Trying Redis in Docker + as-a

README.md

Goal: try redis inside a Docker container

Run Redis Docker image

1. Open docker terminal

• displays docker is configured to use the default machine with IP 192.168.99.100

2. Start redis:alpine prebuilt container from docker hub.

• docker run --name redis -p 6379:6379 -d redis:alpine
• the "alpine" image is very slim (5MB!)
• the running container binds the internal port 6379 to the "outside" world port with same number
• the port 6379 is the default Redis port for simplicity

3. Open Git repo (for example ~/git/training/node)
4. Pick node nvm use 5
5. Create new NPM package npm init -y
6. Install redis Node client npm install --save redis
7. Write small Redis example, like this one

// index.js
var redis = require("redis"),
    client = redis.createClient();
client.on("error", function (err) {
    console.log(err);
});
client.set("akey", "string val", redis.print);
client.get("akey", redis.print);

8. Run the example node index.js and get errors!

$ node index.js 
Error: Redis connection to 127.0.0.1:6379 failed - connect ECONNREFUSED
Error: Redis connection to 127.0.0.1:6379 failed - connect ECONNREFUSED
...

We need to connect to the Redis server running inside the Docker container, not on the host 127.0.0.1. The Docker's virtual machine IP is displayed when the docker terminal starts, or you can look it up using docker-machine ls command. In our case it is 192.168.99.100.

9. Modify the example to take the Redis host address as a parameter

// index.js
var redis = require("redis"),
    client = redis.createClient({
      host: process.env.REDIS_HOST || '127.0.0.1'
    });

10. Start the example again, setting the HOST environment variable first

$ REDIS_HOST=192.168.99.100 node index.js 
Reply: OK
Reply: string val

Longer term

What if there are lots of environment settings to pass? Can we store all environment settings groupped and use bunch of them without accidentally adding them to a public repo (see https://github.com/bahmutov/ban-sensitive-files for example).

I have a tool as-a that allows one to store all groups of private settings that should NOT be checked in a single inside the user's private home folder. In our case, let us install the tool and create the file to keep all our settings

npm install --global as-a
touch ~/.as-a.ini

Create a group with just a single setting for local Docker Redis. I will even add the Docker command as a comment there

; .as-a.ini
; Redis running inside a Docker container
; Start the image as
; docker run --name redis -p 6379:6379 -d redis:alpine
[red-dock]
REDIS_HOST=192.168.99.100

Now run the example without copy / paste or even remembering and showing the actual settings in the console.

$ as-a red-dock node index.js 
Reply: OK
Reply: string val

Nice!

Additional info

• Redis Docker image docs https://hub.docker.com/_/redis/
• If you need more Docker commands, see https://gist.github.com/bahmutov/1003fa86980dda147ff6
• If you need to start services inside the local environment, consider using quickly.