perf(go): cache realtime plate lookups

go/vehicle-gateway/internal/realtime/snapshot_writer_test.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/DATA-DOG/go-sqlmock"
 
@@ -212,6 +213,44 @@ func TestSnapshotWriterBackfillsPlateFromBindingByVIN(t *testing.T) {
 	}
 }
 
+func TestSnapshotWriterCachesBindingPlateByVIN(t *testing.T) {
+	exec := &recordingSnapshotExec{}
+	resolver := &recordingPlateResolver{plate: "沪A12345"}
+	writer := NewSnapshotWriterWithPlateResolver(exec, NewCachedPlateResolver(resolver, time.Hour))
+	event := envelope.FrameEnvelope{
+		Protocol:     envelope.ProtocolGB32960,
+		MessageID:    "0x02",
+		VIN:          "VIN001",
+		EventTimeMS:  1782918600000,
+		ReceivedAtMS: 1782918601000,
+		Fields: map[string]any{
+			envelope.FieldLatitude:  30.590151,
+			envelope.FieldLongitude: 121.069881,
+		},
+	}
+
+	if err := writer.Update(context.Background(), event); err != nil {
+		t.Fatalf("first Update() error = %v", err)
+	}
+	event.EventTimeMS += 1000
+	event.ReceivedAtMS += 1000
+	if err := writer.Update(context.Background(), event); err != nil {
+		t.Fatalf("second Update() error = %v", err)
+	}
+
+	if resolver.calls != 1 {
+		t.Fatalf("plate resolver calls = %d, want 1", resolver.calls)
+	}
+	if len(exec.calls) != 4 {
+		t.Fatalf("exec calls = %d, want 4", len(exec.calls))
+	}
+	for _, index := range []int{0, 2} {
+		if got, want := exec.calls[index].args[2], "沪A12345"; got != want {
+			t.Fatalf("snapshot %d plate arg = %#v, want %q", index, got, want)
+		}
+	}
+}
+
 func TestSnapshotWriterKeepsEventPlateWhenPresent(t *testing.T) {
 	exec := &recordingSnapshotExec{}
 	resolver := &recordingPlateResolver{plate: "沪B99999"}
@@ -358,9 +397,11 @@ type recordingPlateResolver struct {
 	vin   string
 	plate string
 	err   error
+	calls int
 }
 
 func (r *recordingPlateResolver) PlateByVIN(_ context.Context, vin string) (string, error) {
+	r.calls++
 	r.vin = vin
 	return r.plate, r.err
 }