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

  mongo-setup:
    container_name: mongo-setup
    image: mongo
    restart: on-failure
    networks:
      default:
    volumes:
      - ./scripts:/scripts
    entrypoint: [ "/scripts/setup.sh" ] # Make sure this file exists (see below for the setup.sh)
    depends_on:
      - mongo1
      - mongo2
      - mongo3
  
  mongo1:
    hostname: mongo1
    container_name: localmongo1
    image: mongo
    expose:
      - 27017
    ports:
      - 27017:27017
    restart: always
    entrypoint: [ "/usr/bin/mongod", "--bind_ip_all", "--replSet", "rs0", "--journal", "--dbpath", "/data/db", "--enableMajorityReadConcern", "false" ]
    volumes:
      - <VOLUME-DIR>/mongo/data1/db:/data/db # This is where your volume will persist. e.g. VOLUME-DIR = ./volumes/mongodb
      - <VOLUME-DIR>/mongo/data1/configdb:/data/configdb
  mongo2:
    hostname: mongo2
    container_name: localmongo2
    image: mongo
    expose:
      - 27017
    ports:
      - 27018:27017
    restart: always
    entrypoint: [ "/usr/bin/mongod", "--bind_ip_all", "--replSet", "rs0", "--journal", "--dbpath", "/data/db", "--enableMajorityReadConcern", "false" ]
    volumes:
      - <VOLUME-DIR>/mongo/data2/db:/data/db # Note the data2, it must be different to the original set.
      - <VOLUME-DIR>/mongo/data2/configdb:/data/configdb
  mongo3:
    hostname: mongo3
    container_name: localmongo3
    image: mongo
    expose:
      - 27017
    ports:
      - 27019:27017
    restart: always
    entrypoint: [ "/usr/bin/mongod", "--bind_ip_all", "--replSet", "rs0", "--journal", "--dbpath", "/data/db", "--enableMajorityReadConcern", "false" ]
    volumes:
      - <VOLUME-DIR>/mongo/data3/db:/data/db
      - <VOLUME-DIR>/mongo/data3/configdb:/data/configdb

docker.sh

# NOTE: This is the simplest way of achieving a replicaset in mongodb with Docker.
# However if you would like a more automated approach, please see the setup.sh file and the docker-compose file which includes this startup script.

# 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", arbiterOnly: true }
    ]
  }
)

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
})

setup.sh

#!/bin/bash

#MONGODB1=`ping -c 1 mongo1 | head -1  | cut -d "(" -f 2 | cut -d ")" -f 1`
#MONGODB2=`ping -c 1 mongo2 | head -1  | cut -d "(" -f 2 | cut -d ")" -f 1`
#MONGODB3=`ping -c 1 mongo3 | head -1  | cut -d "(" -f 2 | cut -d ")" -f 1`

MONGODB1=mongo1
MONGODB2=mongo2
MONGODB3=mongo3

echo "**********************************************" ${MONGODB1}
echo "Waiting for startup.."
until curl http://${MONGODB1}:27017/serverStatus\?text\=1 2>&1 | grep uptime | head -1; do
  printf '.'
  sleep 1
done

# echo curl http://${MONGODB1}:28017/serverStatus\?text\=1 2>&1 | grep uptime | head -1
# echo "Started.."


echo SETUP.sh time now: `date +"%T" `
mongo --host ${MONGODB1}:27017 <<EOF
var cfg = {
    "_id": "rs0",
    "protocolVersion": 1,
    "version": 1,
    "members": [
        {
            "_id": 0,
            "host": "${MONGODB1}:27017",
            "priority": 2
        },
        {
            "_id": 1,
            "host": "${MONGODB2}:27017",
            "priority": 0
        },
        {
            "_id": 2,
            "host": "${MONGODB3}:27017",
            "priority": 0
        }
    ],settings: {chainingAllowed: true}
};
rs.initiate(cfg, { force: true });
rs.reconfig(cfg, { force: true });
rs.slaveOk();
db.getMongo().setReadPref('nearest');
db.getMongo().setSlaveOk(); 
EOF

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;
  }
}