moby/docs/sources/examples/running_redis_service.rst

title

Running a Redis service

description

Installing and running an redis service

keywords

docker, example, package installation, networking, redis

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.

FROM        ubuntu:12.10
RUN         apt-get update
RUN         apt-get -y install redis-server
EXPOSE      6379
ENTRYPOINT  ["/usr/bin/redis-server"]

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

sudo docker build -t <your username>/redis .

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.

sudo docker run --name redis -d <your username>/redis

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.

sudo docker run --link redis:db -i -t ubuntu:12.10 /bin/bash

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

apt-get update
apt-get -y install redis-server
service redis-server stop

Now we can test the connection. Firstly, let's look at the available environmental variables in our web application container. We can use these to get the IP and port of our redis container.

env
. . .
DB_NAME=/violet_wolf/db
DB_PORT_6379_TCP_PORT=6379
DB_PORT=tcp://172.17.0.33:6379
DB_PORT_6379_TCP=tcp://172.17.0.33:6379
DB_PORT_6379_TCP_ADDR=172.17.0.33
DB_PORT_6379_TCP_PROTO=tcp

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.

redis-cli -h $DB_PORT_6379_TCP_ADDR
redis 172.17.0.33:6379>
redis 172.17.0.33:6379> set docker awesome
OK
redis 172.17.0.33:6379> get docker
"awesome"
redis 172.17.0.33:6379> exit

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