MongoDB Replication and docker
As docker is the hot thing in the systems administration world, and it’s also recommended to have replica sets for mongo DB. And also in general on a production environment so your application is 99.9999% available.
Here are some of the things I’ve learnt when you use docker and mongodb replication.
- The hostname that mongod generates isn’t very useful. You have to change this.
- None of the guides out there are too useful, or show you how to do docker on the same box (which defeats the purpose of replication, but hey its a good dev environment).
So here is my steps
- Define folder for where the data is to be stored (i.e. /data/mongo1 , /data/mongo2)
- Define replica set name (ie. rs0)
- Start up all docker instances
- Connect to one of the servers (i.e. mongo1)
- Do a rs.initiate()
- Do a cfg = rs.conf()
- set cfg.members[0].host to the external address (or address thats visible to your other mongo DB instances) for the server that you did a rs.initiate() on
- Do a rs.reconfig(cfg)
- rs.add() on all the other mongo instances from wthe server you did rs.initiate() on
- Make a change on mongo1 and ensure that the data is replicated across to mongo2.
