go-distributed-sys

Check out the article Building Microservices with Event Sourcing/CQRS in Go using gRPC, NATS Streaming and CockroachDB

Technologies Used:

• Go
• NATS Streaming
• gRPC
• CockroachDB

Compile Proto files

Run the command below from the nats-streaming directory:

protoc -I pb/ pb/*.proto --go_out=plugins=grpc:pb

Set up CockroachDB

Create user

cockroach user set shijuvar --insecure

Create Database

cockroach sql --insecure -e 'CREATE DATABASE ordersdb'

Grant privileges to the shijuvar user

cockroach sql --insecure -e 'GRANT ALL ON DATABASE ordersdb TO shijuvar'

Start CockroachDB Cluster

Start node 1:

cockroach start --insecure
--store=ordersdb-1
--host=localhost
--background

Start node 2:

cockroach start --insecure
--store=ordersdb-2
--host=localhost
--port=26258
--http-port=8081
--join=localhost:26257
--background

Start node 3:

cockroach start --insecure
--store=ordersdb-3
--host=localhost
--port=26259
--http-port=8082
--join=localhost:26257
--background

Start a SQL Shell for CockroachDB:

cockroach sql
--url="postgresql://shijuvar@localhost:26257/ordersdb?sslmode=disable";

Run NATS Streaming Server

nats-streaming-server
--store file
--dir ./data
--max_msgs 0
--max_bytes 0

Basic Workflow in the example:

1. A client app post an Order to an HTTP API.
2. An HTTP API (orderservice) receives the order, then executes a command onto Event Store, which is an immutable log of events, to create an event via its gRPC API (eventstore).
3. The Event Store API executes the command and then publishes an event "order-created" to NATS Streaming server to let other services know that an event is created.
4. The Payment service (paymentservice) subscribes the event “order-created”, then make the payment, and then create an another event “order-payment-debited” via Event Store API.
5. The Query syncing workers (orderquery-store1 and orderquery-store2 as queue subscribers) are also subscribing the event “order-created” that synchronise the data models to provide state of the aggregates for query views.
6. The Event Store API executes a command onto Event Store to create an event “order-payment-debited” and publishes an event to NATS Streaming server to let other services know that the payment has been debited.
7. The restaurant service (restaurantservice) finally approves the order.
8. A Saga coordinator manages the distributed transactions and makes void transactions on failures (to be implemented).