Building Modular monliths that could scale to microservices (only if they need to) - Updated for Chicago JUG
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It’s easy these days to fall into the trap of starting to design your whole application with a microservices architecture…. Because, you know, that’s what everyone is doing, right? But no, no. I’m not going to deny that Microservices have their advantages, specifically in a distributed and scalable world like the one we need to deal with. The problem may be in the approach we are taking. Are we considering the microservices architecture as a goal, or as a means to a purpose? In this talk we will think in a different approach: we will go back to the basics, and see how following DDD, CQRS and Event-Sourcing practices will drive our application design and evolution in such a way that we will start with a monolith but we will have the ability to scale into a microservices architecture more or less easily when (and more importantly: if) we need to.
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Building Modular monliths that could scale to microservices (only if they need to) - Updated for Chicago JUG
- 1. David Gómez G. Developer Advocate . Building monolith applications that can scale to micro services (only if they need to) @AXONIQ @DGOMEZG
- 3. Don’t let the microservices hype ruin your project @AXONIQ @DGOMEZG David Gómez G. Developer Advocate .
- 4. An Exciting New Project Starts @DGOMEZG
- 5. Or you may need to add a new module/feature to an existing project @DGOMEZG
- 6. But this time, you are going to get it right! @DGOMEZG
- 7. We need to scale! We need to go to the cloud(s)! @DGOMEZG
- 8. How others solved similar problems? @DGOMEZG
- 13. You will probably be missing all of these @DGOMEZG
- 15. Problems seem easier to solve when you have enough context @DGOMEZG
- 16. we don’t usually know enough @DGOMEZG @DGOMEZG
- 17. we don’t usually know enough @DGOMEZG
- 18. @DGOMEZG What you need (Your steps) • Separate your different tasks by type • Focus on understanding the problem(s) you need to solve, • Model each problem independently • Be prepared to grow & scale (both in features and in performance) • Don’t couple to other components
- 19. @DGOMEZG Our example: A Conference Management Tool.
- 20. @DGOMEZG Our example: A Conference Management Tool. Dates, Sponsors, Call For Papers, Proposals, Agenda T alks, Tickets, Attendees… Call For Papers, Agenda, Questions, Forums, Tickets, Agenda, speakers, …
- 22. @DGOMEZG Command Query Responsibility Separation CQRS
- 23. @DGOMEZG COMMANDS QUERIES CQRS Separate Queries from Commands @DGOMEZG
- 24. @DGOMEZG CQRS Separate Queries from Commands COMMANDS What actions do require changes in the state of the application? What other changes will be necessary to notify/propagate? @DGOMEZG
- 25. @DGOMEZG CQRS Separate Queries from Commands COMMANDS Define Edition (Dates) Accept/Reject Talk Proposal Open Ticket sales Open Call For Papers Add/Remove Track Define Q&A Channel Submit Proposal Withdraw Proposal Confirm Proposal Join Q&A Channel Buy Ticket Add Talk To My Agenda Ask Questions in Q&A. Rate Talk @DGOMEZG
- 26. @DGOMEZG CQRS Separate Queries from Commands QUERIES What information do the users require? @DGOMEZG
- 27. @DGOMEZG CQRS Separate Queries from Commands QUERIES List Proposals Get Talk Popularity Get Talks Rating Get Questions Get Talk Feedback My Talk Info Conference Agenda My Agenda Q&A Messages @DGOMEZG
- 31. Which map would you prefer? It depends! @DGOMEZG
- 32. @DGOMEZG COMMANDS QUERIES Focus on modelling within the boundaries of each element Command model Projections Keep only relevant information for the action in each model @DGOMEZG
- 33. @DGOMEZG JoinRoom Send Message JoinRoom Command model CreateChatRoom NAME, DESCRIPTION USER, ROOMID, MSG USERID, ROOMID @DGOMEZG
- 34. @DGOMEZG Projections Projections maintain the structure of information close to how it is needed by the client/user ListRooms ROOM, DESCRIPTION, NUM_OF_MEMBERS GetRoomMessages DATE, USER, MSG DATE, USER, MSG DATE, USER, MSG @DGOMEZG
- 35. @DGOMEZG Aggregate A set of objects, relationship and invariants that are considered as one unit with regard to data changes. Define the boundaries in which some invariants are kept. They are a model of part of the domain. @DGOMEZG
- 37. @DGOMEZG Queries UI / API Commands Command Model Projections ? @DGOMEZG
- 38. @DGOMEZG Notify that something has happened Events
- 39. Remember our micro services architecture? @DGOMEZG
- 40. Remember our micro services architecture? @DGOMEZG
- 41. Remember our micro services architecture? Event @DGOMEZG
- 42. @DGOMEZG Queries UI / API Commands Command Model Projections Events @DGOMEZG
- 48. @DGOMEZG Why Event-Sourcing? ProposalUpdated (id: 123, title, Smith) SpeakerChanged (id:123, jDoe) ProposalSubmitted ProposalAccepted ProposalWithdrawn ProposalDraftSent (id: 123) id: 123. Author: John Doe Title: What’s new in Java 17 status: Withdrawn What happened What we store
- 49. @DGOMEZG Why Event-Sourcing? Business Reasons Technical reasons • Reliability of decisions • Auditing / compliance / transparency • Data mining, analytics: value for data • Historic data useful for new features • Guaranteed completeness of event stream • Single point of truth • Concurrency / conflict resolution • Facilitates debugging / forensic analysis • Replay into new read models (scalability with CQRS)
