Wednesday, August 26, 2020

Deploying Flask based 'Hello World' REST API on Heroku Cloud 


Getting Started on Heroku with Python
Basic requirement:
- a free Heroku account
- Python version 3.7 installed locally - see the installation guides for OS X, Windows, and Linux.

- Heroku CLI requires Git 
You can Git from here: git-scm

- For first time Git setup:Getting-Started-First-Time-Git-Setup

Heroku CLI is avaiable for macOS, Windows and Linux.

You use the Heroku CLI to manage and scale your applications, provision add-ons, view your application logs, and run your application locally.

Once installed, you can use the heroku command from your command shell.
On Windows, start the Command Prompt (cmd.exe) or Powershell to access the command shell.

Use the heroku login command to log in to the Heroku CLI:

(base) C:\Users\Ashish Jain>heroku login
heroku: Press any key to open up the browser to login or q to exit:
Opening browser to https://cli-auth.heroku.com/auth/cli/browser/716***J1k
heroku: Waiting for login... - 




(base) C:\Users\Ashish Jain>heroku login
heroku: Press any key to open up the browser to login or q to exit:
Opening browser to https://cli-auth.heroku.com/auth/cli/browser/716***J1k
Logging in... done
Logged in as a***@gmail.com





Create the app


Create an app on Heroku, which prepares Heroku to receive your source code:

When you create an app, a git remote (called heroku) is also created and associated with your local git repository.

Heroku generates a random name (in this case serene-caverns-82714) for your app, or you can pass a parameter to specify your own app name.

(base) C:\Users\Ashish Jain\OneDrive\Desktop>cd myapp

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp>dir
 Directory of C:\Users\Ashish Jain\OneDrive\Desktop\myapp
               0 File(s)              0 bytes

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp>heroku create
Creating app... done, ⬢ rocky-spire-96801
https://rocky-spire-96801.herokuapp.com/ | https://git.heroku.com/rocky-spire-96801.git 

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp>git clone https://git.heroku.com/rocky-spire-96801.git
Cloning into 'rocky-spire-96801'...
warning: You appear to have cloned an empty repository.


Writing a Python Script file

We are at: C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801
We create a Python script: MyRESTAPIUsingPythonScript.py

It has following code:

from flask import Flask, request
from flask_restful import Resource, Api
import os

app = Flask(__name__)
api = Api(app)

class Tracks(Resource):
    def get(self):
        result = "Hello World"
        return result

api.add_resource(Tracks, '/tracks') # URL Route

if __name__ == '__main__':
    port = int(os.environ.get('PORT', 5000))
    app.run(host='0.0.0.0', port=port) 

In the code above:
Heroku dynamically assigns your app a port, so we cannot set the port to a fixed number. Heroku adds the port to the env, so we pull it from there. 


Wrong Code 1
if __name__ == '__main__':
     app.run(port='5002')

Error Logs:
2020-08-26T16:20:58.493306+00:00 app[web.1]: * Running on http://127.0.0.1:5002/ (Press CTRL+C to quit)
...
2020-08-26T16:23:01.745361+00:00 heroku[web.1]: Error R10 (Boot timeout) -> Web process failed to bind to $PORT within 60 seconds of launch
2020-08-26T16:23:01.782641+00:00 heroku[web.1]: Stopping process with SIGKILL
2020-08-26T16:23:01.914043+00:00 heroku[web.1]: Process exited with status 137
2020-08-26T16:23:01.987508+00:00 heroku[web.1]: State changed from starting to crashed

Wrong Code 2
if __name__ == '__main__':
    app.run()

Error logs:
(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>heroku logs
...
   2020-08-26T16:27:43.161519+00:00 app[web.1]: * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
   2020-08-26T16:27:45.000000+00:00 app[api]: Build succeeded
   2020-08-26T16:28:40.527069+00:00 heroku[web.1]: Error R10 (Boot timeout) -> Web process failed to bind to $PORT within 60 seconds of launch
   2020-08-26T16:28:40.548232+00:00 heroku[web.1]: Stopping process with SIGKILL
   2020-08-26T16:28:40.611066+00:00 heroku[web.1]: Process exited with status 137
   2020-08-26T16:28:40.655930+00:00 heroku[web.1]: State changed from starting to crashed 


Wrong Code 3
if __name__ == '__main__':
    app.run(host='0.0.0.0')

