Jbot29

Debugging

The ultimate goal of debugging is to try and find the truth of the situation. Something is off. You expect the code or system to do x and it is off doing y. As we deploy code in different environments, running at crazy scale, or running distributed you can't always step through the code in a debugger or reproduce perfectly but you still need to be able to make progress.

At the end of the day there is code running somewhere in some order. Your goal is to figure out what is actually running. In a perfect universe you could pause and step through all the code running on every cpu in the system until then we are trying to get as close as possible to that level of understanding.

Debugger and logging

Obvisouly if you can run something locally and step through it in a debugger you should but for many systems this is not possible.

Jbot29

Defensive programming

Intro

There are times when working on critical or complex systems where issues manifest but it is difficult to pin down the source.

A set of code may write data and succeed with no issues but then another pieces comes along to read and finds that the data is wrong or incompatible. That is not horrific but when there are several actors it can be difficult to test all those scenerios and when things go south figure out which part introduced the issue.

Functional tests can help but with complex system it is impossible to create test cases for all scenerios.

Jbot29

Intro

I bought this deck of cards from a company called Unstuck Box. Each card has a mental model like Pareto Principle, Hanklons's razor, etc. When you are stuck on a problem you can grab a card randomly and try to apply that model to the problem.

Had the idea to apply that to tech problems.

Ultimately the way to get unstuck is to get more data to build a better mental model of the problem.

Go to ground

Jbot29

#Create a new directory
mkdir test

#cd into that new directory
cd test

#look for all files including hidden
ls -la

Jbot29

Blog Create Form:

We are going to create a html form that accepts data from the user and creates a new blog entry/model.

When a user enters a url in Chrome like /blog, Chrome sends a request to the server for that url with the HTTP verb or action
of GET.

The http request will look like this

GET /blog ....

Jbot29

Using

import sqlite3

Open a database

filename = "test.sqlite"
conn = sqlite3.connect(filename)

Create Table

Jbot29

#Create new git repo

At the same level as manage.py

#Create Heroku account

Go to http://heroku.com and get a free account.

#Install Heroku Toolbelt

Jbot29

https://github.com/new

- Create Public Resources 


Using ssh

https://help.github.com/articles/generating-ssh-keys/

Jbot29

wget https://bootstrap.pypa.io/get-pip.py

if you don't have wget

curl https://bootstrap.pypa.io/get-pip.py > get-pip.py

sudo python get-pip.py

Jbot29

Add code examples to each of this. Add more questions with things you are stuck on with code examples.

Add examples only when you don't remember or get stuck on how to do something. This is a cheat sheet. 

#Variables:

What is a variable?

What is the difference between a variable and a string?