Dockerize MongoDB

Estimated reading time: 5 minutes

Introduction

In this example, we are going to learn how to build a Docker image with MongoDB pre-installed. We’ll also see how to push that image to the Docker Hub registry and share it with others!

Note: This guide will show the mechanics of building a MongoDB container, but you will probably want to use the official image on Docker Hub

Using Docker and containers for deploying MongoDB instances will bring several benefits, such as:

Easy to maintain, highly configurable MongoDB instances;
Ready to run and start working within milliseconds;
Based on globally accessible and shareable images.

Note: If you do not like sudo, you might want to check out Giving non-root access.

Creating a Dockerfile for MongoDB

Let’s create our Dockerfile and start building it:

$ nano Dockerfile

Although optional, it is handy to have comments at the beginning of a Dockerfile explaining its purpose:

    # Dockerizing MongoDB: Dockerfile for building MongoDB images
    # Based on ubuntu:latest, installs MongoDB following the instructions from:
    # http://docs.mongodb.org/manual/tutorial/install-mongodb-on-ubuntu/

Tip: Dockerfiles are flexible. However, they need to follow a certain format. The first item to be defined is the name of an image, which becomes the parent of your Dockerized MongoDB image.

We will build our image using the latest version of Ubuntu from the Docker Hub Ubuntu repository.

# Format: FROM    repository[:version]
FROM       ubuntu:latest

Continuing, we will declare the MAINTAINER of the Dockerfile:

# Format: MAINTAINER Name <email@addr.ess>
MAINTAINER M.Y. Name <myname@addr.ess>

Note: Although Ubuntu systems have MongoDB packages, they are likely to be outdated. Therefore in this example, we will use the official MongoDB packages.

We will begin with importing the MongoDB public GPG key. We will also create a MongoDB repository file for the package manager.

# Installation:
# Import MongoDB public GPG key AND create a MongoDB list file
RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv EA312927
RUN echo "deb http://repo.mongodb.org/apt/ubuntu $(cat /etc/lsb-release | grep DISTRIB_CODENAME | cut -d= -f2)/mongodb-org/3.2 multiverse" | tee /etc/apt/sources.list.d/mongodb-org-3.2.list

After this initial preparation we can update our packages and install MongoDB.

# Update apt-get sources AND install MongoDB
RUN apt-get update && apt-get install -y mongodb-org

Tip: You can install a specific version of MongoDB by using a list of required packages with versions, e.g.: dockerfile RUN apt-get update && apt-get install -y mongodb-org=3.0.1 mongodb-org-server=3.0.1 mongodb-org-shell=3.0.1 mongodb-org-mongos=3.0.1 mongodb-org-tools=3.0.1

MongoDB requires a data directory. Let’s create it as the final step of our installation instructions.

# Create the MongoDB data directory
RUN mkdir -p /data/db

Lastly we set the ENTRYPOINT which will tell Docker to run mongod inside the containers launched from our MongoDB image. And for ports, we will use the EXPOSE instruction.

# Expose port 27017 from the container to the host
EXPOSE 27017

# Set usr/bin/mongod as the dockerized entry-point application
ENTRYPOINT ["/usr/bin/mongod"]

Now save the file and let’s build our image.

Note: The full version of this Dockerfile can be found here.

Building the MongoDB Docker image

With our Dockerfile, we can now build the MongoDB image using Docker. Unless experimenting, it is always a good practice to tag Docker images by passing the --tag option to docker build command.

# Format: docker build --tag/-t <user-name>/<repository> .
# Example:
$ docker build --tag my/repo .

Once this command is issued, Docker will go through the Dockerfile and build the image. The final image will be tagged my/repo.

Pushing the MongoDB image to Docker Hub

All Docker image repositories can be hosted and shared on Docker Hub with the docker push command. For this, you need to be logged-in.

# Log-in
$ docker login

Username:
..

# Push the image
# Format: docker push <user-name>/<repository>
$ docker push my/repo

The push refers to a repository [my/repo] (len: 1)
Sending image list
Pushing repository my/repo (1 tags)
..

Using the MongoDB image

Using the MongoDB image we created, we can run one or more MongoDB instances as daemon process(es).

# Basic way
# Usage: docker run --name <name for container> -d <user-name>/<repository>
$ docker run -p 27017:27017 --name mongo_instance_001 -d my/repo

# Dockerized MongoDB, lean and mean!
# Usage: docker run --name <name for container> -d <user-name>/<repository> --noprealloc --smallfiles
$ docker run -p 27017:27017 --name mongo_instance_001 -d my/repo --smallfiles

# Checking out the logs of a MongoDB container
# Usage: docker logs <name for container>
$ docker logs mongo_instance_001

# Playing with MongoDB
# Usage: mongo --port <port you get from `docker ps`>
$ mongo --port 27017

# If using docker-machine
# Usage: mongo --port <port you get from `docker ps`>  --host <ip address from `docker-machine ip VM_NAME`>
$ mongo --port 27017 --host 192.168.59.103

Tip: If you want to run two containers on the same engine, then you will need to map the exposed port to two different ports on the host

# Start two containers and map the ports
$ docker run -p 28001:27017 --name mongo_instance_001 -d my/repo

$ docker run -p 28002:27017 --name mongo_instance_002 -d my/repo

# Now you can connect to each MongoDB instance on the two ports
$ mongo --port 28001

$ mongo --port 28002

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