C# porting of SDK

[cdangelo-kline]

Dear all,
for our project I'm starting to create a porting of the SDK for C#.
Is there any documentation about how to implement it, the grpc call flow executed by the platform,rules, restrictions etc...

Currently the only information I found is the comment in the proto files, but is not very clear the interaction between numaflow and the UDF/UDS.

Thanks in advance

Claudio

[vigith]

There are two ways to integrate SDKs, one is direct implementation of the gRPC spec or if you are comfortable with FFI (foreign function interface) you can build it on top of the Rust SDK.

Let us know which one you prefer.

[cdangelo-kline]

I'm currently developing a UDS directly in C#, implementing the gRPC services based on the proto file:
https://github.com/numaproj/numaflow/blob/main/pkg/apis/proto/source/v1/source.proto
Although I'm primarily a Java developer, I'm using the Java SDK as a reference to build the C# SDK.
The gRPC server supports both TCP and Unix sockets. When testing with Postman and grpcurl, it appears to be working correctly:
grpcurl -plaintext -unix unix:/var/run/numaflow/source.sock source.v1.Source.IsReady { "ready": true }

Unfortunately, it doesn't seem to work properly within Numaflow. Here's what I see in the logs:

2025-10-17T08:32:00.696348Z INFO numaflow_core::tracker: Processed messages per second processed=0
2025-10-17T08:31:59.811803Z INFO numaflow_core::shared::grpc: Waiting for source client to be ready...
2025-10-17T08:31:59.696486Z INFO numaflow_core::tracker: Processed messages per second processed=0
2025-10-17T08:31:58.809024Z INFO numaflow_core::shared::grpc: Waiting for source client to be ready...
2025-10-17T08:31:58.696399Z INFO numaflow_core::tracker: Processed messages per second processed=0

[cdangelo-kline]

As part of the integration, the IsReady method doesn't seem to be invoked. I've added some logs inside the method, but I don't see them appearing.

[vigith]

I think we have to publish a document on how to implement our gRPC specs to make your life easy. We heavily rely on bi-directional streams, etc.

[syayi]

Hi Claudio,
Thank you for exploring Numaflow! It’s great to hear that you’re interested in the C# SDK. Could you please share how you’re using Numaflow and what your use case is?

[cdangelo-kline]

Hi Syayi,
We have a batch process that needs to handle a large number of records. Currently, it runs step by step, which takes a considerable amount of time.
I'm working on a POC using Numaflow, where the input data is split into chunks so that each task can process a chunk in parallel. We treat the list of chunk metadata as a stream, and each task starts processing as soon as the chunk information arrives in its buffer.

[cdangelo-kline]

Hi all, the last release now works properly. I've developed a C# SDK for source and mapper and the POC seems to work as expected.

Thank you very much for your support.

[vigith]

@cdangelo-kline awesome, let us know whether you will be interested in open sourcing the C# implementation :)