Flask app deployed successfully - Application Error

Question

I'm trying to deploy a simple python flask app to Heroku, I can deploy the app without any issues but I keep getting an Application Error when I try and view it.

I have created the requirements.txt file along with the Procfile file.

GitRepo for project: https://github.com/Karan-Ghatt/password-vault

The error log:

C:\Users\Niku>heroku logs --tail --app=password-vault-flask
2020-06-18T15:34:53.021133+00:00 app[web.1]: raise value
2020-06-18T15:34:53.021133+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 2447, in wsgi_app
2020-06-18T15:34:53.021134+00:00 app[web.1]: response = self.full_dispatch_request()
2020-06-18T15:34:53.021134+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1952, in full_dispatch_request
2020-06-18T15:34:53.021134+00:00 app[web.1]: rv = self.handle_user_exception(e)
2020-06-18T15:34:53.021134+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1821, in handle_user_exception
2020-06-18T15:34:53.021134+00:00 app[web.1]: reraise(exc_type, exc_value, tb)
2020-06-18T15:34:53.021135+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/_compat.py", line 39, in reraise
2020-06-18T15:34:53.021135+00:00 app[web.1]: raise value
2020-06-18T15:34:53.021137+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1950, in full_dispatch_request
2020-06-18T15:34:53.021137+00:00 app[web.1]: rv = self.dispatch_request()
2020-06-18T15:34:53.021138+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1936, in dispatch_request
2020-06-18T15:34:53.021138+00:00 app[web.1]: return self.view_functions[rule.endpoint](**req.view_args)
2020-06-18T15:34:53.021138+00:00 app[web.1]: File "/app/PWGEN.py", line 35, in home
2020-06-18T15:34:53.021138+00:00 app[web.1]: return render_template('home.html')
2020-06-18T15:34:53.021138+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/templating.py", line 138, in render_template
2020-06-18T15:34:53.021139+00:00 app[web.1]: ctx.app.jinja_env.get_or_select_template(template_name_or_list),
2020-06-18T15:34:53.021140+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/jinja2/environment.py", line 930, in get_or_select_template
2020-06-18T15:34:53.021140+00:00 app[web.1]: return self.get_template(template_name_or_list, parent, globals)
2020-06-18T15:34:53.021140+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/jinja2/environment.py", line 883, in get_template
2020-06-18T15:34:53.021140+00:00 app[web.1]: return self._load_template(name, self.make_globals(globals))
2020-06-18T15:34:53.021141+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/jinja2/environment.py", line 857, in _load_template
2020-06-18T15:34:53.021141+00:00 app[web.1]: template = self.loader.load(self, name, globals)
2020-06-18T15:34:53.021141+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/jinja2/loaders.py", line 115, in load
2020-06-18T15:34:53.021141+00:00 app[web.1]: source, filename, uptodate = self.get_source(environment, name)
2020-06-18T15:34:53.021141+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/templating.py", line 60, in get_source
2020-06-18T15:34:53.021142+00:00 app[web.1]: return self._get_source_fast(environment, template)
2020-06-18T15:34:53.021142+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/templating.py", line 89, in _get_source_fast
2020-06-18T15:34:53.021142+00:00 app[web.1]: raise TemplateNotFound(template)
2020-06-18T15:34:53.021147+00:00 app[web.1]: jinja2.exceptions.TemplateNotFound: home.html
2020-06-18T15:34:53.021860+00:00 heroku[router]: at=error code=H13 desc="Connection closed without response" method=GET path="/" host=password-vault-flask.herokuapp.com request_id=ce3a2f0f-cdb8-4c58-9f7b-bf3ce6d0cf4c fwd="94.12.92.223" dyno=web.1 connect=1ms service=13ms status=503 bytes=0 protocol=https
