Deploy to the web a Dash App with Diskcache

1

hi Render community members,
I would like to recommend to my community of ~30k Dash users on YouTube the usage of render instead of Heroku for Dash app deployment to the web.

I’ve deployed a Dash app twice through render’s free tier successfully.

However, when trying to deploy this current dash app that is running a background callback and diskcache, it gave me the following error.

File “/opt/render/project/src/.venv/lib/python3.7/site-packages/dash/long_callback/managers/diskcache_manager.py”, line 40, in init
from missing_imports
ImportError: DiskcacheLongCallbackManager requires extra dependencies which can be installed doing
$ pip install “dash[diskcache]”

As you can see from the requirements.txt file, I declared dash[diskcache]==2.6.1, and this is the gunicorn start command I’m using: gunicorn app:server worker: celery app

The confusing thing is that I deployed the same repo/app successfully to the web using heroku’s free tier, so I’m not sure what needs to be updated for it to work with Render.

2

What about trying to include the dependencies for diskcache directly as per https://github.com/plotly/dash/blob/dev/requires-diskcache.txt ?

John B

3

Thank you for this @John_B
I was able to deploy the app by adding these lines of code to the requirements file that you suggested:

diskcache>=5.2.1
multiprocess>=0.70.12
psutil>=5.8.0

That said, the app stops working after a few clicks on the background callback button. Do you know if one can run background workers on a free tier? Or could it be because “Disks are not supported for free plan services?”

4

You can’t run a background worker on a free plan, no. Webservices only.

John B

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