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no-op StartSpan: always return the parent #2121

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Dec 2, 2021
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no-op StartSpan: always return the parent #2121

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no-op StartSpan: always return the parent
tsloughter Nov 12, 2021
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Merge branch 'main' into noop-start-span
tsloughter Nov 30, 2021
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Update specification/trace/api.md
tsloughter Dec 1, 2021
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Merge branch 'main' into noop-start-span
tsloughter Dec 1, 2021
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Merge branch 'main' into noop-start-span
jmacd Dec 2, 2021
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21 changes: 10 additions & 11 deletions specification/trace/api.md
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Expand Up @@ -790,14 +790,13 @@ for how propagators are to be distributed.
## Behavior of the API in the absence of an installed SDK

In general, in the absence of an installed SDK, the Trace API is a "no-op" API.
This means that operations on a Tracer, or on Spans, should have no side effects and do nothing. However, there
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is one important exception to this general rule, and that is related to propagation of a `SpanContext`:
The API MUST create a [non-recording Span](#wrapping-a-spancontext-in-a-span) with the `SpanContext`
that is in the `Span` in the parent `Context` (whether explicitly given or implicit current) or,
if the parent is a non-recording Span (which it usually always is if no SDK is present),
it MAY return the parent Span back from the creation method.
If the parent `Context` contains no `Span`, an empty non-recording Span MUST be returned instead
(i.e., having a `SpanContext` with all-zero Span and Trace IDs, empty Tracestate, and unsampled TraceFlags).
This means that a `SpanContext` that has been provided by a configured `Propagator`
will be propagated through to any child span and ultimately also `Inject`,
but that no new `SpanContext`s will be created.
This means that operations on a Tracer, or on Spans, should have no side effects
and do nothing. However, there is one important exception to this general rule,
and that is related to propagation of a `SpanContext`: The API MUST return the
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`Span` in the parent `Context` (whether explicitly given or implicit current).
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If the parent `Context` contains no `Span`, an empty non-recording Span MUST be
returned instead (i.e., having a `SpanContext` with all-zero Span and Trace IDs,
empty Tracestate, and unsampled TraceFlags). This means that a `SpanContext`
that has been provided by a configured `Propagator` will be propagated through
to any child span and ultimately also `Inject`, but that no new `SpanContext`s
will be created.