Basic Tutorial for Messaging

NOTE: We use term messages instead of events

This is a good guide: https://www.rabbitmq.com/getstarted.html

Messaging

Producer sends messages
Consumer receives and processes messages

# start consumer
node 1-messaging/index.js c hello_consumer hello_queue
# start producer
node 1-messaging/index.js p hello_producer hello_queue

Worker Queue / Distributed tasks

We can add more consumers to have more processing power

Producer sends messages
Message bus distributes messages evenly to Consumers (usually distributed with round robin)

# start consumer multiple consumers
node 1-messaging/index.js c hello_consumer_first shared_hello_queue
node 1-messaging/index.js c hello_consumer_second shared_hello_queue
# start producer
node 1-messaging/index.js p hello_producer shared_hello_queue

Publish Subscribe / Event driven

Producer sends message (event)
Instead of going to predifined queue it is sent to an exchange
Messge bus routes events from the topic to queues that are attached to it
Consumers will receive every message from their queue

# start consumer multiple consumers
node 2-worker/index.js c hello_consumer_first hello_exchange
node 2-worker/index.js c hello_consumer_second hello_exchange
# start producer
node 2-worker/index.js p hello_producer hello_exchange

Distributed worker queue

Producer sends message (event)
Exchange uses a routing key to send message to correct queue
Consumers will receive every message from their queue

# start consumer multiple consumers
node 3-distributed-queue/index.js c consumer_us distributed_exchange US
node 3-distributed-queue/index.js c consumer_de distributed_exchange DE
# start producer
node 3-distributed-queue/index.js p hello_producer distributed_exchange

Problems

Set up of exchanges more complicated

Request Reply Pattern

Remote Procedure Call / Replies to sender

Replies require an own queue. Producer is also Consumer and Consumer is a Producer...

Client uses a producer to send a message
Server receives a message with consumer
Server sends a message with producer
Client receives a message with consumer

# start server
node 4-rpc/index.js s
# start client
node 4-rpc/index.js c

Star RabbitMQ server with Management UI

$ docker run -d --name example-rabbit -p 5672:5672 -p 15672:15672 rabbitmq:3-management

Port 5672 is for rabbitmq client communication

Port 15672 is for Management UI

Go to http://localhost:15672/ to open Management UI (

username: guest
password: guest

Write some code

AMQP 0-9-1 library and client for Node.JS

example_github_async.js and example_github_promise.js are async versions of https://github.com/squaremo/amqp.node#promise-api-example

ttu/messaging-examples-rabbitmq