Repository navigation
instrument treats an async method behind a sync decorator as sync #2933
Description
What happens
If an async def sits under a plain functools.wraps decorator, @instrument wraps it as a sync function. The span ends as soon as the coroutine object is returned (about 0.1 ms), the record output is <coroutine object ...>, and instrumented calls made while it runs start their own records and lose their span type. OpenAI's AsyncCompletions.create is shaped like this.
Repro
import asyncio
import functools
from trulens.core.otel.instrument import instrument
from trulens.otel.semconv.trace import SpanAttributes
def passthrough(fn):
@functools.wraps(fn)
def wrapper(*a, **k):
return fn(*a, **k)
return wrapper
@instrument(span_type=SpanAttributes.SpanType.RETRIEVAL)
async def retrieve(q):
return ["doc"]
class App:
@instrument()
@passthrough
async def query(self, q):
await asyncio.sleep(0.05)
return str(await retrieve(q))Run App().query("q") inside a recording: you get 2 records instead of 1.
Expected
One record. The span covers the awaited work, the output is "['doc']", and retrieve is a RETRIEVAL child span.
Cause
instrument.__call__ picks the wrapper with inspect.iscoroutinefunction(func), which does not follow __wrapped__.
Activity
feiiiiii5 commentedon Oct 8, 2026
Confirmed on
main@5eaf76ba. With thefunctools.wrapspassthrough decorator,instrumentfalls back to the sync wrapper: the run emits 2 record events instead of 1, the record output is<coroutine object _App.query ...>, and TruSession logs "Could not determine main output of query from coroutine value ...". The span also ends when the coroutine is returned rather than when the awaited work finishes.The cause is that the async detection at
src/core/trulens/core/otel/instrument.py:~703does not unwrap__wrapped__before deciding betweenasync_wrapperandsync_wrapper. Unwrapping first (or usinginspect.iscoroutinefunctionon the unwrapped function, e.g. viafunctools.unwrap) fixes it for the plain-wrapsshape.feiiiiii5 commentedon Oct 8, 2026
Follow-up: handled in open PR #2934.