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One of the great things about Docker is how you can quickly use it to try out applications without having to install it directly on your developer machine. No need to install runtimes like Java or erlang if you don't want to - the container encapsulates all dependencies, and leaves no trace behind when you delete it.

So over the next few days I plan to provide a few short tutorials showing off how to explore various bits of open source software with Docker, starting with Redis. The focus of these tutorials is to familiarize you with the Docker commands needed to create containers and execute custom commands within them, but hopefully you'll learn a few Redis basics along the way too.

Intro

This tutorial shows how you can use Docker to explore Redis. You can run the commands with Docker installed, or Docker for Windows in Linux mode. But you can also use Play with Docker to try this out.

Start a new container running Redis

Here we're giving it a name (redis1) and exposing port 6379 (the Redis default)

docker run -d -p 6379:6379 --name redis1 redis

Check it's running with

docker ps

And view the log output with

docker logs redis1

Run the Redis CLI in the container

We're going to start a new interactive session (-it) inside the running container, and use it to run redis-cli. We could run it directly, but for now, let's just start a shell with sh:

docker exec -it redis1 sh

And now we're attached to our container. Let's run redis-cli:

# redis-cli

Try out some basic Redis commands

If we send a "ping", should get "PONG" back:

127.0.0.1:6379> ping
PONG

Try out some more commands (set a key and increment a counter)

127.0.0.1:6379> set name mark
OK
127.0.0.1:6379> get name
"mark"
127.0.0.1:6379> incr counter
(integer) 1
127.0.0.1:6379> incr counter
(integer) 2
127.0.0.1:6379> get counter
"2"

And when we're done exit out of redis-cli and sh:

127.0.0.1:6379> exit
# exit

Connect from another linked container

Now let's start another container, called client1. We'll base it off the redis image but we're only using it to run the redis-cli so we'll just ask it to run sh in interactive mode -it. This means it won't be running Redis itself. We specify --rm so it will delete itself after the shell exits.

We link it to the redis1 container (which is still running), and it will be referred to from within this container simply as redis.

docker run -it --rm --link redis1:redis --name client1 redis sh

Now in this container let's start redis-cli and connect to redis1 which has the name redis:

# redis-cli -h redis
redis:6379>

And now let's issue some commands. Since we didn't stop the original redis1 container, the keys we created earlier should still be there:

redis:6379> get name
"mark"
redis:6379> get counter
"2"

And now exit out of redis-cli and sh:

redis:6379> exit
# exit

This has actually caused our client1 container to delete itself. So even if we ask to see all containers including stopped ones with:

docker ps -a

We should only see our single Docker container.

Clean up

Let's stop the redis1 container and then delete it.

docker stop redis1
docker rm redis1

We have also downloaded the redis image, which we will see in the list

docker image ls

It's only 83MB, so we may want to keep it for next time we want to run a Redis container, but if we're sure we don't need it anymore, we can remove the image to free up disk space and get us back to exactly where we started before:

docker image rm redis

Summary

As you can see, with just a few basic Docker commands we could run Redis in a container, and even connect to it from another container.

Next up, I'll show you how we can do the same with PostgreSQL, which will give us the opportunity to explore Docker volumes.

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