Almost every interesting application uses at least one infrastructure service such as a database or a message broker. For example, if you tried to build and/or run the Spring Boot-based user registration service you would have discovered that it needs both MongoDB and RabbitMQ.
One option, of course, is to install both of those services on your machine. Unfortunately, installing a service is not always easy. Also, different projects might need different incompatible versions. Moreover, I’m not a fan of cluttering my machine with random services. Fortunately, there is a great way to solve this problem: Docker. You install Docker and use it to run the services that you need as containers.
Docker only directly runs on Linux so if you are using Mac OSX or Windows the first step is to install Boot2Docker (Mac OSX, Window). Boot2Docker installs the Docker command line locally but runs the Docker daemon in a Virtual Box VM. As a result, the user experience is very similar to running Docker directly on Linux.
The following command runs a VM containing the Docker daemon:
$ boot2docker up
You then need to set some environment variables in order for the Docker command line to know the host and port of the Docker daemon.
$ boot2docker shellinit
You can set those variables by simply running this command:
$ $(boot2docker shellinit)
Once you have done that you are ready to start using Docker from you Mac or Windows machine. For example, docker ps shows the running Docker containers.
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
6fcf0779a5e1 dockerfile/mongodb:latest "mongod" 8 days ago Up 8 days 28017/tcp, 0.0.0.0:27017->27017/tcp mongodb
So what about running MongoDB and RabbitMQ? One of the great features of the Docker ecosystem is https://hub.docker.com, which is a website where the community shares Docker images. In particular, you can find images for infrastructure services such as RabbitMQ and MongoDB. You can, for example, run MongoDB with the following command:
docker run -d -p 27017:27017 --name mongodb dockerfile/mongodb
This command will, if necessary, download the dockerfile/mongodb image from Docker Hub and launch the container running MongoDB listening on port 27017. Similarly, you can run RabbitMQ using this command:
docker run -d -p 5672:5672 -p 15672:15672 --name rabbitmq dockerfile/rabbitmq
These containers are, of course, running in the Virtual Box VM so you need to connect to them using the appropriate IP address. Fortunately, boot2docker makes that easy to configure:
export DOCKER_HOST_IP=$(boot2docker ip)
The “boot2docker ip” command outputs the IP address that you use to connect to the containers.
Now that you have setup the MongoDB and RabbitMQ, you can now run the User Registration Service:
docker run -d -p 8080:8080 -e SPRING_DATA_MONGODB_URI -e SPRING_RABBITMQ_HOST --name sb_rest_svc