Introduction To Docker

People's Postcode Lottery - January 2018

What Is Docker?

Docker allows you to package an application with all of its dependencies into a standardized unit for software development.

Why Do We Use It?

Environment Parity

Easier Tooling

Experimentation

Container v Image

Image

• Bundled dependencies
• Distributable
• Build time configuration
• Generally environment independent

Container

• Running instance of an Image
• Runtime configuration

2 Main Components

• Docker Engine
• Docker Compose

Dockerfile

Main Dockerfile Commands

• FROM
• RUN
• VOLUME
• CMD
• COPY/ADD
• ENTRYPOINT
• WORKDIR
• HEALTHCHECK

FROM alpine:3.5

RUN apk add --no-cache bash

ENTRYPOINT bash

FROM alpine:3.5

RUN apk add --no-cache bash

COPY ./demo /var/www

WORKDIR /var/www

ENTRYPOINT bash

Volumes

• Host to Container Mapping:
  • ./secrets:/var/run/secrets
• Container Volumes
  • - /secrets
  • Can be named or unnamed (volumes key in compose file)
• Plugins (Not really used here)

Docker Compose

• Orchestration tool for Docker Engine
• Primarily used for Development
• Create full application stacks
• Define the parity you'll later use in prod

version: '2'

volumes:
    cache:
        driver: local
        driver_opts:
            type: tmpfs
            device: tmpfs
            o: uid=33
    logs:
        driver: local
        driver_opts:
            type: tmpfs
            device: tmpfs
            o: uid=33

networks:
  salesflowmanagerapi_default:
    external: true

services:
    application:
        build:
            dockerfile: ./Dockerfile
            context: .
        entrypoint: /var/www/opt/docker/dev/entrypoint
        environment:
            - SYMFONY_ENVIRONMENT=test
            - BLACKFIRE_SERVER_ID
            - BLACKFIRE_SERVER_TOKEN
        volumes:
            - ./opt/beats/dev/filebeat.yml:/etc/filebeat/filebeat.yml:ro
            - ./opt/elk/dev/logstash/logstash-beats.crt:/etc/pki/tls/certs/logstash-beats.crt:ro
            - ./opt/php/dev/php.ini:/usr/local/etc/php/php.ini:ro
            - ./opt/php/dev/conf.d/:/usr/local/etc/php/conf.d/:ro
            - .:/var/www
            - ../../src:/var/php-src:ro
            - cache:/var/www/var/cache
            - logs:/var/www/var/logs
        depends_on:
            - elk
            - redis
        dns_search:
            - pluk.eeghlan.net
        dns:
            - 172.26.10.2
            - 10.2.0.10
        privileged: true
        tmpfs:
            - /tmp:rw,nodev,noexec,nosuid
        env_file:
            - .env
            - ./src/App/Salesflow/Domain/SalesflowManager/.env
        ports:
            - 80
        networks:
            - salesflowmanagerapi_default

    redis:
        image: redis:alpine

    elk:
      image: sebp/elk
      ports:
          - "5044:5044" # Logstash Beats interface
          - "5601:5601" # Kibana web interface
          - 9200 # Elasticsearch JSON interface
      volumes:
          - ./opt/elk/dev/logstash/logstash.conf:/etc/logstash/logstash.conf
          - ./opt/elk/dev/logstash/logstash-beats.crt:/etc/pki/tls/certs/logstash-beats.crt
          - ./opt/elk/dev/logstash/logstash-beats.key:/etc/pki/tls/private/logstash-beats.key
          - ./opt/elk/dev/logstash/patterns:/opt/logstash/patterns
          - logs:/var/www/app/logs

Important Commands

• Build:
  • docker image build --tag <tag_name> . -f <file_name>
• Start Docker-Compose application
  • docker-compose up
• Stop Docker Compose
  • docker-compose kill
• System Cleanup
  • docker system prune
• Execute into a container (compose)
  • docker-compose exec <container_compose_name> sh
• Execute into a container (Non-Compose)
  • docker container exec -ti <container_id/name> sh
• Run a container
  • docker container run --rm <image_name>:<image_tag>

Deploying Docker

• Build image from repository
• Push image to a Docker Registry
• Create Ansible Playbook
  • Pull docker image
  • Set up dependant services
  • Expose correct environment variables
  • Run container

Questions?