Guidance for building distributed systems and Microservices in Go

Technologies Used:

• Go
• NATS JetStream
• gRPC
• CockroachDB

Compile Proto files

Run the command below from the eventstream directory:

protoc eventstore/*.proto
--go_out=.
--go-grpc_out=.
--go_opt=paths=source_relative
--go-grpc_opt=paths=source_relative
--proto_path=.

Set up CockroachDB

Set up CockroachDB Cluster with three nodes

cockroach start
--insecure
--store=orders-1
--listen-addr=localhost:26257
--http-addr=localhost:8080
--join=localhost:26257,localhost:26258,localhost:26259
--background

cockroach start
--insecure
--store=orders-2
--listen-addr=localhost:26258
--http-addr=localhost:8081
--join=localhost:26257,localhost:26258,localhost:26259
--background

cockroach start
--insecure
--store=orders-3
--listen-addr=localhost:26259
--http-addr=localhost:8082
--join=localhost:26257,localhost:26258,localhost:26259
--background

cockroach init command to perform a one-time initialization of the cluster

cockroach init --insecure --host=localhost:26257

Start a SQL Shell for CockroachDB:

cockroach sql --insecure --host=localhost:26257

Create user

cockroach user set shijuvar --insecure

Create Databases

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

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

Grant privileges to the shijuvar user

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

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

Run NATS JetStream Server

nats-server -js

Basic Workflow in the example:

1. A client app post an Order to an HTTP API (ordersvc)
2. An HTTP API (ordersvc) receives the order, then executes a command onto Event Store, which is an immutable log of events of domain events, to create an event via its gRPC API (eventstoresvc).
3. The Event Store API executes the command and then publishes an event "ORDERS.created" to NATS JetStream server to let other services know that a domain event is created.
4. TThe Payment worker (paymentworker) subscribes the event "ORDERS.created", then make the payment, and then create another event "ORDERS.paymentdebited" via Event Store API.
5. The Event Store API executes a command onto Event Store to create an event "ORDERS.paymentdebited" and publishes an event to NATS JetStream server to let other services know that the payment has been debited.
6. The Query synchronising worker (querymodelworker) subscribes the event "ORDERS.created" that synchronise the query data model to provide state of the aggregates for query views.
7. The review worker (reviewworker) subscribes the event "ORDERS.paymentdebited" and finally approves the order.
8. A Saga coordinator manages the distributed transactions and makes void transactions on failures (to be implemented)