AMQP Lib Topic Controllers

Allows to create controller classes with methods as actions

Create structured, declarative and beautifully organized class-based controllers with heavy decorators usage for AMQP Lib using TypeScript.

Installation

Step #1 - Install package

By NPM:

npm install amqplib-topic-controllers --save

Or by Yarn:

yarn add amqplib-topic-controllers

Step #2 - Install reflect-metadata shim package

By NPM:

npm install reflect-metadata --save

Or by Yarn:

yarn add reflect-metadata

And make sure to import it before you use amqplib-topic-controllers:

import 'routing-controllers';

Step #3 - Install amqplib package

By NPM:

npm install amqplib --save

Or by Yarn:

yarn add amqplib

Step #4 - Code preparations

It's important to set these options in tsconfig.json file of your project:

{
  "compilerOptions": {
    {
      "emitDecoratorMetadata": true,
      "experimentalDecorators": true
    }
  }
}

Step #5 (optional) - install class-validator and class-transformer packages

If you want to use automatic transformations and validations for JSON message content, you should install class-validator and class-transformer packages:

By NPM:

npm install class-validator class-transformer --save

Or by Yarn:

yarn add class-validator class-transformer

Example of usage

Create controller class:

import { Controller, Returnable, Task, JsonMessageContent } from 'amqplib-topic-controllers';
 
function sleep(ms: number) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}
 
interface Metadata {
  name: string;
  createdAt: string;
}
 
export interface SummBody {
  a: number;
  b: number;
}
 
@Controller('test')
export default class TestController {
  private metadata: Metadata;
 
  public constructor(metadata: Metadata) {
    this.metadata = metadata;
  }
 
  @Task()
  public async longJob() {
    console.info('Long job started...');
    await sleep(5000);
    console.info('Long job done.');
  }
 
  @Returnable()
  public getMetadata() {
    return this.metadata;
  }
 
  @Returnable()
  public summ(@JsonMessageContent() { a, b }: SummBody) {
    return {
      summ: a + b,
    };
  }
 
  @Returnable()
  public async asyncSumm(@JsonMessageContent() { a, b }: SummBody) {
    await sleep(750);
    return {
      summ: a + b,
    };
  }
}

Create consumer application:

import 'reflect-metadata';
import { connect } from 'amqplib';
import { bindToChannel } from 'amqplib-topic-controllers';
 
import TestController from './TestController';
 
export const METADATA = {
  name: 'testController',
  createdAt: '2020-08-05T20:55:36.103Z',
};
 
export const EXCHANGE_NAME = 'TestMicroservice';
 
async function main() {
  // Connect to AMQP server
  const connector = await connect({
    hostname: 'localhost',
    port: 5672,
    username: 'guest',
    password: 'guest',
  });
 
  // Create channel to consume messages
  const channel = await connector.createChannel();
 
  // Bind controller class with constructor arguments to channel
  bindToChannel({
    channel,
    exchangeName: EXCHANGE_NAME,
    controllers: [[TestController, METADATA]],
  });
}
 
main().then(
  () => {
    console.log('OK');
  },
  (err) => {
    console.error(err);
    process.exit(1);
  },
);

Application is ready to receive messages. Let's try send something:

import { connect } from 'amqplib';
 
async function main() {
  const correlationId = String(Date.now());
  const { queue } = await channel.assertQueue('', { exclusive: true });
 
  await channel.consume(queue, (message) => {
    if (message && message.properties.correlationId === correlationId) {
      const data = JSON.parse(message.content.toString());
 
      //
      // Must print object:
      // {
      //   name: 'testController',
      //   createdAt: '2020-08-05T20:55:36.103Z',
      // }
      //
      console.log(data);
    }
  });
 
  channel.publish('TestMicroservice', 'test.getMetadata', Buffer.from(''), {
    correlationId,
    replyTo: queue,
  });
}
 
main().then(
  () => {
    console.log('OK');
  },
  (err) => {
    console.error(err);
    process.exit(1);
  },
);

Messages consuming is based on topics with template <ControllerName>.<ActionName>. Topics names calculated by class and method decorators (see reference below).

You also can see example aplication here.

Main reference

bindToChannel(params: BindToChannelParams)

Attaches controllers to existing AMQP connection channel. Asserts exchange with settled name and asserts all needed queues.

interface BindToChannelParams

bindToChannel function parameters. Fields:

• controllers (required, type (Function | [Function, ...any[]])[]) - list of controllers classes to bind. If controller need some constructor parameters, set array, where first item will be controller class and rest items - arguments for constructor. Otherwise, just set controller class.
• channel (required, type Channel | ConfirmChannel) - target channel to bind controllers consumers.
• exchangeName (required, type string) - target exchange for calculated controllers topics.
• delayedExchange (optional, type boolean) - should target exchange use RabbitMQ Delayed Message Plugin. If true function will automatically fix some parameters and create exchange with special type;
• exchangeParams (optional, type Options.AssertExchange) - target exchange configuration (see amqplib "Channel" method "assertExchange" documentation for details). By default, equals { durable: true }.
• logger (optional, type ILogger) - object with methods to log all incoming and outcoming messages. Internal console logger using by default. See interface ILogger below for details.
• errorHeaderName (optional, type string) - name of header, which marks that remote service replied with error. Equals constant AMQPLIB_TOPIC_CONTROLLERS_ERROR_HEADER_NAME ("X-Amqplib-Topic-Controller-Is-Error") by default. See "Error handling" section below for details.
• transformError(error: unknown): any (optional, type Function) - error response builder for producer. May be asynchronous. See "Error handling" section below for details.

interface ILogger

Logger - singature of object with methods to log all incoming and outcoming messages.

