Remove libpf.Trace.Hash

interpreter/apmint/apmint.go

@@ -8,10 +8,11 @@
 package apmint // import "go.opentelemetry.io/ebpf-profiler/interpreter/apmint"
 
 import (
-	"encoding/hex"
 	"errors"
 	"fmt"
+	"hash/fnv"
 	"regexp"
+	"strconv"
 	"unsafe"
 
 	log "github.com/sirupsen/logrus"
@@ -144,31 +145,46 @@ type Instance struct {
 
 var _ interpreter.Instance = &Instance{}
 
+// hashTrace calculates the hash of a trace and returns it.
+// Be aware that changes to this calculation will break the ability to
+// look backwards for the same TraceHash in our backend.
+func hashTrace(trace *libpf.Trace) (hash [16]byte) {
+	var buf [24]byte
+	h := fnv.New128a()
+	for _, uniqueFrame := range trace.Frames {
+		frame := uniqueFrame.Value()
+		_, _ = h.Write(frame.FileID.Bytes())
+		// Using FormatUint() or putting AppendUint() into a function leads
+		// to escaping to heap (allocation).
+		_, _ = h.Write(strconv.AppendUint(buf[:0], uint64(frame.AddressOrLineno), 10))
+	}
+	h.Sum(hash[:0])
+	return
+}
+
 // Detach implements the interpreter.Instance interface.
 func (i *Instance) Detach(ebpf interpreter.EbpfHandler, pid libpf.PID) error {
 	return ebpf.DeleteProcData(libpf.APMInt, pid)
 }
 
 // NotifyAPMAgent sends out collected traces to the connected APM agent.
-func (i *Instance) NotifyAPMAgent(
-	pid libpf.PID, rawTrace *host.Trace, umTraceHash libpf.TraceHash, count uint16) {
+func (i *Instance) NotifyAPMAgent(pid libpf.PID, rawTrace *host.Trace, umTrace *libpf.Trace) {
 	if rawTrace.APMTransactionID == libpf.InvalidAPMSpanID || i.socket == nil {
 		return
 	}
 
-	log.Debugf("Reporting %dx trace hash %s -> TX %s for PID %d",
-		count, umTraceHash.StringNoQuotes(),
-		hex.EncodeToString(rawTrace.APMTransactionID[:]), pid)
-
 	msg := traceCorrMsg{
 		MessageType:      1,
 		MinorVersion:     1,
 		APMTraceID:       rawTrace.APMTraceID,
 		APMTransactionID: rawTrace.APMTransactionID,
-		StackTraceID:     umTraceHash,
-		Count:            count,
+		StackTraceID:     hashTrace(umTrace),
+		Count:            1,
 	}
 
+	log.Debugf("Reporting a trace hash %x -> TX %x for PID %d",
+		msg.StackTraceID[:], rawTrace.APMTransactionID[:], pid)
+
 	if err := i.socket.SendMessage(msg.Serialize()); err != nil {
 		log.Debugf("Failed to send trace mappings to APM agent: %v", err)
 	}

traceutil/traceutil_test.go → interpreter/apmint/hash_test.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-package traceutil
+package apmint // import "go.opentelemetry.io/ebpf-profiler/interpreter/apmint"
 
 import (
 	"testing"
@@ -30,19 +30,23 @@ func newPythonTrace() *libpf.Trace {
 func TestHashTrace(t *testing.T) {
 	tests := map[string]struct {
 		trace  *libpf.Trace
-		result libpf.TraceHash
+		result [16]byte
 	}{
 		"empty trace": {
-			trace:  &libpf.Trace{},
-			result: libpf.NewTraceHash(0x6c62272e07bb0142, 0x62b821756295c58d)},
+			trace: &libpf.Trace{},
+			result: [16]uint8{0x6c, 0x62, 0x27, 0x2e, 0x7, 0xbb, 0x1, 0x42,
+				0x62, 0xb8, 0x21, 0x75, 0x62, 0x95, 0xc5, 0x8d},
+		},
 		"python trace": {
-			trace:  newPythonTrace(),
-			result: libpf.NewTraceHash(0x21c6fe4c62868856, 0xcf510596eab68dc8)},
+			trace: newPythonTrace(),
+			result: [16]byte{0x21, 0xc6, 0xfe, 0x4c, 0x62, 0x86, 0x88, 0x56,
+				0xcf, 0x51, 0x5, 0x96, 0xea, 0xb6, 0x8d, 0xc8},
+		},
 	}
 
 	for name, testcase := range tests {
 		t.Run(name, func(t *testing.T) {
-			assert.Equal(t, testcase.result, HashTrace(testcase.trace))
+			assert.Equal(t, testcase.result, hashTrace(testcase.trace))
 		})
 	}
 }

interpreter/apmint/socket.go

@@ -103,7 +103,7 @@ type traceCorrMsg struct {
 	MinorVersion     uint16
 	APMTraceID       libpf.APMTraceID
 	APMTransactionID libpf.APMTransactionID
-	StackTraceID     libpf.TraceHash
+	StackTraceID     [16]byte
 	Count            uint16
 }
 
@@ -113,7 +113,7 @@ func (m *traceCorrMsg) Serialize() []byte {
 	_ = binary.Write(&buf, binary.LittleEndian, m.MinorVersion)
 	_, _ = buf.Write(m.APMTraceID[:])
 	_, _ = buf.Write(m.APMTransactionID[:])
-	_, _ = buf.Write(m.StackTraceID.Bytes())
+	_, _ = buf.Write(m.StackTraceID[:])
 	_ = binary.Write(&buf, binary.LittleEndian, m.Count)
 	return buf.Bytes()
 }

libpf/trace.go

@@ -41,7 +41,6 @@ func (frames *Frames) Append(frame *Frame) {
 // Trace represents a stack trace.
 type Trace struct {
 	Frames       Frames
-	Hash         TraceHash
 	CustomLabels map[string]string
 }
 

processmanager/manager.go

@@ -26,7 +26,6 @@ import (
 	"go.opentelemetry.io/ebpf-profiler/reporter"
 	"go.opentelemetry.io/ebpf-profiler/times"
 	"go.opentelemetry.io/ebpf-profiler/tracer/types"
-	"go.opentelemetry.io/ebpf-profiler/traceutil"
 	"go.opentelemetry.io/ebpf-profiler/util"
 )
 
@@ -298,12 +297,10 @@ func (pm *ProcessManager) ConvertTrace(trace *host.Trace) (newTrace *libpf.Trace
 			}
 		}
 	}
-	newTrace.Hash = traceutil.HashTrace(newTrace)
 	return newTrace
 }
 
-func (pm *ProcessManager) MaybeNotifyAPMAgent(
-	rawTrace *host.Trace, umTraceHash libpf.TraceHash, count uint16) string {
+func (pm *ProcessManager) MaybeNotifyAPMAgent(rawTrace *host.Trace, umTrace *libpf.Trace) string {
 	pm.mu.RLock()
 	pidInterp, ok := pm.interpreters[rawTrace.PID]
 	pm.mu.RUnlock()
@@ -314,7 +311,7 @@ func (pm *ProcessManager) MaybeNotifyAPMAgent(
 	var serviceName string
 	for _, mapping := range pidInterp {
 		if apm, ok := mapping.(*apmint.Instance); ok {
-			apm.NotifyAPMAgent(rawTrace.PID, rawTrace, umTraceHash, count)
+			apm.NotifyAPMAgent(rawTrace.PID, rawTrace, umTrace)
 
 			if serviceName != "" {
 				log.Warnf("Overwriting APM service name from '%s' to '%s' for PID %d",