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Commit 84b81e3

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Nyholmweaverryan
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Added fixes
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‎messenger/message-recorder.rst

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.. index::
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single: Messenger; Record messages
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Record Events Produced by a Handler
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===================================
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Events Recorder: Handle Events After CommandHandler Is Done
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===========================================================
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In an example application there is a command (a CQRS message) named ``CreateUser``.
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That command is handled by the ``CreateUserHandler`` which creates
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a ``User`` object, stores that object to a database and dispatches a ``UserCreatedEvent``.
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Let's take the example of an application that has a command (a CQRS message) named
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``CreateUser``. That command is handled by the ``CreateUserHandler`` which creates
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a ``User`` object, stores that object to a database and dispatches a ``UserCreated`` event.
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That event is also a normal message but is handled by an *event* bus.
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There are many subscribers to the ``UserCreatedEvent``, one subscriber may send
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a welcome email to the new user. Since we are using the ``DoctrineTransactionMiddleware``
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we wrap all database queries in one database transaction and rollback that transaction
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if an exception is thrown. That means that if an exception is thrown when sending
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the welcome email, then the user will not be created.
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There are many subscribers to the ``UserCreated`` event, one subscriber may send
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a welcome email to the new user. We are using the ``DoctrineTransactionMiddleware``
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to wrap all database queries in one database transaction.
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The solution to this issue is to not dispatch the ``UserCreatedEvent`` in the
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**Problem:** If an exception is thrown when sending the welcome email, then the user
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will not be created because the ``DoctrineTransactionMiddleware`` will rollback the
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Doctrine transaction, in which the user has been created.
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**Solution:** The solution is to not dispatch the ``UserCreated`` event in the
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``CreateUserHandler`` but to just "record" the events. The recorded events will
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be dispatched after ``DoctrineTransactionMiddleware`` has committed the transaction.
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$user = new User($command->getUuid(), $command->getName(), $command->getEmail());
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$this->em->persist($user);
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// "Record" this event to be processed later by "handles_recorded_messages".
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$this->eventRecorder->record(new UserCreatedEvent($command->getUuid());
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}
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}

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