Add a resize command to kubectl.

pkg/kubectl/resize.go

@@ -0,0 +1,93 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kubectl
+
+import (
+	"fmt"
+	"strconv"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
+)
+
+// ResizePrecondition describes a condition that must be true for the resize to take place
+// If CurrentSize == -1, it is ignored.
+// If CurrentResourceVersion is the empty string, it is ignored.
+// Otherwise they must equal the values in the replication controller for it to be valid.
+type ResizePrecondition struct {
+	Size            int
+	ResourceVersion string
+}
+
+type PreconditionError struct {
+	Precondition  string
+	ExpectedValue string
+	ActualValue   string
+}
+
+func (pe *PreconditionError) Error() string {
+	return fmt.Sprintf("Expected %s to be %s, was %s", pe.Precondition, pe.ExpectedValue, pe.ActualValue)
+}
+
+// Validate ensures that the preconditions match.  Returns nil if they are valid, an error otherwise
+func (precondition *ResizePrecondition) Validate(controller *api.ReplicationController) error {
+	if precondition.Size != -1 && controller.Spec.Replicas != precondition.Size {
+		return &PreconditionError{"replicas", strconv.Itoa(precondition.Size), strconv.Itoa(controller.Spec.Replicas)}
+	}
+	if precondition.ResourceVersion != "" && controller.ResourceVersion != precondition.ResourceVersion {
+		return &PreconditionError{"resource version", precondition.ResourceVersion, controller.ResourceVersion}
+	}
+	return nil
+}
+
+type Resizer interface {
+	Resize(namespace, name string, preconditions *ResizePrecondition, newSize uint) (string, error)
+}
+
+func ResizerFor(kind string, c *client.Client) (Resizer, bool) {
+	switch kind {
+	case "ReplicationController":
+		return &ReplicationControllerResizer{c}, true
+	}
+	return nil, false
+}
+
+type ReplicationControllerResizer struct {
+	client.Interface
+}
+
+func (resize *ReplicationControllerResizer) Resize(namespace, name string, preconditions *ResizePrecondition, newSize uint) (string, error) {
+	rc := resize.ReplicationControllers(namespace)
+	controller, err := rc.Get(name)
+	if err != nil {
+		return "", err
+	}
+
+	if preconditions != nil {
+		if err := preconditions.Validate(controller); err != nil {
+			return "", err
+		}
+	}
+
+	controller.Spec.Replicas = int(newSize)
+	// TODO: do retry on 409 errors here?
+	if _, err := rc.Update(controller); err != nil {
+		return "", err
+	}
+	// TODO: do a better job of printing objects here.
+	return "resized", nil
+}