Break deployment controller into separate self-contained files

* rolling.go (has all the logic for rolling deployments)
* recreate.go (has all the logic for recreate deployments)
* sync.go (has all the logic for getting and scaling replica sets)
* rollback.go (has all the logic for rolling back a deployment)
* util.go (contains all the utilities used throughout the controller)

Leave back at deployment_controller.go all the necessary bits for
creating, setting up, and running the controller loop.

Also add package documentation.

pkg/controller/deployment/recreate.go

@@ -0,0 +1,92 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+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 deployment
+
+import (
+	"k8s.io/kubernetes/pkg/apis/extensions"
+	"k8s.io/kubernetes/pkg/controller"
+)
+
+// rolloutRecreate implements the logic for recreating a replica set.
+func (dc *DeploymentController) rolloutRecreate(deployment *extensions.Deployment) error {
+	// Don't create a new RS if not already existed, so that we avoid scaling up before scaling down
+	newRS, oldRSs, err := dc.getAllReplicaSetsAndSyncRevision(deployment, false)
+	if err != nil {
+		return err
+	}
+	allRSs := append(oldRSs, newRS)
+
+	// scale down old replica sets
+	scaledDown, err := dc.scaleDownOldReplicaSetsForRecreate(controller.FilterActiveReplicaSets(oldRSs), deployment)
+	if err != nil {
+		return err
+	}
+	if scaledDown {
+		// Update DeploymentStatus
+		return dc.updateDeploymentStatus(allRSs, newRS, deployment)
+	}
+
+	// If we need to create a new RS, create it now
+	// TODO: Create a new RS without re-listing all RSs.
+	if newRS == nil {
+		newRS, oldRSs, err = dc.getAllReplicaSetsAndSyncRevision(deployment, true)
+		if err != nil {
+			return err
+		}
+		allRSs = append(oldRSs, newRS)
+	}
+
+	// scale up new replica set
+	scaledUp, err := dc.scaleUpNewReplicaSetForRecreate(newRS, deployment)
+	if err != nil {
+		return err
+	}
+	if scaledUp {
+		// Update DeploymentStatus
+		return dc.updateDeploymentStatus(allRSs, newRS, deployment)
+	}
+
+	dc.cleanupDeployment(oldRSs, deployment)
+
+	// Sync deployment status
+	return dc.syncDeploymentStatus(allRSs, newRS, deployment)
+}
+
+// scaleDownOldReplicaSetsForRecreate scales down old replica sets when deployment strategy is "Recreate"
+func (dc *DeploymentController) scaleDownOldReplicaSetsForRecreate(oldRSs []*extensions.ReplicaSet, deployment *extensions.Deployment) (bool, error) {
+	scaled := false
+	for _, rs := range oldRSs {
+		// Scaling not required.
+		if rs.Spec.Replicas == 0 {
+			continue
+		}
+		scaledRS, _, err := dc.scaleReplicaSetAndRecordEvent(rs, 0, deployment)
+		if err != nil {
+			return false, err
+		}
+		if scaledRS {
+			scaled = true
+		}
+	}
+	return scaled, nil
+}
+
+// scaleUpNewReplicaSetForRecreate scales up new replica set when deployment strategy is "Recreate"
+func (dc *DeploymentController) scaleUpNewReplicaSetForRecreate(newRS *extensions.ReplicaSet, deployment *extensions.Deployment) (bool, error) {
+	scaled, _, err := dc.scaleReplicaSetAndRecordEvent(newRS, deployment.Spec.Replicas, deployment)
+	return scaled, err
+}