[masterhugo]

Summary (Part 1 of 4: Native asyncio for gremlin-python 4.0)

This is PR 1 of 4 introducing native asyncio support to gremlin-python for TinkerPop 4.0 over HTTP streaming, without nest_asyncio, background ThreadPoolExecutor pools, or per-connection private event loops (asyncio.new_event_loop()).

Why native asyncio without nest_asyncio?

Currently, AiohttpHTTPTransport creates a private event loop per connection and drives aiohttp synchronously via run_until_complete(). When called from inside an already-running event loop (FastAPI/uvloop, Jupyter notebooks, async AWS Lambda handlers), it fails with RuntimeError: Cannot run the event loop while another loop is running, and nest_asyncio cannot patch Cython-based loops like uvloop.

What is included in PR 1 (Foundation layer)

• gremlin_python/driver/aiohttp/async_transport.py:
  • AsyncBufferedStream: sliding-window bytearray buffer over aiohttp.ClientResponse.content with checkpoint(), restore(), compact(), fill_more(), and read_exactly(). Translates aiohttp.ServerTimeoutError into ReadTimeoutError.
  • AsyncAiohttpHTTPTransport: native aiohttp.ClientSession transport bound directly to asyncio.get_running_loop().
• gremlin_python/driver/async_resultset.py:
  • AsyncResultSet: single-item streaming result set supporting await rs.one() (returning _EXHAUSTED on stream end so None result items are preserved), await rs.all(), and async for item in rs, using asyncio.wait(..., return_when=FIRST_COMPLETED) instead of polling loops.
• gremlin_python/driver/serializer.py:
  • Added GraphBinarySerializersV4.deserialize_async_response_stream(stream) to incrementally decode GraphBinary v4 (0x84) objects and end-of-stream trailers across arbitrary HTTP chunk boundaries.
• tests/unit/driver/test_async_http_streaming.py:
  • 27 unit tests covering AsyncResultSet, AsyncBufferedStream, deserialize_async_response_stream (including 2-byte chunk fragmentation across object/trailer boundaries), and AsyncAiohttpHTTPTransport.

Roadmap of the 4-PR Series

• PR 1 (this PR): AsyncBufferedStream, AsyncAiohttpHTTPTransport, AsyncResultSet, deserialize_async_response_stream
• PR 2: AsyncConnection & AsyncClient (asyncio.Queue connection pool)
• PR 3: AsyncDriverRemoteConnection & AsyncGraphTraversal (async_traversal())
• PR 4: AsyncTransaction (g.tx(), execute_in_tx), integration tests, examples, and documentation

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.54%. Comparing base (a28cd1f) to head (60886f4).
⚠️ Report is 736 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3725      +/-   ##
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+ Coverage     76.35%   77.54%   +1.18%     
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  Files          1012       32     -980     
  Lines         60341     7805   -52536     
  Branches       7075        0    -7075     
============================================
- Hits          46076     6052   -40024     
+ Misses        11548     1425   -10123     
+ Partials       2717      328    -2389     

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