praveen005 / mongodb-replica-set-docker-compose

Remotely connecting to MongoDB Replica Set running on Docker

Disclaimer

⚠️ This Configuration is purely meant for development purposes.

Make necessary changes before using it for production applications.

Contents

• Introduction
• Instructions
• Create a Docker Network
• Start instances of MongoDB
• Initiate the Replica Set
• Check the status of the replica set
• Open Mongo Shell
• Create User with necessary privileges
• Edit the hosts file
• Updated Mongo URI
• Mongo Express
• References

Introduction

MongoDB offers redundancy and high availability through replica sets. These groups of servers maintain identical data copies. In case of a server failure, the remaining members automatically elect a new primary, minimizing downtime and data loss.

Leveraging Docker containers, one can quickly spin up replica sets without needing a dedicated MongoDB installation on your machine.

Instructions

The steps to create a docker cluster are as follows:

1. Create a Docker network.
2. Start three instances of MongoDB.
3. Initiate the Replica Set.
4. Create a Database User.
5. Edit the hosts file

Create a Docker Network

The first step is to create a Docker network. This network will let each of your containers running in this network talk to each other.

To create a network, run the docker network create command:

docker network create mongo-network

To check if the network has been created or not, run the following command:

docker network ls

Note: If you don't create a docker network manually, docker compose will take care of it and create one on its own.

Start instances of MongoDB

First of, pull the images from Docker Hub

Next, run the following docker command:

docker-compose -f docker-compose.yaml up -d

Instead of 'started' you might as well see 'created' if you are running for the first time.

Initiate the Replica Set

Open Mongo Shell

docker exec -it mongo1 mongosh

Run the following command to initiate the replica set:

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

Check the status of the replica set

Run the following command in the mongo shell:

rs.status()

It will look something like this:

