128-bit Trace ID

Datakit-1.8.0 DDTrace-1.4.0-guance

The default trace-id for the DDTrace agent is 64 bits, and the trace-id in the trace data received by Datakit is also 64 bits. Starting from version 1.11.0, support for the W3C protocol and 128-bit trace-ids was added. However, the trace-id sent into the trace remains 64 bits.

To address this, Guance implemented a secondary development to include the trace_128_bit_id in the trace data sent to Datakit. This allows for the linking of traces between DDTrace and OTEL.

For more information, see: GitHub issue

Implementation Method¶

Support for 128-bit traceIDs has been available since dd version 1.11. The current version of Guance is 1.12.1. The startup command parameters are:

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

However, even with these settings, only a 64-bit traceID is serialized and sent out. To pass the 128-bit ID, the transmission protocol structure must be modified, which would result in complete version incompatibility and significant code changes, leading to many potential issues.

Our solution was to add "trace_128_bit_id":xxxxxx to the span's tags. When DK receives the data packet and detects this key, it replaces the original trace_id.

This is done in 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;
    }

After initialization, all spans will contain this key.

However, this alone is not sufficient. Datakit must also filter for trace_128_bit_id and replace the old trace-id.

In the Guance trace system, all trace IDs will become 128 bits.

Modify the collector configuration ddtrace.conf:

# Uncomment to convert span_id and parent_id to hexadecimal strings.
compatible_otel=true

Linking OTEL and DDTrace¶

OTEL clients send HTTP requests to the dd server. OTEL includes traceparent:00-815cf7a2d315279413e6ceb43971225f-14f64a9c3fb05612-01 (W3C standard) in the request header, which contains the version, trace-id, parent-id, and trace-flags.

When dd receives the request and initializes the span, it uses the trace-id as the trace ID and the parent-id as the parent span ID.

Effect:

More¶

Currently, only the linking between DDTrace and OTEL has been implemented; testing with other APM vendors has not yet been conducted.