MongoDB Replica Set Containerization: Keyfile + Auth Quic...

Quick Start

Generate keyfile

openssl rand -base64 756 > mongo-keyfile
chmod 600 mongo-keyfile

docker-compose

version: "3.9"
services:
  mongo1:
    image: mongo:7.0
    ports:
      - "27017:27017"
    volumes:
      - ./mongo1-data:/data/db
      - ./mongo-keyfile:/etc/mongo-keyfile:ro
    command: ["mongod","--replSet","rs0","--bind_ip_all", "--keyFile", "/etc/mongo-keyfile"]
  # ... mongo2, mongo3 similar

Connection URI

mongodb://admin:admin123@localhost:27017/?replicaSet=rs0&authSource=admin

Common Errors

Symptom	Root Cause	Fix
permissions on keyfile are too open	mongo-keyfile not 600	chmod 600
Authentication failed	Wrong password/db	Confirm authSource
ReplicaSetNoPrimary	Not yet elected	Wait or check priority