Example for @gapi infrastructure using rabbitmq and graphql

Installing packages

npm install

Starting RabbitMQ using docker-compose

docker-compose up

Installing @gapi/cli

Before you start the server @gapi/cli needs to be installed

npm i -g @gapi/cli

Starting graphql server

npm start

Open Graphiql Playground in browser

http://localhost:9000/graphiql

Testing subscriptions

There is a mutation called sendMessage

mutation {
  sendMessage(message: "my-message") {
    message
  }
}

The actual code which does the message sending in queue looks like this

@Type(AppType)
@Mutation({
  message: {
    type: new GraphQLNonNull(GraphQLString),
  },
})
sendMessage(root, { message }): IAppType {
  this.pubsub.publish('MY_CHANNEL', { message });
  return { message };
}

Subscribing to message queue from Graphiql Playground

subscription {
  listenForChanges {
    message
  }
}

The actual code for creating this subscription looks like this

@Type(AppType)
@Subscribe(function(this: AppQueriesController) {
  return this.pubsub.asyncIterator('MY_CHANNEL');
})
@Subscription()
listenForChanges(message: IAppType) {
  return message;
}

So actually we are publishing messages to the queue they are send to RabbitMQ and every listener aka subscriber is using listenForChanges subscription query to get the actual changes send by sendMessage mutation.

Opening the RabbitMQ Dashboard

http://142.10.0.5:15672

We should see prompt for login so we can use our default credentials defined inside docker-compose

username: my-user password: my-user-password

Notice that until you have a subscriber to a particular topic the connection with RabbitMQ is lazy and will not be established.

As long as listenForChanges is subscribed using the Graphql Playground we should imidiately see that Exchanges, Queues and Connections are defined.

Changing the environment variables can be done using gapi-cli.conf.yml file

Note: in order for the changes to take effect server needs to be stopped and started again

config:
  # Application configuration
  app:
    local:
      API_PORT: 9000
      NODE_ENV: development
      GRAPHIQL_TOKEN: ''

      AMQP_HOST: 142.10.0.5
      AMQP_PORT: 5672
      AMQP_USER: my-user
      AMQP_PASS: my-user-password
      RABBITMQ_ENABLED: true

If RABBITMQ_ENABLED is commented out internal fake pubsub will be used especially good for development purposes in order to not spin up whole RabbitMQ server

Installing optional Graphql Voyager

This module is really awesome since it gives you a Flow Diagram for all the nodes that are created

The module can be installed using npm

npm install @gapi/voyager

Then import the module inside app.module.ts imports

import { Module } from '@gapi/core';
import { VoyagerModule } from '@gapi/voyager';

@Module({
  imports: [VoyagerModule.forRoot()],
})
export class AppModule {}

To access Voyager go to address http://localhost:9000/voyager

Njoy!