grpc client in docker can't reach server on host - docker

Question

I have a node grpc-server running on localhost and my grpc-client is a python flask server. If the client also runs on localhost directly then everything works as intended. Once I host the client(flask server) in a docker-container it is unable to reach the grpc-server though.
The error simply states:
RPC Target is unavaiable
I can call the flask-api from the host without issues. Also I changed the server address from 'localhost' to 'host.docker.internal', which is getting resolved correctly. Not sure if I am doing something wrong or this just doesn't work. I greatly appreciate any help or suggestions. Thanks!
Code snippets of the server, client and docke-compose :
server.js (Node)
...
const port = 9090;
const url = `0.0.0.0:${port}`;
// gRPC Credentials
import { readFileSync } from 'fs';
let credentials = ServerCredentials.createSsl(
readFileSync('./certs/ca.crt'),
[{
cert_chain: readFileSync('./certs/server.crt'),
private_key: readFileSync('./certs/server.key')
}],
false
)
...
const server = new Server({
"grpc.keepalive_permit_without_calls": 1,
"grpc.keepalive_time_ms": 10000,
});
...
server.bindAsync(
url,
credentials,
(err, port) => {
if (err) logger.error(err);
server.start();
}
);
grpc_call.py (status_update is called by app.py)
import os
import logging as logger
from os.path import dirname, join
import config.base_pb2 as base_pb2
import config.base_pb2_grpc as base_pb2_grpc
import grpc
# Read in ssl files
def _load_credential_from_file(filepath):
real_path = join(dirname(dirname(__file__)), filepath)
with open(real_path, "rb") as f:
return f.read()
# -----------------------------------------------------------------------------
def status_update(info, status, info=""):
SERVER_CERTIFICATE = _load_credential_from_file("config/certs/ca.crt")
SERVER_CERTIFICATE_KEY = _load_credential_from_file("config/certs/client.key")
ROOT_CERTIFICATE = _load_credential_from_file("config/certs/client.crt")
credential = grpc.ssl_channel_credentials(
root_certificates=SERVER_CERTIFICATE,
private_key=SERVER_CERTIFICATE_KEY,
certificate_chain=ROOT_CERTIFICATE,
)
# grpcAddress = "http://localhost"
grpcAddress = "http://host.docker.internal"
grpcFull = grpcAddress + ":9090"
with grpc.secure_channel(grpcFull, credential) as channel:
stub = base_pb2_grpc.ProjectStub(channel)
request = base_pb2.ContainerId(id=int(info), status=status)
try:
response = stub.ContainerStatus(request)
except grpc.RpcError as rpc_error:
logger.error("Error #STATUS_UPDATE")
if rpc_error.code() == grpc.StatusCode.CANCELLED:
logger.error("RPC Request got cancelled")
elif rpc_error.code() == grpc.StatusCode.UNAVAILABLE:
logger.error("RPC Target is unavaiable")
else:
logger.error(
f"Unknown RPC error: code={rpc_error.code()} message={rpc_error.details()}"
)
raise ConnectionError(rpc_error.code())
else:
logger.info(f"Received message: {response.message}")
return
Docker-compose.yaml
version: "3.9"
services:
test-flask:
image: me/test-flask
container_name: test-flask
restart: "no"
env_file: .env
ports:
- 0.0.0.0:8010:8010
command: python3 -m flask run --host=0.0.0.0 --port=8010