget -O /var/log/QueueProcessor.txt http://XXX.XXX.XXX.XXX/PATH/TO/APPLICATION
      So in my blank type application in the OnExecute I am checking the running processes for that name "QueueProcessor" by issuing the linux command:

      ps -aux | grep QueueProcessor|grep -v grep|wc -l
      This command is actually 4 statements with pipes between them.
      1. ps-aux - Lists all running processes
      2. grep QueueProcessor - Shows only those with the word "QueueProcessor" in them.
      3. grep -v grep - Removes the line of the grep statement itself
      4. wc -l - Thats a lower case L there... it counts how many lines are returned.

      For me the number of lines is always 2 when the cron job is running... so the loop only runs while there is only one instance of my application running.

      I am about to test to see if this works for me and will update/edit this post if not.


      • #4
        Just an update to this.... its not working. The fact is since I am calling the application via "wget" its creating an apache process that runs my code... causing an infinite loop since I am unable to find the apache process thats running my code. Even if I could find the apache process thats running my code I wouldn't want to kill it as the same process could be handling other user requests.

        So my next step is to figure out if there is any way to run a Scriptcase application from the console.... aka command line. I don't think thats possible.


        • #5
          You can achieve the infinite-loop in PHP which runs every 5 seconds with something like this:

          ini_set("max_execution_time", 0);
          function doAllTheJob(){
              // here you should do everything you need (database changes, etc)
          Then you just have to make sure that script/application doesn't run multiple times using some kind of lock:

          (the first answer, using socket, seems to fit better) :

          SC Tools: A browser extension to make working with ScriptCase simpler and even more productive.