128-bit Trace ID

Datakit-1.8.0 DDTrace-1.4.0-guance

The default trace-id of the DDTrace agent is 64 bits, and the trace-id in the link data received by Datakit is also 64 bits. Starting from version v1.11.0, W3C protocol support was added, enabling reception of 128-bit trace-ids. However, the trace-id sent into the link remains 64 bits.

For this reason, Guance made a secondary development by placing trace_128_bit_id into the link data and sending it to Datakit together, thus achieving the linkage between DDTrace and OTEL.

You can refer to: GitHub issue

Implementation Method¶

Starting from dd version 1.11, 128-bit traceID is supported. Currently, the version of Guance is 1.12.1. The startup command parameters are:

-Ddd.trace.128.bit.traceid.generation.enabled=true
# Set transparent transmission protocol
-Ddd.trace.propagation.style=tracecontext

However, only within dd can you obtain this 128-length traceID. When serialized and sent out, it is still actually a uint64. To pass this 128-bit ID, the structure in the transmission protocol must be modified. The consequence of this is complete version incompatibility, with significant code changes, leading to many potential issues.

Our approach is to place "trace_128_bit_id":xxxxxx in the tags of spans. After DK receives the data packet, if this key is found, the original trace_id will be replaced.

Placement location span.build:

    private DDSpan buildSpan() {
      DDSpan span = DDSpan.create(timestampMicro, buildSpanContext());
      if (span.isLocalRootSpan()) {
        EndpointTracker tracker = tracer.onRootSpanStarted(span);
        span.setEndpointTracker(tracker);
      }
      span.setTag("trace_128_bit_id", span.getTraceId().toString()); 
      return span;
    }

Afterward, all spans will include this key during initialization.

This is still not sufficient; Datakit must also perform filtering. If there is trace_128_bit_id, then the old trace-id will be replaced.

In the Guance link, all link IDs will become 128 bits.

Modify the collector's ddtrace.conf configuration:

# Remove comments, span_id and parent_id will both be converted to hexadecimal strings.
compatible_otel=true

Linking OTEL and DDTrace¶

OTEL client sends an HTTP request to the dd server: OTEL defaults to including traceparent:00-815cf7a2d315279413e6ceb43971225f-14f64a9c3fb05612-01 (W3C standard) sequentially as version - trace-id - parent-id - trace-flags

Thus, when dd receives the request and initializes the span, it uses the trace-id as the link ID and the parent-id as the parent spanID.

Effect:

More¶

Currently, only the linking of DDTrace and OTEL has been implemented, with no testing done for other APM vendors yet.