Intro to Docker

Unit 4: Docker Compose

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Unit 4- Docker Compose: Agenda

● Creating docker-compose.yml files ● Compose Commands ● Adding Image Building

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Unit 4- Docker Compose: Overview

● Used to configure relationships between containers, as a container will often need to work with other containers. ● Used to save container run settings in an easy-to-read file ● Used to create one-line developer environment startups ● It is a two-part operation, consisting of: ○ YAML file with config for all relationships and dependencies (docker-compose.yaml). Describes solutions for containers, networks, and volumes. ○ CLI tool , docker-compose, used for local dev/test automation using the YAML files.

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Docker Compose: YAML file (Format)

version: ‘3.1’ # if no version is specified, then v1 is assumed. Recommend v2 minimum services: # containers. same as docker run servicename: # a friendly name. this is also DNS name inside network image: # Optional if you use build: command: # Optional, replace the default CMD specified by the image environment: # Optional, same as -e in docker run volumes: # Optional, same as -v in docker run servicename2: volumes: # Optional, same as docker volume create networks: # Optional, same as docker network create

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Docker Compose: YAML file (example)

version: ‘2’ # if no version is specified, then v1 is assumed. Recommend v2 minimum services: wordpress: image: wordpress ports: #(same as using the “-p” option on the command line)

Docker Compose: YAML file (example contin.) #(continued from previous slide…) mysql: image: mariadb environment: MYSQL_ROOT_PASSWORD: examplerootPW MYSQL_DATABASE: wordpress MYSQL_USER: example MYSQL_PASSWORD: examplePW volumes:

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Unit 4: Docker Compose

docker-compose and the CLI

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docker-compose CLI (basic commands)

Most common commands: ● docker-compose up: setup volumes/networks and start all containers ● docker-compose down: stop all containers and remove containers, volumes, and networks (cleanup) Also: ● docker-compose ps: shows you which containers are running ● docker-compose top: lists all the services running inside ● docker-compose logs: view logs when run is used with the -d option

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Lab: Compose File for a Multi-Container Service

Build a basic compose file for a Drupal content management system (CMS) website. See Docker Hub to get the image info. ● Use Drupal image along with the Postgres image for the database. (Documentation on Hub as well) ● Use ports to expose Drupal on 8080 so you can access in browser via http://localhost:8080 ● Be sure to set the environment variable POSTGRES_PASS for postgres. You may also choose to set a value for POSTGRES_USER and POSTGRES_DB, though not necessary, as they will be “postgres” by default. ● Walk through Drupal installation in browser. ● Installation tip: Drupal will assume the DB host is localhost, however the proper name is the its service name. ● Bonus action: Use volumes to store Drupal’s unique data (*will likely be a small file, roughly 10 or so lines)

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Using Compose to Build

● Compose can also build your custom images ● If not found in cache, it will build them with docker-compose up. ● Use docker-compose build to rebuild the image. ● Useful for complex builds that have numerous variables or build arguments.

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Lab: Compose for Run-Time Image Building and Multi-Container Development

● This exercise covers building a custom Drupal image for local testing ● Compose, in this scenario is useful for testing apps, such as: ○ A user learning the Drupal admin UI ○ a software tester evaluating the performance of an app ● Start with Compose file from previous lab ● Make your Dockerfile and docker-compose.yml in the directory compose-lab-2 ● Use the README.md in the directory for details