saga-example

This project shows how to implement the SAGA pattern using MassTransit. The application contains essential settings to work with observability using OpenTelemetry.

Dependencies

• Docker

How to run

After cloning this repository go into the directory and run docker-compose up -d.

Debug

• .NET 6.0
• Visual Studio
• Visual Studio Code

Informations

This solution contains some APIs and some workers (consumers/publishers) that communicate with each other using synchronous communication with HTTP request or asynchronous messaging with RabbitMQ to implementing the SAGA pattern.

Projects

• Cart.Api: API responsible for management the carts;
• Order.Api: API responsible for management the orders;
• Order.Domain: Project responsible for orchestrating the saga;
• Order.Worker: Project responsible for publish the commands and consume the events
• OrderVendor.Worker: Project that simulate an integration with a partner;
• Payment.Api: API responsible for management the payments;
• Payment.Domain: Project responsible to maintain payment contracts (commands/events);
• Payment.Worker: Project that simulate authorize and confirm payments;
• Saga.Core: Cross project to facilitate commons implementations between the projects;

URLs

• Order.Api: http://localhost:4000/swagger/
• Cart.Api: http://localhost:4001/swagger/
• Payment.Api: http://localhost:4002/swagger/
• Jaeger: http://localhost:16686/
• RabbitMQ: http://localhost:15672/ - guest/guest
• MongoDB: mongodb://mongo:mongo@localhost:27017

Diagram

Saga - Workflow

%%{init: {'theme':'forest'}}%%

sequenceDiagram

  participant FE
  participant Order.Api
  participant Cart.Api
  participant Payment.Api
  participant Order.Worker
  participant Payment.Worker
  participant OrderVendor.Worker
  autonumber
  
  rect rgb(191, 223, 255)
    note right of FE: order creation
    FE->>Order.Api: POST /order
    Order.Api->>Cart.Api: PUT - cart/finalize
    Cart.Api->>Order.Api: 200
    Order.Api->>Payment.Api: POST - Payment/pre-authorize
    Payment.Api->>Order.Api: 200
    Order.Api->Order.Api: Create Order
    Order.Api-->>FE: 202 - Accepted
  end

  rect rgb(230, 255, 204)
    note right of Order.Worker: saga execution coordinator
    Order.Worker-->>Payment.Worker: AuthorizePaymentCommand
    Payment.Worker->>Order.Worker: PaymentAuthorizedEvent
    Order.Worker-->>OrderVendor.Worker: IntegrateIndustryCommand
    OrderVendor.Worker->>Order.Worker: IndustryIntegratedEvent
    Order.Worker-->>Payment.Worker: ConfirmPaymentCommand
    Payment.Worker->>Order.Worker: PaymentConfirmedEvent
    Order.Worker-->>Order.Worker: OrderProcessedEvent
    Order.Worker-->>Order.Worker: Update Order
  end

Saga - Failure to integrate with the industry

%%{init: {'theme':'forest'}}%%

sequenceDiagram
  participant FE
  participant Order.Api
  participant Cart.Api
  participant Payment.Api
  participant Order.Worker
  participant Payment.Worker
  participant OrderVendor.Worker
  autonumber

  rect rgb(191, 223, 255)
    note right of FE: order creation
    FE->>Order.Api: POST /order
    Order.Api->>Cart.Api: PUT - cart/finalize
    Cart.Api->>Order.Api: 200
    Order.Api->>Payment.Api: POST - Payment/pre-authorize
    Payment.Api->>Order.Api: 200
    Order.Api->Order.Api: Create Order
    Order.Api-->>FE: 202 - Accepted
  end  
  
  rect rgb(255, 224, 204)
    note right of Order.Worker: saga execution coordinator
    Order.Worker-->>Payment.Worker: AuthorizePaymentCommand
    Payment.Worker->>Order.Worker: PaymentAuthorizedEvent
    Order.Worker-->>OrderVendor.Worker: IntegrateIndustryCommand
    OrderVendor.Worker->>Order.Worker: IndustryFailedEvent
    note right of Payment.Api: compensating transactions
    Order.Worker->>Cart.Api: PUT - cart/reopen
  end