Week 6 Android

Computer Networking ->

Goals for today

0. Intro to Networking -> done

1. Revision of RestAPI on Cloud : Nginx + Python -> done

2. Load Balancer vs Reverse Proxy -> done

3. Adding TLS cert (HTTP to HTTPs) -> done

4. Docker

Debugging the OCR App (from week 5)

Next App: Weather app

Future concepts :

 Async vs Sync Operations :

 Coroutines

 Intro to Dependency Injection

Steps to build so far

1. Build MVP (Minimum viable product) Independent feature in app

2. Integrate in the big app after testing

Rs. 1000 bounty

Live Demo first

Remember we have bounty program fix bug and get Rs. 1000 ($18)

Intro to Networking

open systems interconnection

https://www.cloudflare.com/learning/ddos/glossary/open-systems-interconnection-model-osi/

1. Pen drives, ethernett

2. Exchnage data via Internet

TCP vs UDP

https://meghagarwal.medium.com/tcp-vs-udp-c3dedd91f66d#:~:text=TCP%20is%20a%20communication%20protocol,maintain%20the%20data%20packets'%20order.

TCP :: For secure transmission it make sure that data comes in sequence and without errors
TCP is a reliable and connection-oriented protocol
e.x
Online net-banking transaction

Steps to host a Server

1. Create VM  (Host on any Port e..g 5000)

2. Open the right ports on Azure or any cloud (80 / 443)

3. copy code python3 code of flask server

4. Make sure it never turns off -> docker / pm2 

5. Ngnix / Apache2 for reverse proxy

0.0.0.0 vs 127.0.0.1

python3 http.server -> 127.0.0.1 -> only work on your own computer

python3 http.server -> 0.0.0.0 -> you can share the link http://10.5.0.4:5000 and share data

Make encrypted using TLS cert

cert installation steps:

 https://certbot.eff.org/instructions?ws=nginx&os=ubuntufocal

Problems in our server

1. Turns off sometimes on it's own

2. not easy to share -> you have to make each person install python3, flask etc.

3. Lot of steps to bring machine up

Make sure it never stops

Creating Docker Container

Docker

example : https://github.com/ahmnouira/flask-hello-world

https://github.com/robpco/docker-nginx-uwsgi

Self sufficient computer

 runs consistently regardless of machine

Docker file -> Image

Image -> 

Python3.8

Nginx version 2.1

-> Container

Image is list of  necessary files, libraries, and configuration settings that are needed to run that application

Image vs Container

Image -> once (pyton3.8 nginx 2.1)

Containers can be multiple

Overall Docker

Self contained system allowing

1. Build

2. Run

3. Deploy

Docker 3 parts

1. Docker Engine -> Software that creates images / start containers

2. CLI : Command Line Interface

3. Docker Hub (like GitHub)

not the hub you think

What is Dockerization?

1. it's like new OS with less storage

2. consistent linux os on Windows or Mac

3. Maintain 2 instances easily: e.g. Python 3.7 vs Python 3.9

4. Encapsulation: one system in Docker doesn't know about other system

5. Easy and clear monitoring (one log file for all)

Terminologies

Container – a Virtual OS where we run software same as OS but with minimum storage 

Image – everything you need to run a software including OS version (e.g. python server needs flask, openai libraries on Ubuntu 20)

Steps :

1. Install docker: https://docs.docker.com/engine/install/ubuntu/

2. Create Docker File

3. build

4. run 

DockerFile steps

your image -> like on OS  python python3 ready with libraries

1. Base image -> pyton3.8 3.9 etc

2. Libraries -> like flask etc.

3. Copy files like you copy to the OS

4. Expose ports like 5000 we did 

5. Run docker container

Docker running steps

1. docker build -t <tag name> .

2. docker run <tag name>

e.g. 

1. docker build -t python-server .

2. docker run -p -d 5001:5001 python-server (with port mapping)

-d -> run as independent unit

-p -> port mapping

Example Dockerfile

Docker push

docker login

2. docker tag python-server singhinusa/firstimage

2. docker push singhinusa/firstimage