Hi guys, I can't figure out how to read the return value of a function started in background. I tried to pass some values by reference or by using an object but with no luck.

How can I read the return value of a function called in background (when it's finished)?

For example this code:

function my_random($obj){
	$obj->parameter[0] = 1;
	watchdog('random' , $obj->parameter[0]);
}

function get_info($valori)
{
    $par = new StdClass();
    $par->parameter = array(0);
    $handle = background_process_start('my_random', $par);

    while(!background_process_is_finished($handle)){
    	dpm("wait");
    }

    if(background_process_is_finished($handle)){
    	dpm($par->parameter[0]);
    }

will always print '0', never '1'. Is there a way to do it? I saw that in the end line 574 of the .module is a call_user_func_array($process->callback, $process->args) so passing an object should work.

So is this somehow possible or it's not possible to read the values computed in background inside the main process?

Comments

surfingaround created an issue.

mcdoolz’s picture

mcdoolz CreditAttribution: mcdoolz commented

Hey there; I checked for the background process by storing the handle as a variable then checking for it when a restart of the process was sought.

When the process is started, it gets the variable (the handle for the process) and then uses background_process_get_process(variable) to get the process. If the process is not empty, then we have a process in progress and shouldn't do anything; else we start a process and set the variable anew.

Insofar as a call back when the process is finished goes, I would suggest having the process itself simply fire a function to set whatever value when finished.

I hope that helps.

surfingaround’s picture

surfingaround CreditAttribution: surfingaround commented

Thanks for the comment.

But still I don't get how to retry the return value of the callback!
If I have this code:

function foo(){
   return 1;
}

function bar(){
     background_process_start('foo');
}

where does the '1' returned from the foo() function get stored? I need to read that 1! I tried to pass a reference variable or an object, store the value to be returned in there and then when I look back at the object in the calling function nothing changed!
I think the solution to this stays in the way the 'args' are treated inside the background_process, since they are stored inside a db table and then retrieved when necessary. I tried to create another field called "return_value" in the db and store there the result of the call_user_func_array (which is the return value of the foo() function) but still I can't get it working. Any other idea? There must be an easier way to do this right?

mcdoolz’s picture

mcdoolz CreditAttribution: mcdoolz commented

Specifically speaking, I do not know.

Have you tried looking at the background_process object? That would make sense on the outset..

I haven't gone that far yet, but you can call the process up by handle using the function I showed above; then just spit it out with print_r or dpm.

surfingaround’s picture

surfingaround CreditAttribution: surfingaround commented

Well yeah I tried several times but there is some mess with the db which I cannot understand... even trying to update the db with the newer version of "args" does not help.

EDIT:
I solved by writing in the DB the returned value but it's definitely not a good solution. Still need more ideas.