From what I can tell the firestore client has to be running on the same machine as the emulator, otherwise you end up with a gRPC error: endpoint is neither UDS or TCP loopback address

This makes running the firestore client and emulator in different docker containers impossible (well not exactly - see the monkeypatch).

The reason that this happens is that the client creates local_credentials which gRPC enforces are only used for connections via the loopback adapter or unix sockets.

Description of my setup:
docker container1: Our app which connects to firestore emulator
docker container2: firestore emulator

Possible solutions:

• Use an insecure channel to talk to the emulator
• Create proper credentials to talk to the emulator

My initial thoughts are: just use insecure channel, it is only the emulator. But that might be missing something.

For anyone seeing this issue and wondering if there is a temporary workaround, I'm using this monkeypatch for our testing setup:

import grpc
from google.cloud.firestore_v1.base_client import BaseClient


def monkey_patch_firestore_emulator():
    def _emulator_channel(self, transport):
        if "GrpcAsyncIOTransport" in str(transport.__name__):
            return grpc.aio.insecure_channel(self._emulator_host)
        else:
            return grpc.insecure_channel(self._emulator_host)

    BaseClient._emulator_channel = _emulator_channel


monkey_patch_firestore_emulator()