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>heroku logs
...
2020-08-26T16:35:36.792884+00:00 heroku[web.1]: Starting process with command `python MyRESTAPIUsingPythonScript.py`
2020-08-26T16:35:40.000000+00:00 app[api]: Build succeeded
2020-08-26T16:35:40.100687+00:00 app[web.1]: * Serving Flask app "MyRESTAPIUsingPythonScript" (lazy loading)
2020-08-26T16:35:40.100727+00:00 app[web.1]: * Environment: production
2020-08-26T16:35:40.100730+00:00 app[web.1]: WARNING: This is a development server. Do not use it in a production deployment.
2020-08-26T16:35:40.100738+00:00 app[web.1]: Use a production WSGI server instead.
2020-08-26T16:35:40.100767+00:00 app[web.1]: * Debug mode: off
2020-08-26T16:35:40.103621+00:00 app[web.1]: * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
2020-08-26T16:37:41.234182+00:00 heroku[web.1]: Error R10 (Boot timeout) -> Web process failed to bind to $PORT within 60 seconds of launch
2020-08-26T16:37:41.260167+00:00 heroku[web.1]: Stopping process with SIGKILL
2020-08-26T16:37:41.377892+00:00 heroku[web.1]: Process exited with status 137
2020-08-26T16:37:41.426917+00:00 heroku[web.1]: State changed from starting to crashed 

About "git commit" logs
Every time we do changes and commit, Heroku knows which release this is. See below, it says "Released v6":

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>git add .

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>git commit -m "1012"
[master a4975c0] 1012
 1 file changed, 3 insertions(+), 1 deletion(-)

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>git push
Enumerating objects: 5, done.
Counting objects: 100% (5/5), done.
Delta compression using up to 4 threads
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 423 bytes | 423.00 KiB/s, done.
Total 3 (delta 1), reused 0 (delta 0), pack-reused 0
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Python app detected
remote: -----> No change in requirements detected, installing from cache
remote: -----> Installing pip 20.1.1, setuptools 47.1.1 and wheel 0.34.2
remote: -----> Installing SQLite3
remote: -----> Installing requirements with pip
remote: -----> Discovering process types
remote:        Procfile declares types -> web
remote:
remote: -----> Compressing...
remote:        Done: 45.6M
remote: -----> Launching...
remote:        Released v6 
remote:        https://rocky-spire-96801.herokuapp.com/ deployed to Heroku
remote:
remote: Verifying deploy... done.
To https://git.heroku.com/rocky-spire-96801.git
   0391d70..a4975c0  master -> master 


Define a Procfile

We create a file "Procfile" at: C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801

Based on our code (which is a Python script to run a simple Flask based REST API), we write in Procfile:

web: python MyRESTAPIUsingPythonScript.py 

Procfile naming and location
The Procfile is always a simple text file that is named Procfile without a file extension. For example, Procfile.txt is not valid.
The Procfile must live in your app’s root directory. It does not function if placed anywhere else.

Procfile format
A Procfile declares its process types on individual lines, each with the following format:

[process type]: [command]

    [process type] is an alphanumeric name for your command, such as web, worker, urgentworker, clock, and so on.
    [command] indicates the command that every dyno of the process type should execute on startup, such as rake jobs:work.

The "web" process type 

A Heroku app’s web process type is special: it’s the only process type that can receive external HTTP traffic from Heroku’s routers. If your app includes a web server, you should declare it as your app’s web process.

For example, the Procfile for a Rails web app might include the following process type:

web: bundle exec rails server -p $PORT

In this case, every web dyno executes bundle exec rails server -p $PORT, which starts up a web server.

A Clojure app’s web process type might look like this:

web: lein run -m demo.web $PORT

You can refer to your app’s config vars, most usefully $PORT, in the commands you specify.

This might be the web process type for an executable Java JAR file, such as when using Spring Boot:

web: java -jar target/myapp-1.0.0.jar

More on Procfile here: devcenter.heroku

Deploying to Heroku

A Procfile is not technically required to deploy simple apps written in most Heroku-supported languages—the platform automatically detects the language and creates a default web process type to boot the application server. However, creating an explicit Procfile is recommended for greater control and flexibility over your app.

For Heroku to use your Procfile, add the Procfile to the root directory of your application, then push to Heroku:

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>dir
 Directory of C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801

08/26/2020  09:47 PM    [DIR]          .
08/26/2020  09:47 PM    [DIR]          ..
08/26/2020  09:40 PM               326 MyRESTAPIUsingPythonScript.py
08/26/2020  09:42 PM                41 Procfile
08/26/2020  09:33 PM                22 requirements.txt
               3 File(s)            389 bytes
               2 Dir(s)  65,828,458,496 bytes free

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>git add .

