Taming Command Bus

1. Taming Command Bus Krzysztof Menżyk  @kmenzyk

2. About me Technical Leader at Test infected Believes that software is a craft Loves domain modelling Homebrewer & squash player

3. This talk is not

4. This talk is not DDD*

5. This talk is not CQRS*

6. Back to the PAST

7. BEGAN It all with ...

8. class ProductController extends Controller { //... public function updateAction($id) { if (false === $this->get('security.context')->isGranted('ROLE_ADMIN')) { throw new AccessDeniedException(); } $em = $this->getDoctrine()->getManager(); $product = $em->getRepository('AcmeDemoBundle:Product')->find($id); if (!$product) { throw $this->createNotFoundException('Unable to find Product entity.'); } $request = $this->getRequest(); $editForm = $this->createForm(new ProductType(), $product); $editForm->bind($request); if ($editForm->isValid()) { $product->setLastUpdated(new DateTime); $em->flush(); $message = Swift_Message::newInstance() ->setSubject('Product updated') ->setFrom($this->container->getParameter('acme.product_email.from')) ->setTo($this->container->getParameter('acme.product_email.to')) ->setBody($this->renderView( 'AcmeDemoBundle:Product:email.txt.twig', array('product' => $product)) ) ; $this->get('mailer')->send($message); return $this->redirect( $this->generateUrl('product', array('id' => $id)) ); } return new Response( $this->renderView( 'AcmeDemoBundle:Product:edit.html.twig', array( 'product' => $product, 'edit_form' => $editForm->createView(), ) ) ); } }

9. Controller Driven Design „approach”

10. class ProductController extends Controller { //... public function updateAction($id) { if (false === $this->get('security.context')->isGranted('ROLE_ADMIN')) { throw new AccessDeniedException(); } $em = $this->getDoctrine()->getManager(); $product = $em->getRepository('AcmeDemoBundle:Product')->find($id); if (!$product) { throw $this->createNotFoundException('Unable to find Product entity.'); } $request = $this->getRequest(); $editForm = $this->createForm(new ProductType(), $product); $editForm->bind($request); if ($editForm->isValid()) { $product->setLastUpdated(new DateTime); $em->flush(); $message = Swift_Message::newInstance() ->setSubject('Product updated') ->setFrom($this->container->getParameter('acme.product_email.from')) ->setTo($this->container->getParameter('acme.product_email.to')) ->setBody($this->renderView( 'AcmeDemoBundle:Product:email.txt.twig', array('product' => $product)) ) ; $this->get('mailer')->send($message); return $this->redirect( $this->generateUrl('product', array('id' => $id)) ); } return new Response( $this->renderView( 'AcmeDemoBundle:Product:edit.html.twig', array( 'product' => $product, 'edit_form' => $editForm->createView(), ) ) ); } }

11. class ProductController extends Controller { //... public function updateAction($id) { if (false === $this->get('security.context')->isGranted('ROLE_ADMIN')) { throw new AccessDeniedException(); } $em = $this->getDoctrine()->getManager(); $product = $em->getRepository('AcmeDemoBundle:Product')->find($id); if (!$product) { throw $this->createNotFoundException('Unable to find Product entity.'); } $request = $this->getRequest(); $editForm = $this->createForm(new ProductType(), $product); $editForm->bind($request); if ($editForm->isValid()) { $product->setLastUpdated(new DateTime); $em->flush(); $message = Swift_Message::newInstance() ->setSubject('Product updated') ->setFrom($this->container->getParameter('acme.product_email.from')) ->setTo($this->container->getParameter('acme.product_email.to')) ->setBody($this->renderView( 'AcmeDemoBundle:Product:email.txt.twig', array('product' => $product)) ) ; $this->get('mailer')->send($message); return $this->redirect( $this->generateUrl('product', array('id' => $id)) ); } return new Response( $this->renderView( 'AcmeDemoBundle:Product:edit.html.twig', array( 'product' => $product, 'edit_form' => $editForm->createView(), ) ) ); } } 

12. LAYERS

13. Presentation

14. Presentation Domain

15. Presentation Service Domain

16. Presentation Service Domain Infrastructure

17. Presentation Service Domain Infrastructure

18. Defines an application's boundary with a layer of services. Service Layer

19. Establishes set of available operations. Service Layer

20. Coordinates the application's response in each operation. Service Layer

21. USE Cases

22. USER STORIES

23. Application Layer

24. class Library { public function borrowBook($bookId, $readerId) { // ... } }

25. class LibraryController { public function borrowAction(ServerRequestInterface $request) { // Forms, etc. $this->library->borrowBook($bookId, $readerId); // Response } }