Click to reveal

{
  set: 'myReplicaSet',
  date: ISODate("2023-12-15T18:41:56.010Z"),
  myState: 2,
  term: Long("2"),
  syncSourceHost: 'mongo3:27017',
  syncSourceId: 2,
  heartbeatIntervalMillis: Long("2000"),
  majorityVoteCount: 2,
  writeMajorityCount: 2,
  votingMembersCount: 3,
  writableVotingMembersCount: 3,
  optimes: {
    lastCommittedOpTime: { ts: Timestamp({ t: 1702665709, i: 1 }), t: Long("2") },
    lastCommittedWallTime: ISODate("2023-12-15T18:41:49.912Z"),
    readConcernMajorityOpTime: { ts: Timestamp({ t: 1702665709, i: 1 }), t: Long("2") },
    appliedOpTime: { ts: Timestamp({ t: 1702665709, i: 1 }), t: Long("2") },
    durableOpTime: { ts: Timestamp({ t: 1702665709, i: 1 }), t: Long("2") },
    lastAppliedWallTime: ISODate("2023-12-15T18:41:49.912Z"),
    lastDurableWallTime: ISODate("2023-12-15T18:41:49.912Z")
  },
  lastStableRecoveryTimestamp: Timestamp({ t: 1702665649, i: 1 }),
  electionParticipantMetrics: {
    votedForCandidate: true,
    electionTerm: Long("2"),
    lastVoteDate: ISODate("2023-12-15T18:40:09.903Z"),
    electionCandidateMemberId: 2,
    voteReason: '',
    lastAppliedOpTimeAtElection: { ts: Timestamp({ t: 1702648984, i: 1 }), t: Long("1") },
    maxAppliedOpTimeInSet: { ts: Timestamp({ t: 1702648984, i: 1 }), t: Long("1") },
    priorityAtElection: 1,
    newTermStartDate: ISODate("2023-12-15T18:40:09.933Z"),
    newTermAppliedDate: ISODate("2023-12-15T18:40:10.024Z")
  },
  members: [
    {
      _id: 0,
      name: 'mongo1:27017',
      health: 1,
      state: 2,
      stateStr: 'SECONDARY',
      uptime: 122,
      optime: { ts: Timestamp({ t: 1702665709, i: 1 }), t: Long("2") },
      optimeDate: ISODate("2023-12-15T18:41:49.000Z"),
      lastAppliedWallTime: ISODate("2023-12-15T18:41:49.912Z"),
      lastDurableWallTime: ISODate("2023-12-15T18:41:49.912Z"),
      syncSourceHost: 'mongo3:27017',
      syncSourceId: 2,
      infoMessage: '',
      configVersion: 1,
      configTerm: 2,
      self: true,
      lastHeartbeatMessage: ''
    },
    {
      _id: 1,
      name: 'mongo2:27017',
      health: 1,
      state: 2,
      stateStr: 'SECONDARY',
      uptime: 117,
      optime: { ts: Timestamp({ t: 1702665709, i: 1 }), t: Long("2") },
      optimeDurable: { ts: Timestamp({ t: 1702665709, i: 1 }), t: Long("2") },
      optimeDate: ISODate("2023-12-15T18:41:49.000Z"),
      optimeDurableDate: ISODate("2023-12-15T18:41:49.000Z"),
      lastAppliedWallTime: ISODate("2023-12-15T18:41:49.912Z"),
      lastDurableWallTime: ISODate("2023-12-15T18:41:49.912Z"),
      lastHeartbeat: ISODate("2023-12-15T18:41:54.509Z"),
      lastHeartbeatRecv: ISODate("2023-12-15T18:41:55.986Z"),
      pingMs: Long("0"),
      lastHeartbeatMessage: '',
      syncSourceHost: 'mongo3:27017',
      syncSourceId: 2,
      infoMessage: '',
      configVersion: 1,
      configTerm: 2
    },
    {
      _id: 2,
      name: 'mongo3:27017',
      health: 1,
      state: 1,
      stateStr: 'PRIMARY',
      uptime: 117,
      optime: { ts: Timestamp({ t: 1702665709, i: 1 }), t: Long("2") },
      optimeDurable: { ts: Timestamp({ t: 1702665709, i: 1 }), t: Long("2") },
      optimeDate: ISODate("2023-12-15T18:41:49.000Z"),
      optimeDurableDate: ISODate("2023-12-15T18:41:49.000Z"),
      lastAppliedWallTime: ISODate("2023-12-15T18:41:49.912Z"),
      lastDurableWallTime: ISODate("2023-12-15T18:41:49.912Z"),
      lastHeartbeat: ISODate("2023-12-15T18:41:55.990Z"),
      lastHeartbeatRecv: ISODate("2023-12-15T18:41:55.988Z"),
      pingMs: Long("0"),
      lastHeartbeatMessage: '',
      syncSourceHost: '',
      syncSourceId: -1,
      infoMessage: '',
      electionTime: Timestamp({ t: 1702665609, i: 1 }),
      electionDate: ISODate("2023-12-15T18:40:09.000Z"),
      configVersion: 1,
      configTerm: 2
    }
  ],
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1702665709, i: 1 }),
    signature: {
      hash: Binary.createFromBase64("AAAAAAAAAAAAAAAAAAAAAAAAAAA=", 0),
      keyId: Long("0")
    }
  },
  operationTime: Timestamp({ t: 1702665709, i: 1 })
}

See in the status log above as to which one is Primary node. If say 'mongo2' is primary, get into 'mongo2' shell to create the database user.

To exit from the current mongo shell:

exit

To get into primary node shell(say 'mongo2' is primary):

docker exec -it mongo2 mongosh

Create User with necessary privileges

use admin

db.createUser(
  {
    user: "writeUser",
    pwd: "secret",
    roles: [
      { role: "readWrite", db: "admin" },
      { role: "dbAdmin", db: "admin" }
    ]
  }
)

You are now good to go!

Edit the hosts file

Navigate to the following directory in your computer:

C:\Windows\System32\drivers\etc

Check for hosts file. Open with administrative privileges and add the following IPs to hosts mapping:

127.0.0.1 mongo1
127.0.0.2 mongo2
127.0.0.3 mongo3

Updated Mongo URI

mongodb://writeUser:secret@mongo1:27017,mongo2:27017,mongo3:27017/?replicaSet=myReplicaSet

Mongo Express

References

• Using Docker to Deploy a MongoDB Cluster

• Creating Database User

• Connection string

• IP Binding

• Authentication