reporter: attach thread ID to emitted profiles (#20)

get thread ID from bpf_get_current_uid_gid (based on
https://man7.org/linux/man-pages/man7/bpf-helpers.7.html)

and pass it down through the trace to the reporter. attach it to
the emitted pprof as a label

host/host.go

@@ -55,6 +55,7 @@ type Trace struct {
 	Hash             TraceHash
 	KTime            util.KTime
 	PID              util.PID
+	TID              util.TID
 	APMTraceID       libpf.APMTraceID
 	APMTransactionID libpf.APMTransactionID
 }

libpf/libpf.go

@@ -81,6 +81,7 @@ type TraceAndCounts struct {
 	ContainerName  string
 	APMServiceName string
 	PID            util.PID
+	TID            util.TID
 }
 
 type FrameMetadata struct {

reporter/datadog_reporter.go

@@ -75,7 +75,8 @@ type DatadogReporter struct {
 
 // ReportTraceEvent enqueues reported trace events for the Datadog reporter.
 func (r *DatadogReporter) ReportTraceEvent(trace *libpf.Trace, timestamp libpf.UnixTime64,
-	comm, podName, containerID, containerName, apmServiceName string, pid util.PID) {
+	comm, podName, containerID, containerName, apmServiceName string,
+	pid util.PID, tid util.TID) {
 	traceEvents := r.traceEvents.WLock()
 	defer r.traceEvents.WUnlock(&traceEvents)
 
@@ -95,6 +96,7 @@ func (r *DatadogReporter) ReportTraceEvent(trace *libpf.Trace, timestamp libpf.U
 		containerName:  containerName,
 		apmServiceName: apmServiceName,
 		pid:            pid,
+		tid:            tid,
 		timestamps:     []uint64{uint64(timestamp)},
 	}
 }
@@ -567,6 +569,13 @@ func addTraceLabels(labels map[string][]string, i traceFramesCounts) {
 	if i.pid != 0 {
 		labels["process_id"] = append(labels["process_id"], fmt.Sprintf("%d", i.pid))
 	}
+
+	if i.tid != 0 {
+		// The naming has an impact on the backend side,
+		// this is why we use "thread id" instead of "thread_id"
+		// This is also consistent with ddprof.
+		labels["thread id"] = append(labels["thread id"], fmt.Sprintf("%d", i.tid))
+	}
 }
 
 // getDummyMappingIndex inserts or looks up a dummy entry for interpreted FileIDs.

reporter/iface.go

@@ -41,7 +41,8 @@ type TraceReporter interface {
 	// and caches it for reporting to the backend. It returns true if the event was
 	// enqueued for reporting, and false if the event was ignored.
 	ReportTraceEvent(trace *libpf.Trace, timestamp libpf.UnixTime64,
-		comm, podName, containerID, containerName, apmServiceName string, pid util.PID)
+		comm, podName, containerID, containerName, apmServiceName string,
+		pid util.PID, tid util.TID)
 
 	// SupportsReportTraceEvent returns true if the reporter supports reporting trace events
 	// via ReportTraceEvent().

reporter/otlp_reporter.go

@@ -67,6 +67,7 @@ type traceFramesCounts struct {
 	containerName  string
 	apmServiceName string
 	pid            util.PID
+	tid            util.TID
 	timestamps     []uint64 // in nanoseconds
 }
 
@@ -125,7 +126,7 @@ func (r *OTLPReporter) SupportsReportTraceEvent() bool { return true }
 // ReportTraceEvent enqueues reported trace events for the OTLP reporter.
 func (r *OTLPReporter) ReportTraceEvent(trace *libpf.Trace,
 	timestamp libpf.UnixTime64, comm, podName, containerID,
-	containerName, apmServiceName string, pid util.PID) {
+	containerName, apmServiceName string, pid util.PID, tid util.TID) {
 	traceEvents := r.traceEvents.WLock()
 	defer r.traceEvents.WUnlock(&traceEvents)
 
