SpanContext.trace_id is 128 bits and differs from DDtrace implementations in other languages (Node.js, Java, etc.)

[thanhj]

Summary of problem

In various languages like Java and JavaScript, the dd-trace library stores the 64-bit SpanContext._trace_id, with the additional higher-order bits of the trace ID stored in spanContext._trace.tags['_dd.p.tid']. However, for DDTracePy, the library takes a different approach by combining the 64-bit trace ID from the x-datadog-trace-id header with the higher-order bits from the _dd.p.tid header. Consequently, the SpanContext.trace_id in DDTracePy extends to 128 bits. This discrepancy leads to inconsistencies when attempting to retrieve the trace_id from SpanContext.

In our scenario, we aimed to utilize the trace_id as a uniform identifier for logging across various services. Unfortunately, the varied trace_id lengths across different DDTrace implementations have presented significant challenges for us. To mitigate these issues, we've been compelled to manually adjust the SpanContext.trace_id from 128 bits to 64 bits in all our Python-based services.

Which version of dd-trace-py are you using?

2.x

Which version of pip are you using?

N/A

Which libraries and their versions are you using?

N/A

References:

• [Python] https://github.com/DataDog/dd-trace-py/blob/main/ddtrace/propagation/http.py
• [Js] https://github.com/DataDog/dd-trace-js/blob/master/packages/dd-trace/src/opentracing/propagation/text_map.js

[emmettbutler]

Thanks for pointing this out, @thanhj.

cc @ZStriker19

[ZStriker19]

Hi @thanhj, one option for you could be to do something similar to this method whenever you grab the context.span_id. Just basically always make sure you're injecting the lower 64 bits into your logs to correlate. Would that work for your use case?

[thanhj]

Hi @ZStriker19,
I didn't mean to find a workaround solution, as we already did it by shifting from 128-bit to 64-bit str((1 << 64) - 1 & context.trace_id).
However, I would suggest to treat the trace_id consistent to 64-bit to align with the other languages.

[kevin-ip]

Setting DD_TRACE_128_BIT_TRACEID_GENERATION_ENABLED to false seems updating the trace ID to 64-bit.