Step 19: Making Decisions with a Workflow
Making Decisions with a Workflow¶
Having a state for a model is quite common. The comment state is only determined by the spam checker. What if we add more decision factors?
We might want to let the website admin moderate all comments after the spam checker. The process would be something along the lines of:
- Start with a
submitted
state when a comment is submitted by a user; - Let the spam checker analyze the comment and switch the state to either
potential_spam
,ham
, orrejected
; - If not rejected, wait for the website admin to decide if the comment is good
enough by switching the state to
published
orrejected
.
Implementing this logic is not too complex, but you can imagine that adding more rules would greatly increase the complexity. Instead of coding the logic ourselves, we can use the Symfony Workflow Component:
1 | $ symfony composer req workflow
|
Describing Workflows¶
The comment workflow can be described in the config/packages/workflow.yaml
file:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | framework:
workflows:
comment:
type: state_machine
audit_trail:
enabled: "%kernel.debug%"
marking_store:
type: 'method'
property: 'state'
supports:
- App\Entity\Comment
initial_marking: submitted
places:
- submitted
- ham
- potential_spam
- spam
- rejected
- published
transitions:
accept:
from: submitted
to: ham
might_be_spam:
from: submitted
to: potential_spam
reject_spam:
from: submitted
to: spam
publish:
from: potential_spam
to: published
reject:
from: potential_spam
to: rejected
publish_ham:
from: ham
to: published
reject_ham:
from: ham
to: rejected
|
To validate the workflow, generate a visual representation:
1 | $ symfony console workflow:dump comment | dot -Tpng -o workflow.png
|

Note
The dot
command is a part of the Graphviz utility.
Using a Workflow¶
Replace the current logic in the message handler with the workflow:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 | --- a/src/MessageHandler/CommentMessageHandler.php
+++ b/src/MessageHandler/CommentMessageHandler.php
@@ -6,19 +6,28 @@ use App\Message\CommentMessage;
use App\Repository\CommentRepository;
use App\SpamChecker;
use Doctrine\ORM\EntityManagerInterface;
+use Psr\Log\LoggerInterface;
use Symfony\Component\Messenger\Handler\MessageHandlerInterface;
+use Symfony\Component\Messenger\MessageBusInterface;
+use Symfony\Component\Workflow\WorkflowInterface;
class CommentMessageHandler implements MessageHandlerInterface
{
private $spamChecker;
private $entityManager;
private $commentRepository;
+ private $bus;
+ private $workflow;
+ private $logger;
- public function __construct(EntityManagerInterface $entityManager, SpamChecker $spamChecker, CommentRepository $commentRepository)
+ public function __construct(EntityManagerInterface $entityManager, SpamChecker $spamChecker, CommentRepository $commentRepository, MessageBusInterface $bus, WorkflowInterface $commentStateMachine, LoggerInterface $logger = null)
{
$this->entityManager = $entityManager;
$this->spamChecker = $spamChecker;
$this->commentRepository = $commentRepository;
+ $this->bus = $bus;
+ $this->workflow = $commentStateMachine;
+ $this->logger = $logger;
}
public function __invoke(CommentMessage $message)
@@ -28,12 +37,21 @@ class CommentMessageHandler implements MessageHandlerInterface
return;
}
- if (2 === $this->spamChecker->getSpamScore($comment, $message->getContext())) {
- $comment->setState('spam');
- } else {
- $comment->setState('published');
- }
- $this->entityManager->flush();
+ if ($this->workflow->can($comment, 'accept')) {
+ $score = $this->spamChecker->getSpamScore($comment, $message->getContext());
+ $transition = 'accept';
+ if (2 === $score) {
+ $transition = 'reject_spam';
+ } elseif (1 === $score) {
+ $transition = 'might_be_spam';
+ }
+ $this->workflow->apply($comment, $transition);
+ $this->entityManager->flush();
+
+ $this->bus->dispatch($message);
+ } elseif ($this->logger) {
+ $this->logger->debug('Dropping comment message', ['comment' => $comment->getId(), 'state' => $comment->getState()]);
+ }
}
}
|
The new logic reads as follows:
- If the
accept
transition is available for the comment in the message, check for spam; - Depending on the outcome, choose the right transition to apply;
- Call
apply()
to update the Comment via a call to thesetState()
method; - Call
flush()
to commit the changes to the database; - Re-dispatch the message to allow the workflow to transition again.
As we haven’t implemented the admin validation, the next time the message is consumed, the “Dropping comment message” will be logged.
Let’s implement an auto-validation until the next chapter:
1 2 3 4 5 6 7 8 9 10 11 12 | --- a/src/MessageHandler/CommentMessageHandler.php
+++ b/src/MessageHandler/CommentMessageHandler.php
@@ -50,6 +50,9 @@ class CommentMessageHandler implements MessageHandlerInterface
$this->entityManager->flush();
$this->bus->dispatch($message);
+ } elseif ($this->workflow->can($comment, 'publish') || $this->workflow->can($comment, 'publish_ham')) {
+ $this->workflow->apply($comment, $this->workflow->can($comment, 'publish') ? 'publish' : 'publish_ham');
+ $this->entityManager->flush();
} elseif ($this->logger) {
$this->logger->debug('Dropping comment message', ['comment' => $comment->getId(), 'state' => $comment->getState()]);
}
|
Run symfony server:log
and add a comment in the frontend to see all
transitions happening one after the other.
- « Previous Step 18: Going Async
- Next » Step 20: Emailing Admins
This work, including the code samples, is licensed under a Creative Commons BY-NC-SA 4.0 license.