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>git commit -m "first commit"
[master (root-commit) ff73728] first commit
 3 files changed, 18 insertions(+)
 create mode 100644 MyRESTAPIUsingPythonScript.py
 create mode 100644 Procfile
 create mode 100644 requirements.txt 

As opposed to what appears on the Heroku documentation, we simply have to do "git push" now. Otherwise we see following errors:
(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>git push heroku master
 fatal: 'heroku' does not appear to be a git repository
 fatal: Could not read from remote repository.
 
 Please make sure you have the correct access rights and the repository exists.
 
 (base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>git push master
 fatal: 'master' does not appear to be a git repository
 fatal: Could not read from remote repository.
 
 Please make sure you have the correct access rights and the repository exists.
 
(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>git push
 Enumerating objects: 5, done.
 Counting objects: 100% (5/5), done.
 Delta compression using up to 4 threads
 Compressing objects: 100% (3/3), done.
 Writing objects: 100% (5/5), 585 bytes | 292.00 KiB/s, done.
 Total 5 (delta 0), reused 0 (delta 0), pack-reused 0
 remote: Compressing source files... done.
 remote: Building source:
 remote:
 remote: -----> Python app detected
 remote: -----> Installing python-3.6.12
 remote: -----> Installing pip 20.1.1, setuptools 47.1.1 and wheel 0.34.2
 remote: -----> Installing SQLite3
 remote: -----> Installing requirements with pip
 remote:        Collecting flask
 remote:          Downloading Flask-1.1.2-py2.py3-none-any.whl (94 kB)
 remote:        Collecting flask_restful
 remote:          Downloading Flask_RESTful-0.3.8-py2.py3-none-any.whl (25 kB)
 remote:        Collecting click>=5.1
 remote:          Downloading click-7.1.2-py2.py3-none-any.whl (82 kB)
 remote:        Collecting Jinja2>=2.10.1
 remote:          Downloading Jinja2-2.11.2-py2.py3-none-any.whl (125 kB)
 remote:        Collecting Werkzeug>=0.15
 remote:          Downloading Werkzeug-1.0.1-py2.py3-none-any.whl (298 kB)
 remote:        Collecting itsdangerous>=0.24
 remote:          Downloading itsdangerous-1.1.0-py2.py3-none-any.whl (16 kB)
 remote:        Collecting pytz
 remote:          Downloading pytz-2020.1-py2.py3-none-any.whl (510 kB)
 remote:        Collecting aniso8601>=0.82
 remote:          Downloading aniso8601-8.0.0-py2.py3-none-any.whl (43 kB)
 remote:        Collecting six>=1.3.0
 remote:          Downloading six-1.15.0-py2.py3-none-any.whl (10 kB)
 remote:        Collecting MarkupSafe>=0.23
 remote:          Downloading MarkupSafe-1.1.1-cp36-cp36m-manylinux1_x86_64.whl (27 kB)
 remote:        Installing collected packages: click, MarkupSafe, Jinja2, Werkzeug, itsdangerous, flask, pytz, aniso8601, six, flask-restful
 remote:        Successfully installed Jinja2-2.11.2 MarkupSafe-1.1.1 Werkzeug-1.0.1 aniso8601-8.0.0 click-7.1.2 flask-1.1.2 flask-restful-0.3.8 itsdangerous-1.1.0 pytz-2020.1 six-1.15.0
 remote: -----> Discovering process types
 remote:        Procfile declares types -> web
 remote:
 remote: -----> Compressing...
 remote:        Done: 45.6M
 remote: -----> Launching...
 remote:        Released v3
 remote:        https://rocky-spire-96801.herokuapp.com/ deployed to Heroku
 remote:
 remote: Verifying deploy... done.
 To https://git.heroku.com/rocky-spire-96801.git
  * [new branch]      master -> master 

Checking Heroku process status 
(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>heroku ps
  Free dyno hours quota remaining this month: 550h 0m (100%)
  Free dyno usage for this app: 0h 0m (0%)
  For more information on dyno sleeping and how to upgrade, see:
  https://devcenter.heroku.com/articles/dyno-sleeping
  