26. class Library { public function borrowBook($bookId, $readerId) { if (null === $bookId || null === $readerId) { throw new InvalidArgumentException(); } $this->logging->debug('A reader is borrowing a book'); $this->connection->beginTransaction(); try { $book = $this->books->get($bookId); $book->borrowBy($readerId); $this->books->add($book); $this->connection->commit(); } catch (Exception $e) { $this->connection->rollBack(); $this->logging->debug('Ooops! Bad luck.'); throw $e; } $this->logging->debug('Success!'); } }

31. borrowBook($bookId, $readerId)

32. new BorrowBook($bookId, $readerId)

33. COMMAND

34. not a class/object MESSAGE

35. Messaging Flavors by @mathiasverraes

36. Messaging Flavors by @mathiasverraes Imperative

37. Messaging Flavors by @mathiasverraes Imperative Command

38. Messaging Flavors by @mathiasverraes Imperative Interrogatory Command

39. Messaging Flavors by @mathiasverraes Imperative Interrogatory Command QUERY

40. Messaging Flavors by @mathiasverraes Imperative Interrogatory Informational Command QUERY

41. Messaging Flavors by @mathiasverraes Imperative Interrogatory Informational Command QUERY EVENT

42. Messaging Flavors by @mathiasverraes Imperative Interrogatory Informational Command QUERY EVENT

43. Captures THE INTENT of the user

44. Supports Ubiquitous LANGUAGE

45. Borrow Book Give Book Back Register User Start Subscription Hire Employee

46. Contains THE INPUT to carry out the task

47. final class BorrowBook { public $bookId; public $readerId; public function __construct($bookId, $readerId) { $this->bookId = $bookId; $this->readerId = $readerId; } }

48. Should be IMMUTABLE

49. final class BorrowBook { private $bookId; private $readerId; public function __construct($bookId, $readerId) { $this->bookId = $bookId; $this->readerId = $readerId; } public function getBookId() { return $this->bookId; } public function getReaderId() { return $this->readerId; } }

50. Must be VALID

51. final class BorrowBook { private $bookId; private $readerId; public function __construct($bookId, $readerId) { Assertion::notNull($bookId); Assertion::notNull($readerId); $this->bookId = $bookId; $this->readerId = $readerId; } public function getBookId() { return $this->bookId; } public function getReaderId() { return $this->readerId; } }

52. INTERPRET How to a command?

53. COMMAND Handler

54. per command ONE HANDLER

55. Returns NO VALUE

56. final class BorrowBookHandler { public function handle(BorrowBook $command) { $this->logging->debug('A reader is borrowing a book'); $this->connection->beginTransaction(); try { $book = $this->books->get($command->getBookId()); $book->borrowBy($command->getReaderId()); $this->books->add($book); $this->connection->commit(); } catch (Exception $e) { $this->connection->rollBack(); $this->logging->debug('Ooops! Bad luck.'); throw $e; } $this->logging->debug('Success!'); } }

58. One more thing ...

59. The BUS

60. COMMAND BUS

61. Hands over THE COMMAND to THE HANDLEr

62. Handler C Command Bus Handler BHandler A

63. Handler C Command C Command Bus Handler BHandler A

64. Handler C Command Bus Handler BHandler A Command C

65. Handler C Command Bus Handler BHandler A Command C

66. Handler C Command Bus Handler BHandler A

67. Single ENTRY POINT to the application

68. interface CommandBus { public function handle($command); }

69. class LibraryController { public function borrowAction(ServerRequestInterface $request) { // Forms, etc. $this->commandBus->handle(new BorrowBook($bookId, $readerId)); // Response } }

70. class SomeOtherController { public function someOtherAction(ServerRequestInterface $request) { // Forms, etc. $command = $form->getData(); $this->commandBus->handle($command); // Response } }

71. class SomeOtherController { public function someOtherAction(ServerRequestInterface $request) { // Forms, etc. $command = $form->getData(); $this->commandBus->handle($command); // Response } }

72. class BorrowBookCli { protected function execute(InputInterface $input, OutputInterface $output) { // get $command from the input somehow $this->commandBus->handle($command); // ... } }

