Merge pull request #25178 from zmerlynn/random_max_target_pools

Automatic merge from submit-queue

GCE: Allow node count to exceed GCE TargetPool maximums

```release-note
If the cluster node count exceeds the GCE TargetPool maximum (currently 1000),
randomly select which nodes are members of Kubernetes External Load Balancers.
```


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If we would exceeded the TargetPool API maximums, instead just
randomly select some subsection of the nodes to include in the TP
instead.

pkg/cloudprovider/providers/gce/gce.go

@@ -36,6 +36,7 @@ import (
 	utilerrors "k8s.io/kubernetes/pkg/util/errors"
 	"k8s.io/kubernetes/pkg/util/flowcontrol"
 	netsets "k8s.io/kubernetes/pkg/util/net/sets"
+	"k8s.io/kubernetes/pkg/util/rand"
 	"k8s.io/kubernetes/pkg/util/sets"
 	"k8s.io/kubernetes/pkg/util/wait"
 
@@ -68,6 +69,9 @@ const (
 	// are iterated through to prevent infinite loops if the API
 	// were to continuously return a nextPageToken.
 	maxPages = 25
+
+	// TargetPools can only support 1000 VMs.
+	maxInstancesPerTargetPool = 1000
 )
 
 // GCECloud is an implementation of Interface, LoadBalancer and Instances for Google Compute Engine.
@@ -95,6 +99,11 @@ type Config struct {
 	}
 }
 
+type instRefSlice []*compute.InstanceReference
+
+func (p instRefSlice) Len() int      { return len(p) }
+func (p instRefSlice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
+
 func init() {
 	cloudprovider.RegisterCloudProvider(ProviderName, func(config io.Reader) (cloudprovider.Interface, error) { return newGCECloud(config) })
 }
@@ -853,11 +862,22 @@ func (gce *GCECloud) createForwardingRule(name, serviceName, region, ipAddress s
 	return nil
 }
 
+func restrictTargetPool(instances []string, max int) []string {
+	if len(instances) <= max {
+		return instances
+	}
+	rand.Shuffle(sort.StringSlice(instances))
+	return instances[:max]
+}
+
 func (gce *GCECloud) createTargetPool(name, serviceName, region string, hosts []*gceInstance, affinityType api.ServiceAffinity) error {
 	var instances []string
 	for _, host := range hosts {
 		instances = append(instances, makeHostURL(gce.projectID, host.Zone, host.Name))
 	}
+	// Choose a random subset of nodes to send traffic to, if we
+	// exceed API maximums.
+	instances = restrictTargetPool(instances, maxInstancesPerTargetPool)
 	pool := &compute.TargetPool{
 		Name:            name,
 		Description:     fmt.Sprintf(`{"kubernetes.io/service-name":"%s"}`, serviceName),
@@ -1075,6 +1095,42 @@ func (gce *GCECloud) ensureStaticIP(name, serviceName, region, existingIP string
 	return address.Address, existed, nil
 }
 
+// computeUpdate takes the existing TargetPool and the set of running
+// instances and returns (toAdd, toRemove), the set of instances to
+// reprogram on the TargetPool this reconcile. max restricts the
+// number of nodes allowed to be programmed on the TargetPool.
+func computeUpdate(tp *compute.TargetPool, instances []*gceInstance, max int) ([]*compute.InstanceReference, []*compute.InstanceReference) {
+	existing := sets.NewString()
+	for _, instance := range tp.Instances {
+		existing.Insert(hostURLToComparablePath(instance))
+	}
+
+	var toAdd []*compute.InstanceReference
+	var toRemove []*compute.InstanceReference
+	for _, host := range instances {
+		link := host.makeComparableHostPath()
+		if !existing.Has(link) {
+			toAdd = append(toAdd, &compute.InstanceReference{Instance: link})
+		}
+		existing.Delete(link)
+	}
+	for link := range existing {
+		toRemove = append(toRemove, &compute.InstanceReference{Instance: link})
+	}
+
+	if len(tp.Instances)+len(toAdd)-len(toRemove) > max {
+		// TODO(zmerlynn): In theory, there are faster ways to handle
+		// this if room is much smaller than len(toAdd). In practice,
+		// meh.
+		room := max - len(tp.Instances) + len(toRemove)
+		glog.Infof("TargetPool maximums exceeded, shuffling in %d instances", room)
+		rand.Shuffle(instRefSlice(toAdd))
+		toAdd = toAdd[:room]
+	}
+
+	return toAdd, toRemove
+}
+
 // UpdateLoadBalancer is an implementation of LoadBalancer.UpdateLoadBalancer.
 func (gce *GCECloud) UpdateLoadBalancer(service *api.Service, hostNames []string) error {
 	hosts, err := gce.getInstancesByNames(hostNames)
@@ -1087,27 +1143,11 @@ func (gce *GCECloud) UpdateLoadBalancer(service *api.Service, hostNames []string
 	if err != nil {
 		return err
 	}
-	existing := sets.NewString()
-	for _, instance := range pool.Instances {
-		existing.Insert(hostURLToComparablePath(instance))
-	}
 