  === web (Free): python MyRESTAPIUsingPythonScript.py (1)
  web.1: restarting 2020/08/26 21:51:56 +0530 (~ 41s ago)
  
(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>heroku ps
  Free dyno hours quota remaining this month: 550h 0m (100%)
  Free dyno usage for this app: 0h 0m (0%)
  For more information on dyno sleeping and how to upgrade, see:
  https://devcenter.heroku.com/articles/dyno-sleeping
  
  === web (Free): python MyRESTAPIUsingPythonScript.py (1)
  web.1: up 2020/08/26 22:28:06 +0530 (~ 12m ago) 

Check Logs

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>heroku logs
  2020-08-26T15:55:49.855840+00:00 app[api]: Initial release by user a***@gmail.com
2020-08-26T15:55:49.855840+00:00 app[api]: Release v1 created by user a***@gmail.com
2020-08-26T15:55:49.992678+00:00 app[api]: Enable Logplex by user a***@gmail.com
2020-08-26T15:55:49.992678+00:00 app[api]: Release v2 created by user a***@gmail.com
2020-08-26T16:20:26.000000+00:00 app[api]: Build started by user a***@gmail.com
2020-08-26T16:20:51.873133+00:00 app[api]: Release v3 created by user a***@gmail.com
2020-08-26T16:20:51.873133+00:00 app[api]: Deploy ff73728d by user a***@gmail.com
2020-08-26T16:20:51.891792+00:00 app[api]: Scaled to web@1:Free by user a***@gmail.com
2020-08-26T16:20:55.659055+00:00 heroku[web.1]: Starting process with command `python MyRESTAPIUsingPythonScript.py`
2020-08-26T16:20:58.489161+00:00 app[web.1]: * Serving Flask app "MyRESTAPIUsingPythonScript" (lazy loading)
2020-08-26T16:20:58.489192+00:00 app[web.1]: * Environment: production
2020-08-26T16:20:58.489257+00:00 app[web.1]: WARNING: This is a development server. Do not use it in a production deployment.
2020-08-26T16:20:58.489350+00:00 app[web.1]: Use a production WSGI server instead.
2020-08-26T16:20:58.489393+00:00 app[web.1]: * Debug mode: off
2020-08-26T16:20:58.493306+00:00 app[web.1]: * Running on http://127.0.0.1:5002/ (Press CTRL+C to quit)
2020-08-26T16:21:00.000000+00:00 app[api]: Build succeeded
2020-08-26T16:28:40.527069+00:00 heroku[web.1]: Error R10 (Boot timeout) -> Web process failed to bind to $PORT within 60 seconds of launch
2020-08-26T16:28:40.548232+00:00 heroku[web.1]: Stopping process with SIGKILL
2020-08-26T16:28:40.611066+00:00 heroku[web.1]: Process exited with status 137
2020-08-26T16:28:40.655930+00:00 heroku[web.1]: State changed from starting to crashed
...
2020-08-26T16:43:04.803725+00:00 heroku[web.1]: State changed from crashed to starting
2020-08-26T16:43:07.586143+00:00 heroku[web.1]: Starting process with command `python MyRESTAPIUsingPythonScript.py`
2020-08-26T16:43:09.742529+00:00 app[web.1]: * Serving Flask app "MyRESTAPIUsingPythonScript" (lazy loading)
2020-08-26T16:43:09.742547+00:00 app[web.1]: * Environment: production
2020-08-26T16:43:09.742586+00:00 app[web.1]: WARNING: This is a development server. Do not use it in a production deployment.
2020-08-26T16:43:09.742625+00:00 app[web.1]: Use a production WSGI server instead.
2020-08-26T16:43:09.742662+00:00 app[web.1]: * Debug mode: off
2020-08-26T16:43:09.745322+00:00 app[web.1]: * Running on http://0.0.0.0:32410/ (Press CTRL+C to quit)
2020-08-26T16:43:09.847177+00:00 heroku[web.1]: State changed from starting to up
2020-08-26T16:43:12.000000+00:00 app[api]: Build succeeded 

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>heroku open

In Firefox browser with URL: https://rocky-spire-96801.herokuapp.com/

Not Found

The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.

In Firefox at URL: https://rocky-spire-96801.herokuapp.com/tracks







In Chrome at URL: https://rocky-spire-96801.herokuapp.com/tracks




Logout 

(base) C:\Users\Ashish Jain\OneDrive\Desktop\myapp\rocky-spire-96801>heroku logout
Logging out... done
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