73. IMPLEMENT Let's the stupid thing

74. class SimpleCommandBus implements CommandBus { private $handlers; public function __construct(array $handlers) { $this->handlers = $handlers; } public function handle($command) { $commandName = get_class($command); if (!isset($this->handlers[$commandName])) { throw new InvalidArgumentException('No handler'); } $this->handlers[$commandName]->handle($command); } }

75. new SimpleCommandBus([ BorrowBook::class => $borrowBookHandler, GiveBookBack::class => $giveBookBackHandler, ]);

76. That's it?

77. Do not TRY IT at home

78. class SimpleCommandBus implements CommandBus { private $handlers; public function __construct(array $handlers) { $this->handlers = $handlers; } public function handle($command) { $commandName = get_class($command); if (!isset($this->handlers[$commandName])) { throw new InvalidArgumentException('No handler'); } $this->handlers[$commandName]->handle($command); } }

79. Cross cutting concerns

80. interface CommandBus { public function handle($command); }

81. DECORATOR

82. class CommandBusWithAddedBehavior implements CommandBus { public function __construct(CommandBus $originalCommandBus) { $this->originalCommandBus = $originalCommandBus; } public function handle($command) { // do anything you want $this->originalCommandBus->handle($command); // do even more } }

83. new CommandBusWithAddedBehavior( new SimpleCommandBus([ BorrowBook::class => $borrowBookHandler, GiveBookBack::class => $giveBookBackHandler, ]) );

84. Command Bus Decorator Decorator Command

86. class TransactionalCommandBus implements CommandBus { public function __construct($innerCommandBus, $connection) { $this->innerCommandBus = $innerCommandBus; $this->connection = $connection; } public function handle($command) { $this->connection->beginTransaction(); try { $this->innerCommandBus->handle($command); $this->connection->commit(); } catch (Exception $exception) { $this->connection->rollBack(); throw $e; } } }

88. class LoggingCommandBus implements CommandBus { public function __construct($innerCommandBus, $logger) { $this->innerCommandBus = $innerCommandBus; $this->logger = $logger; } public function handle($command) { $commandClass = get_class($command); $this->logger->debug('Started handling ' . $commandClass); try { $this->innerCommandBus->handle($command); } catch (Exception $exception) { $this->logger->debug('Error while handling ' . $commandClass); throw $e; } $this->logger->debug('Finished handling ' . $commandClass); } }

90. final class BorrowBookHandler { public function handle(BorrowBook $command) { $book = $this->books->get($command->getBookId()); $book->borrowBy($command->getReaderId()); $this->books->add($book);'Success!'); } }

91. Easy to TEST

92. But...

93. new LoggingCommandBus( new TransactionalCommandBus( new SimpleCommandBus([ BorrowBook::class => $borrowBookHandler, GiveBookBack::class => $giveBookBackHandler, ]), $connection ), $logger );

94. Can we do better?

95. Yes We can!

96. CHAIN OF RESPONSIBILITY

97. interface CommandBusMiddleware { public function handle($command, callable $next); }

98. Command Handler Middleware Command Middleware Middleware

99. class AddedBehaviorMiddleware implements CommandBusMiddleware { public function handle($command, callable $next) { // do anything you want $next($command); // do even more } }

100. new CommandBusSupportingMiddleware([ new AddedBehaviorMiddleware(), new CommandHandlerMiddleware([ BorrowBook::class => $borrowBookHandler, GiveBookBack::class => $giveBookBackHandler, ]) ]);

101. new CommandBusSupportingMiddleware([ new LoggingMiddleware($logger), new TransactionalMiddleware($connection), new CommandHandlerMiddleware([ BorrowBook::class => $borrowBookHandler, GiveBookBack::class => $giveBookBackHandler, ]) ]);

102. Transactions Logging Security Performance Metrics Audit log You name it

103. Command Bus libraries

104. by @matthiasnoback Simple Bus

105. by @rosstuck TACTICIAN

106. by @qandidate-labs BROADWAY

107. Use them and contribute

108. Like we DID

109. Krzysztof Menżyk  @kmenzyk Thanks! Taming Command Bus

110. PHOTO CREDITS https://flic.kr/p/F2qhc7 https://flic.kr/p/zMzVzW https://flic.kr/p/F4j2fH https://flic.kr/p/5a5d3b https://flic.kr/p/vXAK3D

Taming Command Bus

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Taming Command Bus