Docker Basics Cheat Sheet by amicheletti

Different pieces of the app are called “services” For example, a service for storing applic­ation data in a database, a service for the front-end, etc.

Services are just “conta­iners in produc­tion.” A service only runs one image, but it manages for example what ports it should use and how many replicas of the container should run.

To define a service, you'll need an

docker­-co­mpo­se.yml

file.

For example:

version: "­3"

services:

  web:

    image: amiche­let­ti/­get­-st­art­ed:­part1

    deploy:

      replicas: 5

      resources:

        limits:

          cpus: "­0.1­"

          memory: 50M

      restar­t_p­olicy:

        condition: on-failure

    ports:

      - "­80:­80"

    networks:

      - webnet

networks:

  webnet:

Here you define the image to be loaded, how many replicas, the resource limits and the restart condit­ions.

To run it you must first start:

docker swarm init

Then run it giving a name:

docker stack deploy -c docker­-co­mpo­se.yml <ap­p_n­ame>

To see the details of containers running in your service, run:

docker stack ps <ap­p_n­ame>

Now each time you request your app (via browser, for example), the load-b­alancer will help you distri­buting the requests to each replica.

To put it down,

docker stack rm <ap­p_n­ame>

This puts down the app, but not the "­one­-no­de" swarm we created. Use:

docker swarm leave --force