140 lines
4.3 KiB
Go
140 lines
4.3 KiB
Go
/*
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Copyright 2014 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package server
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import (
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"errors"
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"fmt"
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"net/http"
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"github.com/golang/glog"
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utilruntime "k8s.io/apimachinery/pkg/util/runtime"
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"k8s.io/apiserver/pkg/server/healthz"
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restclient "k8s.io/client-go/rest"
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)
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// PostStartHookFunc is a function that is called after the server has started.
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// It must properly handle cases like:
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// 1. asynchronous start in multiple API server processes
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// 2. conflicts between the different processes all trying to perform the same action
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// 3. partially complete work (API server crashes while running your hook)
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// 4. API server access **BEFORE** your hook has completed
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// Think of it like a mini-controller that is super privileged and gets to run in-process
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// If you use this feature, tag @deads2k on github who has promised to review code for anyone's PostStartHook
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// until it becomes easier to use.
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type PostStartHookFunc func(context PostStartHookContext) error
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// PostStartHookContext provides information about this API server to a PostStartHookFunc
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type PostStartHookContext struct {
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// LoopbackClientConfig is a config for a privileged loopback connection to the API server
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LoopbackClientConfig *restclient.Config
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}
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// PostStartHookProvider is an interface in addition to provide a post start hook for the api server
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type PostStartHookProvider interface {
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PostStartHook() (string, PostStartHookFunc, error)
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}
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type postStartHookEntry struct {
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hook PostStartHookFunc
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// done will be closed when the postHook is finished
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done chan struct{}
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}
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// AddPostStartHook allows you to add a PostStartHook.
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func (s *GenericAPIServer) AddPostStartHook(name string, hook PostStartHookFunc) error {
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if len(name) == 0 {
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return fmt.Errorf("missing name")
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}
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if hook == nil {
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return nil
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}
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s.postStartHookLock.Lock()
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defer s.postStartHookLock.Unlock()
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if s.postStartHooksCalled {
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return fmt.Errorf("unable to add %q because PostStartHooks have already been called", name)
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}
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if _, exists := s.postStartHooks[name]; exists {
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return fmt.Errorf("unable to add %q because it is already registered", name)
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}
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// done is closed when the poststarthook is finished. This is used by the health check to be able to indicate
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// that the poststarthook is finished
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done := make(chan struct{})
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s.AddHealthzChecks(postStartHookHealthz{name: "poststarthook/" + name, done: done})
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s.postStartHooks[name] = postStartHookEntry{hook: hook, done: done}
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return nil
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}
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// RunPostStartHooks runs the PostStartHooks for the server
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func (s *GenericAPIServer) RunPostStartHooks() {
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s.postStartHookLock.Lock()
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defer s.postStartHookLock.Unlock()
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s.postStartHooksCalled = true
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context := PostStartHookContext{LoopbackClientConfig: s.LoopbackClientConfig}
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for hookName, hookEntry := range s.postStartHooks {
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go runPostStartHook(hookName, hookEntry, context)
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}
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}
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func runPostStartHook(name string, entry postStartHookEntry, context PostStartHookContext) {
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var err error
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func() {
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// don't let the hook *accidentally* panic and kill the server
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defer utilruntime.HandleCrash()
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err = entry.hook(context)
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}()
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// if the hook intentionally wants to kill server, let it.
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if err != nil {
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glog.Fatalf("PostStartHook %q failed: %v", name, err)
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}
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close(entry.done)
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}
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// postStartHookHealthz implements a healthz check for poststarthooks. It will return a "hookNotFinished"
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// error until the poststarthook is finished.
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type postStartHookHealthz struct {
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name string
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// done will be closed when the postStartHook is finished
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done chan struct{}
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}
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var _ healthz.HealthzChecker = postStartHookHealthz{}
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func (h postStartHookHealthz) Name() string {
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return h.name
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}
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var hookNotFinished = errors.New("not finished")
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func (h postStartHookHealthz) Check(req *http.Request) error {
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select {
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case <-h.done:
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return nil
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default:
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return hookNotFinished
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}
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}
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