Chapter 6

config/packages/messenger.yaml

@@ -10,12 +10,6 @@ framework:
                     - doctrine_ping_connection
                     - doctrine_close_connection
                     - doctrine_transaction
-            projection.bus:
-                default_middleware: allow_no_handlers
-                middleware:
-                    - doctrine_ping_connection
-                    - doctrine_close_connection
-                    - doctrine_transaction
             query.bus:
                 default_middleware: allow_no_handlers
                 middleware:
@@ -24,47 +18,56 @@ framework:
                 default_middleware: allow_no_handlers
                 middleware:
                     - validation
-        transports:
-            async_commands: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/commands'
-            sync_commands: 'sync://'
-            events: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/events'
-            query: 'sync://'
-            failed_messages: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/failed-messages'
-            projections: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/projections'
+            projection.bus:
+                default_middleware: allow_no_handlers
+                middleware:
+                    - doctrine_ping_connection
+                    - doctrine_close_connection
+                    - doctrine_transaction
+
+        transports:
+            # Command Transports
+            commands_async: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/commands'
+            commands_sync: 'sync://'
+
+            # Event Transports
+            events_async: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/events'
+            events_sync: 'sync://'
+
+            # Query Transports
+            # It makes no sense to queries to
+            # have an async transport. It has
+            # to be sync so the customer can
+            # get back the response
+            queries_sync: 'sync://'
+
+            # Projection Transports
+            projections_async: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/projections'
+            projections_sync: 'sync://'
+
+            # Dead letter box
+            failed_messages: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/failed_messages'
 
-            chapter7_sync_commands: 'sync://'
-            chapter7_async_commands: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/chapter7_commands'
-            chapter7_events: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/chapter7_events'
-            chapter7_sync_queries: 'sync://'
-            chapter7_sync_projections: 'sync://'
-            chapter7_async_projections: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/chapter7_projections'
-            chapter7_failed_messages: '%env(MESSENGER_TRANSPORT_BASE_DSN)%/chapter7_failed_messages'
         routing:
-            # Consider Signing up an Author is a sync command.
             # With a proper UX, almost all the commands should
             # be run asynchronously.
-            # TODO: Review this comment
+            Cheeper\Chapter7\Application\Command: commands_async
 
-            # Domain Events are sent to asynchronous
-            # transport to be processed later.
-            Cheeper\AllChapters\DomainModel\DomainEvent: [events, projections]
+            # However, some commands can be defined to
+            # be run synchronously.
+            Cheeper\Chapter7\Application\Author\Command\SignUpCommand: commands_sync
 
-            # Chapter 4
-            Cheeper\Chapter4\Application\Author\Command\SignUpWithoutEvents\SignUpCommand: async_commands
+            # Events can be run synchronously, however
+            # all the benefits like performance and
+            # transaction isolation comes when using
+            # the asynchronous transport.
+            Cheeper\Chapter7\DomainModel\DomainEvent: events_async
 
-            # Chapter 5
-            # Queries are executed synchronously
-            # in the same request that data is requested.
-            Cheeper\Chapter5\Application\Query: query
+            # Queries must be synchronous. Their responses
+            # need to be back to the customers.
+            Cheeper\Chapter7\Application\Query: queries_sync
 
-            # Chapter 6
-            Cheeper\Chapter6\Application\Author\Command\FollowCommand: async_commands
-
-            # End of Chapter 6
-
-            # Chapter 7
-            Cheeper\Chapter7\Application\Command: chapter7_sync_commands
-            Cheeper\Chapter7\DomainModel\DomainEvent: chapter7_events
-            Cheeper\Chapter7\Application\Projection: chapter7_async_projections
-            Cheeper\Chapter7\Application\Query: chapter7_sync_queries
-            # End of Chapter 7
+            # Projections should run asynchronously by default.
+            # However, it's possible to run some synchronously
+            # without getting the performance benefits.
+            Cheeper\Chapter7\Application\Projection: projections_async

src/Cheeper/Chapter6/Application/Author/Command/FollowCommand.php

@@ -4,8 +4,10 @@ declare(strict_types=1);
 
 namespace Cheeper\Chapter6\Application\Author\Command;
 
+use Cheeper\Chapter6\Application\Command;
+
 //snippet follow-command
-final class FollowCommand
+final class FollowCommand implements Command
 {
     private function __construct(
         private string $fromAuthorId,

src/Cheeper/Chapter6/Application/Author/Projection/CountFollowersProjection.php

@@ -4,8 +4,10 @@ declare(strict_types=1);
 
 namespace Cheeper\Chapter6\Application\Author\Projection;
 
