CODEWITHSUNDEEP
mongodbdocker-composereplicaset
Namhoon Lee
Namhoon Lee

Reputation: 178

MongoDB Error: Unable to reach primary for set [set_name] when connect to mongo replica set

I'm trying to connect to MongoDB replica set consists of 3 mongo docker-container, but Error Message: Unable to reach primary for set rs0 occurs.

Git Repository: https://github.com/frontalnh/mongodb-replica-set

I made docker swarm consists of 3 MongoDB docker-container and map each port to localhost: 27017, 27018, 27019

Connecting to a single mongo docker-container is possible by below command

mongo localhost:27017

But When I try to connect to Replica set consists of 3 by below command,

Error Message: Unable to reach primary for set rs0 occurs

Command

mongo "mongodb://localhost:27017,localhost:27018,localhost:27019/testdb?replicaSet=rs0"

Configuration

cfg = {
  _id: 'rs0',
  members: [
    { _id: 0, host: 'mongo-rs0-1:27017' },
    { _id: 1, host: 'mongo-rs0-2:27017' },
    { _id: 2, host: 'mongo-rs0-3:27017' }
  ]
};
cfg.protocolVersion = 1;
rs.reconfig(cfg, { force: true });

Docker Compose

version: '3'

services:
  mongo-rs0-1:
    image: 'mongo-start'
    build: ./mongo-rs0-1
    ports:
      - '27017:27017' # left is computer's port right side is docker internal port
    volumes:
      - ./mongo-rs0-1/data:/data/db
    depends_on:
      - 'mongo-rs0-2'
      - 'mongo-rs0-3'

  mongo-rs0-2:
    image: 'mongo'
    command: --replSet rs0
    command: --config ./conf/mongo.conf
    ports:
      - '27018:27017'
    volumes:
      - ./mongo-rs0-2/data:/data/db
      - ./mongo-rs0-2/conf:/conf

  mongo-rs0-3:
    image: 'mongo'
    command: --replSet rs0
    command: --config ./conf/mongo.conf
    ports:
      - '27019:27017'
    volumes:
      - ./mongo-rs0-3/data:/data/db
      - ./mongo-rs0-2/conf:/conf

  setup-rs:
    image: 'setup-rs'
    build: ./setup
    depends_on:
      - 'mongo-rs0-1' # mongo-rs0-1 서비스가 실행중이어야 해당 서비스가 실행될 수 있다.

  adminmongo:
    image: 'mrvautin/adminmongo'
    ports:
      - '1234:1234'

Upvotes: 11

Views: 15607

Answers (3)

Mitko Keckaroski
Mitko Keckaroski

Reputation: 1040

Just restart the current primary node. Repeat this until the desired node become primary. After that, you are able to run mongos.

Note: Make sure that there isn't traffic to the database.

Upvotes: 1

Kassaï-迈克-Kaym
Kassaï-迈克-Kaym

Reputation: 5

You were maybe running the other node of the replica set in fork mode and you turned off your computer at some point. Restarting those nodes in fork mode by doing mongod --config [your_config_file.conf] --fork fixed the problem for me.

What happens when all other secondary nodes are unreachable is that the primary node becomes secondary therefore you will be unable to elect a new primary.

Try to restart the other nodes using their configuration files and you're good to go.

Upvotes: 0

Namhoon Lee
Namhoon Lee

Reputation: 178

I solved it by register host name in localhost

Anyone who needs mongo replica set in localhost can setup replica set with docker-compose.

https://github.com/frontalnh/mongodb-replica-set

Upvotes: 2

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