MongoDb Replica Set

Commands to create local mongo replica set

Run docker compose (first time, run with environments MONGO_INITDB_ROOT_PASSWORD etc to create admin. On the linux server they are not always properly readed for no reason… After initializing mongo, remove environments from compose file)

docker compose up -d

It problems with auth file access, check: Keyfile Access or use trick with entrypoint:

entrypoint:
  - bash
  - -c
  - |
      chmod 400 /etc/mongo/authKey
      chown 999:999 /etc/mongo/authKey
      exec docker-entrypoint.sh "$@"

Login as a admin

docker exec -it mongodb mongo --host mongodb:27017 -u admin -p <password> --authenticationDatabase admin

Setup replica set config (add secondary database)

config = {
      "_id" : "rs0",
      "members" : [
        {
          "_id" : 0,
          "host" : "mongodb:27017",
					"priority" : 2
        },
        {
          "_id" : 1,
          "host" : "mongodb2:27017",
					"priority" : 1
        },
      ]
      };

Initialize cluster

rs.initiate(config);

Add new node to existing replica set

rs.add("mongodb2:27017")

Check current config

rs.conf()

Change replica set config by just assign new config (would be better the hosts to be DNS host then ip addresses)

use local;

config = {
      "_id" : "rs0",
      "members" : [
        {
          "_id" : 0,
          "host" : "<ip/host>:27017",
					"priority" : 2
        },
        {
          "_id" : 1,
          "host" : "<ip/host>:27018",
					"priority" : 1
        },
      ]
      };

rs.reconfig(config);

How to connect:

You must use directConnection=true connection option

mongodb://order-book-alts:<password>@mongodb:27017/on_chain_data?replicaSet=rs0&authSource=admin&directConnection=true