Lecture 10: Heroku, Workers, and Postgres

Question 1

What are the basic files needed to create a Heroku App?

Answer 1

• Procfile
• requirements.txt
• runtime.txt
• webapp.py

Question 2

What does the runtime file specify?

Answer 2

The language/runtime to use

Question 3

What does the requirements file specify?

Answer 3

The modules/libraries to install in the environment –

Question 4

What does the Procfile file specify?

Answer 4

The command(s) we want to run when our application is deployed

• Defines a process type (web/worker/clock)
• Tell gunicorn to look for the webapp.py file

Question 5

What does the webapp file specify?

Answer 5

The web application code

• Consists of a single app() function definition

Question 6

Which files help set up our application environment?

Answer 6

• requirements.txt

- runtime.txt

Question 7

What does the app() function in the webapp file do?

Answer 7

Hooks into WSGI and allows Python to specify a

response when receiving a request

Question 8

What do we specify in the webapp file?

Answer 8

• Data (streaming bytes)
• Status (HTTP status code)
• Response Headers

Question 9

What commands do you run to create a new heroku deployment with Git

Answer 9

git init
git add .
git commit
heroku create
git push heroku master

Question 10

Describe the storage between processes

Answer 10

• Individual processes are run in a semi-sandboxed manner

- They don’t have direct access to the same files

Question 11

What is the database were using with Heroku?

Answer 11

PostgreSQL

Question 12

How do you connect to PostgreSQL?

Answer 12

requirements. txt file:
- add ‘psycopg2’ line to

webapp. py file:
- In a try/except
- Define DATABASE_URL
- Create DB connection
- Create cursor
- Create table and execute query on cursor
- conn.commit()
- conn.close()

Question 13

What is the command to scale workers to 1

Answer 13

heroku ps:scale worker=1

Question 14

What does heroku ps:stop worker do?

Answer 14

• Puts the proccess into idle

- The process will keep on restarting

Question 15

How do you kill a worker process?

Answer 15

Scale workers to 0

heroku ps:scale worker=0