feat: add async source transformer

[kohlisid]

fixes #70

[codecov]

Codecov Report

Attention: Patch coverage is 96.34146% with 3 lines in your changes missing coverage. Please review.

Project coverage is 94.26%. Comparing base (0d87b8f) to head (77953fa).

Files with missing lines	Patch %	Lines
...flow/sourcetransformer/servicer/_async_servicer.py	96.61%	0 Missing and 2 partials ⚠️
pynumaflow/sourcetransformer/async_server.py	94.73%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #230      +/-   ##
==========================================
+ Coverage   94.19%   94.26%   +0.07%     
==========================================
  Files          58       60       +2     
  Lines        2359     2441      +82     
  Branches      119      124       +5     
==========================================
+ Hits         2222     2301      +79     
- Misses        100      101       +1     
- Partials       37       39       +2     

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[kohlisid]

Testing async sleep

async def my_handler(keys: list[str], datum: Datum) -> Messages:
    val = datum.value
    event_time = datum.event_time
    messages = Messages()
    current_datetime = datetime.now()
    # Get the current date and time
    current_time = current_datetime.time()
    print(f"BS: {current_time}")
    await asyncio.sleep(5)
    current_datetime = datetime.now()
    current_time = current_datetime.time()
    print(f"AS: {current_time}")
    messages.append(Message(value=val, event_time=event_time))

    return messages

readBatchSize: 2

coder@empty-44a6c781:/workspace/empty$ kubectl logs simple-pipeline-in-0-hlk99 -f
+ python example.py
BS: 22:04:50.015658
BS: 22:04:50.015766
AS: 22:04:55.020848
AS: 22:04:55.020998
BS: 22:04:55.023170
BS: 22:04:55.023238
AS: 22:05:00.026655
AS: 22:05:00.026788
BS: 22:05:00.028047
BS: 22:05:00.028122
AS: 22:05:05.031671
AS: 22:05:05.031804

[kohlisid]

read batch size : 10

r$ kubectl logs simple-pipeline-in-0-nngd6 -f
+ python example.py

BS: 23:09:13.998727
BS: 23:09:13.998855
BS: 23:09:13.998928
BS: 23:09:13.998989
BS: 23:09:13.999050
BS: 23:09:13.999114
BS: 23:09:13.999169
BS: 23:09:13.999223
BS: 23:09:13.999278
BS: 23:09:13.999327

AS: 23:09:19.004380
AS: 23:09:19.004530
AS: 23:09:19.004565
AS: 23:09:19.004589
AS: 23:09:19.004610
AS: 23:09:19.004631
AS: 23:09:19.004651
AS: 23:09:19.004666
AS: 23:09:19.004684
AS: 23:09:19.004703

BS: 23:09:19.008078
BS: 23:09:19.008166
BS: 23:09:19.008222
BS: 23:09:19.008273
BS: 23:09:19.008323
BS: 23:09:19.008373
BS: 23:09:19.008424
BS: 23:09:19.008475
BS: 23:09:19.008526
BS: 23:09:19.008571

AS: 23:09:24.012147
AS: 23:09:24.012275
AS: 23:09:24.012306
AS: 23:09:24.012329
AS: 23:09:24.012350
AS: 23:09:24.012371
AS: 23:09:24.012392
AS: 23:09:24.012411
AS: 23:09:24.012432
AS: 23:09:24.012452

[kohlisid]

User exception - caught on Numa

2025/06/18 23:16:31 failed c.grpcClt.SourceTransformFn stream.Recv: NonRetryable: UDF_EXECUTION_ERROR(transformer): Exception('USER PANIC - Uncaught')
{"level":"error","ts":"2025-06-18T23:16:31.758003221Z","logger":"numaflow","caller":"forward/data_forward.go:313","msg":"failed to apply source transformer","error":"gRPC client.SourceTransformFn failed, NonRetryable: UDF_EXECUTION_ERROR(transformer): Exception('USER PANIC - Uncaught')","stacktrace":"github.com/numaproj/numaflow/pkg/sources/forward.(*DataForward).forwardAChunk\n\t/home/runner/work/numaflow/numaflow/pkg/sources/forward/data_forward.go:313\ngithub.com/numaproj/numaflow/pkg/sources/forward.(*DataForward).Start.func1\n\t/home/runner/work/numaflow/numaflow/pkg/sources/forward/data_forward.go:149"}