concept message queue in category docker

This is an excerpt from Manning's book Bootstrapping Microservices with Docker, Kubernetes and Terraform MEAP V08. Login to get full access to this book.

Figure 5.6. An indirect message isn’t explicitly sent to a microservice, instead the message is placed in a queue and can be handled later

This is an excerpt from Manning's book Learn Docker in a Month of Lunches. Login to get full access to this book.

Docker also makes it easy to bring third-party software into your application, adding features without writing your own code. Docker Hub is a public service where teams share software that runs in containers. The CNCF publishes a map of open source projects you can use for everything from monitoring to message queues, and they’re all available for free from Docker Hub.

21 Asynchronous communication with a message queue

This is the final full chapter of the book, and it introduces a new way for the components of a system to communicate: sending and receiving messages using a queue. Message queues have been around for a very long time--they’re a way of decoupling components so instead of making a direct connection to communicate with each other, they send messages to the queue. The queue can deliver messages to one or many recipients, and that adds a lot of flexibility to your architecture.

Message queues are server components that just run until you stop them. Redis listens for connections on port 6379, and that same address is used by clients to send messages and by servers to listen for messages. You’ll see from your container logs that Redis is up and running just a few seconds after you start the container--my output is in figure 21.2.

Figure 21.2 A message queue is just like any other background container, waiting for connections.

# switch to the exercise folder:
 cd ch21/exercises/todo-list
 
 # start the message queue:
 docker-compose up -d message-queue
 
 # check the logs:
 docker container logs todo-list_message-queue_1
 
 # and check active connections:
 curl http://localhost:8222/connz