[Workflow] Introducing the workflow component #11882

lyrixx · 2014-09-08T16:55:24Z

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Tests pass?	not yet
Fixed tickets	n/a
License	MIT
Doc PR	n/a

TODO:

Add tests
Add PHP doc
Add Symfony fullstack integration (Config, DIC, command to dump the state-machine into graphiz format)

So why another component?

This component take another approach that what you can find on Packagist.

Here, the workflow component is not tied to a specific object like with Finite. It means that the component workflow is stateless and can be a symfony service.

Some code:

#!/usr/bin/env php
<?php

require __DIR__.'/vendor/autoload.php';

use Symfony\Component\EventDispatcher\Debug\TraceableEventDispatcher;
use Symfony\Component\EventDispatcher\EventDispatcher;
use Symfony\Component\Stopwatch\Stopwatch;
use Symfony\Component\Workflow\Definition;
use Symfony\Component\Workflow\Dumper\GraphvizDumper;
use Symfony\Component\Workflow\Marking;
use Symfony\Component\Workflow\MarkingStore\PropertyAccessorMarkingStore;
use Symfony\Component\Workflow\MarkingStore\ScalarMarkingStore;
use Symfony\Component\Workflow\Transition;
use Symfony\Component\Workflow\Workflow;

class Foo
{
    public $marking;

    public function __construct($init = 'a')
    {
        $this->marking = $init;
        $this->marking = [$init => 1];
    }
}

$fooDefinition = new Definition(Foo::class);
$fooDefinition->addPlaces([
    'a', 'b', 'c', 'd', 'e', 'f', 'g',
]);

//                                           name  from        to
$fooDefinition->addTransition(new Transition('t1', 'a',        ['b', 'c']));
$fooDefinition->addTransition(new Transition('t2', ['b', 'c'],  'd'));
$fooDefinition->addTransition(new Transition('t3', 'd',         'e'));
$fooDefinition->addTransition(new Transition('t4', 'd',         'f'));
$fooDefinition->addTransition(new Transition('t5', 'e',         'g'));
$fooDefinition->addTransition(new Transition('t6', 'f',         'g'));

$graph = (new GraphvizDumper())->dump($fooDefinition);

$ed = new TraceableEventDispatcher(new EventDispatcher(), new Stopwatch(), new \Monolog\Logger('app'));

// $workflow = new Workflow($fooDefinition, new ScalarMarkingStore(), $ed);
$workflow = new Workflow($fooDefinition, new PropertyAccessorMarkingStore(), $ed);

$foo = new Foo(isset($argv[1]) ? $argv[1] : 'a');

$graph = (new GraphvizDumper())->dump($fooDefinition, $workflow->getMarking($foo));

dump([
    'AvailableTransitions' => $workflow->getAvailableTransitions($foo),
    'CurrentMarking' => clone $workflow->getMarking($foo),
    'can validate t1' => $workflow->can($foo, 't1'),
    'can validate t3' => $workflow->can($foo, 't3'),
    'can validate t6' => $workflow->can($foo, 't6'),
    'apply t1' => clone $workflow->apply($foo, 't1'),
    'can validate t2' => $workflow->can($foo, 't2'),
    'apply t2' => clone $workflow->apply($foo, 't2'),
    'can validate t1 bis' => $workflow->can($foo, 't1'),
    'can validate t3 bis' => $workflow->can($foo, 't3'),
    'can validate t6 bis' => $workflow->can($foo, 't6'),
]);

The workflown:

The output:

array:10 [
  "AvailableTransitions" => array:1 [
    0 => Symfony\Component\Workflow\Transition {#4
      -name: "t1"
      -froms: array:1 [
        0 => "a"
      ]
      -tos: array:2 [
        0 => "b"
        1 => "c"
      ]
    }
  ]
  "CurrentMarking" => Symfony\Component\Workflow\Marking {#19
    -places: array:1 [
      "a" => true
    ]
  }
  "can validate t1" => true
  "can validate t3" => false
  "can validate t6" => false
  "apply t1" => Symfony\Component\Workflow\Marking {#22
    -places: array:2 [
      "b" => true
      "c" => true
    ]
  }
  "apply t2" => Symfony\Component\Workflow\Marking {#47
    -places: array:1 [
      "d" => true
    ]
  }
  "can validate t1 bis" => false
  "can validate t3 bis" => true
  "can validate t6 bis" => false
]

webmozart · 2014-09-08T17:09:39Z

Hi @lyrixx, thank you for your PR! Before I review the code in detail, I'd like to know why you don't propose your changes to yohang/Finite? Their code and docs look useful so far, and I'd rather see an existing project improved than starting completely new efforts.

lyrixx · 2014-09-08T17:22:18Z

@webmozart Actually, I did not start this work (as you can see in the commit history). But I think he did not PR finite because the initial design was flawed. So a full rewrite was needed. Then, adding this kind of component to symfony will give more visibility and a community support than in a standalone library (as good as it can be). Finally, as sate on symfony.com Symfony is a set of reusable PHP components and this kind of component deserve much more visibility. I see too much people implementing kind of state machine, instead of using a real one, just because they did not know this problematic exists and there are solutions.

stof · 2014-09-08T17:24:48Z

Symfony/Bridge/Twig/Extension/WorkflowExtension.php

+    public function getFunctions()
+    {
+        return array(
+            'can' => new \Twig_Function_Method($this, 'canTransition'),


IMO, can is too generic as name. The risk of conflicts is too high here, and it is probably not clear in templates

Indeed, isEnabled would be a better name

is_enabled is still far too generic. You can have many enabled things which have nothing to do with workflows (users can be enabled in Symfony for instance).

Thus, I don't see how is_enabled would give you the meaning of being allowed to follow this transition

isEnabled is the exact Petrinet term for saying a transition may fire. Maybe transition_enabled or workflow_transition_enabled would be better to avoid confusion with other enabled things yes

Because a state machine is a graph the real term is "transition exists" or something like that. Whether or not you can move from one state to another depends on the presence (or absence) of an edge between nodes, but there is no flag "enabled".

@kingcrunch this is wrong. Even if the transition exists on the current state, you might not be able to apply it because of guards

What about throwing exception when transition is not applyable?

the goal of this function is to be able to knwo whether you can perform this transition. the use case is knowing whether you should display a button triggering it in the interface. Exceptions have nothing to do here. This function does not attempt to apply the transition, but only to know whether it is possible

Didn't look at the file the function was...

cordoval · 2014-09-08T17:36:50Z

@lyrixx i agree that it needs visibility. However, I would like to know the thoughts of @winzou https://github.com/winzou/state-machine (more official imo than finite lib) since his has reached a good level. Sylius already uses this successfully and several other projects (though still a simple SM). Going to a petri net implementation (this other is not but related http://github.com/vespolina/workflow) cc/ @iampersistent could be very good, but the state of this component is not that right now and there seems to be a big gap. reference workflowpatterns.com. Other than that 👍 to learn of a good colored petri net attempt!

stof · 2014-09-08T17:36:57Z

Symfony/Component/Workflow/Dumper/GraphvizDumper.php

+     */
+    private function dotize($id)
+    {
+        return strtolower(preg_replace('/[^\w]/i', '_', $id));


you don't need to transform the states and transformation names if you apply escaping on the node names properly instead

stof · 2014-09-08T18:29:57Z

@cordoval https://github.com/winzou/state-machine suffers from the same architecture flaw than Finite: the state machine is built around the object, so you cannot make it a service. If you have several objects which need to follow the workflow, you need to instantiate a separate state machine for each of them.

