Add W3C-specified trace flags to v1 Span proto #503
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Isn't this a duplciate of #384? |
Oh, yes! |
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@Oberon00 We are planning to merge this soon. Please take a last look, etc ;) |
| // MUST not assume that 24 most significant bits will be zero. | ||
| // When creating new spans, the most-significant 24-bits MUST be | ||
| // zero. To read the 8-bit W3C trace flag (use flags & | ||
| // SPAN_FLAGS_TRACE_FLAGS_MASK). [Optional]. |
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I think "when creating new spans" may still be confusing in the context of the protocol spec / a proto comment as it could be understood as "creating new span messages", especially since the remainder seems to assume that "new spans" have a 32 bit flags field. I could not find a shorter unambiguous way than this:
| // MUST not assume that 24 most significant bits will be zero. | |
| // When creating new spans, the most-significant 24-bits MUST be | |
| // zero. To read the 8-bit W3C trace flag (use flags & | |
| // SPAN_FLAGS_TRACE_FLAGS_MASK). [Optional]. | |
| // MUST not assume that 24 most significant bits will be zero. | |
| // To read the 8-bit W3C trace flag, use `flags & SPAN_FLAGS_TRACE_FLAGS_MASK`. | |
| // | |
| // When creating span messages, if the message is logically forwarded from another source | |
| // with an equivalent flags fields (i.e., usually another OTLP span message), the field SHOULD | |
| // be copied as-is. If creating from a source that does not have an equivalent flags field | |
| // (such as a runtime representation of an OpenTelemetry span), the high 24 bits MUST | |
| // be set to zero. | |
| // | |
| // [Optional]. |
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Also, there seems to be a typo in:
To read the 8-bit W3C trace flag (use flags & SPAN_FLAGS_TRACE_FLAGS_MASK).
I assumed it should mean:
To read the 8-bit W3C trace flag, use
flags & SPAN_FLAGS_TRACE_FLAGS_MASK.
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@carlosalberto @jmacd I think we forgot to apply an analogous change to the flags field in the link object.
Co-authored-by: Christian Neumüller <christian+github@neumueller.me>
As discussed in open-telemetry/opentelemetry-specification#3411 and #382, the OpenTelemetry Span object does not record the trace flags that were provided in its Trace Context.
For a tail sampler to sample spans using mechanism consistent with head sampling, the flags must be available in the protocol. W3C reserves 8 bits for these flags, of which two are defined. I've added 32-bit fields in the protocol for the span and the span link here.