- 53. Location Transparency A component should neither be aware of nor make any assumptions about the location of other components Furthermore, it should not even know which components it interacts with @DGOMEZG
- 54. @DGOMEZG
- 55. @DGOMEZG 1. Keep the independent models
- 56. @DGOMEZG 1. Keep the independent models
- 57. @DGOMEZG 1. Keep the independent models
- 58. @DGOMEZG 1. Keep the independent models CQRS + DDD
- 59. @DGOMEZG Event Sourcing (sync modules) + Message Bus Event store
- 61. @DGOMEZG Command Model data class CreateRoomCommand( @TargetAggregateIdentifier val roomId: String, val name: String) data class JoinRoomCommand( @TargetAggregateIdentifier val roomId: String, val participant: String) data class PostMessageCommand( @TargetAggregateIdentifier val roomId: String, val participant: String, val message: String) data class LeaveRoomCommand( @TargetAggregateIdentifier val roomId: String, val participant: String)
- 62. @DGOMEZG Event Model data class RoomCreatedEvent( val roomId: String, val name: String) data class ParticipantJoinedRoomEvent( val roomId: String, val participant: String) data class MessagePostedEvent( val roomId: String, val participant: String, val message: String) data class ParticipantLeftRoomEvent( val roomId: String, val participant: String)
- 63. @DGOMEZG Aggregate @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; public ChatRoom() { } }
- 64. @DGOMEZG Aggregate: Handling a Command @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; @CommandHandler public ChatRoom() { } }
- 65. @DGOMEZG Aggregate: Handling a Command @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; @CommandHandler public ChatRoom(CreateRoomCommand command) { } }
- 66. @DGOMEZG Aggregate: Handling a Command @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; @CommandHandler public ChatRoom(CreateRoomCommand command) { apply(new RoomCreatedEvent(command.getRoomId(), command.getName())); } }
- 67. @DGOMEZG Aggregate: Handling a Command @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; @CommandHandler public ChatRoom(CreateRoomCommand command) { apply(new RoomCreatedEvent(command.getRoomId(), command.getName())); } @CommandHandler public void handle(JoinRoomCommand command) { } }
- 68. @DGOMEZG Aggregate: Handling a Command @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; @CommandHandler public ChatRoom(CreateRoomCommand command) { apply(new RoomCreatedEvent(command.getRoomId(), command.getName())); } @CommandHandler public void handle(JoinRoomCommand command) { apply(new ParticipantJoinedRoomEvent(command.getRoomId(), command.getParticipant())); } }
- 69. @DGOMEZG Aggregate: Handling a Command @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; @CommandHandler public void handle(JoinRoomCommand command) { apply(new ParticipantJoinedRoomEvent(command.getRoomId(), command.getParticipant())); } }
- 70. @DGOMEZG Aggregate: Handling a Command @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; @CommandHandler public void handle(JoinRoomCommand command) { apply(new ParticipantJoinedRoomEvent(command.getRoomId(), command.getParticipant())); } @EventSourcingHandler public void on() { } }
- 71. @DGOMEZG Aggregate: Handling a Command @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; @CommandHandler public void handle(JoinRoomCommand command) { apply(new ParticipantJoinedRoomEvent(command.getRoomId(), command.getParticipant())); } @EventSourcingHandler public void on(ParticipantJoinedRoomEvent event) { } }
- 72. @DGOMEZG Aggregate: Handling a Command @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; @CommandHandler public void handle(JoinRoomCommand command) { apply(new ParticipantJoinedRoomEvent(command.getRoomId(), command.getParticipant())); } @EventSourcingHandler public void on(ParticipantJoinedRoomEvent event) { this.participants.add(event.getParticipant()); } }
- 73. @DGOMEZG Aggregate: Command Validation @Aggregate public class ChatRoom { @AggregateIdentifier private String roomId; private Set<String> participants; @CommandHandler public void handle(JoinRoomCommand command) if (…) { pply(new ParticipantJoinedRoomEvent(command.getRoomId(), command.getParticipant())); } @EventSourcingHandler public void on(ParticipantJoinedRoomEvent event) { this.participants.add(event.getParticipant()); } }
- 74. @DGOMEZG Location Transparency. Sync other components @Component public class RoomSummaryProjection { private final RoomSummaryRepository roomSummaryRepository; @EventHandler public void on(RoomCreatedEvent event) { roomSummaryRepository.save(new RoomSummary(event.getRoomId(), event.getName())); } @EventHandler public void on(ParticipantJoinedRoomEvent event) { roomSummaryRepository.findById(event.getRoomId()) .ifPresent(RoomSummary"#addParticipant); } }
- 75. @DGOMEZG Handling Queries @Component public class RoomSummaryProjection { private final RoomSummaryRepository roomSummaryRepository; @QueryHandler public List<String> handle(RoomParticipantsQuery query) { return roomSumaryRepository.findRoomParticipants(query.getRoomId()) .stream() .map(RoomParticipant"#getParticipant).sorted() .collect(toList())event.getName())); } }
- 79. @DGOMEZG Useful Resources https://lp.axoniq.io/chicago-jug The slides Code-sample & tutorial repo Free DDD, CQRS & ES courses eventmodeling.org Domain-Driven Design https://lp.axoniq.io/chicago-jug