Note that when I'm saying architecture flaw, it does not mean it is entirely bad. But it does not fit in a DI context. It depends of the architecture of your projects (putting the state machine in the object itself can look the right way when using active record with propel for instance: http://williamdurand.fr/StateMachineBehavior/)

cordoval · 2014-09-08T18:37:37Z

i see, so the idea is to freeze things into the container as well. I am getting the gist of it now. Agree 👍

peterrehm · 2014-09-08T18:38:07Z

@lyrixx In the sample code in the PR you have a typo with $foor where you meant $foo. And also the variable $order should be renamed to $foo or $foo/$foor should be renamed to $order.

florianv · 2014-09-08T18:44:42Z

Symfony/Component/Workflow/Event/GuardEvent.php

+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class GuardEvent extends Event


Normally guards are attached to the transitions and part of the workflow definition (which could be persisted)

trompette · 2014-09-08T18:56:23Z

I contributed a small component for a project we did at Alter Way: https://github.com/alterway/component-workflow. I'm not sure if it is possible, but some ideas could be shared.

lyrixx · 2016-06-22T15:19:11Z

I think I have fixed all reported issues.

fabpot · 2016-06-23T12:40:16Z

Thank you @lyrixx.

… lyrixx) This PR was merged into the 3.2-dev branch. Discussion ---------- [Workflow] Introducing the workflow component | Q | A | ------------- | --- | Bug fix? | no | New feature? | yes | BC breaks? | no | Deprecations? | no | Tests pass? | not yet | Fixed tickets | n/a | License | MIT | Doc PR | n/a TODO: * [x] Add tests * [x] Add PHP doc * [x] Add Symfony fullstack integration (Config, DIC, command to dump the state-machine into graphiz format) So why another component? This component take another approach that what you can find on [Packagist](https://packagist.org/search/?q=state%20machine). Here, the workflow component is not tied to a specific object like with [Finite](https://github.com/yohang/Finite). It means that the component workflow is stateless and can be a symfony service. Some code: ```php #!/usr/bin/env php <?php require __DIR__.'/vendor/autoload.php'; use Symfony\Component\EventDispatcher\Debug\TraceableEventDispatcher; use Symfony\Component\EventDispatcher\EventDispatcher; use Symfony\Component\Stopwatch\Stopwatch; use Symfony\Component\Workflow\Definition; use Symfony\Component\Workflow\Dumper\GraphvizDumper; use Symfony\Component\Workflow\Marking; use Symfony\Component\Workflow\MarkingStore\PropertyAccessorMarkingStore; use Symfony\Component\Workflow\MarkingStore\ScalarMarkingStore; use Symfony\Component\Workflow\Transition; use Symfony\Component\Workflow\Workflow; class Foo { public $marking; public function __construct($init = 'a') { $this->marking = $init; $this->marking = [$init => true]; } } $fooDefinition = new Definition(Foo::class); $fooDefinition->addPlaces([ 'a', 'b', 'c', 'd', 'e', 'f', 'g', ]); // name from to $fooDefinition->addTransition(new Transition('t1', 'a', ['b', 'c'])); $fooDefinition->addTransition(new Transition('t2', ['b', 'c'], 'd')); $fooDefinition->addTransition(new Transition('t3', 'd', 'e')); $fooDefinition->addTransition(new Transition('t4', 'd', 'f')); $fooDefinition->addTransition(new Transition('t5', 'e', 'g')); $fooDefinition->addTransition(new Transition('t6', 'f', 'g')); $graph = (new GraphvizDumper())->dump($fooDefinition); $ed = new TraceableEventDispatcher(new EventDispatcher(), new Stopwatch(), new \Monolog\Logger('app')); // $workflow = new Workflow($fooDefinition, new ScalarMarkingStore(), $ed); $workflow = new Workflow($fooDefinition, new PropertyAccessorMarkingStore(), $ed); $foo = new Foo(isset($argv[1]) ? $argv[1] : 'a'); $graph = (new GraphvizDumper())->dump($fooDefinition, $workflow->getMarking($foo)); dump([ 'AvailableTransitions' => $workflow->getAvailableTransitions($foo), 'CurrentMarking' => clone $workflow->getMarking($foo), 'can validate t1' => $workflow->can($foo, 't1'), 'can validate t3' => $workflow->can($foo, 't3'), 'can validate t6' => $workflow->can($foo, 't6'), 'apply t1' => clone $workflow->apply($foo, 't1'), 'can validate t2' => $workflow->can($foo, 't2'), 'apply t2' => clone $workflow->apply($foo, 't2'), 'can validate t1 bis' => $workflow->can($foo, 't1'), 'can validate t3 bis' => $workflow->can($foo, 't3'), 'can validate t6 bis' => $workflow->can($foo, 't6'), ]); ``` The workflown: ![workflow](https://cloud.githubusercontent.com/assets/408368/14183999/4a43483c-f773-11e5-9c8b-7f157e0cb75f.png) The output: ``` array:10 [ "AvailableTransitions" => array:1 [ 0 => Symfony\Component\Workflow\Transition {#4 -name: "t1" -froms: array:1 [ 0 => "a" ] -tos: array:2 [ 0 => "b" 1 => "c" ] } ] "CurrentMarking" => Symfony\Component\Workflow\Marking {#19 -places: array:1 [ "a" => true ] } "can validate t1" => true "can validate t3" => false "can validate t6" => false "apply t1" => Symfony\Component\Workflow\Marking {#22 -places: array:2 [ "b" => true "c" => true ] } "apply t2" => Symfony\Component\Workflow\Marking {#47 -places: array:1 [ "d" => true ] } "can validate t1 bis" => false "can validate t3 bis" => true "can validate t6 bis" => false ] ``` Commits ------- 078e27f [Workflow] Added initial set of files 17d59a7 added the first more-or-less working version of the Workflow component

