amqplib and express example

This application demonstrates how to use amqplib with express in response to this issue. Points of note are:

Assertion of RabbitMQ topology on application start
Automated recovery following connection or channel errors
Detects and reports
- saturated channels
- unroutable messages
- unacknowledged publishes
Provides graceful startup and shutdown

There are several ways of using amqplib, each with different trade-offs. Alternative approaches might open/close a channel for each publish command, or maintain a pool of permanently open channels. Others may perfer performance over reliability and not use a confirm channel. The code would also have been more coherent if I had used async/await, but the original poster I was responding to was experiencing difficulty with promises, so I went with them instead.

Prerequisite

Node 12

Starting the app

npm install
docker run -d --name rabbitmq -p 5672:5672 -p 15672:15672 rabbitmq:3-management
sleep 10
DEBUG='amqplib-express-example:*' node index.js

Exercising the app

curl -H "Content-Type: application/json" -X POST -d '{ "email": "foo@bar.com" }' http://localhost:3000/api/user/forgot-password

Unless you create a queue and bind it to the user-exchange the application will report that messages are returned

Testing automated recovery (connection close)

docker restart rabbitmq

Testing automated recovery (connection error)

docker kill rabbitmq
docker restart rabbitmq

Testing automated recovery (heartbeat timeout)

docker pause rabbitmq
sleep 5
docker unpause rabbitmq