Docker Basics: Docker Compose

Create, configure, and run a multi-container application using Docker Compose and this introductory tutorial.

Docker Compose is a tool that allows you to run multi-container applications. With compose we can use yaml files to configure our application’ services and then using a single command to create and start all of the configured services. I use this tool a lot when it comes to local development in a microservice environment. It is also lightweight and needs just a small effort. Instead of managing how to run each service while developing, you can have the environment and services needed preconfigured and focus on the service that you currently develop.

With docker compose , we can configure a network for our services, volumes, mount-points, environmental variables — just about everything.

To showcase this we are going to solve a problem. Our goal would be to extract data from MongoDB using Grafana. Grafana does not have out-of-the-box support for MongoD, therefore,e we will have to use a plugin.

The first step is to create our networks. Creating a network is not necessary since your services, once started, will join the default network. We will make a showcase of using custom networks, and have a network for backend services and a network for frontend services. Apparently, network configuration can get more advanced and specify custom network drivers or even configure static addresses.

version: '3.5'

networks:
  frontend:
    name: frontend-network
  backend:
    name: backend-network
    internal: true

The backend network is going to be internal so there won’t be any outbound connectivity to the containers attached to it.

Then we will setup our MongoDB instance.

version: '3.5'

services:
  mongo:
    image: mongo
    restart: always
    environment:
      MONGO_INITDB_ROOT_USERNAME: ${MONGO_USER}
      MONGO_INITDB_ROOT_PASSWORD: ${MONGO_PASSWORD}
    volumes:
      - ${DB_PATH}:/data/db
    networks:
      - backend

As you see, we specified a volume. Volumes can also be specified separately and attached to a service. We used environmental variables for the root account, and you might also have noticed that the password is going to be provided through environmental variables. The same applies for the volume path, too. You can have a more advanced configuration for volumes in your compose configuration and reference them from your service.

Our next goal is to set up the proxy server which will be in the middle of our Grafana and MongoDB server. Since it needs a custom Dockerfile to create it, we will do it through docker-compose. Compose has the capability to spin up a service by specifying the docker file.

So let’s start with the Dockerfile.

FROM node

WORKDIR /usr/src/mongografanaproxy

COPY . /usr/src/mongografanaproxy

EXPOSE 3333

RUN cd /usr/src/mongografanaproxy
RUN npm install
ENTRYPOINT ["npm","run","server"]

Then let’s add it to compose.

version: '3.5'

services:
  mongo-proxy:
    build:
      context: .
      dockerfile: ProxyDockerfile
    restart: always
    networks:
      - backend

And the same will be done to the Grafana image that we want to use. Instead of using a ready Grafana image, we will create one with the plugin preinstalled.

FROM grafana/grafana

COPY . /var/lib/grafana/plugins/mongodb-grafana

EXPOSE 3000

version: '3.5'

services:
  grafana:
    build:
      context: .
      dockerfile: GrafanaDockerfile
    restart: always
    ports:
      - 3000:3000
    networks:
      - backend
      - frontend

Let’s wrap them all together:

version: '3.5'

services:
  mongo:
    image: mongo
    restart: always
    environment:
      MONGO_INITDB_ROOT_USERNAME: ${MONGO_USER}
      MONGO_INITDB_ROOT_PASSWORD: ${MONGO_PASSWORD}
    volumes:
      - ${DB_PATH}:/data/db
    networks:
      - backend
  mongo-proxy:
    build:
      context: .
      dockerfile: ProxyDockerfile
    restart: always
    networks:
      - backend
  grafana:
    build:
      context: .
      dockerfile: GrafanaDockerfile
    restart: always
    ports:
      - 3000:3000
    networks:
      - backend
      - frontend
networks:
  frontend:
    name: frontend-network
  backend:
    name: backend-network
    internal: true

So let’s run them all together.

docker-compose -f stack.yaml build
MONGO_USER=root MONGO_PASSWORD=root DB_PATH=~/grafana-mongo  docker-compose -f stack.yaml up

This code can be found on Github, and for more, check out the Docker Images, Docker Containers, and Docker registry posts.

Originally published by Emmanouil Gkatziouras at https://dzone.com

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