gRPC
9 FAILED_PRECONDITION
The operation was rejected because the system is not in a state required for the operation's execution. For example, deleting a non-empty directory.
When You See This Code
The request is valid on its own, but the system's current state doesn't allow it — like trying to delete a non-empty directory or update a resource that has been modified concurrently.
How to Fix
Bring the system into the required state before retrying. For example, empty the directory first, or re-read the resource to get the latest version before updating.