2020-06-18T15:34:53.638914+00:00 app[web.1]: 10.37.207.144 - - [18/Jun/2020:15:34:53 +0000] "GET /favicon.ico HTTP/1.1" 404 232 "https://password-vault-flask.herokuapp.com/" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.97 Safari/537.36"
2020-06-18T15:34:53.644280+00:00 heroku[router]: at=info method=GET path="/favicon.ico" host=password-vault-flask.herokuapp.com request_id=270c59f0-022a-49b5-be47-b16bfc22eb9a fwd="94.12.92.223" dyno=web.1 connect=0ms service=2ms status=404 bytes=400 protocol=https
2020-06-18T16:07:52.192127+00:00 heroku[web.1]: Idling
2020-06-18T16:07:52.194760+00:00 heroku[web.1]: State changed from up to down
2020-06-18T16:07:53.045347+00:00 heroku[web.1]: Stopping all processes with SIGTERM
2020-06-18T16:07:53.082141+00:00 app[web.1]: [2020-06-18 16:07:53 +0000] [4] [INFO] Handling signal: term
2020-06-18T16:07:53.082152+00:00 app[web.1]: [2020-06-18 16:07:53 +0000] [11] [INFO] Worker exiting (pid: 11)
2020-06-18T16:07:53.082153+00:00 app[web.1]: [2020-06-18 16:07:53 +0000] [10] [INFO] Worker exiting (pid: 10)
2020-06-18T16:07:53.182532+00:00 app[web.1]: [2020-06-18 16:07:53 +0000] [4] [INFO] Shutting down: Master
2020-06-18T16:07:53.289093+00:00 heroku[web.1]: Process exited with status 0
2020-06-18T16:27:26.355336+00:00 heroku[web.1]: Unidling
2020-06-18T16:27:26.356958+00:00 heroku[web.1]: State changed from down to starting
2020-06-18T16:27:29.523669+00:00 heroku[web.1]: Starting process with command `gunicorn --bind 0.0.0.0:53996 PWGEN:app`
2020-06-18T16:27:32.013100+00:00 app[web.1]: [2020-06-18 16:27:32 +0000] [4] [INFO] Starting gunicorn 20.0.4
2020-06-18T16:27:32.013732+00:00 app[web.1]: [2020-06-18 16:27:32 +0000] [4] [INFO] Listening at: http://0.0.0.0:53996 (4)
2020-06-18T16:27:32.013852+00:00 app[web.1]: [2020-06-18 16:27:32 +0000] [4] [INFO] Using worker: sync
2020-06-18T16:27:32.018992+00:00 app[web.1]: [2020-06-18 16:27:32 +0000] [10] [INFO] Booting worker with pid: 10
2020-06-18T16:27:32.040657+00:00 app[web.1]: [2020-06-18 16:27:32 +0000] [11] [INFO] Booting worker with pid: 11
2020-06-18T16:27:32.261102+00:00 app[web.1]: False
2020-06-18T16:27:32.283106+00:00 app[web.1]: False
2020-06-18T16:27:32.309791+00:00 heroku[web.1]: State changed from starting to up
2020-06-18T16:27:33.411211+00:00 app[web.1]: [2020-06-18 16:27:33 +0000] [11] [ERROR] Socket error processing request.
2020-06-18T16:27:33.411336+00:00 app[web.1]: Traceback (most recent call last):
2020-06-18T16:27:33.411338+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/gunicorn/workers/sync.py", line 134, in handle
2020-06-18T16:27:33.411339+00:00 app[web.1]: self.handle_request(listener, req, client, addr)
2020-06-18T16:27:33.411340+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/gunicorn/workers/sync.py", line 190, in handle_request
2020-06-18T16:27:33.411340+00:00 app[web.1]: util.reraise(*sys.exc_info())
2020-06-18T16:27:33.411341+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/gunicorn/util.py", line 625, in reraise
2020-06-18T16:27:33.411342+00:00 app[web.1]: raise value
2020-06-18T16:27:33.411343+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/gunicorn/workers/sync.py", line 175, in handle_request
2020-06-18T16:27:33.411343+00:00 app[web.1]: respiter = self.wsgi(environ, resp.start_response)
2020-06-18T16:27:33.411343+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 2464, in __call__
2020-06-18T16:27:33.411344+00:00 app[web.1]: return self.wsgi_app(environ, start_response)
2020-06-18T16:27:33.411344+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 2450, in wsgi_app
2020-06-18T16:27:33.411345+00:00 app[web.1]: response = self.handle_exception(e)
2020-06-18T16:27:33.411345+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1867, in handle_exception
