Creating a Mongo replicaset using docker: Mongo replicaset + Nodejs + Docker Compose

This is a Docker tutorial for creating a Mongo replica set using docker compose and also a couple more containers to experiment with the replica set, above is the vid and below you will find some of the steps followed.

Steps

• Pre-reqs
• Have node.js installed
• And docker installed (make sure you have docker-compose as well)
• Create a container for defining configurations for a mongo instance
• Create a container for setting up the replica set
• Create a simple node app using expressjs and mongoose (A modified version from the previous video)
• Create a docker-compose file with the mongo and setup containers and two additional containers for experimenting with the replica set
• Build, Run and experiment with your new containers

Create a dockerfile for the first mongo container (not really needed but you could configure more stuff if needed)

• Include container with mongo preinstalled: 
• FROM mongo
• Create default/working directory: 
• WORKDIR /usr/src/configs
• Copy mongo's configurations file into the container
  
• COPY mongo.conf .
• Expose the default port for a mongo container
• EXPOSE 27017
• Initialize the container using the config file
• CMD ["--config", "./mongo.conf"]

Create a dockerfile for setting up the replica set

• Include a container with mongo preinstalled so we can easily use the mongo shell:
• FROM mongo
• Create default/working directory: 
• WORKDIR /usr/src/configs
• Copy the scripts needed for configuring the replica set:  
• COPY replicaSet.js .
• COPY setup.sh .
• Execute the setup shell script
• CMD ["./setup.sh"]

Create a docker-compose.yml file

• Version for the docker-compose file:
• version: '3'
• The list of services and their respective configurations: 
• services:
• Our first mongo container: mongo-rs0-1
  

• The name of each service, they can also work as a way to identify each service and connect to them within a container (for example you could connect to the mongo database using the name of the service: mongodb://mongo-rs0-1/test):
  
• mongo-rs0-1
• The name of the image that we want to build
• image: mongo-start
• The folder in which the dockerfile is located (if you have everything in the same folder then just adding "build: ./" would suffice)
• build: ./mongo-rs0-1
• The ports to expose and to which ports on the host machine to map them (host-port:container-port)
• ports:
        - "27017:27017"
• Which folders from the host machine should be shared to the container.
• volumes:
        - ./mongo-rs0-1/data:/data/db
• Declare that we require this container to be up and running before the current one does
• depends_on:
        - "mongo-rs0-2" and - "mongo-rs0-3"
• Our database services: mongo-rs0-2 and mongo-rs0-3
• The only difference here is that we are using the default mongo image and given that I specify the command to be executed
  
• Our setup service: setup-rs
  
• The name of each service:
  
• setup-rs
• The name of the image that we want to reuse from dockerhub
• image: setup-rs
• The folder in which the dockerfile is located
  • build: ./setup
• An optional but useful service for browsing our database: adminmongo
• The name of each service:
  
•  adminmongo
•  The name of the image that we want to reuse from dockerhub
• image: "mrvautin/adminmongo"
• The ports to expose for this particular container
• ports:
        - "1234:1234"

Build & Run

• Build the container:
• docker-compose build
• Run the container (will also build any necessary container)
• docker-compose up
• If you don't know the ip for your newly created node+express app use the ip used by the docker machine
• docker-machine ip
• Open the web app in your browser
• http://THE-IP:3000/testFind
• Adminmongo  UI
  
• http://THE-IP:1234/
• Start different specific services on your docker-compose file just add the name to each service
• docker-compose up mongo-rs0-1 adminmongo
• docker-compose up service-name-1 service-name-2 ...
• See a list of the currently running containers in your machine
• docker ps
• Query for the replica set status
• docker exec mongodb-replicaset_mongo-rs0-1_1 bash -c 'mongo --eval "rs.status();"'
• Stop a specific running container
• docker stop mongodb-replicaset_mongo-rs0-1_1

Resources

Github link for the code
Mongo Replication - Replica Set
Deploy a Replica Set for Testing and Development
Mongo - Docker Hub
Replication Options - Configuration File Options
Write Scripts for the mongo Shell