Help:Toolforge/Building container images/My first Buildpack Python tool

Python webservices are used by many existing tools. Python is a high-level, interpreted programming language with many available libraries for making webservices and integrating with MediaWiki.

This stub webservice is designed to get a sample Python application installed onto Toolforge using the new build service, as quickly as possible. The application is written using the Flask framework.

The guide will teach you how to:

• Create a new tool
• Run a Python 3 WSGI webservice on Kubernetes

• Basic knowledge of Python
• Basic knowledge of SSH
• Basic knowledge of the Unix command line
• Basic knowledge of Git

• A Toolforge account

1. Follow the Toolforge quickstart guide to create a Toolforge tool and SSH into Toolforge.
   • For the examples in this tutorial, sample-python-buildpack-app is used to indicate places where your unique tool name is used in another command.
2. Make sure to create a git repository for the tool, you can get one like this:
   1. Log into the toolforge admin page
   2. Select your tool
   3. On the left side panel, under Git repositories click create repository
   4. Copy the url in the Clone section
      1. There's a private url, that we will use to clone it locally, starting with "git": git@gitlab-ssh.wikimedia.org:toolforge-repos/sample-python-buildpack-app.git
      2. And a public one, that we will use to build the app in toolforge, starting with "https": https://gitlab.wikimedia.org/toolforge-repos/sample-python-buildpack-app.git

What is Flask?

Flask is a popular web development framework for Python.

What is gunicorn?

Gunicorn is a web server popular for running Python applications.

Clone your tool git repository

You will have to clone the tool repository to be able to add code to it, on your local computer (with git installed) you can run:

laptop:~$ gitclonegit@gitlab-ssh.wikimedia.org:toolforge-repos/sample-python-buildpack-app.git
laptop:~$ cdsample-python-buildpack-app

That will create a folder called sample-python-buildpack-app. We are going to put the code in that folder.

Add the Flask and gunicorn dependencies

laptop:~sample-python-buildpack-app$ cat>requirements.txt<<EOF
flask
gunicorn
EOF

Create a 'hello world' WSGI application

# -*-coding:utf-8-*-
#
# ThisfileispartoftheToolforgeflaskWSGItutorial
#
# Copyright(C)2017BryanDavisandcontributors
#
# Thisprogramisfreesoftware:youcanredistributeitand/ormodifyit
# underthetermsoftheGNUGeneralPublicLicenseaspublishedbytheFree
# SoftwareFoundation,eitherversion3oftheLicense,or(atyouroption)
# anylaterversion.
#
# Thisprogramisdistributedinthehopethatitwillbeuseful,butWITHOUT
# ANYWARRANTY;withouteventheimpliedwarrantyofMERCHANTABILITYor
# FITNESSFORAPARTICULARPURPOSE.SeetheGNUGeneralPublicLicensefor
# moredetails.
#
# YoushouldhavereceivedacopyoftheGNUGeneralPublicLicensealong
# withthisprogram.Ifnot,see<http://www.gnu.org/licenses/>.
import flask
app = flask.Flask(__name__)
@app.route('/')
def index():
 return 'Hello World!'

Code on Toolforge must always be licensed under an Open Source Initiative (OSI) approved license. See the Right to fork policy for more information on this Toolforge policy.

Create the Procfile

The Procfile is based on heroku's procfile, though we don't support all it's features, for now we only use the web entry point to get the command your server will be start with:

laptop:~sample-python-buildpack-app$ cat>Procfile<<EOF
web: gunicorn --workers=4 --bind=0.0.0.0 --forwarded-allow-ips=* app:app
EOF

Commit your changes and push

laptop:~sample-python-buildpack-app$ gitadd.
laptop:~sample-python-buildpack-app$ gitcommit-m"First commit"
laptop:~sample-python-buildpack-app$ gitpushoriginmain

Build the image

Now we have to ssh to login.toolforge.org and start the build for the image:

laptop:~sample-python-buildpack-app$ sshlogin.toolforge.org# or the equivalent with PuTTY
dcaro@tools-sgebastion-10$ becomesample-python-buildpack-app
tools.sample-python-buildpack-app@tools-sgebastion-10$ toolforgebuildstarthttps://gitlab.wikimedia.org/toolforge-repos/sample-python-buildpack-app.git

Wait for the build to finish

You can check the status of the build like this:

tools.sample-python-buildpack-app@tools-sgebastion-10:~$ toolforgebuildshow

You have to wait for the status to be Status: ok.

Start the webservice

tools.sample-python-buildpack-app@tools-sgebastion-10$ toolforgewebservicebuildservicestart--mount=none
Starting webservice.

Once the webservice is started, navigate to https://sample-python-buildpack-app.toolforge.org in your web browser, and see a 'Hello World!' message. It might take a few minutes until it is reachable.

You can see the code used in this example here: https://gitlab.wikimedia.org/toolforge-repos/sample-python-buildpack-app

See Help:Toolforge/Build_Service#Troubleshooting.

• Git repository 'tool-my-first-flask-oauth-tool' on Phabricator
• My-first-flask-oauth-tool on Toolforge
• Help:Toolforge/My first Django OAuth tool
• Help:Toolforge/My first NodeJS OAuth tool

Support and administration of the WMCS resources is provided by Wikimedia Foundation staff and Wikimedia movement volunteers. Please reach out with questions and join the conversation:

• Toolforge
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• Python