core-dtx

DoNewsCode/core is a service container that elegantly bootstrap and coordinate twelve-factor apps in Go. This is a distributed transaction plugin of core.

Support

• sagas
  Package sagas implements the orchestration based saga pattern.
  See https://microservices.io/patterns/data/saga.html

• tcc

Introduction

A saga is a sequence of local transactions. Each local transaction updates the database and publishes a message or event to trigger the next local transaction in the saga. If a local transaction fails because it violates a business rule then the saga executes a series of compensating transactions that undo the changes that were made by the preceding local transactions.

Usage

The saga is managed by sagas.Registry. Each saga step has an forward operation and a rollback counterpart. They must be registered beforehand by calling Registry.AddStep. A new endpoint will be returned to the caller. Use the returned endpoint to perform transactional operation.

	store := sagas.NewInProcessStore()
	registry := sagas.NewRegistry(store)
	addOrder := registry.AddStep(&sagas.Step{
		Name: "Add Order",
		Do: func(ctx context.Context, request interface{}) (response interface{}, err error) {
			resp, err := orderEndpoint(ctx, request.(OrderRequest))
			if err != nil {
				return nil, err
			}
			return resp, nil
		},
		Undo: func(ctx context.Context, req interface{}) (response interface{}, err error) {
			return orderCancelEndpoint(ctx, req)
		},
	})
	makePayment := registry.AddStep(&sagas.Step{
		Name: "Make Payment",
		Do: func(ctx context.Context, request interface{}) (response interface{}, err error) {
			resp, err := paymentEndpoint(ctx, request.(PaymentRequest))
			if err != nil {
				return nil, err
			}
			return resp, nil
		},
		Undo: func(ctx context.Context, req interface{}) (response interface{}, err error) {
			return paymentCancelEndpoint(ctx)
		},
	})

Initiate the transaction by calling registry.StartTX. Pass the context returned to the transaction branches. You can rollback or commit at your will. If the TX.Rollback is called, the previously registered rollback operations will be applied automatically, on condition that the forward operation is indeed executed within the transaction.

	tx, ctx := registry.StartTX(context.Background())
	resp, err := addOrder(ctx, OrderRequest{Sku: "1"})
	if err != nil {
		tx.Rollback(ctx)
	}
	resp, err = makePayment(ctx, PaymentRequest{})
	if err != nil {
		tx.Rollback(ctx)
	}
	tx.Commit(ctx)

Integration

The package leader exports configuration in this format:

saga:
    sagaTimeoutSecond: 600
    recoverIntervalSecond: 60

To use package sagas with package core:

	var c *core.C = core.Default()
	c.Provide(sagas.Providers)
	c.Invoke(func(registry *sagas.Registry) {
		tx, ctx := registry.StartTX(context.Background())
		resp, err := addOrder(ctx, OrderRequest{Sku: "1"})
		if err != nil {
			tx.Rollback(ctx)
		}
		resp, err = makePayment(ctx, PaymentRequest{})
		if err != nil {
			tx.Rollback(ctx)
		}
		tx.Commit(ctx)
	})