Docker composer...What is it

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Docker Compose is a tool that allows us to manage Multi-container applications (projects with multiple containers working together) using only one setup file.

If compared, visualize:

Docker Engine is a "crane driver" who lifts one container at a time.

Docker Compose is the "Chief Conductor" who holds the tree and instructs all cabinets (Node.js, Nginx, Database) to be placed in the correct position and connected automatically.

What functions does Docker Compose perform?

Its main function is to turn cumbersome procedures into simple ones. Through the process as follows:

1.Defining specification (Definition)

Instead of typing long run commands one container at a time, you write everything into a single docker-compose.yml file, such as:

What image will be used?

Which port must be opened?

Which Database needs to be connected to?

2. Single Command Orchestration

When the file is prepared, you use one command, docker compose up. Docker Compose will act:

Build: Create Image for every Service as specified.

Create: Create a simulated network to allow containers to talk to each other

Start: Start the operation of every container simultaneously in the correct order.

3. Service Dependencies

It can be defined as "must complete the Database and then run Node.js" through the Depends _ on command to prevent the project from crashing because the app cannot find the database.

Benefits you can get (from the mai-app project)

Save time: No need to type the docker building command and the docker run separately several times.

Infrastructure as Code: The docker-compos.yml file is like a project document. Anyone who gets this file will be able to run a project exactly like you.

Clean Environment: When deprecated, just order the docker compose down, the system immediately sweeps the container and network generated.

Summary of workflow

Write the Dockerfile of each Service (e.g. Node.js).

Write docker-compos.yml to put everything together.

Run the docker compose up to start the entire system.