Docker Compose Tutorial – Process, Feature, and Use Cases

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1. Objective – Docker Compose

Today, we will see Docker Compose Tutorial. Moreover, we will look at Docker Compose features and use cases. Also, we will see Compose Versions, Build and installation. Along with this, we will discuss the Docker Compose examples.

In order to define and run multi-container Docker applications, there is a tool we have, that tool is what we call Docker Compose. 

So, let’s begin Docker Compose Tutorial.

Docker Compose Tutorial - Process, Feature, and Use Cases

Docker Compose Tutorial – Process, Feature, and Use Cases

2. What is Docker Compose?

While our Docker application includes more than one container, at that time building, running, as well as connecting the containers from separate Dockerfiles is definitely time-consuming. So, as a solution to this problem, Docker Compose permits us to use a YAML file to define multi-container apps. It is possible to configure as many containers as we want, how they should be built and connected, and where data should be stored. We can run a single command to build, run, and configure all of the containers when the YAML file is complete.

In addition, Compose works in several environments like staging, production, testing, development, as well as CI workflows.

3. How to Use Docker Compose?

Basically, using Compose in Docker is a three-step process:

  1. At very first, define app’s environment with a Dockerfile hence we can reproduce it anywhere.
  2. Afterwards, define the services that make up the app in docker-compose.yml hence it can be run together in an isolated environment.
  3. Further, run docker-compose up and Compose starts and then it runs the entire app.

Below you can see, how a docker-compose.yml looks like:

version: '3'
services:
 web:
   build: .
   ports:
   - "5000:5000"
   volumes:
   - .:/code
   - logvolume01:/var/log
   links:
   - redis
 redis:
   image: redis
volumes:
 logvolume01: {}

4. Docker Compose Command

In order to manage the whole lifecycle of the application, Docker Compose has several commands:

  • Start, stop, and rebuild services
  • View the status of running services
  • Stream the log output of running services
  • Run a one-off command on a service

5. Features of Docker Compose

There are some features of Compose in Docker which makes it effective, such as:

  1. Multiple isolated environments on a single host
  2. Preserve volume data when containers are created
  3. Only recreate containers that have changed
  4. Variables and moving a composition between environments

Let’s learn all these features in brief:

i. Multiple isolated environments on a single host

In order to isolate environments from each other, Compose uses a project name. We can make use of this project name in various different contexts, like:

  • On a dev host, in order to create multiple copies of a single environment, like while we want to run a stable copy for each feature branch of a project.
  • Moreover, on a CI server, in order to keep builds from interfering with each other, we can set the project name to a unique build number.
  • And, on a shared host or dev host, in order to prevent different projects, that may use the same service names, from interfering with each other.

Here, the default project name is the basename of the project directory. However, by using the -p command line option or the COMPOSE_PROJECT_NAME environment variable, we can set a custom project name.

ii. Preserve volume data when containers are created

All volumes used by our services is preserved by Compose. When docker-compose up runs, it copies the volumes from the old container to the new container, if it finds any containers from previous runs. As its best feature, this process ensures that any data we’ve created in volumes isn’t lost.

iii. Only recreate containers that have changed

In order to create a container, Compose caches the configuration used. Moreover, Compose re-uses the existing containers, when we restart a service that has not changed. Here, Re-using containers, simply means that we can make changes to our environment very quickly.

iv. Variables and moving a composition between environments

In the Compose file, Compose supports variables. Basically, to customize our composition for different environments or different users,  we can use these variables.

In addition, by using the extends field or by creating multiple Compose files, we can extend a Compose file.

6. Docker Compose Use Cases

In many different ways, we can use Compose. So, here we are listing some  of the common use cases of Docker Compose:

i. Development Environments

While we are developing software, the ability to run an application in an isolated environment as well as interact with it is very crucial. So, in order to create the environment and interact with it, we can use the Compose command line tool.

In addition, to document and configure all of the application’s service dependencies (databases, queues, caches, web service APIs, etc), the Compose file offers a way. Moreover, we can create and start one or more containers for each dependency with a single command (docker-compose up), by using the Compose command line tool.

Furthermore, these features together offer a convenient way for developers to get started on a project.

ii. Automated Testing Environments

The automated test suite is an important part of any Continuous Deployment or Continuous Integration process. However, Automated end-to-end testing needs an environment in which to run tests. Yet,  to create and destroy isolated testing environments for our test suite, Compose offers a convenient way. And, we can create and destroy these environments in just a few commands, by defining the full environment in a Compose file:

$ docker-compose up -d
$ ./run_tests
$ docker-compose down

iii. Single Host Deployments

Well, traditionally, Compose has been focused on the development and testing workflows. Although, we’re making progress on more production-oriented features, with each release. In order to deploy to a remote Docker Engine, we can use Compose. However, the Docker Engine may be a single instance provisioned either with Docker Machine or an entire Docker Swarm cluster.

So, this was in Docker Compose Tutorial. Hope you like our explanation.

7. Conclusion

Hence, we have seen the concept of Docker Compose in detail. Also, we discussed its features as well as use cases for better understanding. Though, if any doubt occurs, feel free to ask through the comment tab. We are happy to help. Keep visiting, keep learning!

Reference for Docker

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