robinduval · 2016-06-23T14:35:47Z

Happy merge @lyrixx

parweb · 2016-07-03T18:48:47Z

@lyrixx , you did a great job.

I implemented the component in my project, but I don't understand something.

The "announce" event ?

Can you explain a bit what's the propose of this ?
Or a use case ?

guard ----> leave ----> transition ----> enter
those events i see clearly what can i do at what moment but announce it's not clear.
Because it's about the next state.

lyrixx · 2016-07-03T22:58:16Z

Hello @parweb

The announce event is here to fit some needs asked in this comment. If it's still not clear for you, don't hesitate to ask ;)

parweb · 2016-07-03T23:07:10Z

@lyrixx i think i understand the purpose better now.

When a new transition is available an event is fire ?

lyrixx · 2016-07-04T08:35:19Z

Yes.

tacman · 2016-07-19T22:30:51Z

Is there any other documentation besides the first post in this issue? Is that documentation still current? I've been using the demo app code (https://github.com/lyrixx/SFLive-Paris2016-Workflow), but now need to dynamically create a workflow instead of coding it in the config file. Thanks.

hacfi · 2016-07-20T08:13:18Z

@tacman Afaik not yet! The goal is to have the docs ready when 3.2 will be released which according to http://symfony.com/doc/current/contributing/community/releases.html is November 2016.

cravler · 2016-07-25T06:41:23Z

Is this doable?

lyrixx · 2016-07-25T09:26:04Z

yes

cravler · 2016-07-25T09:27:58Z

Example?

lyrixx · 2016-07-25T09:32:57Z

@cravler Could you, please, be polite and make real sentences. I'm not a bot.

places: [a, b, c, d]
transitions:
  t1: { from: a , to: [b, c]}
  t2: { from: [b, c] , to: d}

cravler · 2016-07-25T11:38:54Z

Step 1

Step 2

OR

Step 3

Step 4

mdwheele · 2016-07-25T11:53:30Z

@cravler You should really add more to your comments so intent is clear. I have extra time, so I'll guess.

If your intent is that the order in which paid and sent are marked matters, then you should be using some form of sequential processing. In this case, when t1 fires, both paid and sent are immediately marked. In fact, there is no "Step 2" and "Step 3". "Step 1" is accurate. The next marking would be something similar to your "Step 3" except packed should not be marked (which is what I'm assuming green means). The next marking after t2 fires would be that delivered be marked with no other places marked.

You probably want something like:

(pseudo-markup; unsure if this is valid configuration for workflow component)

places: [packed, paid, sent, delivered]
transitions:
  t1: { from: packed, to: paid}
  t2: { from: paid, to: sent}
  t3: { from: sent, to: delivered}

Go check out http://www.workflowpatterns.com. It is a valuable resource for learning how these data structures work and gives you some hints on what patterns exist and what they're good for. Most should be able to be implemented using this component from what I have seen.

mdwheele · 2016-07-25T12:00:52Z

When a new transition is available an event is fire ?

