genericapiserver: move packages

Towards a sane k8s.io/apiserver package structure.

pkg/genericapiserver/server/hooks.go

@@ -0,0 +1,140 @@
+/*
+Copyright 2014 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 genericapiserver
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+
+	"github.com/golang/glog"
+
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/apiserver/pkg/healthz"
+	"k8s.io/kubernetes/pkg/client/restclient"
+)
+
+// PostStartHookFunc is a function that is called after the server has started.
+// It must properly handle cases like:
+//  1. asynchronous start in multiple API server processes
+//  2. conflicts between the different processes all trying to perform the same action
+//  3. partially complete work (API server crashes while running your hook)
+//  4. API server access **BEFORE** your hook has completed
+// Think of it like a mini-controller that is super privileged and gets to run in-process
+// If you use this feature, tag @deads2k on github who has promised to review code for anyone's PostStartHook
+// until it becomes easier to use.
+type PostStartHookFunc func(context PostStartHookContext) error
+
+// PostStartHookContext provides information about this API server to a PostStartHookFunc
+type PostStartHookContext struct {
+	// LoopbackClientConfig is a config for a privileged loopback connection to the API server
+	LoopbackClientConfig *restclient.Config
+}
+
+// PostStartHookProvider is an interface in addition to provide a post start hook for the api server
+type PostStartHookProvider interface {
+	PostStartHook() (string, PostStartHookFunc, error)
+}
+
+type postStartHookEntry struct {
+	hook PostStartHookFunc
+
+	// done will be closed when the postHook is finished
+	done chan struct{}
+}
+
+// AddPostStartHook allows you to add a PostStartHook.
+func (s *GenericAPIServer) AddPostStartHook(name string, hook PostStartHookFunc) error {
+	if len(name) == 0 {
+		return fmt.Errorf("missing name")
+	}
+	if hook == nil {
+		return nil
+	}
+
+	s.postStartHookLock.Lock()
+	defer s.postStartHookLock.Unlock()
+
+	if s.postStartHooksCalled {
+		return fmt.Errorf("unable to add %q because PostStartHooks have already been called", name)
+	}
+	if _, exists := s.postStartHooks[name]; exists {
+		return fmt.Errorf("unable to add %q because it is already registered", name)
+	}
+
+	// done is closed when the poststarthook is finished.  This is used by the health check to be able to indicate
+	// that the poststarthook is finished
+	done := make(chan struct{})
+	s.AddHealthzChecks(postStartHookHealthz{name: "poststarthook/" + name, done: done})
+	s.postStartHooks[name] = postStartHookEntry{hook: hook, done: done}
+
+	return nil
+}
+
+// RunPostStartHooks runs the PostStartHooks for the server
+func (s *GenericAPIServer) RunPostStartHooks() {
+	s.postStartHookLock.Lock()
+	defer s.postStartHookLock.Unlock()
+	s.postStartHooksCalled = true
+
+	context := PostStartHookContext{LoopbackClientConfig: s.LoopbackClientConfig}
+
+	for hookName, hookEntry := range s.postStartHooks {
+		go runPostStartHook(hookName, hookEntry, context)
+	}
+}
+
+func runPostStartHook(name string, entry postStartHookEntry, context PostStartHookContext) {
+	var err error
+	func() {
+		// don't let the hook *accidentally* panic and kill the server
+		defer utilruntime.HandleCrash()
+		err = entry.hook(context)
+	}()
+	// if the hook intentionally wants to kill server, let it.
+	if err != nil {
+		glog.Fatalf("PostStartHook %q failed: %v", name, err)
+	}
+
+	close(entry.done)
+}
+
+// postStartHookHealthz implements a healthz check for poststarthooks.  It will return a "hookNotFinished"
+// error until the poststarthook is finished.
+type postStartHookHealthz struct {
+	name string
+
+	// done will be closed when the postStartHook is finished
+	done chan struct{}
+}
+
+var _ healthz.HealthzChecker = postStartHookHealthz{}
+
+func (h postStartHookHealthz) Name() string {
+	return h.name
+}
+
+var hookNotFinished = errors.New("not finished")
+
+func (h postStartHookHealthz) Check(req *http.Request) error {
+	select {
+	case <-h.done:
+		return nil
+	default:
+		return hookNotFinished
+	}
+}