MongoDB Replica Set / docker-compose / mongoose transaction with persistent volume

a-mongodb-replica-set-docker-compose-readme.md

This will guide you through setting up a replica set in a docker environment using.

• Docker Compose
• MongoDB Replica Sets
• Mongoose
• Mongoose Transactions

Thanks to https://gist.github.com/asoorm for helping with their docker-compose file!

docker-compose.yml

  mongo1:
    hostname: mongo1
    container_name: localmongo1
    image: mongo
    expose:
      - 27017
    ports:
      - 27017:27017
    restart: always
    entrypoint: [ "/usr/bin/mongod", "--bind_ip_all", "--replSet", "rs0" ]
    volumes:
      - <VOLUME-DIR>:/data/db # This is where your volume will persist. e.g. VOLUME-DIR = ./volumes/mongodb
  mongo2:
    hostname: mongo2
    container_name: localmongo2
    image: mongo
    expose:
      - 27017
    ports:
      - 27018:27017
    restart: always
    entrypoint: [ "/usr/bin/mongod", "--bind_ip_all", "--replSet", "rs0" ]
  mongo3:
    hostname: mongo3
    container_name: localmongo3
    image: mongo
    expose:
      - 27017
    ports:
      - 27019:27017
    restart: always
    entrypoint: [ "/usr/bin/mongod", "--bind_ip_all", "--replSet", "rs0" ]

docker.sh

# run this after setting up the docker-compose This will instantiate the replica set.
# The id and hostname's can be tailored to your liking, however they MUST match the docker-compose file above.
docker-compose up -d
docker exec -it localmongo1 mongo

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

exit

mongoose.js

// If on a linux server, use the hostname provided by the docker compose file
// e.g. HOSTNAME = mongo1, mongo2, mongo3

// If on MacOS add the following to your /etc/hosts file.
// 127.0.0.1  mongo1
// 127.0.0.1  mongo2
// 127.0.0.1  mongo3
// And use localhost as the HOSTNAME
mongoose.connect('mongodb://<HOSTNAME>:27017,<HOSTNAME>:27018,<HOSTNAME>:27019/<DBNAME>', {
  useNewUrlParser : true,
  useFindAndModify: false, // optional
  useCreateIndex  : true,
  replicaSet      : 'rs0', // We use this from the entrypoint in the docker-compose file
})

transaction.js

async function transaction() {
  // Start the transaction.
  const session = await ModelA.startSession();
  session.startTransaction();
  
  try {
    const options = { session };

    // Try and perform operation on Model.
    const a = await ModelA.create([{ ...args }], options);

    // If the first operation succeeds this next one will get called.
    await ModelB.create([{ ...args }], options);

    // If all succeeded with no errors, commit and end the session.
    await session.commitTransaction();
    session.endSession();
    return a;
  } catch (e) {
    // If any error occured, the whole transaction fails and throws error.
    // Undos changes that may have happened.
    await session.abortTransaction();
    session.endSession();
    throw e;
  }
}