MongoDB ReplicaSet with Docker Compose

With the docker-compose.yml file, you can easily create replicaSet.

Some things from me

• I have created and tested on Windows and Ubuntu environments.

• Some instructions suggested using the hosts of each service like mongo1:27017, mongo2:27017,... in the ReplicaSet Config. However, it didn't work for me. I tried connecting to MongoDB Compass but encountered the error getaddrinfo ENOTFOUND mongo1. Finally, I found this solution. Link

• In my opinion, the names of each service only work within the scope of Docker Compose. So, if you include it in the ReplicaSet Config. Compass tries to find the reference of that service name in /etc/hosts. But since that name is not defined in /etc/hosts, it gives an error.

• As you can see, in the rs-init.sh file, I am using localhost.mongors.com (or host.docker.internal? for Window) in the ReplicaSet Config. The purpose is to allow containers to connect to each other without needing to use the names of each service.

How to use this one?

Use Makefile

1. Create docker network and run all container in the docker-compose.yml file.

   make createnet
   
   make up

2. Make sure you have this one in /etc/hosts 😅.

   On Window environment, the path should be C:/Windows/System32/drivers/etc/hosts.

   # Added by Docker Desktop
   192.168.1.244 host.docker.internal 
   192.168.1.244 gateway.docker.internal
   # To allow the same kube context to work on the host and the container:
   127.0.0.1 kubernetes.docker.internal
   127.0.0.1 localhost.mongors.com     ### this one

   On Ubuntu environment, the path should be /etc/hosts.

   # Your system has configured 'manage_etc_hosts' as True.
   # As a result, if you wish for changes to this file to persist
   # then you will need to either
   # a.) make changes to the master file in /etc/cloud/templates/hosts.debian.tmpl
   # b.) change or remove the value of 'manage_etc_hosts' in
   #     /etc/cloud/cloud.cfg or cloud-config from user-data
   #
   127.0.0.1 localhost, localhost.mongors.com      ### this one

3. Init ReplicaSet Config.

   docker compose exec mongo3 ./docker-entrypoint-initdb.d/rs-init.sh
   
   # or
   make initrs

   Now, if you connect to a certain service, you will receive the following output.

   PS ...\mongodb-replicaset-docker-compose> make dbshell
   docker compose exec mongo2 mongo
   MongoDB shell version v4.4.23
   connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb
   Implicit session: session { "id" : UUID("e35ed408-0b4b-45cd-af22-2cca1efd4977") }
   MongoDB server version: 4.4.23
   ---
   The server generated these startup warnings when booting:
           2023-07-30T04:41:31.422+00:00: Access control is not enabled for the database. Read and write access to data and configuration is unrestricted
           2023-07-30T04:41:31.423+00:00: You are running this process as the root user, which is not recommended
           2023-07-30T04:41:31.423+00:00: /sys/kernel/mm/transparent_hugepage/enabled is 'always'. We suggest setting it to 'never'
   ---
   rs0:SECONDARY> 

4. Let try to connect.

   mongodb://localhost.mongors.com:2727,localhost.mongors.com:2728,localhost.mongors.com:2729/?replicaSet=rs0

   😁