2020-06-18T16:27:33.411345+00:00 app[web.1]: reraise(exc_type, exc_value, tb)
2020-06-18T16:27:33.411346+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/_compat.py", line 39, in reraise
2020-06-18T16:27:33.411346+00:00 app[web.1]: raise value
2020-06-18T16:27:33.411346+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 2447, in wsgi_app
2020-06-18T16:27:33.411347+00:00 app[web.1]: response = self.full_dispatch_request()
2020-06-18T16:27:33.411347+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1952, in full_dispatch_request
2020-06-18T16:27:33.411347+00:00 app[web.1]: rv = self.handle_user_exception(e)
2020-06-18T16:27:33.411348+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1821, in handle_user_exception
2020-06-18T16:27:33.411348+00:00 app[web.1]: reraise(exc_type, exc_value, tb)
2020-06-18T16:27:33.411349+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/_compat.py", line 39, in reraise
2020-06-18T16:27:33.411349+00:00 app[web.1]: raise value
2020-06-18T16:27:33.411349+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1950, in full_dispatch_request
2020-06-18T16:27:33.411350+00:00 app[web.1]: rv = self.dispatch_request()
2020-06-18T16:27:33.411350+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1936, in dispatch_request
2020-06-18T16:27:33.411351+00:00 app[web.1]: return self.view_functions[rule.endpoint](**req.view_args)
2020-06-18T16:27:33.411351+00:00 app[web.1]: File "/app/PWGEN.py", line 35, in home
2020-06-18T16:27:33.411351+00:00 app[web.1]: return render_template('home.html')
2020-06-18T16:27:33.411352+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/templating.py", line 138, in render_template
2020-06-18T16:27:33.411352+00:00 app[web.1]: ctx.app.jinja_env.get_or_select_template(template_name_or_list),
2020-06-18T16:27:33.411354+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/jinja2/environment.py", line 930, in get_or_select_template
2020-06-18T16:27:33.411354+00:00 app[web.1]: return self.get_template(template_name_or_list, parent, globals)
2020-06-18T16:27:33.411354+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/jinja2/environment.py", line 883, in get_template
2020-06-18T16:27:33.411355+00:00 app[web.1]: return self._load_template(name, self.make_globals(globals))
2020-06-18T16:27:33.411355+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/jinja2/environment.py", line 857, in _load_template
2020-06-18T16:27:33.411356+00:00 app[web.1]: template = self.loader.load(self, name, globals)
2020-06-18T16:27:33.411356+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/jinja2/loaders.py", line 115, in load
2020-06-18T16:27:33.411356+00:00 app[web.1]: source, filename, uptodate = self.get_source(environment, name)
2020-06-18T16:27:33.411357+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/templating.py", line 60, in get_source
2020-06-18T16:27:33.411357+00:00 app[web.1]: return self._get_source_fast(environment, template)
2020-06-18T16:27:33.411357+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/templating.py", line 89, in _get_source_fast
2020-06-18T16:27:33.411358+00:00 app[web.1]: raise TemplateNotFound(template)
2020-06-18T16:27:33.411366+00:00 app[web.1]: jinja2.exceptions.TemplateNotFound: home.html
2020-06-18T16:27:33.412092+00:00 heroku[router]: at=error code=H13 desc="Connection closed without response" method=GET path="/" host=password-vault-flask.herokuapp.com request_id=27f18f98-5e77-43f3-9a03-be65a6262d9e fwd="94.12.92.223" dyno=web.1 connect=0ms service=8ms status=503 bytes=0 protocol=https

I don't seem to understand why this is not working, any insight would be greatly appreciated!

Answer 1

Fix this line. It should be

app = Flask(__name__, template_folder='./templates')