kvserver: annotate Replica.Send with pprof labels

This commit adds pprof labels to Send methods, as a proper replacement of the
no longer working (since Go 1.17) unnamed parameters hack. Adding labels is
conditional to the CPU profile cluster setting, to avoid the profiling cost and
extra allocations in pprof.Do context construction during normal operation.

Release note: None

pkg/kv/kvserver/replica_send.go

@@ -13,6 +13,7 @@ package kvserver
 import (
 	"context"
 	"reflect"
+	"runtime/pprof"
 
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/batcheval"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/concurrency"
@@ -24,6 +25,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/txnwait"
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/settings"
+	"github.com/cockroachdb/cockroach/pkg/settings/cluster"
 	"github.com/cockroachdb/cockroach/pkg/util/circuit"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
@@ -109,38 +111,17 @@ func (r *Replica) Send(
 // SendWithWriteBytes is the implementation of Send with an additional
 // *StoreWriteBytes return value.
 func (r *Replica) SendWithWriteBytes(
-	ctx context.Context, ba roachpb.BatchRequest,
+	ctx context.Context, req roachpb.BatchRequest,
 ) (*roachpb.BatchResponse, *StoreWriteBytes, *roachpb.Error) {
-	return r.sendWithoutRangeID(ctx, &ba)
-}
-
-// sendWithoutRangeID used to be called sendWithRangeID, accepted a `_forStacks
-// roachpb.RangeID` argument, and had the description below. Ever since Go
-// switched to the register-based calling convention though, this stopped
-// working, giving essentially random numbers in the goroutine dumps that were
-// misleading. It has thus been "disarmed" until Go produces useful values
-// again.
-//
-// See (internal): https://cockroachlabs.slack.com/archives/G01G8LK77DK/p1641478596004700
-//
-// sendWithRangeID takes an unused rangeID argument so that the range
-// ID will be accessible in stack traces (both in panics and when
-// sampling goroutines from a live server). This line is subject to
-// the whims of the compiler and it can be difficult to find the right
-// value, but as of this writing the following example shows a stack
-// while processing range 21 (0x15) (the first occurrence of that
-// number is the rangeID argument, the second is within the encoded
-// BatchRequest, although we don't want to rely on that occurring
-// within the portion printed in the stack trace):
-//
-// github.com/cockroachdb/cockroach/pkg/storage.(*Replica).sendWithRangeID(0xc420d1a000, 0x64bfb80, 0xc421564b10, 0x15, 0x153fd4634aeb0193, 0x0, 0x100000001, 0x1, 0x15, 0x0, ...)
-func (r *Replica) sendWithoutRangeID(
-	ctx context.Context, ba *roachpb.BatchRequest,
-) (_ *roachpb.BatchResponse, _ *StoreWriteBytes, rErr *roachpb.Error) {
-	var br *roachpb.BatchResponse
-
+	if r.store.cfg.Settings.CPUProfileType() == cluster.CPUProfileWithLabels {
+		defer pprof.SetGoroutineLabels(ctx)
+		// Note: the defer statement captured the previous context.
+		ctx = pprof.WithLabels(ctx, pprof.Labels("range_str", r.rangeStr.String()))
+		pprof.SetGoroutineLabels(ctx)
+	}
 	// Add the range log tag.
 	ctx = r.AnnotateCtx(ctx)
+	ba := &req
 
 	// Record summary throughput information about the batch request for
 	// accounting.
@@ -177,6 +158,7 @@ func (r *Replica) sendWithoutRangeID(
 	}
 
 	// Differentiate between read-write, read-only, and admin.
+	var br *roachpb.BatchResponse
 	var pErr *roachpb.Error
 	var writeBytes *StoreWriteBytes
 	if isReadOnly {

pkg/kv/kvserver/replica_test.go

@@ -13452,8 +13452,7 @@ func TestProposalNotAcknowledgedOrReproposedAfterApplication(t *testing.T) {
 
 	// Round trip another proposal through the replica to ensure that previously
 	// committed entries have been applied.
-	_, _, pErr = tc.repl.sendWithoutRangeID(ctx, &ba)
-	if pErr != nil {
+	if _, pErr := tc.repl.Send(ctx, ba); pErr != nil {
 		t.Fatal(pErr)
 	}
 	log.Flush()