Methods to implement:

• consume(queue: string, message: Message): void - log incoming message;
• reply(queue: string, corellationId: unknown): void - log reply;
• error(queue: string, message: Message, err: unknown) - log error;

Error handling

Package automatically catch all errors thrown by your actions. Every error will be logged. If action is returnable, error will be returned in content of reply message.

Reply message will be marked by special header. Header will contain stringified true value. Name of this header is value of constant AMQPLIB_TOPIC_CONTROLLERS_ERROR_HEADER_NAME ("X-Amqplib-Topic-Controller-Is-Error") by default, but you can change it by errorHeaderName option of bindToChannel function.

Content of error message will be JSON string. By default it will maps into object like this:

{
  "error": "Error: Some error"
}

But you can override this behavior by transformError option of bindToChannel function. Error builder must receive error as first argument and return any entity which can be stringified by JSON.stringify function. Error builder can be asynchronous (return Promise).

Decorators reference

Class decorators

Controller(name?: string): ClassDecorator

Decorator factory which marks class as controller. Every controller class must be marked by this decorator or it will be skipped.

Argument name defines name of controller (<ControllerName> in <ControllerName>.<ActionName> topic template). If it's not settled, decorator will try to get name from displayName static property or from name of class. Otherwise, error will be thrown.

Method decorators

Action(name): MethodDecorator

Decorator factory which marks method as simple action - it's consumes message and acknowleges it.

Argument name defines name of action (<ActionName> in <ControllerName>.<ActionName> topic template). If it's not settled, decorator will try to get name for method name. Otherwise, error will be thrown.

Task(name): MethodDecorator

Decorator factory which marks method as task action - action which is not aknowleging ({ noAck: true }). This decorator may be usefull for some heavy activities which does not need to response.

Argument name defines name of action (<ActionName> in <ControllerName>.<ActionName> topic template). If it's not settled, decorator will try to get name for method name. Otherwise, error will be thrown.

Returnable(params?: string | { json?: boolean, name?: string }): MethodDecorator

Decorator factory which marks method as returnable action - action which replies to producer with it's result (or just to "say" that is done). This decorator can be used to build some RPC-like APIs based on AMQP.

Argument params is object with optional fields:

• name (type string, optional) - defines name of action (<ActionName> in <ControllerName>.<ActionName> topic template). If it's not settled, decorator will try to get name for method name. Otherwise, error will be thrown.
• json (type boolean, optional) - if true, result of method will be sended to producer as stringified JSON document. Otherwise, result of method will be just casted to string. Default value is true.

You can pass string value as argument. This will be equivalent of { name: string } argument.

Method arguments decorators (Injectors)

By default, amqplib-topic-controllers does not set arguments to method. Injectors allows you to pass message data to action methods.

Message(): ParameterDecorator

Injects full AMQP message to parameter, without any parsing.

RawMessageContent(): ParameterDecorator

Injects raw message content (type Buffer) to parameter, without any parsing and encoding.

StringMessageContent(encoding?: BufferEncoding): ParameterDecorator

Injects stringified message content (type string) to parameter - just decodes Buffer.

Argument encoding defines encoding of source message content. By default, content will be stringified by contentEncoding AMQP message property or "as-is" (.toString());

MessageProperties(): ParameterDecorator

Injects message properties (see amqplib documentation for "Channel" method "consume" for details).

MessageProperty(name: keyof MessageProperties): ParameterDecorator

Injects concrete message property (see amqplib documentation for "Channel" method "consume" for details).

Argument name is required and defines name of property to inject.

MessageFields(): ParameterDecorator

Injects message fields (see amqplib documentation for "Channel" method "consume" for details).

MessageField(name: keyof MessageFields): ParameterDecorator

Injects concrete message field (see amqplib documentation for "Channel" method "consume" for details).

Argument name is required and defines name of field to inject.

JsonMessageContent(options?: BufferEncoding | JsonMessageContentOptions | null | undefined): ParameterDecorator

Inject message content as parsed JavaScript object (result of JSON.parse) - decodes Buffer and pass string to JSON.parse. Optionally, object can be transformed into instance of given class and validated.

Argument options is object with optional fields (interface JsonMessageContentOptions):

• encoding (type BufferEncoding, subtype of string) - defines encoding of source message content. By default, content will be stringified by contentEncoding AMQP message property or "as-is" (.toString());
• transform (type boolean) - should content will be transformed by class-transformer package;
• validate (type boolean) - should content will be validated by class-validator package;
• targetClass (type TargetClass) - class to transform JSON response by class-transformer;

When transform is true, option targetClass is required (or error will be thrown). When validate is true, options transform and targetClass are required (or error will be thrown).

You can pass BufferEncoding/string value as argument. This will be equivalent of { encoding: string } argument.

ValidInstanceContent(targetClass: TargetClass, encoding?: BufferEncoding | null | undefined)

Alias for JsonMessageContent({ targetClass: TargetClass, encoding, validate: true, transform: true }). Injects instantiated and validated content body object.

interface TargetClass

Class of entity to transform and validate JSON body:

interface TargetClass {
  new (...args: any[]): any;
}

For developers

Environment requirements:

To build and test package you need this:

• Node.JS v12.18.2+;
• Yarn v1.22.4+;
• Docker v19.03.12+;
• Docker Compose v1.26.2;
• GNU Make v4.2.1+;
• Python 3.8.2+;

Package building

By lifecycle script:

yarn build

Or directly by GNU Make:

make

Testing

Build package, start test Docker containers and run tests

yarn test

It runs test.py file with full testing cycle.