Add Host to PodSpec and add a predicate to make the scheduler work.

pkg/api/types.go

@@ -452,6 +452,11 @@ type PodSpec struct {
 	RestartPolicy RestartPolicy `json:"restartPolicy,omitempty"`
 	// NodeSelector is a selector which must be true for the pod to fit on a node
 	NodeSelector map[string]string `json:"nodeSelector,omitempty"`
+
+	// Host is a request to schedule this pod onto a specific host.  If it is non-empty,
+	// the the scheduler simply schedules this pod onto that host, assuming that it fits
+	// resource requirements.
+	Host string `json:"host,omitempty"`
 }
 
 // PodStatus represents information about the status of a pod. Status may trail the actual

pkg/api/v1beta1/conversion.go

@@ -204,12 +204,14 @@ func init() {
 			if err := s.Convert(&in, &out.Manifest, 0); err != nil {
 				return err
 			}
+			out.Host = in.Host
 			return nil
 		},
 		func(in *PodState, out *newer.PodSpec, s conversion.Scope) error {
 			if err := s.Convert(&in.Manifest, &out, 0); err != nil {
 				return err
 			}
+			out.Host = in.Host
 			return nil
 		},
 
@@ -265,6 +267,7 @@ func init() {
 			if err := s.Convert(&in.Spec, &out.DesiredState.Manifest, 0); err != nil {
 				return err
 			}
+			out.DesiredState.Host = in.Spec.Host
 			if err := s.Convert(&in.Status, &out.CurrentState, 0); err != nil {
 				return err
 			}
@@ -286,6 +289,7 @@ func init() {
 			if err := s.Convert(&in.DesiredState.Manifest, &out.Spec, 0); err != nil {
 				return err
 			}
+			out.Spec.Host = in.DesiredState.Host
 			if err := s.Convert(&in.CurrentState, &out.Status, 0); err != nil {
 				return err
 			}
@@ -361,6 +365,7 @@ func init() {
 			if err := s.Convert(&in.Spec, &out.DesiredState.Manifest, 0); err != nil {
 				return err
 			}
+			out.DesiredState.Host = in.Spec.Host
 			if err := s.Convert(&in.ObjectMeta.Labels, &out.Labels, 0); err != nil {
 				return err
 			}
@@ -370,6 +375,7 @@ func init() {
 			if err := s.Convert(&in.DesiredState.Manifest, &out.Spec, 0); err != nil {
 				return err
 			}
+			out.Spec.Host = in.DesiredState.Host
 			if err := s.Convert(&in.Labels, &out.ObjectMeta.Labels, 0); err != nil {
 				return err
 			}

pkg/api/v1beta1/types.go

@@ -830,6 +830,11 @@ type PodSpec struct {
 	RestartPolicy RestartPolicy `json:"restartPolicy,omitempty" description:"restart policy for all containers within the pod; one of RestartPolicyAlways, RestartPolicyOnFailure, RestartPolicyNever"`
 	// NodeSelector is a selector which must be true for the pod to fit on a node
 	NodeSelector map[string]string `json:"nodeSelector,omitempty" description:"selector which must match a node's labels for the pod to be scheduled on that node"`
+
+	// Host is a request to schedule this pod onto a specific host.  If it is non-empty,
+	// the the scheduler simply schedules this pod onto that host, assuming that it fits
+	// resource requirements.
+	Host string `json:"host,omitempty" description:"host requested for this pod"`
 }
 
 // BoundPod is a collection of containers that should be run on a host. A BoundPod

pkg/api/v1beta2/conversion.go

@@ -155,6 +155,7 @@ func init() {
 			if err := s.Convert(&in.Spec, &out.DesiredState.Manifest, 0); err != nil {
 				return err
 			}
+			out.DesiredState.Host = in.Spec.Host
 			if err := s.Convert(&in.Status, &out.CurrentState, 0); err != nil {
 				return err
 			}
@@ -176,6 +177,7 @@ func init() {
 			if err := s.Convert(&in.DesiredState.Manifest, &out.Spec, 0); err != nil {
 				return err
 			}
+			out.Spec.Host = in.DesiredState.Host
 			if err := s.Convert(&in.CurrentState, &out.Status, 0); err != nil {
 				return err
 			}
@@ -251,6 +253,7 @@ func init() {
 			if err := s.Convert(&in.Spec, &out.DesiredState.Manifest, 0); err != nil {
 				return err
 			}
+			out.DesiredState.Host = in.Spec.Host
 			if err := s.Convert(&in.ObjectMeta.Labels, &out.Labels, 0); err != nil {
 				return err
 			}
@@ -260,6 +263,7 @@ func init() {
 			if err := s.Convert(&in.DesiredState.Manifest, &out.Spec, 0); err != nil {
 				return err
 			}
+			out.Spec.Host = in.DesiredState.Host
 			if err := s.Convert(&in.Labels, &out.ObjectMeta.Labels, 0); err != nil {
 				return err
 			}
@@ -323,12 +327,14 @@ func init() {
 			if err := s.Convert(&in, &out.Manifest, 0); err != nil {
 				return err
 			}
+			out.Host = in.Host
 			return nil
 		},
 		func(in *PodState, out *newer.PodSpec, s conversion.Scope) error {
 			if err := s.Convert(&in.Manifest, &out, 0); err != nil {
 				return err
 			}
+			out.Host = in.Host
 			return nil
 		},
 		func(in *newer.Service, out *Service, s conversion.Scope) error {

