Docker Compose

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Prerequisites

Loose Agenda

Play with docker-compose Orchestrate multiple container images

Step by Step

Single image example

In a playground directory, create a new file named docker-compose.yml and enter the following text

services:
  redis:
    image: redis

In a terminal instance opened to today’s playground directory run docker-compose up --d

Once that finishes, run docker ps -a to see that a container was started.

Connect to our container with docker exec -it docker-compose_redis_1 redis-cli.

You should now be in the container’s redis-cli process.

Run the following commands to see that redis is functioning as expected:

KEYS *
SET day non-zero
KEYS *
GET day

Run docker-compose down in the terminal instance to shut down and clean up the containers.

Single Dockerfile example

In the playground directory, create a new file named Dockerfile and enter the following text

FROM redis

In the playground directory, create a new file named docker-compose-dockerfile.yml and enter the following text

  redis:
    build: .

Run docker compose -f docker-compose-dockerfile.yml up -d to start containers per the docker-compose definition. Again, run docker ps -a to see that a container was started.

Connect to our container with docker exec -it docker-compose_redis_1 redis-cli.

You should now be in the container’s redis-cli process.

Run the following commands again to see that redis is functioning as expected:

KEYS *
SET day non-zero
KEYS *
GET day

In the terminal instance let’s clean up with ` docker-compose -f docker-compose-dockerfile.yml down`

Volume mounting with Postgres and PgAdmin

Now let’s play with Postgres and Docker-Compose.

Create a sql directory within which create an init.sql file with the following contents.

CREATE DATABASE nonzero;

Alongside init.sql in the sql directory, create a pgadmin_servers.json file. This file will be used to tell PGAdmin about the Postgres instance we will be creating.

{
    "Servers":{
        "1": {
            "Name": "Docker-Compose",
            "Group": "Local Servers",
            "Port": 5432,
            "Username": "docker",
            "Host": "postgres",
            "SSLMode": "prefer",
            "MaintenanceDB": "postgres"
        }
    }
}

Additionally create a docker-compose-postgres.yml with the following content

version: '3'
services:
    postgres:
        image: postgres:11
        restart: always
        ports:
        - 5432:5432
        environment:
        - POSTGRES_USER=docker
        - POSTGRES_PASSWORD=docker
        volumes:
        - ./sql/init.sql:/docker-entrypoint-initdb.d/init.sql

    pgadmin:
        image: dpage/pgadmin4
        restart: always
        ports:
        - 5431:80    
        depends_on: 
            - postgres
        environment:
            PGADMIN_DEFAULT_EMAIL: $${PGADMIN_DEFAULT_EMAIL:-user@domain.org}
            PGADMIN_DEFAULT_PASSWORD: $${PGADMIN_DEFAULT_PASSWORD:-docker}
            PGADMIN_CONFIG_SERVER_MODE: 'False'
            PGADMIN_SERVER_JSON_FILE: '/pgadmin4/servers.json'
        volumes:
        - ./sql/pgadmin_servers.json:/pgadmin4/servers.json

Run docker compose -f docker-compose-postgres.yml up to start containers per the docker-compose definition.

Navigate to http://localhost:5431/browser/ and browser into Local Servers > Docker-Compose > Databases to see that our nonzero database was created.

Run docker compose -f docker-compose-postgres.yml down to shut down and clean up our containers.

Image coordination with Flyway against Postgres

Let’s add Flyway to our Postgres Docker-Compose definition.

Create a new file in the sql directory named V1.0.0__Table.sql with the following contents

CREATE EXTENSION IF NOT EXISTS "uuid-ossp";

CREATE TABLE nonzerotable (
   id uuid PRIMARY KEY DEFAULT uuid_generate_v4(),
   name TEXT NOT NULL,
   age INT NOT NULL,
   address CHAR(50)
);

We’ll modify our docker-compose-postgres.yml to the following

version: '3'
services:
    flyway:
      image: flyway/flyway:7.7.1
      environment:
           - FLYWAY_USER=docker
           - FLYWAY_PASSWORD=docker
      command: migrate 
                -url=jdbc:postgresql://postgres:5432/nonzero 
                -locations=filesystem:/flyway/sql 
                -connectRetries=60
                -mixed=true
      volumes:
        - ./sql:/flyway/sql
      depends_on:
        - postgres
        
    postgres:
        image: postgres:11
        restart: always
        ports:
        - 5432:5432
        environment:
        - POSTGRES_USER=docker
        - POSTGRES_PASSWORD=docker
        volumes:
        - ./sql/init.sql:/docker-entrypoint-initdb.d/init.sql

    pgadmin:
        image: dpage/pgadmin4
        restart: always
        ports:
        - 5431:80    
        depends_on: 
            - postgres
        environment:
            PGADMIN_DEFAULT_EMAIL: $${PGADMIN_DEFAULT_EMAIL:-user@domain.org}
            PGADMIN_DEFAULT_PASSWORD: $${PGADMIN_DEFAULT_PASSWORD:-docker}
            PGADMIN_CONFIG_SERVER_MODE: 'False'
            PGADMIN_SERVER_JSON_FILE: '/pgadmin4/servers.json'
        volumes:
        - ./sql/pgadmin_servers.json:/pgadmin4/servers.json

Run docker compose -f docker-compose-postgres.yml up to start containers per the docker-compose definition.

Navigate to http://localhost:5431/browser/ and browser into Local Servers > Docker-Compose > Databases to see that our nonzero database now contains a nonzerotable.

Run docker compose -f docker-compose-postgres.yml down to shut down and clean up our containers.

Health Checking

Note the retries occuring in the Flyway container defined in the previous section. We eventually reach the desired state due to the connectRetries argument in the Flyway container. We can also do this with health checks.

version: '3'
services:
    flyway:
      image: flyway/flyway:7.7.1
      depends_on:
        postgres:
          condition: service_healthy
      environment:
           - FLYWAY_USER=docker
           - FLYWAY_PASSWORD=docker
      command: migrate 
                -url=jdbc:postgresql://postgres:5432/nonzero 
                -locations=filesystem:/flyway/sql 
                -connectRetries=60
                -mixed=true
      volumes:
        - ./sql:/flyway/sql
        
    postgres:
        image: postgres:11
        restart: always
        ports:
        - 5432:5432
        environment:
        - POSTGRES_USER=docker
        - POSTGRES_PASSWORD=docker
        volumes:
        - ./sql/init.sql:/docker-entrypoint-initdb.d/init.sql
        healthcheck:
            test: ["CMD-SHELL", "pg_isready -U docker"]
            interval: 5s
            timeout: 5s
            retries: 5

    pgadmin:
        image: dpage/pgadmin4
        restart: always
        ports:
        - 5431:80    
        depends_on: 
            - postgres
        environment:
            PGADMIN_DEFAULT_EMAIL: $${PGADMIN_DEFAULT_EMAIL:-user@domain.org}
            PGADMIN_DEFAULT_PASSWORD: $${PGADMIN_DEFAULT_PASSWORD:-docker}
            PGADMIN_CONFIG_SERVER_MODE: 'False'
            PGADMIN_SERVER_JSON_FILE: '/pgadmin4/servers.json'
        volumes:
        - ./sql/pgadmin_servers.json:/pgadmin4/servers.json

Running docker compose -f docker-compose-postgres.yml up will now show the flyway container waiting for the postgres container to report healthy before executing.

Congratulations on a non-zero day!