Details
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Bug
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Status: Closed
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Blocker
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Resolution: Not A Problem
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7.0.0
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None
Description
hi
I'm busy trying to build a python Arrow server on a docker container. The rationale for moving it into a container is to isolate components of my program so if there's an exception/performance issue where something gobbles all the memory I'm able to quickly kill the container without bringing down the entire program.
I'm having problems connecting a local python script client to the server in the container. I'm not sure if it's a certificate issue /grpc issue/arrow server config issue. Going to break down what I've done below. Any help would be appreciated 
- Grabbed the arrow python server from the github repo.
- Since I want to implement secure communication I'll need a certificate - self-signed should be fine for development. Generate development certificate using dotnet dev-certs. After trusting certificate, export it using cmd in windows.
dotnet dev-certs https --trust
dotnet dev-certs https -ep "test.pfx" -p testpassword
1. My understanding is that the Arrow server only accepts .crt and .key files for public private key. I used WSL and SSL to convert the pfx file using this article from IBM.
2. Placing the public and private key in the same folder as my server script - I adjust the code as follows to not need to pass things in via args.
scheme = "grpc+tls" with open("testPublicKey.crt", "rb") as cert_file: tls_cert_chain = cert_file.read() with open("testPrivateKey.key", "rb") as key_file: tls_private_key = key_file.read() tls_certificates.append((tls_cert_chain, tls_private_key))
My client code is a slimmed-down version of the one on the repo as a test I want to push some dummy data into the server.
import pyarrow import pyarrow.flight import pandas as pd# Assumes that data is a Dataframe def pushToServer(name, data, client): objectToSend = pyarrow.Table.from_pandas(data) writer, _ = client.do_put(pyarrow.flight.FlightDescriptor.for_path(name), objectToSend.schema) writer.write_table(objectToSend) writer.close() def getClient(): return pyarrow.flight.FlightClient("grpc+tcp://localhost:5005") def main(): client = getClient() data = {'Country': ['Belgium', 'India', 'Brazil'], 'Capital': ['Brussels', 'New Delhi', 'Brasilia'], 'Population': [11190846, 1303171035, 207847528]} df = pd.DataFrame(data, columns=['Country', 'Capital', 'Population']) pushToServer("PredictedValues", df, client)if __name__ == '__main__': try: main() except Exception as e: print(e)
3. Running this on my local machine is fine- now I want to move the server into the container. I set up the docker file in the same folder as server script. See below (I know it's not ideal, but it does the job)
FROM mcr.microsoft.com/dotnet/sdk EXPOSE 5005 COPY server.py /home
build the image and run the container as below
docker build -t test . docker run -it -p 5005:5005 test
4. In the container, I quickly get python and pyarrow installed and then start the server
apt-get update apt-get install python3.10 python3-pip pip install pyarrow //start server time cd home python3 server.py //responds with "Serving on grpc+tls://localhost:5005"
5. Since the ports are mapped when we started the container, I rerun the client on my local and I'm greeted with this error on the client end.
gRPC returned unavailable error, with message: failed to connect to all addresses. Client context: IOError: Could not write record batch to stream. Detail: Internal. gRPC client debug context: {"created":"@1648805430.279000000","description":"Failed to pick subchannel","file":"C:\vcpkg\buildtrees\grpc\src\2180080eb4-87c05d756b.clean\src\core\ext\filters\client_channel\client_channel.cc","file_line":3159,"referenced_errors":[{"created":"@1648805430.279000000","description":"failed to connect to all addresses","file":"C:\vcpkg\buildtrees\grpc\src\2180080eb4-87c05d756b.clean\src\core\lib\transport\error_utils.cc","file_line":147,"grpc_status":14}]}. Additionally, could not finish writing record batches before closing
Putting a try-catch on the server-side doesn't provide any more info, unfortunately.
I've already ruled out that I might have a dodgy certificate. I've used the same certificate to set up a basic C# kestrel server in a container using HTTPS. I've also tried the above using a C# server with the same issue.
Is there any obvious I'm missing in the config? I haven't found any examples where people use certificates with pyarrow, so a bit at a loss.
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