proc,service: expose goroutine pprof labels in api

Labels can help in identifying a particular goroutine during debugging.

Fixes #1763

_fixtures/goroutineLabels.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"context"
+	"runtime"
+	"runtime/pprof"
+)
+
+func main() {
+	ctx := context.Background()
+	labels := pprof.Labels("k1", "v1", "k2", "v2")
+	runtime.Breakpoint()
+	pprof.Do(ctx, labels, f)
+}
+
+var dummy int
+
+func f(ctx context.Context) {
+	a := dummy
+	runtime.Breakpoint()
+	dummy++
+	dummy = a
+}

pkg/proc/proc_test.go

@@ -2305,6 +2305,27 @@ func TestIssue561(t *testing.T) {
 	})
 }
 
+func TestGoroutineLables(t *testing.T) {
+	withTestProcess("goroutineLabels", t, func(p proc.Process, fixture protest.Fixture) {
+		assertNoError(proc.Continue(p), t, "Continue()")
+		g, err := proc.GetG(p.CurrentThread())
+		assertNoError(err, t, "GetG()")
+		if len(g.Labels) != 0 {
+			t.Fatalf("No labels expected")
+		}
+
+		assertNoError(proc.Continue(p), t, "Continue()")
+		g, err = proc.GetG(p.CurrentThread())
+		assertNoError(err, t, "GetG()")
+		if v := g.Labels["k1"]; v != "v1" {
+			t.Errorf("Unexpected label value k1=%v", v)
+		}
+		if v := g.Labels["k2"]; v != "v2" {
+			t.Errorf("Unexpected label value k2=%v", v)
+		}
+	})
+}
+
 func TestStepOut(t *testing.T) {
 	testseq2(t, "testnextprog", "main.helloworld", []seqTest{{contContinue, 13}, {contStepout, 35}})
 }

pkg/proc/variables.go

@@ -210,6 +210,8 @@ type G struct {
 	variable *Variable
 
 	Unreadable error // could not read the G struct
+
+	Labels map[string]string // G's pprof labels
 }
 
 // Defer returns the top-most defer of the goroutine.
@@ -558,6 +560,27 @@ func (v *Variable) parseG() (*G, error) {
 
 	status, _ := constant.Int64Val(v.fieldVariable("atomicstatus").Value)
 	f, l, fn := v.bi.PCToLine(uint64(pc))
+
+	var labels map[string]string
+	if labelsVar := v.loadFieldNamed("labels"); labelsVar != nil && len(labelsVar.Children) == 1 {
+		if address := labelsVar.Children[0]; address.Addr != 0 {
+			labelMapType, _ := v.bi.findType("runtime/pprof.labelMap")
+			if labelMapType != nil {
+				labelMap := newVariable("", address.Addr, labelMapType, v.bi, v.mem)
+				labelMap.loadValue(loadFullValue)
+				labels = map[string]string{}
+				// iterate through map as it is done in other places
+				for i := range labelMap.Children {
+					if i % 2 == 0 {
+						k := labelMap.Children[i]
+						v := labelMap.Children[i+1]
+						labels[constant.StringVal(k.Value)] = constant.StringVal(v.Value)
+					}
+				}
+			}
+		}
+	}
+
 	g := &G{
 		ID:         int(id),
 		GoPC:       uint64(gopc),
@@ -573,6 +596,7 @@ func (v *Variable) parseG() (*G, error) {
 		stkbarPos:  int(stkbarPos),
 		stackhi:    stackhi,
 		stacklo:    stacklo,
+		Labels:     labels,
 	}
 	return g, nil
 }

service/api/conversions.go

@@ -263,6 +263,7 @@ func ConvertGoroutine(g *proc.G) *Goroutine {
 		GoStatementLoc: ConvertLocation(g.Go()),
 		StartLoc:       ConvertLocation(g.StartLoc()),
 		ThreadID:       tid,
+		Labels:         g.Labels,
 	}
 	if g.Unreadable != nil {
 		r.Unreadable = g.Unreadable.Error()

service/api/types.go

@@ -308,6 +308,8 @@ type Goroutine struct {
 	// ID of the associated thread for running goroutines
 	ThreadID   int    `json:"threadID"`
 	Unreadable string `json:"unreadable"`
+	// Goroutine's pprof labels
+	Labels map[string]string `json:"labels,omitempty"`
 }
 
 // DebuggerCommand is a command which changes the debugger's execution state.