Client receives out-of-order stream

[Xiaokun Luan]

Hi all, I have a server implemented in Scala using zio-grpc, and a client in Python.

I found that sometimes the stream received by the client is out of order. For example, the sequence of data sent by the server is [1, 2, 3, 4, 5], but those received by the client are [1, 2, 4, 3, 5]. Though I'm new to grpc, I don't think this is an expected behavior.

According to my testing results, this happens rarely, and usually only one or two pairs of adjacent items are swapped. I have checked and made sure that the sequence is scrambled after sending, so the error should not be on the server side.

I'm still working on a minimal example, and I cannot help wondering has anyone had a similar situation? Any things that could go wrong? Or maybe I didn't do it in the right way? Any help or advice would be appreciated.

Below is some relevant information:

OS: Ubuntu 22.04

Python version: 3.10.13

grpcio version: 1.51.1  (couldn't find 1.50.1)

grpcio-tools version: 1.51.1

grpc version: 4.25.3

Scala version: 2.13.13

grpc-netty version: 1.50.1

[apo...@google.com]

Are you sending this sequence of data on the same stream? Using a bidirectional or server-streaming RPC, for example?

This should indeed not be happening. Without knowing more, I would guess that the data is being accidentally written to the stream in a bad orders, when this happens. Otherwise, a reproduction may help.

[Xiaokun Luan]

Thanks for your reply, here is a minimal example: https://drive.google.com/file/d/1Eew2sOhjSt2tCBEupE1glo6PALYkB0t1/view

Running this example on my machine gives me something like:

Expected: [0, 1, 2, ...]

Got:           [0, 1, 2, ...]

Diff:           [x, y, ...]

[yas...@google.com]

This might be something to raise with maintainers of https://github.com/scalapb/zio-grpc. I'm not sure if they monitor this forum.