feat: add trace_id pprof label (#89)

* feat: add trace_id pprof label

* perf: parse trace_id hex without allocating substrings

* fix: guard setTraceId against malformed trace IDs

Author: marcsanmi

README.md

@@ -7,9 +7,7 @@ link traces with the profiling data, and find specific lines of code related to
 * Because of how sampling profilers work, spans shorter than the sample interval may not be captured. By default pyroscope CPU profiler probes stack traces 100 times per second, meaning that spans shorter than 10ms may not be captured.
 
 
-Java code can be easily instrumented with otel-profiling-java package -
-a `OpenTelemetry` implementation, that annotates profiling data with span IDs which makes it possible to filter
-out profile of a particular trace span in Pyroscope.
+Java code can be easily instrumented with the otel-profiling-java package, an `OpenTelemetry` implementation that annotates profiling data with `trace_id` and `span_id` labels, which makes it possible to filter the profile of a particular trace (or trace span) in Pyroscope.
 
 Visit [docs](https://grafana.com/docs/pyroscope/latest/configure-client/trace-span-profiles/java-span-profiles/) page for usage and configuration documentation.
 

gradle.properties

@@ -1,4 +1,4 @@
-pyroscope_version=2.5.1
+pyroscope_version=2.6.0
 # x-release-please-start-version
 otel_profiling_version=2.0.6
 # x-release-please-end

lib/src/main/java/io/otel/pyroscope/PyroscopeOtelSpanProcessor.java

@@ -63,6 +63,14 @@ public void onStart(Context parentContext, ReadWriteSpan span) {
 
         span.setAttribute(ATTRIBUTE_KEY_PROFILE_ID, strProfileId);
         asprof.setTracingContext(spanId, spanName);
+        // W3C trace ID is 32 hex chars (128 bits). Parse directly into two longs
+        // to avoid the String#substring allocations on this hot path.
+        String traceId = span.getSpanContext().getTraceId();
+        try {
+            asprof.setTraceId(parseHex64(traceId, 0), parseHex64(traceId, 16));
+        } catch (NumberFormatException | IndexOutOfBoundsException e) {
+            asprof.setTraceId(0, 0);
+        }
     }
 
     @Override
@@ -71,6 +79,7 @@ public void onEnd(ReadableSpan span) {
             return;
         }
         asprof.setTracingContext(0, 0);
+        asprof.setTraceId(0L, 0L);
     }
 
     public static long parseSpanId(String strProfileId) {
@@ -84,6 +93,25 @@ public static long parseSpanId(String strProfileId) {
         }
     }
 
+    static long parseHex64(String s, int offset) {
+        long result = 0L;
+        for (int i = 0; i < 16; i++) {
+            int c = s.charAt(offset + i);
+            int nibble;
+            if (c >= '0' && c <= '9') {
+                nibble = c - '0';
+            } else if (c >= 'a' && c <= 'f') {
+                nibble = c - 'a' + 10;
+            } else if (c >= 'A' && c <= 'F') {
+                nibble = c - 'A' + 10;
+            } else {
+                throw new NumberFormatException("invalid hex char in trace_id at index " + (offset + i));
+            }
+            result = (result << 4) | nibble;
+        }
+        return result;
+    }
+
     public static boolean isRootSpan(ReadableSpan span) {
         SpanContext parent = span.getParentSpanContext();
         boolean noParent = parent == SpanContext.getInvalid();

otel-extension/src/main/java/io/otel/pyroscope/PyroscopeOtelSpanProcessor.java

@@ -52,14 +52,21 @@ public void onStart(Context parentContext, ReadWriteSpan span) {
 
         span.setAttribute(ATTRIBUTE_KEY_PROFILE_ID, strProfileId);
         api.setTracingContext(spanId, spanName);
+        try {
+            api.setTraceId(span.getSpanContext().getTraceId());
+        } catch (NumberFormatException | IndexOutOfBoundsException e) {
+            api.clearTraceId();
+        }
     }
 
     @Override
     public void onEnd(ReadableSpan span) {
         if (configuration.rootSpanOnly && !isRootSpan(span)) {
             return;
         }
-        getProfiler().setTracingContext(0, 0);
+        ProfilerApi api = getProfiler();
+        api.setTracingContext(0, 0);
+        api.clearTraceId();
     }
 
     public static long parseSpanId(String strProfileId) {