@@ -145,6 +146,7 @@ func (r *OTLPReporter) ReportTraceEvent(trace *libpf.Trace,
 		containerName:  containerName,
 		apmServiceName: apmServiceName,
 		pid:            pid,
+		tid:            tid,
 		timestamps:     []uint64{uint64(timestamp)},
 	}
 }
@@ -708,6 +710,7 @@ func getSampleAttributes(profile *profiles.Profile, i traceFramesCounts) []uint6
 	addAttr(semconv.ThreadNameKey, i.comm)
 	addAttr(semconv.ServiceNameKey, i.apmServiceName)
 	addAttr("process_id", strconv.Itoa(int(i.pid)))
+	addAttr(semconv.ThreadIDKey, strconv.Itoa(int(i.tid)))
 
 	return indices
 }

support/ebpf/native_stack_trace.ebpf.c

@@ -805,6 +805,7 @@ static inline
 int collect_trace(struct pt_regs *ctx) {
   // Get the PID and TGID register.
   u64 id = bpf_get_current_pid_tgid();
+  u64 tid = id & 0xFFFFFFFF;
   u64 pid = id >> 32;
 
   if (pid == 0) {
@@ -824,6 +825,7 @@ int collect_trace(struct pt_regs *ctx) {
   }
 
   Trace *trace = &record->trace;
+  trace->tid = tid;
   trace->pid = pid;
   trace->ktime = ktime;
   if (bpf_get_current_comm(&(trace->comm), sizeof(trace->comm)) < 0) {

support/ebpf/types.h

@@ -516,6 +516,8 @@ typedef struct __attribute__((packed)) ApmCorrelationBuf {
 typedef struct Trace {
   // The process ID
   u32 pid;
+  // The thread ID
+  u32 tid;
   // Monotonic kernel time in nanosecond precision.
   u64 ktime;
   // The current COMM of the thread of this Trace.

tracehandler/tracehandler.go

@@ -159,7 +159,7 @@ func (m *traceHandler) HandleTrace(bpfTrace *host.Trace) {
 	if m.reporter.SupportsReportTraceEvent() {
 		m.reporter.ReportTraceEvent(umTrace, timestamp,
 			bpfTrace.Comm, meta.PodName, meta.ContainerID, meta.ContainerName,
-			svcName, bpfTrace.PID)
+			svcName, bpfTrace.PID, bpfTrace.TID)
 		return
 	}
 	m.reporter.ReportCountForTrace(umTrace.Hash, timestamp, 1,

tracehandler/tracehandler_test.go

@@ -90,7 +90,7 @@ func (m *mockReporter) ReportCountForTrace(traceHash libpf.TraceHash,
 func (m *mockReporter) SupportsReportTraceEvent() bool { return false }
 
 func (m *mockReporter) ReportTraceEvent(_ *libpf.Trace,
-	_ libpf.UnixTime64, _, _, _, _, _ string, _ util.PID) {
+	_ libpf.UnixTime64, _, _, _, _, _ string, _ util.PID, _ util.TID) {
 }
 
 type mockContainerMetadataHandler struct{}

tracer/tracer.go

@@ -853,13 +853,14 @@ func (t *Tracer) loadBpfTrace(raw []byte) *host.Trace {
 		APMTraceID:       *(*libpf.APMTraceID)(unsafe.Pointer(&ptr.apm_trace_id)),
 		APMTransactionID: *(*libpf.APMTransactionID)(unsafe.Pointer(&ptr.apm_transaction_id)),
 		PID:              util.PID(ptr.pid),
+		TID:              util.TID(ptr.tid),
 		KTime:            util.KTime(ptr.ktime),
 	}
 
 	// Trace fields included in the hash:
 	//  - PID, kernel stack ID, length & frame array
 	// Intentionally excluded:
-	//  - ktime, COMM, APM trace, APM transaction ID
+	//  - ktime, COMM, TID, APM trace, APM transaction ID
 	ptr.comm = [16]C.char{}
 	ptr.apm_trace_id = C.ApmTraceID{}
 	ptr.apm_transaction_id = C.ApmSpanID{}

util/util.go

@@ -25,6 +25,9 @@ func (p PID) Hash32() uint32 {
 	return uint32(p)
 }
 
+// TID represent a thread ID
+type TID int32
+
 // HashString turns a string into a 64-bit hash.
 func HashString(s string) uint64 {
 	h := fnv.New64a()