Introduction to Docker Containers

Micro-Services Academy, June 2020

Yonatan Bitton/@bityob

Link To Slides bit.ly/introdocker

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Docker commands for later

Notes:

docker pull docker.io/bityob/docker-python-app
docker pull nginx

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Agenda

• Micro Services
• Containers
• Docker

Notes:

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What is a Monolitic Service

In software engineering, a monolithic application describes a single-tiered software application... code are combined into a single program from a single platform.

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What is a Monolitic Service

Notes:

Source: https://bits.citrusbyte.com/microservices/

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Strengths of the Monolithic Architecture

• Less cross-cutting concerns
• Easier debugging and testing
• Simple to deploy

Notes:

https://www.n-ix.com/microservices-vs-monolith-which-architecture-best-choice-your-business/

• Cross-cutting concerns are the concerns that affect the whole application such as logging, handling, caching, and performance monitoring. Only one application so it is easier to handle it.
• Since a monolithic app is a single indivisible unit, you can run end-to-end testing much faster.
• Easier deployment. When it comes to monolithic applications, you do not have to handle many deployments - just one file or directory.

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Weaknesses of the Monolithic Architecture

• Understanding
• Making changes
• Scalability
• New technology barriers

Notes:

https://www.n-ix.com/microservices-vs-monolith-which-architecture-best-choice-your-business/

• When a monolithic application scales up, it becomes too complicated to understand
• It is harder to implement changes in such a large and complex application with highly tight coupling. Any code change affects the whole system so it has to be thoroughly coordinated. This makes the overall development process much longer.
• Scalability. You cannot scale components independently, only the whole application.
• New technology barriers. It is extremely problematic to apply a new technology in a monolithic application because then the entire application has to be rewritten.

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What is a Micro Service

Source: Medium/startlovingyourself

Note:

• Describe what is a micro service
• After we explained what is a monolithic service, we can see how differ are micro services
• Not only one service which does everything, but multiple services, each with it's own responsibility
• Easy to scale, easy to develop each part

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Why Micro-services?

• Single Responsibility Principle
• Application is easier to understand, develop and test
• Allows high scalability and reusability
• Parallelizes development
• Enable continuous delivery and deployment
• Better fault isolation
• Code can be written in different languages

Note:

Source:

Idan's vNext Architecture presentation - https://microsoft.sharepoint.com/teams/osg_core_ens/wcd/Shared%20Documents/Architecture/WD%20ATP%20vNext%20Architecture.pptx

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Micro Services using Containers

Source: RedbadgerTeam

Notes:

• Containers are a technology which best fit to this need of micro services
• What are containers?

Links -

https://blog.red-badger.com/blog/deploy-a-microservices-application-as-though-it-was-a-monolith http://blog.enabled.com.au/microservices-innovation/

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World before Containers

Notes:

• Different size, weights etc.
• Need addoption in all roads

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What are Containers

Notes:

• Container with same size
• All cargo inside, all fits
• Osim Historia - https://www.ranlevi.com/2017/03/09/osim_historia_ep212_containers_part1/

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What is Docker

Docker is an open platform for developing, shipping, and running applications.

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

Notes:

• Docker is a container implementaion

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Docker vs VMs

Notes:

• Same kernel for all apps

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Docker Benefits

• Fast (deployment, migration, restarts)
• Secure
• Lightweight (save disk & CPU)
• Open Source
• Portable software
• Microservices and integrations (APIs)
• Simplify DevOps
• Version control capabilities
• Easy configuration (Dockerfile)

Notes:

• Avoid "Works on my machine."
• Ship container images with all their dependencies
• Break image into layers
• Only ship layers that have changed
• Save disk, network, memory usage

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Common Docker usages

• Sandbox environment (develop, test, debug, educate)
• Continuous Integration & Deployment
• Scaling apps
• Development collaboration
• Local development

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Technology behind Docker

• Linux x86-64
• Go language
• Namespaces (pid, net, ipc, mnt, uts)
• Control Groups (cgroups)
• Union file systems (UnionFS)
• Client - Server (deamon) architecture
• Container format (libcontainer)

Notes:

Namespaces - provide a layer of isolation Control Groups - limits an application to a specific set of resources. UnionFS - It allows files and directories of separate file systems, known as branches, to be transparently overlaid, forming a single coherent file system Continer Format - All together

https://docs.docker.com/engine/docker-overview/

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The Docker architecture

See more at Understanding docker

Notes:

• images
• container

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Docker components/objects

• (Docker) client
• daemon/engine
• registry
• image
• container
• Dockerfile

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Docker client

It is the primary user interface to Docker. It accepts commands from the user and communicates back and forth with a Docker daemon.

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Docker daemon/engine

It runs on a host machine. The user does not directly interact with the daemon, but instead through the Docker client with the RESTful api or sockets.

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Docker distribution/registry

A (hosted) service containing repositories of images which responds to the Registry API.

Notes:

• Go to registry docker hub

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The docker image

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The docker container

Notes:

• Docker push/pull only new layers

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The Dockerfile

A Dockerfile is a text document that contains all the commands a user could call on the command line to create an image.

Notes:

• Later we will dive in, after demo of running docker

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Docker Run With Port Mapping

Notes:

• Demo

docker run -d -p 8080:80 nginx

http://localhost:8080

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Docker Run With File System Mount

Notes:

• Demo docker run -p 8888:80 -v c:/Users/yobitton/Documents/Code/presentations/intro-docker/examples/nginx:/usr/share/nginx/html nginx

Change file, see changes...

Browser - http://localhost:8888/

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Docker Common Commands

Notes:

• Demo

• Images list

• Nginx logs (detached, after access the page once)

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Convert An App into Docker Image

Notes:

• Demo (from wsl)

bit@YOBITTON-surface:/mnt/c/Users/yobitton/Documents/Code/presentations/intro-docker/examples/webapp$ python3 app.py INFO: Started server process [1018] INFO: Waiting for application startup. INFO: Uvicorn running on http://127.0.0.1:5000 (Press CTRL+C to quit)

http://localhost:5000/ -> Hello Micro Services... http://localhost:5000/name/yonatan -> Hello Yonatan http://localhost:5000/index -> read index file

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Overview of Dockerfile for our App

Notes:

• Explain each line

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Build the image

Pull the image

Repo Link bit.ly/pythonweb

Notes:

docker build . -t docker.io/bityob/docker-python-app

docker pull docker.io/bityob/docker-python-app

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Run the application using Docker

Notes:

Demo (from windows) -

docker run --name webapp -p 5555:5000 docker.io/bityob/docker-python-app

C:\WINDOWS\system32>docker run -p 5555:5000 docker.io/bityob/docker-python-app INFO: Started server process [6] INFO: Waiting for application startup. INFO: Uvicorn running on http://0.0.0.0:5000 (Press CTRL+C to quit) INFO: ('172.17.0.1', 48992) - "GET / HTTP/1.1" 200 INFO: ('172.17.0.1', 48992) - "GET /favicon.ico HTTP/1.1" 404

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SSH into the container

Notes:

docker exec -it webapp bash

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Instead of Resources

• Awesome Docker (list of Docker resources)
• Docker cheat sheet (GitHub, Docker Pdf)
• Docker aliases/shortcuts
• Docker Tips examples/tips
• Introduction to Docker (US PyCon 2016, Slides)

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Questions?

Slides bit.ly/introdocker, Docker Repo bit.ly/pythonweb

In this presentation I used Reveal.js and slides/ideas from theodorosploumis.