-	var toAdd []*compute.InstanceReference
-	var toRemove []*compute.InstanceReference
-	for _, host := range hosts {
-		link := host.makeComparableHostPath()
-		if !existing.Has(link) {
-			toAdd = append(toAdd, &compute.InstanceReference{Instance: link})
-		}
-		existing.Delete(link)
-	}
-	for link := range existing {
-		toRemove = append(toRemove, &compute.InstanceReference{Instance: link})
-	}
-
-	if len(toAdd) > 0 {
-		add := &compute.TargetPoolsAddInstanceRequest{Instances: toAdd}
-		op, err := gce.service.TargetPools.AddInstance(gce.projectID, gce.region, loadBalancerName, add).Do()
+	toAdd, toRemove := computeUpdate(pool, hosts, maxInstancesPerTargetPool)
+	if len(toRemove) > 0 {
+		rm := &compute.TargetPoolsRemoveInstanceRequest{Instances: toRemove}
+		op, err := gce.service.TargetPools.RemoveInstance(gce.projectID, gce.region, loadBalancerName, rm).Do()
 		if err != nil {
 			return err
 		}
@@ -1116,9 +1156,9 @@ func (gce *GCECloud) UpdateLoadBalancer(service *api.Service, hostNames []string
 		}
 	}
 
-	if len(toRemove) > 0 {
-		rm := &compute.TargetPoolsRemoveInstanceRequest{Instances: toRemove}
-		op, err := gce.service.TargetPools.RemoveInstance(gce.projectID, gce.region, loadBalancerName, rm).Do()
+	if len(toAdd) > 0 {
+		add := &compute.TargetPoolsAddInstanceRequest{Instances: toAdd}
+		op, err := gce.service.TargetPools.AddInstance(gce.projectID, gce.region, loadBalancerName, add).Do()
 		if err != nil {
 			return err
 		}
@@ -1134,10 +1174,14 @@ func (gce *GCECloud) UpdateLoadBalancer(service *api.Service, hostNames []string
 	if err != nil {
 		return err
 	}
-	if len(updatedPool.Instances) != len(hosts) {
+	wantInstances := len(hosts)
+	if wantInstances > maxInstancesPerTargetPool {
+		wantInstances = maxInstancesPerTargetPool
+	}
+	if len(updatedPool.Instances) != wantInstances {
 		glog.Errorf("Unexpected number of instances (%d) in target pool %s after updating (expected %d). Instances in updated pool: %s",
-			len(updatedPool.Instances), loadBalancerName, len(hosts), strings.Join(updatedPool.Instances, ","))
-		return fmt.Errorf("Unexpected number of instances (%d) in target pool %s after update (expected %d)", len(updatedPool.Instances), loadBalancerName, len(hosts))
+			len(updatedPool.Instances), loadBalancerName, wantInstances, strings.Join(updatedPool.Instances, ","))
+		return fmt.Errorf("Unexpected number of instances (%d) in target pool %s after update (expected %d)", len(updatedPool.Instances), loadBalancerName, wantInstances)
 	}
 	return nil
 }

pkg/cloudprovider/providers/gce/gce_test.go

@@ -19,6 +19,9 @@ package gce
 import (
 	"reflect"
 	"testing"
+
+	compute "google.golang.org/api/compute/v1"
+	"k8s.io/kubernetes/pkg/util/rand"
 )
 
