Merge pull request #3632 from brakthehack/wfu-cb

Property Collector updates should be triggered on the empty FilterSet

property/collector.go

@@ -264,9 +264,12 @@ func (p *Collector) RetrieveOne(ctx context.Context, obj types.ManagedObjectRefe
 
 // WaitForUpdatesEx waits for any of the specified properties of the specified
 // managed object to change. It calls the specified function for every update it
-// receives. If this function returns false, it continues waiting for
+// receives an update - including the empty filter set, which can occur if no
+// objects are eligible for updates.
+//
+// If this function returns false, it continues waiting for
 // subsequent updates. If this function returns true, it stops waiting and
-// returns.
+// returns upon receiving the first non-empty filter set.
 //
 // If the Context is canceled, a call to CancelWaitForUpdates() is made and its
 // error value is returned.
@@ -313,6 +316,12 @@ func (p *Collector) WaitForUpdatesEx(
 			opts.Truncated = *set.Truncated
 		}
 
+		if len(set.FilterSet) == 0 {
+			// Trigger callbacks in case callers need to be notified
+			// of the empty filter set.
+			_ = onUpdatesFn(make([]types.ObjectUpdate, 0))
+		}
+
 		for _, fs := range set.FilterSet {
 			if opts.PropagateMissing {
 				for i := range fs.ObjectSet {

property/collector_test.go

@@ -18,6 +18,7 @@ package property_test
 
 import (
 	"context"
+	"fmt"
 	"testing"
 	"time"
 
@@ -110,6 +111,64 @@ func TestWaitForUpdatesEx(t *testing.T) {
 	}, model)
 }
 
+func TestWaitForUpdatesExEmptyUpdateSet(t *testing.T) {
+	model := simulator.VPX()
+	model.Datacenter = 1
+	model.Cluster = 0
+	model.Pool = 0
+	model.Machine = 0
+	model.Autostart = false
+
+	simulator.Test(func(ctx context.Context, c *vim25.Client) {
+		// Set up the finder and get a VM.
+		finder := find.NewFinder(c, true)
+		datacenter, err := finder.DefaultDatacenter(ctx)
+		if err != nil {
+			t.Fatalf("default datacenter not found: %s", err.Error())
+		}
+		finder.SetDatacenter(datacenter)
+		vmList, err := finder.VirtualMachineList(ctx, "*")
+		if len(vmList) != 0 {
+			t.Fatalf("vmList != 0")
+		}
+
+		pc, err := property.DefaultCollector(c).Create(ctx)
+		if err != nil {
+			t.Fatalf("failed to create new property collector: %s", err.Error())
+		}
+
+		// Start a goroutine to wait for updates on any VMs.
+		// Since there are no VMs in the filter set, we expect to
+		// receive an empty update set.
+		chanResult := make(chan error)
+		cancelCtx, cancel := context.WithCancel(ctx)
+		go func() {
+			defer close(chanResult)
+			_ = pc.WaitForUpdatesEx(
+				cancelCtx,
+				&property.WaitOptions{},
+				func(updates []types.ObjectUpdate) bool {
+					var err error
+					if len(updates) > 0 {
+						err = fmt.Errorf("unexpected update")
+					}
+					chanResult <- err
+					cancel()
+					return true
+				})
+		}()
+
+		select {
+		case <-ctx.Done():
+			t.Fatalf("timed out while waiting for updates")
+		case err := <-chanResult:
+			if err != nil {
+				t.Fatalf("error while waiting for updates: %s", err.Error())
+			}
+		}
+	}, model)
+}
+
 func TestRetrievePropertiesOneAtATime(t *testing.T) {
 	model := simulator.VPX()
 	model.Datacenter = 1