+use Cheeper\Chapter6\Application\Projection;
+
 //snippet count-followers
-final class CountFollowersProjection
+final class CountFollowersProjection implements Projection
 {
     public static function ofAuthor(string $authorId): self
     {

src/Cheeper/Chapter6/Application/Command.php

@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cheeper\Chapter6\Application;
+
+interface Command
+{
+}

src/Cheeper/Chapter6/Application/Projection.php

@@ -0,0 +1,11 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cheeper\Chapter6\Application;
+
+//snippet projection
+interface Projection
+{
+}
+//end-snippet

src/Cheeper/Chapter6/Application/ProjectionBus.php

@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cheeper\Chapter6\Application;
+
+//snippet projection-bus
+interface ProjectionBus
+{
+    public function project(Projection $projection): void;
+}
+//end-snippet

src/Cheeper/Chapter6/Infrastructure/Application/Author/Projection/SagaStyle/SymfonyAuthorFollowedEventHandler.php

@@ -4,16 +4,16 @@ declare(strict_types=1);
 
 namespace Cheeper\Chapter6\Infrastructure\Application\Author\Projection\SagaStyle;
 
-use App\Messenger\CommandBus;
 use Cheeper\Chapter4\DomainModel\Author\AuthorFollowed;
 use Cheeper\Chapter6\Application\Author\Projection\CountFollowersProjection;
+use Cheeper\Chapter6\Application\ProjectionBus;
 use Symfony\Component\Messenger\Handler\MessageSubscriberInterface;
 
-//snippet symfony-author-followed-handler-in-saga-style
-final class SymfonyAuthorFollowedHandler implements MessageSubscriberInterface
+//snippet code
+final class SymfonyAuthorFollowedEventHandler implements MessageSubscriberInterface
 {
     public function __construct(
-        private CommandBus $commandBus
+        private ProjectionBus $projectionBus
     ) {
     }
 
@@ -27,7 +27,7 @@ final class SymfonyAuthorFollowedHandler implements MessageSubscriberInterface
 
     public function handlerAuthorFollowed(AuthorFollowed $event): void
     {
-        $this->commandBus->handle(
+        $this->projectionBus->project(
             CountFollowersProjection::ofAuthor($event->toAuthorId())
         );
     }

src/Cheeper/Chapter6/Infrastructure/Application/Author/Projection/SymfonyAuthorFollowedEventHandler.php

@@ -10,7 +10,7 @@ use Cheeper\Chapter6\Application\Author\Projection\CountFollowersProjection;
 use Symfony\Component\Messenger\Handler\MessageSubscriberInterface;
 
 //snippet symfony-author-followed-handler
-final class SymfonyAuthorFollowedHandler implements MessageSubscriberInterface
+final class SymfonyAuthorFollowedEventHandler implements MessageSubscriberInterface
 {
     public function __construct(
         private CountFollowersProjectionHandler $projector

src/Cheeper/Chapter6/Infrastructure/Application/Author/Projection/SymfonyAuthorUnfollowedEventHandler.php

@@ -10,7 +10,7 @@ use Cheeper\Chapter6\Application\Author\Projection\CountFollowersProjection;
 use Symfony\Component\Messenger\Handler\MessageSubscriberInterface;
 
 //snippet symfony-author-unfollowed-handler
-final class SymfonyAuthorUnfollowedHandler implements MessageSubscriberInterface
+final class SymfonyAuthorUnfollowedEventHandler implements MessageSubscriberInterface
 {
     public function __construct(
         private CommandBus $commandBus

src/Cheeper/Chapter6/Infrastructure/Application/Author/Projection/SymfonyCountFollowersProjectionHandler.php

@@ -11,7 +11,7 @@ use Cheeper\Chapter6\Application\Author\Projection\CountFollowersProjectionHandl
 use Symfony\Component\Messenger\Handler\MessageSubscriberInterface;
 
 //snippet symfony-projector-count-followers
-final class SymfonyCountFollowersProjector implements MessageSubscriberInterface
+final class SymfonyCountFollowersProjectionHandler implements MessageSubscriberInterface
 {
     public function __construct(
         private CountFollowersProjectionHandler $projector

tests/Cheeper/Tests/Chapter6/Application/Author/Projection/CountFollowersProjectionHandlerTest.php

@@ -5,15 +5,12 @@ declare(strict_types=1);
 namespace Cheeper\Tests\Chapter6\Application\Author\Projection;
 
 use Cheeper\AllChapters\DomainModel\Author\AuthorDoesNotExist;
-use Cheeper\AllChapters\DomainModel\Author\AuthorId;
-use Cheeper\AllChapters\DomainModel\Cheep\CheepDate;
-use Cheeper\AllChapters\DomainModel\Cheep\CheepId;
-use Cheeper\AllChapters\DomainModel\Cheep\CheepMessage;
 use Cheeper\Chapter6\Application\Author\Projection\CountFollowersProjection;
 use Cheeper\Chapter6\Application\Author\Projection\CountFollowersProjectionHandler;
 use Doctrine\ORM\EntityManagerInterface;
 use PHPUnit\Framework\TestCase;
 
+#snippet code
 final class CountFollowersProjectionHandlerTest extends TestCase
 {
     /**
@@ -106,3 +103,4 @@ final class CountFollowersProjectionHandlerTest extends TestCase
         return $mock;
     }
 }
+#end-snippet