 func TestGetRegion(t *testing.T) {
@@ -148,3 +151,112 @@ func TestScrubDNS(t *testing.T) {
 		}
 	}
 }
+
+func TestRestrictTargetPool(t *testing.T) {
+	const maxInstances = 5
+	tests := []struct {
+		instances []string
+		want      []string
+	}{
+		{
+			instances: []string{"1", "2", "3", "4", "5"},
+			want:      []string{"1", "2", "3", "4", "5"},
+		},
+		{
+			instances: []string{"1", "2", "3", "4", "5", "6"},
+			want:      []string{"4", "3", "5", "2", "6"},
+		},
+	}
+	for _, tc := range tests {
+		rand.Seed(5)
+		got := restrictTargetPool(append([]string{}, tc.instances...), maxInstances)
+		if !reflect.DeepEqual(got, tc.want) {
+			t.Errorf("restrictTargetPool(%v) => %v, want %v", tc.instances, got, tc.want)
+		}
+	}
+}
+
+func TestComputeUpdate(t *testing.T) {
+	const maxInstances = 5
+	const fakeZone = "us-moon1-f"
+	tests := []struct {
+		tp           []string
+		instances    []string
+		wantToAdd    []string
+		wantToRemove []string
+	}{
+		{
+			// Test adding all instances.
+			tp:           []string{},
+			instances:    []string{"0", "1", "2"},
+			wantToAdd:    []string{"0", "1", "2"},
+			wantToRemove: []string{},
+		},
+		{
+			// Test node 1 coming back healthy.
+			tp:           []string{"0", "2"},
+			instances:    []string{"0", "1", "2"},
+			wantToAdd:    []string{"1"},
+			wantToRemove: []string{},
+		},
+		{
+			// Test node 1 going healthy while node 4 needs to be removed.
+			tp:           []string{"0", "2", "4"},
+			instances:    []string{"0", "1", "2"},
+			wantToAdd:    []string{"1"},
+			wantToRemove: []string{"4"},
+		},
+		{
+			// Test exceeding the TargetPool max of 5 (for the test),
+			// which shuffles in 7, 5, 8 based on the deterministic
+			// seed below.
+			tp:           []string{"0", "2", "4", "6"},
+			instances:    []string{"0", "1", "2", "3", "5", "7", "8"},
+			wantToAdd:    []string{"7", "5", "8"},
+			wantToRemove: []string{"4", "6"},
+		},
+		{
+			// Test all nodes getting removed.
+			tp:           []string{"0", "1", "2", "3"},
+			instances:    []string{},
+			wantToAdd:    []string{},
+			wantToRemove: []string{"0", "1", "2", "3"},
+		},
+	}
+	for _, tc := range tests {
+		rand.Seed(5) // Arbitrary RNG seed for deterministic testing.
+
+		// Dummy up the gceInstance slice.
+		var instances []*gceInstance
+		for _, inst := range tc.instances {
+			instances = append(instances, &gceInstance{Name: inst, Zone: fakeZone})
+		}
+		// Dummy up the TargetPool URL list.
+		var urls []string
+		for _, inst := range tc.tp {
+			inst := &gceInstance{Name: inst, Zone: fakeZone}
+			urls = append(urls, inst.makeComparableHostPath())
+		}
+		gotAddInsts, gotRem := computeUpdate(&compute.TargetPool{Instances: urls}, instances, maxInstances)
+		var wantAdd []string
+		for _, inst := range tc.wantToAdd {
+			inst := &gceInstance{Name: inst, Zone: fakeZone}
+			wantAdd = append(wantAdd, inst.makeComparableHostPath())
+		}
+		var gotAdd []string
+		for _, inst := range gotAddInsts {
+			gotAdd = append(gotAdd, inst.Instance)
+		}
+		if !reflect.DeepEqual(wantAdd, gotAdd) {
+			t.Errorf("computeTargetPool(%v, %v) => added %v, wanted %v", tc.tp, tc.instances, gotAdd, wantAdd)
+		}
+		_ = gotRem
+		// var gotRem []string
+		// for _, inst := range gotRemInsts {
+		// 	gotRem = append(gotRem, inst.Instance)
+		// }
+		// if !reflect.DeepEqual(tc.wantToRemove, gotRem) {
+		// 	t.Errorf("computeTargetPool(%v, %v) => removed %v, wanted %v", tc.tp, tc.instances, gotRem, tc.wantToRemove)
+		// }
+	}
+}

pkg/util/rand/rand.go

@@ -65,3 +65,19 @@ func String(length int) string {
 	}
 	return string(b)
 }
+
+// A type that satisfies the rand.Shufflable interface can be shuffled
+// by Shuffle. Any sort.Interface will satisfy this interface.
+type Shufflable interface {
+	Len() int
+	Swap(i, j int)
+}
+
+func Shuffle(data Shufflable) {
+	rng.Lock()
+	defer rng.Unlock()
+	for i := 0; i < data.Len(); i++ {
+		j := rng.rand.Intn(i + 1)
+		data.Swap(i, j)
+	}
+}

pkg/util/rand/rand_test.go

@@ -18,6 +18,8 @@ package rand
 
 import (
 	"math/rand"
+	"reflect"
+	"sort"
 	"strings"
 	"testing"
 )
@@ -71,3 +73,14 @@ func TestPerm(t *testing.T) {
 		}
 	}
 }
+
+func TestShuffle(t *testing.T) {
+	Seed(5) // Arbitrary RNG seed for deterministic testing.
+	have := []int{0, 1, 2, 3, 4}
+	want := []int{3, 2, 4, 1, 0} // "have" shuffled, with RNG at Seed(5).
+	got := append([]int{}, have...)
+	Shuffle(sort.IntSlice(got))
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Shuffle(%v) => %v, want %v", have, got, want)
+	}
+}