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Buffer per-request StreamableHTTP streams to avoid serial-router head-of-line block (#2934)

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Max 2026-06-22 16:20:45 +01:00 • committed by GitHub
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1 changed files with 292 additions and 188 deletions
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102
tests/shared/test_streamable_http.py
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@ -1634,84 +1634,6 @@ async def test_handle_sse_event_skips_empty_data() -> None:
await read_stream.aclose()
@pytest.mark.anyio
async def test_priming_event_not_sent_for_old_protocol_version() -> None:
"""_maybe_send_priming_event skips for old protocol versions (backwards compat)."""
# Create a transport with an event store
transport = StreamableHTTPServerTransport(
"/mcp",
event_store=SimpleEventStore(),
)
# Create a mock stream writer
write_stream, read_stream = anyio.create_memory_object_stream[dict[str, Any]](1)
try:
# Call _maybe_send_priming_event with OLD protocol version - should NOT send
await transport._maybe_send_priming_event("test-request-id", write_stream, "2025-06-18")
# Nothing should have been written to the stream
assert write_stream.statistics().current_buffer_used == 0
# Now test with NEW protocol version - should send
await transport._maybe_send_priming_event("test-request-id-2", write_stream, "2025-11-25")
# Should have written a priming event
assert write_stream.statistics().current_buffer_used == 1
finally:
await write_stream.aclose()
await read_stream.aclose()
@pytest.mark.anyio
async def test_priming_event_not_sent_without_event_store() -> None:
"""_maybe_send_priming_event returns early when no event_store is configured."""
# Create a transport WITHOUT an event store
transport = StreamableHTTPServerTransport("/mcp")
# Create a mock stream writer
write_stream, read_stream = anyio.create_memory_object_stream[dict[str, Any]](1)
try:
# Call _maybe_send_priming_event - should return early without sending
await transport._maybe_send_priming_event("test-request-id", write_stream, "2025-11-25")
# Nothing should have been written to the stream
assert write_stream.statistics().current_buffer_used == 0
finally:
await write_stream.aclose()
await read_stream.aclose()
@pytest.mark.anyio
async def test_priming_event_includes_retry_interval() -> None:
"""_maybe_send_priming_event includes the retry field when retry_interval is set."""
# Create a transport with an event store AND retry_interval
transport = StreamableHTTPServerTransport(
"/mcp",
event_store=SimpleEventStore(),
retry_interval=5000,
)
# Create a mock stream writer
write_stream, read_stream = anyio.create_memory_object_stream[dict[str, Any]](1)
try:
# Call _maybe_send_priming_event with new protocol version
await transport._maybe_send_priming_event("test-request-id", write_stream, "2025-11-25")
# Should have written a priming event with retry field
assert write_stream.statistics().current_buffer_used == 1
# Read the event and verify it has retry field
event = await read_stream.receive()
assert "retry" in event
assert event["retry"] == 5000
finally:
await write_stream.aclose()
await read_stream.aclose()
@pytest.mark.anyio
async def test_close_sse_stream_callback_not_provided_for_old_protocol_version() -> None:
"""close_sse_stream callbacks are only provided for protocol versions that support polling."""
@ -1744,30 +1666,6 @@ async def test_close_sse_stream_callback_not_provided_for_old_protocol_version()
assert session_msg_new.metadata.close_standalone_sse_stream is not None
@pytest.mark.anyio
async def test_priming_event_not_sent_for_unknown_protocol_version() -> None:
"""_maybe_send_priming_event treats unrecognized version strings conservatively.
A garbage version must not be mistaken for a future one (lexicographically
"zzz" sorts after every date-shaped revision).
"""
transport = StreamableHTTPServerTransport(
"/mcp",
event_store=SimpleEventStore(),
)
write_stream, read_stream = anyio.create_memory_object_stream[dict[str, Any]](1)
try:
await transport._maybe_send_priming_event("test-request-id", write_stream, "zzz")
# Nothing should have been written to the stream
assert write_stream.statistics().current_buffer_used == 0
finally:
await write_stream.aclose()
await read_stream.aclose()
@pytest.mark.anyio
async def test_close_sse_stream_callback_not_provided_for_unknown_protocol_version() -> None:
"""close_sse_stream callbacks are withheld when the client's version is unrecognized."""