RabbitMQ RPC library

This library will take care of RPC requests and messaging between microservices. It is easy to bind to our existing controllers to RMQ routes. You can use it with any NodeJS framework.

Start

First, install the package:

npm i rabbitmq-messages

Then you need to extend your controller with RMQController:

import { RMQController, RMQRoute } from 'rabbitmq-messages';

export class AppController extends RMQController {
    constructor() {
        super({
            exchangeName: 'my_exchange',
            connections: [
                {
                    login: 'admin',
                    password: 'admin',
                    host: 'localhost',
                },
            ],
        });
    }
}

In super() you pass connection options =:

• exchangeName (string) - Exchange that will be used to send messages to.
• connections (Object[]) - Array of connection parameters. You can use RQM cluster by using multiple connections.

Additionally, you can use optional parameters:

• queueName (string) - Queue name which your microservice would listen and bind topics specified in '@RMQRoute' decorator to this queue. If this parameter is not specified, your microservice could send messages and listen to reply or send notifications, but it couldn't get messages or notifications from other services. Example:

super({
    exchangeName: 'my_exchange',
    connections: [
        {
            login: 'admin',
            password: 'admin',
            host: 'localhost',
        },
    ],
    queueName: 'my-service-queue',
});

• prefetchCount (boolean) - You can read more here.
• isGlobalPrefetchCount (boolean) - You can read more here.
• reconnectTimeInSeconds (number) - Time in seconds before reconnection retry. Default is 5 seconds.
• queueArguments (object) - You can read more about queue parameters here.
• messagesTimeout (number) - Number of milliseconds 'post' method will wait for the response before a timeout error. Default is 30 000.
• isQueueDurable (boolean) - Makes created queue durable. Default is true.
• isExchangeDurable (boolean) - Makes created exchange durable. Default is true.
• logMessages (boolean) - Enable printing all sent and recieved messages in console with its route and content. Default is false.

Sending messages

To send message with RPC topic use send() method in your controller or service:

// In TypeScript
this.send<number[], number>('sum.rpc', [1, 2, 3]);
// Or in JavaScript
this.send('sum.rpc', [1, 2, 3]);

This method returns a Promise. First type - is a type you send, and the second - you recive.

• 'sum.rpc' - name of subscription topic that you are sending to.
• [1, 2, 3] - data payload. To get a reply:

this.send('sum.rpc', [1, 2, 3]).then(reply => {
    //...
});

If you want to just notify services:

// In TypeScript
this.notify < string > ('info.none', 'My data');
// Or in JavaScript
this.notify('info.none', 'My data');

This method returns a Promise.

• 'info.none' - name of subscription topic that you are notifying.
• 'My data' - data payload.

Recieving messages

To listen for messages bind your controller methods to subscription topics with RMQRoute() decorator:

export class AppController extends RMQController {
    //...

    @RMQRoute('sum.rpc')
    sum(numbers: number[]): number {
        return numbers.reduce((a, b) => a + b, 0);
    }

    @RMQRoute('info.none')
    info(data: string) {
        console.log(data);
    }
}

Return value will be send back as a reply in RPC topic. In 'sum.rpc' example it will send sum of array values. And sender will get 6:

this.send('sum.rpc', [1, 2, 3]).then(reply => {
    // reply: 6
});

Each '@RMQRoute' topic will be automatically bound to queue specified in 'queueName' option. If you want to return an Error just throw it in youe method:

@RMQRoute('my.rpc')
myMethod(numbers: number[]): number {
	//...
	throw new Error('Error message')
	//...
}

Disconnecting

If you want to close connection, for example, if you are using RMQ in testing tools, use disconnect() method;

Breaking Changes

v0.5.0

• 'subscriptions' parameters is no longer supported. Queue will be automatically bound to all '@RMQRoute' in RMQController.