сделал packages.jpg

vendor/google.golang.org/grpc/picker_wrapper.go

@@ -28,21 +28,26 @@ import (
 	"google.golang.org/grpc/internal/channelz"
 	istatus "google.golang.org/grpc/internal/status"
 	"google.golang.org/grpc/internal/transport"
+	"google.golang.org/grpc/stats"
 	"google.golang.org/grpc/status"
 )
 
 // pickerWrapper is a wrapper of balancer.Picker. It blocks on certain pick
 // actions and unblock when there's a picker update.
 type pickerWrapper struct {
-	mu         sync.Mutex
-	done       bool
-	idle       bool
-	blockingCh chan struct{}
-	picker     balancer.Picker
+	mu            sync.Mutex
+	done          bool
+	idle          bool
+	blockingCh    chan struct{}
+	picker        balancer.Picker
+	statsHandlers []stats.Handler // to record blocking picker calls
 }
 
-func newPickerWrapper() *pickerWrapper {
-	return &pickerWrapper{blockingCh: make(chan struct{})}
+func newPickerWrapper(statsHandlers []stats.Handler) *pickerWrapper {
+	return &pickerWrapper{
+		blockingCh:    make(chan struct{}),
+		statsHandlers: statsHandlers,
+	}
 }
 
 // updatePicker is called by UpdateBalancerState. It unblocks all blocked pick.
@@ -95,6 +100,7 @@ func (pw *pickerWrapper) pick(ctx context.Context, failfast bool, info balancer.
 	var ch chan struct{}
 
 	var lastPickErr error
+
 	for {
 		pw.mu.Lock()
 		if pw.done {
@@ -129,6 +135,20 @@ func (pw *pickerWrapper) pick(ctx context.Context, failfast bool, info balancer.
 			continue
 		}
 
+		// If the channel is set, it means that the pick call had to wait for a
+		// new picker at some point. Either it's the first iteration and this
+		// function received the first picker, or a picker errored with
+		// ErrNoSubConnAvailable or errored with failfast set to false, which
+		// will trigger a continue to the next iteration. In the first case this
+		// conditional will hit if this call had to block (the channel is set).
+		// In the second case, the only way it will get to this conditional is
+		// if there is a new picker.
+		if ch != nil {
+			for _, sh := range pw.statsHandlers {
+				sh.HandleRPC(ctx, &stats.PickerUpdated{})
+			}
+		}
+
 		ch = pw.blockingCh
 		p := pw.picker
 		pw.mu.Unlock()