Debugging errors #55

sayanb · 2019-01-10T06:38:04Z

My code:

        $pool = Pool::create();

    	foreach ($xmlNode->childNodes as $item) {
            $pool[] = async(function () use ($item) {
                     //do stuff
                      ...
                     //do more stuff
                     ...
                }
            })->then(function ($output) {
                //handle success
            })->catch(function ($ex) {
                echo PHP_EOL . "something happened, exception. Error: ".$ex->getMessage();
            })->timeout(function () {
                echo PHP_EOL . "timed out";
            });
    	}
        await($pool);

Output:

something happened, exception. Error:
something happened, exception. Error:
something happened, exception. Error:
something happened, exception. Error:
something happened, exception. Error:
something happened, exception. Error:
something happened, exception. Error:
something happened, exception. Error:
something happened, exception. Error:
something happened, exception. Error:

How do I debug the issue? The exception message doesn't seem to be showing. If I just log the exception, instead of the message, I get:

something happened, exception. Error: Spatie\Async\Output\ParallelError in /home/sayan/Documents/Programming/spatie_test/vendor/spatie/async/src/Output/ParallelError.php:11
Stack trace:
#0 /home/sayan/Documents/Programming/spatie_test/vendor/spatie/async/src/Process/ParallelProcess.php(126): Spatie\Async\Output\ParallelError::fromException('')
#1 /home/sayan/Documents/Programming/spatie_test/vendor/spatie/async/src/Process/ProcessCallbacks.php(51): Spatie\Async\Process\ParallelProcess->resolveErrorOutput()
#2 /home/sayan/Documents/Programming/spatie_test/vendor/spatie/async/src/Pool.php(197): Spatie\Async\Process\ParallelProcess->triggerError()
#3 /home/sayan/Documents/Programming/spatie_test/vendor/spatie/async/src/Pool.php(285): Spatie\Async\Pool->markAsFailed(Object(Spatie\Async\Process\ParallelProcess))
#4 /home/sayan/Documents/Programming/spatie_test/vendor/spatie/async/src/Runtime/ParentRuntime.php(70): Spatie\Async\Pool->Spatie\Async{closure}(17, Array)
#5 /home/sayan/Documents/Programming/spatie_test/vendor/spatie/async/src/helpers.php(15): Spatie\Async\Runtime\ParentRuntime::createProcess(Object(Closure))
#6 /home/sayan/Documents/Programming/spatie_test/test.php(84): async(Object(Closure))
#7 /home/sayan/Documents/Programming/spatie_test/test.php(50): Test->getListings(Object(DOMElement))
#8 /home/sayan/Documents/Programming/spatie_test/test.php(221): Test->process()
#9 {main}

The text was updated successfully, but these errors were encountered:

brendt · 2019-01-10T07:33:54Z

Difficult to say what to do in this specific case, but I'd like to help you debug this further.

The starting point would be https://github.com/spatie/async/blob/master/src/Process/ParallelProcess.php#L117

When a child processes encounters an error, it will serialize it and pass it to the parent process. This is where that is handled. I'd start by inspecting the output from getErrorOutput, to see what's passed from the child process to the parent.

If there's no useful information in the output, we'll have to look in the child process itself. Take a look at https://github.com/spatie/async/blob/master/src/Runtime/ChildRuntime.php. The try/catch is what's passing the exception to the parent process. There's two ways of debugging the child process:

either run the child process on its own, or write the output from within the child process to a file. The latter is often the more easy one. You could for example write the message of the caught exception to a log file.

brendt · 2019-01-10T07:34:47Z

Please let me know when you found what happened, if possible I'd like this package to handle all errors in a debugable way.

sayanb · 2019-01-10T08:17:28Z

Thanks @brendt . In my code example, where should I look for getErrorOutput()? I see that it's a method in ParallelProcess class, whereas the exception class is ParallelError. .

brendt · 2019-01-10T10:29:40Z

Sorry if I didn't make myself clear: it's possible that there's in issue within this package with error handling, and these debug tips should be done in the vendor files.

Another option is to fork this repo locally and link it via your composer file.

sayanb · 2019-01-11T02:56:19Z

I decided to implement this in a CodeIgniter 3 project, and now I am getting some warnings.

