Dockerizing a Redis service

Dockerizing a Redis service

Very simple, no frills, Redis service attached to a web application using a link.

Create a Docker container for Redis

Firstly, we create a Dockerfile for our new Redis image.

Next we build an image from our Dockerfile. Replace <your username> with your own user name.

Run the service

Use the image we’ve just created and name your container redis.

Running the service with -d runs the container in detached mode, leaving the container running in the background.

Importantly, we’re not exposing any ports on our container. Instead we’re going to use a container link to provide access to our Redis database.

Create your web application container

Next we can create a container for our application. We’re going to use the -link flag to create a link to the redis container we’ve just created with an alias of db. This will create a secure tunnel to the redis container and expose the Redis instance running inside that container to only this container.

Once inside our freshly created container we need to install Redis to get the redis-cli binary to test our connection.

As we’ve used the --link redis:db option, Docker has created some environment variables in our web application container.

We can see that we’ve got a small list of environment variables prefixed with DB. The DB comes from the link alias specified when we launched the container. Let’s use the DB_PORT_6379_TCP_ADDR variable to connect to our Redis container.

We could easily use this or other environment variables in our web application to make a connection to our redis container.