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Arash Yazdanibakhsh
Arash Yazdanibakhsh

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Running a MongoDB Replica Set Locally: Docker Desktop & Native Windows Setup

When developing modern applications, a replica set configuration is essential to simulate production environments that leverage MongoDB’s high availability and redundancy. In this article, I’ll share two approaches:

Deploying a MongoDB Replica Set Using Docker Desktop
Running a MongoDB Replica Set Natively on Windows Without Docker Desktop
Each method has its merits depending on your environment and constraints.

  1. Deploying a MongoDB Replica Set with Docker Desktop Docker is a great way to quickly spin up isolated environments. In this section, we’ll create a replica set using a custom Docker network and a Docker Compose file.

Step 1: Create a Docker Network

First, create an external Docker network that all MongoDB containers will share. Open your terminal and run:

docker network create mongo-cluster
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Step 2: Prepare the docker-compose.yml File

Create a docker-compose.yml file with the following configuration. This file defines three services — one primary and two secondaries. Each service is configured to run with the replica set parameter ( — replSet rs0) and bind to all IP addresses:

version: ‘3.8’

services:

mongo-primary:

image: mongo:latest

container_name: mongo-primary

restart: always

command: mongod — replSet rs0 — bind_ip_all

ports:

- 27017:27017

volumes:

- E:/Program Files/MongoDB/primary/data:/data/db

networks:

- mongo-cluster

mongo-secondary1:

image: mongo:latest

container_name: mongo-secondary1

restart: always

command: mongod — replSet rs0 — bind_ip_all

ports:

- 27018:27017

volumes:

- E:/Program Files/MongoDB/secondary1/data:/data/db

networks:

- mongo-cluster

mongo-secondary2:

image: mongo:latest

container_name: mongo-secondary2

restart: always

command: mongod — replSet rs0 — bind_ip_all

ports:

- 27019:27017

volumes:

- E:/Program Files/MongoDB/secondary2/data:/data/db

networks:

- mongo-cluster

networks:

mongo-cluster:

external: true
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Note: Adjust the volume paths (E:/Program Files/MongoDB/…) to your local directories as needed.

Step 3: Start the Containers

In the directory containing your docker-compose.yml file, execute:

docker-compose up -d
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This command starts the three containers in detached mode.

Step 4: Initialize the Replica Set

Connect to the Primary Container:
Run the following command to open an interactive Mongo shell (mongosh) session inside the primary container:

docker exec -it mongo-primary mongosh
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Initiate the Replica Set:
Within the shell, execute:

rs.initiate({_id: “rs0”,members: [{ _id: 0, host: “host.docker.internal:27017”},{ _id: 1, host: “host.docker.internal:27018” },{ _id: 2, host: “host.docker.internal:27019” }]});
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Verify the Setup:
Run:

rs.status();
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This command shows the status of your replica set. After the verification Run:

Exit
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And go to step 5.

Step 5: Verify Data Persistence

Check your Docker volumes to ensure data is being persisted:

docker volume ls
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Connection String

Connect your application using the following connection string:

mongodb://host.docker.internal:27017,host.docker.internal:27018,host.docker.internal:27019/?replicaSet=rs0

Tip: If host.docker.internal fails to resolve on Windows, add the following entry to your hosts file:
127.0.0.1 host.docker.internal

  1. Running a MongoDB Replica Set Natively on Windows (Without Docker Desktop) If you prefer or need to run MongoDB directly on Windows without containerization, follow these steps.

Step 1: Download and Install mongosh

Make sure you have mongosh installed. This shell will help you manage and interact with your replica set.

Step 2: Configure MongoDB via mongod.cfg

Prepare separate configuration files for each MongoDB instance. Below is an example configuration (mongod.cfg) for one node:

`

`

mongod.conf

Where and how to store data.

storage:

dbPath: C:\Program Files\MongoDB\Server\7.0\data

Where to write logging data.

systemLog:

destination: file

logAppend: true

path: C:\Program Files\MongoDB\Server\7.0\log\mongod.log

Network interfaces

net:

port: 27017

bindIp: 127.0.0.1

Replica set configuration

replication:

replSetName: “rs0”`

`
Note: Create a similar configuration file for each MongoDB instance, ensuring that the port numbers and data directories are unique (e.g., 27017, 27018, 27019).

Step 3: Start the MongoDB Instances

Run each MongoDB server instance as an administrator. You can launch them manually using a command prompt or create a batch file. For example, to run the instance on port 27017, execute:


“C:\Program Files\MongoDB\Server\7.1\bin\mongod” — config “C:\Program Files\MongoDB\Server\7.1\bin\mongod.cfg”

For convenience, you can create a .bat file with the following content:

`
@echo off

start “MongoDB 7.1” “C:\Program Files\MongoDB\Server\7.1\bin\mongod” — config “C:\Program Files\MongoDB\Server\7.1\bin\mongod.cfg”

start “MongoDB 7.2” “C:\Program Files\MongoDB\Server\7.2\bin\mongod” — config “C:\Program Files\MongoDB\Server\7.2\bin\mongod.cfg”

`
*Run the batch file as an administrator.
*
Step 4: Manually Initiate the Replica Set

Launch the Primary Instance:
If not already running, start the primary node with:
mongod — port 27017 — dbpath “C:\Program Files\MongoDB\Server\7.0\data” — replSet rs0

Connect with mongosh:
Open mongosh as an administrator and execute:

`
rs.initiate({_id: “rs0”,members: [{ _id: 0, host: “127.0.0.1:27017” },{ _id: 1,host: “127.0.0.1:27018” },{ _id: 2, host: “127.0.0.1:27019” }]});

`
Step 5: Optionally Install as Windows Services

For an even smoother development experience, you can install each MongoDB instance as a Windows service. Run the following commands as an administrator:

`

“C:\Program Files\MongoDB\Server\7.1\bin\mongod.exe” — config “C:\Program Files\MongoDB\Server\7.1\bin\mongod.cfg” — install — serviceName “MongoDB7.1”

“C:\Program Files\MongoDB\Server\7.2\bin\mongod.exe” — config “C:\Program Files\MongoDB\Server\7.2\bin\mongod.cfg” — install — serviceName “MongoDB7.2”
`

Then, register the services with:

`
sc.exe create “MongoDB7.1” binPath= “\”C:\Program Files\MongoDB\Server\7.1\bin\mongod.exe\” — service — config=\”C:\Program Files\MongoDB\Server\7.1\bin\mongod.cfg\”” DisplayName= “MongoDB 7.1” start= auto

sc.exe create “MongoDB7.2” binPath= “\”C:\Program Files\MongoDB\Server\7.2\bin\mongod.exe\” — service — config=\”C:\Program Files\MongoDB\Server\7.2\bin\mongod.cfg\”” DisplayName= “MongoDB 7.2” start= auto
`

Finally, start the services:

`
net start MongoDB7.1

net start MongoDB7.2
`

Note: Running MongoDB as a Windows service may present some challenges; evaluate this option based on your project needs.

Conclusion

Both methods enable you to run a MongoDB replica set locally for testing and development:

Docker Desktop: Provides an isolated, containerized environment that closely mirrors cloud deployments. It’s quick to set up and perfect for multi-node configurations without polluting your host system.
Native Windows Setup: Offers a more traditional approach, especially when containerization is not an option. This method uses configuration files, command-line instructions, and optional Windows service installation.
By understanding and leveraging these approaches, you can develop and test applications that depend on MongoDB’s replica set features with confidence.

Happy coding!

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