The full code now:

<?php 
use Spatie\Async\Pool;
use Spatie\Async\Process;

class Paralleltest extends MY_Controller {

    public function spatie() {
    	$cities = array(
    		array('sydney', 'melbourne', 'brisbane'),
    		array('san francisco', 'boston', 'detroit'),
    		array('london, manchester, bristol'),
    		array('beijing, shanghai, shenzhen'),
    		array('kolkata', 'mumbai', 'delhi')
    	);

    	$start = time();
    	$pool = Pool::create();

    	echo PHP_EOL . "is parallelism supported? " . Pool::isSupported();

		foreach ($cities as $key => $city) {
			echo PHP_EOL . "sending city list ".json_encode($city)." to child, which will capitalise them and sleep for 5 seconds";
		    
		    $pool[] = async(function () use ($city) {
		        foreach ($city as $cityKey => $cityVal) {
		        	$upperCity = $this->capitalize($cityVal);
		        	$city[$cityKey] = $upperCity;
		        }
		        
		        sleep(5);
		        return json_encode($city);
		    })->then(function ($output) {
		        echo PHP_EOL . "back in main thread, got $output from child thread";
		    })->catch(function ($exception) {
        		echo PHP_EOL . "something happened. Error: " . $exception->getMessage();
    		});
		}

		await($pool);
		$end = time();
		echo PHP_EOL . "goodbye from parent. Time taken: " . ($end - $start) . PHP_EOL;
    }

    private function capitalize($cityVal) {
    	return strtoupper($cityVal);
    }
    
}

The logs are

is parallelism supported? 1
sending city list ["sydney","melbourne","brisbane"] to child, which will capitalise them and sleep for 5 seconds
sending city list ["san francisco","boston","detroit"] to child, which will capitalise them and sleep for 5 seconds
sending city list ["london, manchester, bristol"] to child, which will capitalise them and sleep for 5 seconds
sending city list ["beijing, shanghai, shenzhen"] to child, which will capitalise them and sleep for 5 seconds
sending city list ["kolkata","mumbai","delhi"] to child, which will capitalise them and sleep for 5 seconds
something happened. Error: PHP Warning: Class 'Paralleltest' not found in /home/sayan/Documents/Programming/testing/vendor/opis/closure/src/SerializableClosure.php on line 232
PHP Warning: call_user_func() expects parameter 1 to be a valid callback, no array or string given in /home/sayan/Documents/Programming/testing/vendor/spatie/async/src/Runtime/ChildRuntime.php on line 25

something happened. Error: PHP Warning: Class 'Paralleltest' not found in /home/sayan/Documents/Programming/testing/vendor/opis/closure/src/SerializableClosure.php on line 232
PHP Warning: call_user_func() expects parameter 1 to be a valid callback, no array or string given in /home/sayan/Documents/Programming/testing/vendor/spatie/async/src/Runtime/ChildRuntime.php on line 25

goodbye from parent. Time taken: 0

sayanb · 2019-01-11T02:58:41Z

Note, if I replace

$upperCity = $this->capitalize($cityVal);

with

$upperCity = strtoupper($cityVal);
It works, so the issue seems to be in the child failing to create the object somehow?

brendt · 2019-01-11T07:40:42Z

Yeah, you cannot simply reference the $this context from within a child process. Remember that it's a completely new PHP process, and only the function passed in the async function will be executed there.

Take a look at tasks if you want to better structure your code: https://github.com/spatie/async#working-with-tasks

I'm going to close this issue for now, as there doesn't seem to be a problem in the package. But feel free to keep commenting.

sayanb · 2019-01-11T08:09:41Z

Thank you. If the README.md could be updated with a simple example of this library working in an object-oriented setup (similar to the async/await examples, with actual code), it would be really helpful! I had a look at the Tasks link, but the usage wasn't exactly clear to me.

developeronboard · 2020-02-19T12:37:44Z

yes sayanb real case examples are not found..did you found any codes related to this??if so kindly reply me.

iprastha · 2021-05-13T09:50:06Z

Thank you. If the README.md could be updated with a simple example of this library working in an object-oriented setup (similar to the async/await examples, with actual code), it would be really helpful! I had a look at the Tasks link, but the usage wasn't exactly clear to me.

I'm in the same position, with codeigniter 3 project as well. Did you find any solution to this?

brendt closed this as completed Jan 11, 2019

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Debugging errors #55

Debugging errors #55

sayanb commented Jan 10, 2019

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iprastha commented May 13, 2021

Debugging errors #55

Debugging errors #55

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sayanb commented Jan 10, 2019

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brendt commented Jan 10, 2019

sayanb commented Jan 10, 2019

brendt commented Jan 10, 2019

sayanb commented Jan 11, 2019

sayanb commented Jan 11, 2019

brendt commented Jan 11, 2019

sayanb commented Jan 11, 2019

developeronboard commented Feb 19, 2020

iprastha commented May 13, 2021