vttablet tx throttler: healthcheck all cells if cells unspecified

Signed-off-by: Tim Vaillancourt <tim@timvaillancourt.com>

go/vt/vttablet/tabletserver/txthrottler/tx_throttler.go

@@ -119,7 +119,7 @@ func tryCreateTxThrottler(config *tabletenv.TabletConfig, topoServer *topo.Serve
 	if len(config.TxThrottlerHealthCheckCells) > 0 {
 		// Clone tsv.TxThrottlerHealthCheckCells so that we don't assume tsv.TxThrottlerHealthCheckCells
 		// is immutable.
-		healthCheckCells := make([]string, len(config.TxThrottlerHealthCheckCells))
+		healthCheckCells = make([]string, len(config.TxThrottlerHealthCheckCells))
 		copy(healthCheckCells, config.TxThrottlerHealthCheckCells)
 	} else {
 		ctx, cancel := context.WithTimeout(context.Background(), topo.RemoteOperationTimeout)

go/vt/vttablet/tabletserver/txthrottler/tx_throttler_test.go

@@ -26,6 +26,7 @@ import (
 	"time"
 
 	"github.com/golang/mock/gomock"
+	"github.com/stretchr/testify/assert"
 
 	"vitess.io/vitess/go/vt/discovery"
 	"vitess.io/vitess/go/vt/topo"
@@ -58,7 +59,7 @@ func TestEnabledThrottler(t *testing.T) {
 	defer mockCtrl.Finish()
 
 	defer resetTxThrottlerFactories()
-	ts := memorytopo.NewServer("cell1", "cell2")
+	ts := memorytopo.NewServer("cell1", "cell2", "cell3")
 
 	mockHealthCheck := NewMockHealthCheck(mockCtrl)
 	hcCall1 := mockHealthCheck.EXPECT().Subscribe()
@@ -144,3 +145,30 @@ func TestEnabledThrottler(t *testing.T) {
 	}
 	throttler.Close()
 }
+
+func TestTryCreateTxThrottler(t *testing.T) {
+	allCells := []string{"cell1", "cell2", "cell3"}
+	ts := memorytopo.NewServer(allCells...)
+
+	// Check specified cells are used for healthchecks
+	{
+		config := tabletenv.NewDefaultConfig()
+		config.EnableTxThrottler = true
+		config.TxThrottlerHealthCheckCells = []string{"cell1"}
+
+		txThrottler, err := tryCreateTxThrottler(config, ts)
+		assert.Nil(t, err)
+		assert.Equal(t, config.TxThrottlerHealthCheckCells, txThrottler.config.healthCheckCells)
+	}
+	// Check tx throttler uses all known cells for healthchecks
+	// when TxThrottlerHealthCheckCells is empty/undef
+	{
+		config := tabletenv.NewDefaultConfig()
+		config.EnableTxThrottler = true
+		config.TxThrottlerHealthCheckCells = []string{} // empty
+
+		txThrottler, err := tryCreateTxThrottler(config, ts)
+		assert.Nil(t, err)
+		assert.Equal(t, allCells, txThrottler.config.healthCheckCells)
+	}
+}