Make cloud providers be plugins

cmd/apiserver/apiserver.go

@@ -28,8 +28,6 @@ import (
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/apiserver"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider"
-	"github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider/gce"
-	"github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider/vagrant"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/master"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
 	verflag "github.com/GoogleCloudPlatform/kubernetes/pkg/version/flag"
@@ -77,23 +75,13 @@ func main() {
 		glog.Fatalf("-etcd_servers flag is required.")
 	}
 
-	var cloud cloudprovider.Interface
-	switch *cloudProvider {
-	case "gce":
-		var err error
-		cloud, err = gce_cloud.NewGCECloud()
-		if err != nil {
-			glog.Fatalf("Couldn't connect to GCE cloud: %#v", err)
-		}
-	case "vagrant":
-		var err error
-		cloud, err = vagrant_cloud.NewVagrantCloud()
-		if err != nil {
-			glog.Fatalf("Couldn't connect to vagrant cloud: %#v", err)
-		}
-	default:
+	cloud, err := cloudprovider.GetCloudProvider(*cloudProvider)
+	if err != nil {
+		glog.Fatalf("Couldn't init cloud provider %q: %#v", *cloudProvider, err)
+	}
+	if cloud == nil {
 		if len(*cloudProvider) > 0 {
-			glog.Infof("Unknown cloud provider: %s", *cloudProvider)
+			glog.Fatalf("Unknown cloud provider: %s", *cloudProvider)
 		} else {
 			glog.Info("No cloud provider specified.")
 		}

cmd/apiserver/plugins.go

@@ -0,0 +1,25 @@
+/*
+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 main
+
+// This file exists to force the desired plugin implementations to be linked.
+// This should probably be part of some configuration fed into the build for a
+// given binary target.
+import (
+	_ "github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider/gce"
+	_ "github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider/vagrant"
+)

pkg/cloudprovider/gce/gce.go

@@ -39,6 +39,10 @@ type GCECloud struct {
 	instanceRE string
 }
 
+func init() {
+	cloudprovider.RegisterCloudProvider("gce", func() (cloudprovider.Interface, error) { return newGCECloud() })
+}
+
 func getProjectAndZone() (string, string, error) {
 	client := http.Client{}
 	url := "http://metadata/computeMetadata/v1/instance/zone"
@@ -63,8 +67,8 @@ func getProjectAndZone() (string, string, error) {
 	return parts[1], parts[3], nil
 }
 
-// NewGCECloud creates a new instance of GCECloud.
-func NewGCECloud() (*GCECloud, error) {
+// newGCECloud creates a new instance of GCECloud.
+func newGCECloud() (*GCECloud, error) {
 	projectID, zone, err := getProjectAndZone()
 	if err != nil {
 		return nil, err

pkg/cloudprovider/plugins.go

@@ -0,0 +1,56 @@
+/*
+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 cloudprovider
+
+import (
+	"sync"
+
+	"github.com/golang/glog"
+)
+
+// Factory is a function that returns a cloudprovider.Interface.
+type Factory func() (Interface, error)
+
+// All registered cloud providers.
+var providersMutex sync.Mutex
+var providers = make(map[string]Factory)
+
+// RegisterCloudProvider registers a cloudprovider.Factory by name.  This
+// is expected to happen during app startup.
+func RegisterCloudProvider(name string, cloud Factory) {
+	providersMutex.Lock()
+	defer providersMutex.Unlock()
+	_, found := providers[name]
+	if found {
+		glog.Fatalf("Cloud provider %q was registered twice", name)
+	}
+	glog.Infof("Registered cloud provider %q", name)
+	providers[name] = cloud
+}
+
+// GetCloudProvider creates an instance of the named cloud provider, or nil if
+// the name is not known.  The error return is only used if the named provider
+// was known but failed to initialize.
+func GetCloudProvider(name string) (Interface, error) {
+	providersMutex.Lock()
+	defer providersMutex.Unlock()
+	f, found := providers[name]
+	if !found {
+		return nil, nil
+	}
+	return f()
+}

pkg/cloudprovider/vagrant/vagrant.go

@@ -36,6 +36,10 @@ type VagrantCloud struct {
 	saltAuth string
 }
 
+func init() {
+	cloudprovider.RegisterCloudProvider("vagrant", func() (cloudprovider.Interface, error) { return newVagrantCloud() })
+}
+
 // SaltToken is an authorization token required by Salt REST API
 type SaltToken struct {
 	Token string `json:"token"`
@@ -63,8 +67,8 @@ type SaltMinionsResponse struct {
 	Minions []SaltMinions `json:"return"`
 }
 
-// NewVagrantCloud creates a new instance of VagrantCloud configured to talk to the Salt REST API.
-func NewVagrantCloud() (*VagrantCloud, error) {
+// newVagrantCloud creates a new instance of VagrantCloud configured to talk to the Salt REST API.
+func newVagrantCloud() (*VagrantCloud, error) {
 	return &VagrantCloud{
 		saltURL:  "http://127.0.0.1:8000",
 		saltUser: "vagrant",