Parminder Singh

Lead UI Engineer @ Swiggy

Agenda

  • Intro
  • Architecture & Theory - Deep dive
  • Installation
  • Docker Images
  • Docker Containers
  • Docker Compose
  • Docker Volume
  • Examples - Dev & Prod Setup

What is Docker

"Docker is the only independent container platform that enables organizations to seamlessly - build, share and run any application, anywhere​"

Build, Ship and Run

What is Docker

"Docker is the only independent container platform that enables organizations to seamlessly - build, share and run any application, anywhere​"

Build, Ship and Run

  • Company Docker Inc
  • Container runtime & orchestration engine
  • Docker open source project Moby

What is Docker

Build, Ship and Run

  • Based out of SF by Solomon Hykes
  • Started as PaaS provider called "dotCloud"
  • dotCloud used LXC (Linux Containers)
  • Later, they created a tool for building images named as Docker
  • dotCloud rebranded to Docker
  • Has Enterprise Edition and Community Edition
  • Available as Open Source Project Moby

Docker Inc

Why use Docker?

  • Dev/Prod parody
  • Exactly same environments guarantee
  • Decouple Infra from Application development
  • CI/CD out of the box
  • Developer productivity - Onboarding
  • App isolation - DDoS attack limits to one container, building microservices
  • Debugging capabilties - Running prod env on dev

Architecture Deep Dive

Containers

Architecture

  • Client - Server architecture
  • Client CLI talks to the docker daemon (server)
  • Demon handles - building, running, managing docker objects
  • They communicate using Rest API using Unix sockets or network interface
  • Docker Registry - Store docker images

Docker Objects

Images

  • Read only template for creating docker container.
  • An Image could be based out of other images.
  • It consists of instructions and app binaries, filesystems. 

Containers

  • Runnable instance of Docker Image
  • Attached to network and volumes.
  • We can create new images based on a running container
  • Level of isolation among containers can be configured

Virtualization

  • Emulation or Full Virtualisation
  • Host OS intercepts Guest OS software instructions
  • Entirely software centric, no hardware
  • System resource overhead, slow low performance
  • Eg: VMware Player, VirtualBox
  • Para Virtualisation
  • Runs directly on the hardware, or “bare-metal”
  • Guest OS are modified to work with VM
  • Eg: Xen, KVM
  • Container based or OS Level Virtualisation
  • Multiple isolated executions on single Kernel
  • Best performance & dynamic resource management
  • Eg: Docker, LXC, OpenVZ, Warden

Docker Engine

Docker vs VM

Docker Engine

Docker Engine

Docker Engine

  • Container runtime code was taken out from docker demon & put in OCI layer
  • runc became the implementation of the OCI runtime spec
  • It was light wrapper around libcontainer only
  • containerd manages images and lifecycle of the containers - stop, pause, start, delete 
  • containerd forks the instance of runc for new containers
  • runc process exits after creating container
  • shim becomes the parent of the running container

Docker Engine

Docker Image

  • Read only template for creating containers.
  • A bunch of files and a manifest
  • Build time construct
  • Can't delete image till all it's containers are deleted
  • Built using Dockerfile
  • Multiple layers - Each layer is extension to previous layer
  • Each layer has app binaries, file systems and libraries

Manifest File

Docker Container

  • Containers add a run time read-write layer on top of the image file system.
  • All changes done during runtime are made in the top writable layer.
  • These changes can be saved and committed to create new image.

Docker Container

Containerising the App - Dockerfile

  • Create Dockerfile for the application
  • Build a docker image using it
  • Run the docker image to run container for the app.

Multi-Stage Build

  • Keep the docker images size small
  • Multiple FROM instructions
  • Selectively copy artifacts from one stage to another

Docker Compose

  • For defining and running multi-container Docker application
  • Commands used to start, stop, pause etc all containers at once

Docker Volume

  • Preferred mechanism for persisting data generated by and used by Docker containers
  • Can be used to
    • Mount/Map directory or file from host to container
    • Create a shared space or directory for containers
docker run -it -p 3000:3000 -v ${PWD}/src:/app/src image-name
version: '3'
services:
  server:
    build: ./
    ports:
      - 5000:5000
    volumes:
      - ./server/src:/server/src

Examples

Thank You

@paramsingh_66174

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