Altair chart is blank by default on Google App Engine Dash app - google-app-engine

Question

I am trying to migrate a working Dash app from the Heroku free platform to Google App Engine. The app works as expected both locally and on Heroku
The app loads on GAE
However the default query doesnt seem get parsed correctly on GAE, resulting in blank visualisations. If you select dropdown options the charts will load. It seems most likely to be a version conflict or a setting on GAE.
I have made the necessary changes to the app.yaml file as below:
runtime: python39
entrypoint: gunicorn -b :$PORT src.app:server
My requirements.txt is as follow:
gunicorn
altair
pandas
dash
dash_bootstrap_components
plotly
I have reviewed the callback but dont see a problem. I have included some code below for the callbacks, since I thought they may be the most relevant code. (raw_trees is just a loaded csv file)
# Set up callbacks/backend
#app.callback(
Output("bar", "srcDoc"),
Output("timeline", "srcDoc"),
Output("diameter", "srcDoc"),
Output("density", "srcDoc"),
Output("map", "figure"),
Input("picker_date", "start_date"),
Input("picker_date", "end_date"),
Input("filter_neighbourhood", "value"),
Input("filter_cultivar", "value"),
Input("slider_diameter", "value"),
Input("map", "selectedData"),
)
def main_callback(
start_date, end_date, neighbourhood, cultivar, diameter_range, selectedData
):
# Build new dataset and call all charts
# Date input Cleanup
if start_date is None:
start_date = "2022-01-01"
if end_date is None:
end_date = "2022-05-30"
start_date = pd.Timestamp(date.fromisoformat(start_date))
end_date = pd.Timestamp(date.fromisoformat(end_date))
filtered_trees = raw_trees
# Filter by selection from big map
if selectedData is not None:
selectedTrees = []
if "points" in selectedData:
if selectedData["points"] is not None:
for point in selectedData["points"]:
# print(point)
selectedTrees.append(point["customdata"][-1])
# print(selectedTrees)
filtered_trees = filtered_trees[filtered_trees["TREE_ID"].isin(selectedTrees)]
# Filter by neighbourhood
if neighbourhood:
filtered_trees = filtered_trees[
filtered_trees["NEIGHBOURHOOD_NAME"].isin(neighbourhood)
]
# Filter by date
filtered_trees = filtered_trees[
(
(filtered_trees["BLOOM_START"] <= start_date)
& (filtered_trees["BLOOM_END"] >= start_date)
)
| (
(filtered_trees["BLOOM_START"] <= end_date)
& (filtered_trees["BLOOM_END"] >= end_date)
)
| (filtered_trees["BLOOM_START"].between(start_date, end_date))
| (filtered_trees["BLOOM_END"].between(start_date, end_date))
]
# Filter by Diameter
filtered_trees = filtered_trees[
filtered_trees["DIAMETER"].between(diameter_range[0], diameter_range[1])
]
if cultivar:
filtered_trees = filtered_trees[filtered_trees["CULTIVAR_NAME"].isin(cultivar)]
bar = bar_plot(filtered_trees)
timeline = timeline_plot(filtered_trees)
diameter = diameter_plot(filtered_trees)
density = density_map(filtered_trees)
big_map = street_map(filtered_trees)
return bar, timeline, diameter, density, big_map
Thanks for any help or insight, This is my first effort on GAE. Alternatively i would consider a more appropriate alternative for my deployment if anyone has a suggestion of that nature.
The entire project is here

Answer 1

After trying a second hosting solution (render) i had the same issue. I was able to solve it on render by increasing the worker timeout in the gunicorn like so:
web: gunicorn src.app:server --timeout 1000
This is likely just due to the resource constraints on these free accounts, and this constraint is likely the issue on GAE as well, though the timeout flag didnt work in the entrypoint there.