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:title: Running a Redis service
:description: Installing and running an redis service
:keywords: docker, example, package installation, networking, redis
.. _running_redis_service:
Redis Service
=============
.. include:: example_header.inc
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.
.. code-block:: bash
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.
.. code-block:: bash
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.
.. code-block:: bash
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.
.. code-block:: bash
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.
.. code-block:: bash
apt-get update
apt-get -y install redis-server
service redis-server stop
As we've used the ``--link redis:db`` option, Docker has created some environment
variables in our web application container.
.. code-block:: bash
env | grep DB_
# Should return something similar to this with your values
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.
.. code-block:: bash
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.
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