This is an example of how to setup a highly available redis using Docker.
All you need is Docker and Docker-Compose.
Clone the repository and startup everything
docker-compose up -d
Now the fun can begin.
Let's take a look at the redissentinel container logs.
docker-compose logs redissentinel
It should say something like this at the end
redissentinel_1 | [1] 02 Apr 11:34:12.018 # +monitor master mymaster 172.17.0.203 6379 quorum 1
redissentinel_1 | [1] 02 Apr 11:34:12.019 * +slave slave 172.17.0.205:6379 172.17.0.205 6379 @ mymaster 172.17.0.203 6379
The important parts are +monitor master mymaster and +slave slave. It means
the sentinel is watching the master and knows about the slave.
Now we know the redis cluster is running correctly. Let's take a look at our "app". Make sure it is running and printing every 15 seconds. (in each loop it writes to redis, that way we test that high availability is achieved later)
docker-compose logs app
It should look something like this
app_1 | ------------
app_1 | ---LOOP 0---
app_1 | ------------
app_1 | ------------
app_1 | ---LOOP 1---
app_1 | ------------
app_1 | ------------
app_1 | ---LOOP 2---
app_1 | ------------
app_1 | ------------
app_1 | ---LOOP 3---
app_1 | ------------
...
To follow everything that's going to happen you might want to open 3 terminals.
One dislaying the redissentinel log. One displaying the app log and one to
kill the master redis server.
Stop the master with
docker-compose stop redismaster
You should notice that redis-sentinel promotes the redis-slave to be the new master and the "app" keeps printing as if nothing ever happened.
Hint: redis sentinel remembers this by writing to it's config file. So make sure to
git checkout sentinel.confit to reset when you do multiple runs.
That's it, have fun!