MongoDB Docker and Operations

Introduction

Running mongod in Docker is the fastest way to share a dev database across teammates. Production adds persistent volumes, authentication, replica sets, backups, and upgrade planning. This chapter covers mongod.conf, Compose patterns, mongodump, and operational habits linked to Atlas for managed hosting.

Prerequisites

Single-Node Docker (Development)

yaml

Connect:

bash

mongosh "mongodb://root:devrootpass@127.0.0.1:27017/?authSource=admin"

Create app user with least privilege:

javascript

use hello_demo
db.createUser({
  user: "app_user",
  pwd: "app_pass",
  roles: [{ role: "readWrite", db: "hello_demo" }]
})

App URI:

text

mongodb://app_user:app_pass@127.0.0.1:27017/hello_demo?authSource=hello_demo

mongod.conf Highlights

Production mongod.conf (conceptual):

yaml

Section	Purpose
`storage.wiredTiger`	Cache size—leave RAM headroom for OS
`security.authorization`	Require users
`replication.replSetName`	Enable replica set (transactions, HA)

Mount config in Docker:

yaml

volumes:
  - ./mongod.conf:/etc/mongod.conf
command: ["mongod", "--config", "/etc/mongod.conf"]

Three-Node Replica Set (Dev Sketch)

yaml

services:
  mongo1:
    image: mongo:7
    command: ["mongod", "--replSet", "rs0", "--bind_ip_all"]
    ports: ["27017:27017"]
  mongo2:
    image: mongo:7
    command: ["mongod", "--replSet", "rs0", "--bind_ip_all"]
  mongo3:
    image: mongo:7
    command: ["mongod", "--replSet", "rs0", "--bind_ip_all"]

Init once:

javascript

rs.initiate({
  _id: "rs0",
  members: [
    { _id: 0, host: "mongo1:27017" },
    { _id: 1, host: "mongo2:27017" },
    { _id: 2, host: "mongo3:27017" }
  ]
})

Connection string:

text

mongodb://app_user:pass@mongo1:27017,mongo2:27017,mongo3:27017/hello_demo?replicaSet=rs0

Details — Replica Sets.

Resource Limits

yaml

services:
  mongo:
    deploy:
      resources:
        limits:
          cpus: "2"
          memory: 4G

Without limits, MongoDB can consume host RAM under load.

Backup With mongodump

bash

mongodump --uri="mongodb://app_user:pass@127.0.0.1:27017/hello_demo" --out=./backup-$(date +%F)

Restore:

bash

mongorestore --uri="mongodb://app_user:pass@127.0.0.1:27017" --drop ./backup-2026-05-28/hello_demo

Warning

--drop deletes existing data before restore. Test on staging first.

Schedule backups with cron or use Atlas snapshots.

Import / Export

Already covered for data migration — Insert and Import/Export.

Upgrades

Replica set rolling upgrade (concept):

Upgrade secondaries one at a time
Step down primary, upgrade former primary
Verify db.version() and app smoke tests

Always read release notes for breaking changes.

Logging and Monitoring

Signal	Tool
Slow queries	Profiler, Atlas Performance Advisor — Performance
Server metrics	`db.serverStatus()`, Prometheus exporter
Disk	`db.stats()`, volume alerts

Full Stack Compose Reference

See Project: MongoDB + Redis + API for api + mongo + redis.

FAQ

Docker MongoDB for production?

Possible with replica set, auth, backups, and monitoring—many teams use Atlas instead.

bindIp 127.0.0.1 breaks remote connect?

Yes—use 0.0.0.0 inside Docker network or proper firewall rules — Troubleshooting.

WiredTiger cache too large?

Set cacheSizeGB below 50% of RAM on dedicated DB hosts.

Sharding in Docker?

Possible for learning; production sharded clusters are ops-heavy — Sharding intro.

systemd on bare metal?

systemctl enable mongod, config in /etc/mongod.conf, logs via journalctl -u mongod.