Failed flask heroku deployment

Question

I am trying to host a Flask web application on Heroku, while I use these steps to get my web application hosted:

{git init
git add .
git commit -m "Initial commmit"

heroku create bukkit-list
git remote -v
git push heroku master}

After I do all of this, I get absolutely no error in my terminal, but the flask application is still not working. The logs for Heroku are given below.

2022-02-12T09:27:20.056100+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/" host=bukkit-list.herokuapp.com request_id=cd77d2eb-110d-4943-bae1-18601c9f90b7 fwd="103.79.250.41" dyno= connect= service= status=503 bytes= protocol=https

2022-02-12T09:27:20.601039+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/favicon.ico" host=bukkit-list.herokuapp.com request_id=5fe216d1-0f09-4777-8c6f-bee6b4b53f74 fwd="103.79.250.41" dyno= connect= service= status=503 bytes= protocol=https

2022-02-12T09:27:29.589547+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/" host=bukkit-list.herokuapp.com request_id=169389de-b2ed-43a3-ae8e-1203558e9c86 fwd="103.79.250.41" dyno= connect= service= status=503 bytes= protocol=https

2022-02-12T09:27:47.095193+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/" host=bukkit-list.herokuapp.com request_id=316fd6b2-9ffc-40ea-bee5-f0b3630a2948 fwd="103.79.250.41" dyno= connect= service= status=503 bytes= protocol=https

2022-02-12T09:27:48.317531+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/favicon.ico" host=bukkit-list.herokuapp.com request_id=6416476f-2e45-4dd2-a2f9-85fdcccb5883 fwd="103.79.250.41" dyno= connect= service= status=503 bytes= protocol=https

2022-02-12T09:28:17.730376+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/" host=bukkit-list.herokuapp.com request_id=3a7058d4-9796-4a62-8ec5-4be44728f638 fwd="103.79.250.41" dyno= connect= service= status=503 bytes= protocol=https

2022-02-12T09:28:18.395460+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/favicon.ico" host=bukkit-list.herokuapp.com request_id=57d66c4d-8fe9-4801-8d9d-a65d9986b808 fwd="103.79.250.41" dyno= connect= service= status=503 bytes= protocol=https

My app.py code

from flask import Flask, redirect, render_template, request
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///tasks.db'

app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)

class Task(db.Model):
   sno = db.Column(db.Integer, primary_key = True)
   title = db.Column(db.String(200), nullable=False)
   desc = db.Column(db.String(500), nullable=False)

   def __repr__(self) -> str:
       return f'{self.title} - {self.sno}'

# Routes
@app.route('/')
def home():
    return render_template('home.html')

# Task list area ==========================================
@app.route('/taskList')
def taskList():
    taskList = Task.query.all()
    return render_template('taskList.html', taskList=taskList)

@app.route('/delete/<int:sno>')
def delete(sno):
    task = Task.query.filter_by(sno=sno).first()
    db.session.delete(task)
    db.session.commit()
    return redirect('/taskList')

@app.route('/addTask')
def addTask():
    return redirect('/TaskEditor_Add')

# Add task area =============================================
@app.route('/TaskEditor_Add', methods=["GET", "POST"])
def TaskEditor_Add():
    state = "Add - Task"
    if request.method == "POST":
        title = request.form['title']
        desc = request.form['desc']
        if (title.isspace() or desc.isspace()):
            state = "Invalid Task"
        else:
            task = Task(title=title, desc=desc)
            db.session.add(task)
            db.session.commit()
            state = "Task added"
            return redirect("/taskList")

    return render_template('addTask.html', state=state)

# Update an existing todo area ================================
@app.route('/TaskEditor_Edit/<int:sno>', methods=["POST", "GET"])
def TaskEditor_Edit(sno):
    task = Task.query.filter_by(sno=sno).first()
    state="Edit Task"
    if request.method == "POST":
        title = request.form['title']
        desc = request.form['desc']
        if (title.isspace() or desc.isspace()):
            state = "Invalid Task"
        else:
           task.title = title
           task.desc = desc
           db.session.add(task)
           db.session.commit()
           return redirect('/taskList')

    return render_template('editTask.html', task=task, state=state)


if __name__ == "__main__":
    app.run(debug=True)    ```

The procfile only has this single line of code which is down below:

web:gunicorn app:app

score 0 · Answer 1 · edited Feb 14 '22 at 16:00

I also deployed a website in Heroku with Flask and an SQL database a few days ago, and I got a similar error. First of all, in the Procfile add a space between the web: and the gunicorn like so:

web: gunicorn hello:app - this is how they write it in their documentation.

Second, make sure your requirement.txt file is updated and display the gunicorn in it.

Try changing the database to PostgreSQL. You can configure one in the resource tab:

And in your code you will need to change these lines:

import os
uri = os.getenv("DATABASE_URL")
if uri and uri.startswith("postgres://"):
    uri = uri.replace("postgres://", "postgresql://", 1)

app.config['SQLALCHEMY_DATABASE_URI'] = uri

You can read about why you need to add those here.

Failed flask heroku deployment

My app.py code

1 Answers1