account-email-services

Account and Email Services

This sample shows how to author an AsyncAPI spec for a simple 2 microservices architecture defined in Understanding AsyncAPIs with a Practical Example blog post:

Installation

First, install the following tools:

• AsyncAPI CLI
• AsyncAPI Generator

Also install MQTT that we will need later:

npm install mqtt -g

Define AsyncAPI 2.6.0 specs

Define account-service-2.6.yaml for the Account Service. The key part is the subscribe operation that says "This service publishes messages to the user/signedup channel:

channels:
  user/signedup:
    subscribe:
      operationId: publishUserSignedUp
      message:
      ...

Define email-service-2.6.yaml for the Email Service. The key part is the publish operation that says "This service receives messages from the user/signedup channel:

channels:
  user/signedup:
    publish:
      operationId: receiveUserSignedUp
      message:
      ...

Note: Since most of account-service-2.6.yaml and email-service-2.6.yaml are the same, you can instead created a common-2.6.yaml to encapsulate the common config and simply refer to hem from account-service-common-2.6.yaml and email-service-common-2.6.yaml.

Define AsyncAPI 3.0.0 specs

Here's the same specs in AsyncAPI 3.0.0.

Define account-service-3.0.yaml for the Account Service. The key part is the publishUserSignedUp operation with send action that says "This service sends messages to the user/signedup channel:

operations:
  publishUserSignedUp:
    action: send
    channel:
      $ref: '#/channels/user~1signedup'
    messages:
      - $ref: '#/channels/user~1signedup/messages/publishUserSignedUp.message'

Define email-service-3.0.yaml for the Email Service. The key part is the receiveUserSignedUp operation with receive action that says "This service receives messages on the user/signedup channel:

operations:
  receiveUserSignedUp:
    action: receive
    channel:
      $ref: '#/channels/user~1signedup'
    messages:
      - $ref: '#/channels/user~1signedup/messages/receiveUserSignedUp.message'

Validate AsyncAPI specs

Validate AsyncAPI file:

asyncapi validate account-service-2.6.yaml
asyncapi validate email-service-2.6.yaml

asyncapi validate account-service-3.0.yaml
asyncapi validate email-service-3.0.yaml

Generate code from the AsyncAPI specs

Generate code from the AsyncAPI spec:

asyncapi generate fromTemplate email-service-2.6.yaml @asyncapi/nodejs-template -o email-service-2.6 -p server=test

asyncapi generate fromTemplate email-service-3.0.yaml @asyncapi/nodejs-template -o email-service-3.0 -p server=test

Install dependencies:

cd email-service-2.6
npm install

cd email-service-3.0
npm install

Start the generated application:

node test-email-service-2.6.js
node test-email-service-3.0.js

SUB  Subscribed to user/signedup
Email Service 1.0.0 is ready!

Send message to the generated application:

mqtt pub -t 'user/signedup' -h 'test.mosquitto.org' -m '{"displayName": "Mete", "email": "[email protected]"}'

You should see the email service receive the message:

← user/signedup was received:
{ displayName: 'Mete', email: '[email protected]' }

If you feel adventurous, you can try to generate more code for other languages, for example Java spring:

asyncapi generate fromTemplate email-service-2.6.yaml @asyncapi/java-spring-template -o email-service-spring-2.6