ordering-microservices-example

This is an example application showing the usage of 2 microservices to form a basic ordering system. It also shows inter-service communication techniques both synchronous and asynchronous.

Domain Overview

The domain consists of an Accounting service and an Ordering service. Each service is called by clients using their REST API which is exposed through an API Gateway. Services talk to each other synchronously using gRPC and asynchronously using RabbitMQ.

Each service has its own self-contained SQL Server database. Services do not and should not access the database for any other service. For this reason the Ordering SQL Server database has an Accounts table to maintain a list of Accounts to link to orders. Using synchronous and asynchronous messaging it is able to keep that table in sync with the Accounts SQL Server database.

Accounting

The accounting service is used to manage customer accounts. An account only consists of an Id which is used as the primary key on the database table.

classDiagram
    class Account
    Account : +int Id

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When a new account is created, a message is published to RabbitMQ so that any other services can keep their data in sync.

Ordering

The ordering service is used to manage orders. An order must be linked to an Account.

classDiagram
    class Order
    Order: +int Id
    Order: +decimal Cost
    Order: +int AccountId
    Order "*" -- "1" Account
    class Account
    Account: +int Id

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When the Ordering service starts up it calls a gRPC endpoint on the Account service to retrieve the list of accounts. It then inserts any missing accounts into the Ordering SQL Server database.

While the Ordering service is running, it is listening for the RabbitMQ message that is published by the Account service whenever a new account is created. It then consumes that message and inserts the new account into the Ordering SQL Server database.

Kubernetes

The K8S folder contains the Kubernetes deployment files. Use kubectl create to create the resources from each file.

• kubectl create accounting-mssql.yml
• kubectl create ordering-mssql.yml
• kubectl create rabbitmq.yml

Wait a minute and you should be able to access the services running in Docker on your machine

Service	Host	Port	Username	Password
RabbitMQ	localhost	15672	guest	guest
Ordering MSSQL	localhost	1434	sa	pa55w0rd!
Accounting MSSQL	localhost	1433	sa	pa55w0rd!

You can then either do a dotnet run inside the Accounting and Ordering projects or you can do a docker build . inside each project and upload the resulting images to Docker Hub. If you go the second route don't forget to tag the images accordingly and then update the image name inside the accounting-service.yml and ordering-service.yml deployment files before running a kubectl create on those files.

If running the services inside Kubernetes you will also need to kubectl create ingress.yml to deploy the API Gateway. You will notice that the API Gateway is using the acme.com host for local testing so you will need to edit your hosts file c:\windows\system32\drivers\etc\hosts to redirect that url to localhost by adding the following on a new line

127.0.0.1 acme.com

The base URL for each service is

Service	Local	Kubernetes
Ordering	http://localhost:5274	http://acme.com
Accounting	http://localhost:5124	http://acme.com

Endpoints for each service are as follows

Service	Method	Name	Endpoint
Accounting	POST	CreateAccount	/api/accounts
Accounting	GET	GetAccounts	/api/accounts
Ordering	POST	CreateOrder	/api/accounts/1/orders
Ordering	GET	GetOrdersForAccount	/api/accounts/1/orders
Ordering	GET	GetOrderForAccount	/api/accounts/1/orders/1

Testing

To run the unit test suite run the following command from the root of the repository (at the solution level)

dotnet test