Getting Started With Docker Compose

Docker Compose is a tool for defining and running multi-container Docker applications. With Compose, you use a Compose file to configure your application’s services. Then, using a single command, you create and start all the services from your configuration.

Steps for implementing Docker Compose:

1. Create your Dockerfiles for each service.

2. Define services to run your application in the docker-compose.yml file.

3. Start and run your entire application with the help of the docker-compose.yml file.

Prerequisites

1. Install Docker (Link – Docker setup)

2. Install Docker Compose (Link – Docker compose setup)

Create a Dockerfile

A Dockerfile is a text document where we specify all the commands that are required to run a service. Name it Dockerfile and put this in the project directory.

Sample Dockerfile:

# Scala and sbt Dockerfile
#
# https://github.com/hseeberger/scala-sbt
#

# Pull base image
FROM openjdk:8

ENV SCALA_VERSION 2.12.1
ENV SBT_VERSION 0.13.15

# Scala expects this file
RUN touch /usr/lib/jvm/java-8-openjdk-amd64/release

# Install Scala
## Piping curl directly in tar
RUN \
curl -fsL http://downloads.typesafe.com/scala/$SCALA_VERSION/scala-$SCALA_VERSION.tgz | tar xfz – -C /root/ && \
echo >> /root/.bashrc && \
echo ‘export PATH=~/scala-$SCALA_VERSION/bin:$PATH’ >> /root/.bashrc

# Install sbt
RUN \
curl -L -o sbt-$SBT_VERSION.deb http://dl.bintray.com/sbt/debian/sbt-$SBT_VERSION.deb && \
dpkg -i sbt-$SBT_VERSION.deb && \
rm sbt-$SBT_VERSION.deb && \
apt-get update && \
apt-get install sbt && \
sbt sbtVersion

# Define working directory
WORKDIR /root

Create a docker-compose.yml File

Create a file named docker-compose.yml in your project directory.

Sample docker-compose.yml file:

zookeeper:
image: zookeeper:3.4
ports:
– 2181:2181
kafka:
image: ches/kafka:latest
ports:
– 9092:9092
links:
– zookeeper:3.4
myElastic:
image: elasticsearch:2.4.0
ports:
– 9200:9200

This means you have specified all your services that you need to run the complete application. With these services, you have to specify the image name, port to be run, and links — where we specify the dependencies of a particular service over any other service. So, to start all the services in order to run the application, we just need to up the docker-compose file and we're done. The application will be up and running.

Run the docker-compose.yml File

The command to up the container is docker-compose up, while the command to stop is docker-compose stop. Note that you need to traverse to the directory where the docker-compose.yml file is present and then you can explore the following commands.

Commands

You can check all the docker compose commands by typing the docker-compose –help command on your terminal.

References

• Open Source

• Docker Documentation

• Docker Hub