Troubleshooting FastAPI Application Deployment on Render with Poetry

I’m deploying a FastAPI Python application on Render and using Poetry for package and dependency management. The deployment process involves running poetry install to set up the environment and then executing a command to connect to a database on PlanetScale and start the server.

However, I’m encountering an issue where it seems like Render is using Python 3.7 to run the application, despite specifying python_version as 3.11.2 in the environment variables. This is my current assumption, but I’m not certain if it’s the cause of the problem.

The error message in the build logs is:

RuntimeError: The lock file is not compatible with the current version of Poetry. Upgrade Poetry to be able to read the lock file or, alternatively, regenerate the lock file with the poetry lock command.
I’m seeking guidance on how to resolve this issue and successfully deploy my FastAPI application on Render. Any help or pointers would be greatly appreciated. PS: I am using the lates version of poetry. I have tried regenerating the lock file but when I push the changes it still shows the same erros. Tried also clearing build cache and redeploying again but nothing so far. Dev env is running with no errors.

Hi there,

We will be able to best assist you if you reach out to us privately via the Render Dashboard and you specify which service you are referring to.


Render Support Engineer, MT (UTC-6)

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