Microservice Example

A microservice example using nodejs.

Requirements

RabbitMQ (optional: with management)

Setting up RabbitMQ

This example uses Docker to run RabbitMQ.

• If using a Mac you’ll need to use boot2docker to run Docker containers. See: https://docs.docker.com/installation/mac/

• Get the RabbitMQ Docker image with management:

docker run -d -e RABBITMQ_NODENAME=my-rabbit --name my-rabbit -p 5672:5672 -p 15672:15672 rabbitmq:3-management

(See: https://registry.hub.docker.com/__/rabbitmq/)

This command runs RabbitMQ with management console. It explicitly maps the ports, which also maps the IPs. This might differ when running on Linux / Mac because of boot2docker. On Linux you might be able to use the localhost IP, on Mac you need to use boot2docker IP.

• Now you can access management portal at:

http://[boot2dockerIP]:15672, guest, guest

• You can access the RabbitMQ message broker using:

host: [boot2dockerIP]
port: 5672
login: 'guest'
password: 'guest'
vhost: '/'

Running the project

• Clone the project
• Install the dependancies
• Have RabbitMQ running
• Update connect.js to contain the RabbitMQ host IP
• run each service independently:

1. nodemon service/monitor.js
2. nodemon service/need.js
3. nodemon service/solution.js
4. nodemon service/solutionSelector.js
5. nodemon service/membership.js

What this code is attempting to achieve:

• A message / expressed need gets put onto the message bus
• A solution gets appended to the message
• As more information is added to the message, a more adequate solution is presented
• The best solution for a message is printed out

Overview of logic flow:

• RabbitMQ message broker runs
• To interact with the message broker we create an exchange
• Messages are sent/retrieved from the message broker using a Publish/Subscribe model
• Messages are published to the message broker (via the exchange)
• Messages are retrieved from the message broker via a queue that subscribes to messages (via the exchange)

Publish messages to the exchange

1. Connect to RabbitMQ
2. On connected, get a handle to an exchange [*]
3. Publish message using the exchange

Subscribe to messages on the exchange

1. Connect to RabbitMQ
2. On connected, get a handle to an exchange [*]
3. Create a queue & bind it to the exchange
4. Subscribe to messages using the queue

[*] Get a handle to the exchange from the exchange-name - creates a new exchange if non-existant, otherwise returns the existing exchange