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Make use_span more flexible (closes #147). #154

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merged 4 commits into from
Sep 24, 2019
Merged

Make use_span more flexible (closes #147). #154

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a7f170b
Make use_span more flexible (closes #147).
Oberon00 Sep 19, 2019
991c333
Fix types.
Oberon00 Sep 19, 2019
2b22987
Remove usesless `as span`.
Oberon00 Sep 23, 2019
8812366
Fix overly long line in docstring.
Oberon00 Sep 24, 2019
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18 changes: 12 additions & 6 deletions opentelemetry-api/src/opentelemetry/trace/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -415,7 +415,8 @@ def start_span(
is equivalent to::

span = tracer.create_span(name)
with tracer.use_span(span):
span.start()
with tracer.use_span(span, end_on_exit=True):
do_work()

Args:
Expand Down Expand Up @@ -472,17 +473,22 @@ def create_span(
return INVALID_SPAN

@contextmanager # type: ignore
def use_span(self, span: "Span") -> typing.Iterator[None]:
def use_span(
self, span: "Span", end_on_exit: bool = False
) -> typing.Iterator[None]:
"""Context manager for controlling a span's lifetime.

Start the given span and set it as the current span in this tracer's
context.
Set the given span as the current span in this tracer's context.

On exiting the context manager stop the span and set its parent as the
current span.
On exiting the context manager set the span that was previously active
as the current span (this is usually but not necessarily the parent of
the given span). If ``end_on_exit`` is ``True``, then the span is also
ended when exiting the context manager.

Args:
span: The span to start and make current.
end_on_exit: Whether to end the span automatically when leaving the
context manager.
"""
# pylint: disable=unused-argument,no-self-use
yield
Expand Down
23 changes: 15 additions & 8 deletions opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -423,7 +423,10 @@ def start_span(
kind: trace_api.SpanKind = trace_api.SpanKind.INTERNAL,
) -> typing.Iterator["Span"]:
"""See `opentelemetry.trace.Tracer.start_span`."""
with self.use_span(self.create_span(name, parent, kind)) as span:

span = self.create_span(name, parent, kind)
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This approach seems weird, not sure if other Python libraries have similar concept of using a ContextManager with an optional flag to avoid clean up (e.g. using open(filename, 'rb', close_on_exit=False) as f:).
Is it possible to use the following approach?

span = self.create_span(name, parent, kind)
span.start()
self.use_span(span)
do_something()
span.end()

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Only example I could find was closefd in the built-in open function (https://docs.python.org/3/library/functions.html#open). But I know in .NET there are similar examples where you choose whether some TextReader should close the underlying file.

See also #97 (comment)

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Is it possible to use the following approach?

The problem with that is that after span.end(), the span is still active (which may be what you want if you have async children, but not in the general case).

span.start()
with self.use_span(span, end_on_exit=True):
yield span

def create_span(
Expand Down Expand Up @@ -460,16 +463,20 @@ def create_span(
)

@contextmanager
def use_span(self, span: "Span") -> typing.Iterator["Span"]:
def use_span(
self, span: Span, end_on_exit: bool = False
) -> typing.Iterator[Span]:
"""See `opentelemetry.trace.Tracer.use_span`."""
span.start()
span_snapshot = self._current_span_slot.get()
self._current_span_slot.set(span)
try:
yield span
span_snapshot = self._current_span_slot.get()
self._current_span_slot.set(span)
try:
yield span
finally:
self._current_span_slot.set(span_snapshot)
finally:
self._current_span_slot.set(span_snapshot)
span.end()
if end_on_exit:
span.end()

def add_span_processor(self, span_processor: SpanProcessor) -> None:
"""Registers a new :class:`SpanProcessor` for this `Tracer`.
Expand Down