tx throttler: healthcheck all cells if --tx-throttler-healthcheck-cells is undefined

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

@@ -17,7 +17,6 @@ limitations under the License.
 package txthrottler
 
 import (
-	"fmt"
 	"strings"
 	"sync"
 	"time"
@@ -114,10 +113,22 @@ func tryCreateTxThrottler(config *tabletenv.TabletConfig, topoServer *topo.Serve
 		return nil, err
 	}
 
-	// Clone tsv.TxThrottlerHealthCheckCells so that we don't assume tsv.TxThrottlerHealthCheckCells
-	// is immutable.
-	healthCheckCells := make([]string, len(config.TxThrottlerHealthCheckCells))
-	copy(healthCheckCells, config.TxThrottlerHealthCheckCells)
+	var healthCheckCells []string
+	if len(config.TxThrottlerHealthCheckCells) > 0 {
+		// Clone tsv.TxThrottlerHealthCheckCells so that we don't assume tsv.TxThrottlerHealthCheckCells
+		// is immutable.
+		healthCheckCells = make([]string, len(config.TxThrottlerHealthCheckCells))
+		copy(healthCheckCells, config.TxThrottlerHealthCheckCells)
+	} else {
+		ctx, cancel := context.WithTimeout(context.Background(), topo.RemoteOperationTimeout)
+		defer cancel()
+
+		var err error
+		healthCheckCells, err = topoServer.GetKnownCells(ctx)
+		if err != nil {
+			return nil, err
+		}
+	}
 
 	return newTxThrottler(&txThrottlerConfig{
 		enabled:          true,
@@ -216,9 +227,6 @@ func newTxThrottler(config *txThrottlerConfig) (*TxThrottler, error) {
 		if err != nil {
 			return nil, err
 		}
-		if len(config.healthCheckCells) == 0 {
-			return nil, fmt.Errorf("empty healthCheckCells given. %+v", config)
-		}
 	}
 	return &TxThrottler{
 		config: config,

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"
@@ -144,3 +145,26 @@ func TestEnabledThrottler(t *testing.T) {
 	}
 	throttler.Close()
 }
+
+func TestTryCreateTxThrottler(t *testing.T) {
+	allCells := []string{"cell1", "cell2", "cell3"}
+	ts := memorytopo.NewServer(allCells...)
+
+	config := tabletenv.NewDefaultConfig()
+	config.EnableTxThrottler = true
+
+	// Check tx throttler uses all known cells for healthchecks
+	// when TxThrottlerHealthCheckCells is empty/undef
+	{
+		txThrottler, err := tryCreateTxThrottler(config, ts)
+		assert.Nil(t, err)
+		assert.Equal(t, allCells, txThrottler.config.healthCheckCells)
+	}
+	// Check specified cells are used for healthchecks
+	{
+		config.TxThrottlerHealthCheckCells = []string{"cell1"}
+		txThrottler, err := tryCreateTxThrottler(config, ts)
+		assert.Nil(t, err)
+		assert.Equal(t, config.TxThrottlerHealthCheckCells, txThrottler.config.healthCheckCells)
+	}
+}