pkg/api/v1beta2/types.go

@@ -831,6 +831,11 @@ type PodSpec struct {
 	RestartPolicy RestartPolicy `json:"restartPolicy,omitempty" description:"restart policy for all containers within the pod; one of RestartPolicyAlways, RestartPolicyOnFailure, RestartPolicyNever"`
 	// NodeSelector is a selector which must be true for the pod to fit on a node
 	NodeSelector map[string]string `json:"nodeSelector,omitempty" description:"selector which must match a node's labels for the pod to be scheduled on that node"`
+
+	// Host is a request to schedule this pod onto a specific host.  If it is non-empty,
+	// the the scheduler simply schedules this pod onto that host, assuming that it fits
+	// resource requirements.
+	Host string `json:"host,omitempty" description:"host requested for this pod"`
 }
 
 // BoundPod is a collection of containers that should be run on a host. A BoundPod

pkg/api/v1beta3/types.go

@@ -461,6 +461,11 @@ type PodSpec struct {
 	RestartPolicy RestartPolicy `json:"restartPolicy,omitempty"`
 	// NodeSelector is a selector which must be true for the pod to fit on a node
 	NodeSelector map[string]string `json:"nodeSelector,omitempty"`
+
+	// Host is a request to schedule this pod onto a specific host.  If it is non-empty,
+	// the the scheduler simply schedules this pod onto that host, assuming that it fits
+	// other requirements.
+	Host string `json:"host,omitempty" description:"host requested for this pod"`
 }
 
 // PodStatus represents information about the status of a pod. Status may trail the actual

pkg/scheduler/predicates.go

@@ -162,6 +162,13 @@ func (n *NodeSelector) PodSelectorMatches(pod api.Pod, existingPods []api.Pod, n
 	return selector.Matches(labels.Set(minion.Labels)), nil
 }
 
+func PodFitsHost(pod api.Pod, existingPods []api.Pod, node string) (bool, error) {
+	if len(pod.Spec.Host) == 0 {
+		return true, nil
+	}
+	return pod.Spec.Host == node, nil
+}
+
 func PodFitsPorts(pod api.Pod, existingPods []api.Pod, node string) (bool, error) {
 	existingPorts := getUsedPorts(existingPods...)
 	wantPorts := getUsedPorts(pod)

pkg/scheduler/predicates_test.go

@@ -124,6 +124,52 @@ func TestPodFitsResources(t *testing.T) {
 	}
 }
 
+func TestPodFitsHost(t *testing.T) {
+	tests := []struct {
+		pod  api.Pod
+		node string
+		fits bool
+		test string
+	}{
+		{
+			pod:  api.Pod{},
+			node: "foo",
+			fits: true,
+			test: "no host specified",
+		},
+		{
+			pod: api.Pod{
+				Spec: api.PodSpec{
+					Host: "foo",
+				},
+			},
+			node: "foo",
+			fits: true,
+			test: "host matches",
+		},
+		{
+			pod: api.Pod{
+				Spec: api.PodSpec{
+					Host: "bar",
+				},
+			},
+			node: "foo",
+			fits: false,
+			test: "host doesn't match",
+		},
+	}
+
+	for _, test := range tests {
+		result, err := PodFitsHost(test.pod, []api.Pod{}, test.node)
+		if err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+		if result != test.fits {
+			t.Errorf("unexpected difference for %s: got: %v expected %v", test.test, test.fits, result)
+		}
+	}
+}
+
 func TestPodFitsPorts(t *testing.T) {
 	tests := []struct {
 		pod          api.Pod

plugin/pkg/scheduler/algorithmprovider/defaults/defaults.go

@@ -37,6 +37,8 @@ func defaultPredicates() util.StringSet {
 		factory.RegisterFitPredicate("NoDiskConflict", algorithm.NoDiskConflict),
 		// Fit is determined by node selector query
 		factory.RegisterFitPredicate("MatchNodeSelector", algorithm.NewSelectorMatchPredicate(factory.MinionLister)),
+		// Fit is determined by the presence of the Host parameter and a string match
+		factory.RegisterFitPredicate("HostName", algorithm.PodFitsHost),
 	)
 }