Hosting tutorial Dash app on Render: AttributeError: module 'main' has no attribute 'server'

Dash Python
1

During the weekend I spent 6-7 hours working on setting up a Dash page on Render following this tutorial:

It worked at first and I was able to make minor changes. At one point it broke down, and gave the error below. Even after changing the code again and again and recreating the version I hard working prior I can’t fix this error. If anyone can solve this it would be a great help.

I followed this tutorial: Deploy your Python Data App to the Web for Free - Dash - YouTube
The setup for the webservice on Render follows the instructions in the video

The error message I get is very long in the Render window, but it is this:

Aug 13 10:06:54 PM  Traceback (most recent call last):
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/util.py", line 414, in import_app
Aug 13 10:06:54 PM      app = getattr(mod, name)
Aug 13 10:06:54 PM  AttributeError: module 'main' has no attribute 'server'
Aug 13 10:06:54 PM  
Aug 13 10:06:54 PM  During handling of the above exception, another exception occurred:
Aug 13 10:06:54 PM  
Aug 13 10:06:54 PM  Traceback (most recent call last):
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/bin/gunicorn", line 8, in <module>
Aug 13 10:06:54 PM      sys.exit(run())
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/wsgiapp.py", line 67, in run
Aug 13 10:06:54 PM      WSGIApplication("%(prog)s [OPTIONS] [APP_MODULE]").run()
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/base.py", line 236, in run
Aug 13 10:06:54 PM      super().run()
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/base.py", line 72, in run
Aug 13 10:06:54 PM      Arbiter(self).run()
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/arbiter.py", line 58, in __init__
Aug 13 10:06:54 PM      self.setup(app)
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/arbiter.py", line 118, in setup
Aug 13 10:06:54 PM      self.app.wsgi()
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/base.py", line 67, in wsgi
Aug 13 10:06:54 PM      self.callable = self.load()
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/wsgiapp.py", line 58, in load
Aug 13 10:06:54 PM      return self.load_wsgiapp()
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/wsgiapp.py", line 48, in load_wsgiapp
Aug 13 10:06:54 PM      return util.import_app(self.app_uri)
Aug 13 10:06:54 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/util.py", line 418, in import_app
Aug 13 10:06:54 PM      raise AppImportError("Failed to find attribute %r in %r." % (name, module))
Aug 13 10:06:54 PM  gunicorn.errors.AppImportError: Failed to find attribute 'server' in 'main'.
Aug 13 10:06:57 PM  ==> Using Node version 14.17.0 (default)
Aug 13 10:06:57 PM  ==> Docs on specifying a Node version: https://render.com/docs/node-version
Aug 13 10:06:59 PM  ==> Starting service with 'gunicorn main:server'
Aug 13 10:07:05 PM  Traceback (most recent call last):
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/util.py", line 414, in import_app
Aug 13 10:07:05 PM      app = getattr(mod, name)
Aug 13 10:07:05 PM  AttributeError: module 'main' has no attribute 'server'
Aug 13 10:07:05 PM  
Aug 13 10:07:05 PM  During handling of the above exception, another exception occurred:
Aug 13 10:07:05 PM  
Aug 13 10:07:05 PM  Traceback (most recent call last):
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/bin/gunicorn", line 8, in <module>
Aug 13 10:07:05 PM      sys.exit(run())
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/wsgiapp.py", line 67, in run
Aug 13 10:07:05 PM      WSGIApplication("%(prog)s [OPTIONS] [APP_MODULE]").run()
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/base.py", line 236, in run
Aug 13 10:07:05 PM      super().run()
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/base.py", line 72, in run
Aug 13 10:07:05 PM      Arbiter(self).run()
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/arbiter.py", line 58, in __init__
Aug 13 10:07:05 PM      self.setup(app)
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/arbiter.py", line 118, in setup
Aug 13 10:07:05 PM      self.app.wsgi()
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/base.py", line 67, in wsgi
Aug 13 10:07:05 PM      self.callable = self.load()
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/wsgiapp.py", line 58, in load
Aug 13 10:07:05 PM      return self.load_wsgiapp()
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/app/wsgiapp.py", line 48, in load_wsgiapp
Aug 13 10:07:05 PM      return util.import_app(self.app_uri)
Aug 13 10:07:05 PM    File "/opt/render/project/src/.venv/lib/python3.7/site-packages/gunicorn/util.py", line 418, in import_app
Aug 13 10:07:05 PM      raise AppImportError("Failed to find attribute %r in %r." % (name, module))
Aug 13 10:07:05 PM  gunicorn.errors.AppImportError: Failed to find attribute 'server' in 'main'.

My current code is:

from dash import Dash, dcc, html, Input, Output
import plotly.express as px
import pandas as pd

df_airports = pd.read_csv(
    "https://raw.githubusercontent.com/plotly/datasets/master/2011_february_us_airport_traffic.csv"
)

app = Dash(__name__)
#app.title("SR Test App")

server = app.server

app.layout = html.Div(
    [
        dcc.Graph(id="graph"),
        html.P(
            "Enter the type of graph you want to plot: (scatter_geo or scatter_mapbox)"
        ),
        dcc.Dropdown(
            id="type",
            options=["scatter_mapbox", "scatter_geo"],
            value="scatter_mapbox",
            clearable=False,
        ),
    ]
)


@app.callback(
    Output("graph", "figure"),
    Input("type", "value"),
)
    
def generate_chart(values):
    fig = px.scatter_mapbox(
        df_airports,
        lat="lat",
        lon="long",
        hover_data=["airport", "city", "state", "cnt"],
        size="cnt",
        color="cnt",
        zoom=3 )
    fig.update_layout(mapbox_style="open-street-map")
    
    # Set the size of the plot
    fig.update_layout(width=1000, height=3000)

    return fig


if __name__ == "__main__":
    app.run_server(debug=True)
2

The error indicates a wrongly configured entrypoint. What’s the name of the file for which you posted the code? What command did you run on Render to start the app?

3

Hi Emil

The Python file is called main.py and on Render I just click ‘deploy latest commit’, so running the code from GitHub.

What is surprising to me is that the file name and the deploy method are both unchanged. I seem to do everything the exact same as when it was working.

4

I have now tried running it locally, and it works right away. So there is something wrong with the hosting on Render. The weird part is that I’m 99% sure I did not change the settings on Render, so I don’t see how it could work at first only to fail later. One odd possibility is that I ran out of hosting time on the free plan, but surely they would have told me so then.