@parweb That's exactly correct! The immediate use-case I had for this at the time was integration of a workflow with a work item delegator as part of a workflow management system. In the language of Workflow Nets, "places" are called "conditions" and "transitions" are called "tasks". Some tasks are "user / input triggered" meaning that they do not fire immediately upon becoming enabled. An enabled task becomes a "work item" available for work applied by some resource. This is why it is handy to know when a transition becomes enabled; so that a collaborator can delegate responsibility for a work item to one or more candidate resources. Once the work item is completed (outside the scope of this component) then the task (transition) will be fired and the Petri net goes on functioning as per usual.

cravler · 2016-07-25T12:59:47Z

I asked about this: Interleaved Parallel Routing

mdwheele · 2016-07-25T13:21:43Z

I asked about this: Interleaved Parallel Routing

I believe you could implement Interleaved Parallel Routing (implementation guide) with this component. You have guards / guard events to be able to hook into the execution of the petri net. However, you'll need to implement something to carry the state required to implement the rest, I imagine.

Keep in mind, this package implements a Petri net first and dips its toes into the "pool of Workflow Nets". That said, it does not carry many of the common workflow net building blocks you'd expect in a WFMS offering (nor should it, in my opinion).

Many workflow-net constructs are able to be projected to a lower-level PT-net form, but will require a bit of orchestration around primitives. The linked document above shows a PT-net implementation of a net similar to the graphic you linked. It is clearly not as graceful, but the graphic linked was also an abstraction used for demonstrative purposes.

lutangar · 2016-08-03T14:24:10Z

src/Symfony/Component/Workflow/Workflow.php

+
+        foreach ($this->definition->getTransitions() as $transition) {
+            if ($this->doCan($subject, $marking, $transition)) {
+                $this->dispatcher->dispatch(sprintf('workflow.%s.announce.%s', $this->name, $transition->getName()), $event);


@lyrixx @mdwheele I might be wrong, but I was expecting the dispatched event to hold the announced transition instead of the initial transition.
From where the availabilty of the transition originated from, might not be what's matter the most here.
After all, the use case was to announce which transition are now available.

Hello @lutangar ;

I'm not sure to understand what you want. Anyway, If you want a new feature, or to change an existing one, please open a new issue, it will be easier to discuss about it there. And feel free to ping me ;)

javiereguiluz · 2016-08-04T10:23:36Z

I'm locking this pull request because it's generating too many messages:

If you want to report an error or ask for a new feature, please create a new issue.
If you are looking for documentation, see Workflow Component Documentation.

Thank you all for this long discussion!

lyrixx changed the title ~~[WIP][Worflow] Introducing the workflow component~~ [WIP][Workflow] Introducing the workflow component Sep 8, 2014

stof reviewed Sep 8, 2014
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florianv reviewed Sep 8, 2014
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lyrixx force-pushed the component-workflow branch from 20eb0da to 376a605 Compare June 22, 2016 15:16

fabpot and others added 2 commits June 23, 2016 14:28

added the first more-or-less working version of the Workflow component

17d59a7

[Workflow] Added initial set of files

078e27f

lyrixx force-pushed the component-workflow branch from 376a605 to 078e27f Compare June 23, 2016 12:35

fabpot merged commit 078e27f into symfony:master Jun 23, 2016

lyrixx deleted the component-workflow branch June 23, 2016 12:43

bendavies mentioned this pull request Jun 23, 2016

[RFC] Symfony Workflow Sylius/Sylius#5335

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lyrixx mentioned this pull request Jun 23, 2016

[Workflow] Add documentation for the Workflow Component symfony/symfony-docs#6677

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lutangar reviewed Aug 3, 2016
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symfony locked and limited conversation to collaborators Aug 4, 2016

[Workflow] Introducing the workflow component #11882

[Workflow] Introducing the workflow component #11882

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