add ability to pre-configure poststarthooks for apiservers

Kubernetes-commit: f14f4c933ee01d219ffbfa846875171e179019b7

pkg/server/config.go

@@ -23,6 +23,7 @@ import (
 	"net"
 	"net/http"
 	goruntime "runtime"
+	"runtime/debug"
 	"sort"
 	"strconv"
 	"strings"
@@ -116,6 +117,8 @@ type Config struct {
 	EnableMetrics             bool
 
 	DisabledPostStartHooks sets.String
+	// done values in this values for this map are ignored.
+	PostStartHooks map[string]PostStartHookConfigEntry
 
 	// Version will enable the /version endpoint if non-nil
 	Version *version.Info
@@ -282,6 +285,7 @@ func NewConfig(codecs serializer.CodecFactory) *Config {
 		HandlerChainWaitGroup:       new(utilwaitgroup.SafeWaitGroup),
 		LegacyAPIGroupPrefixes:      sets.NewString(DefaultLegacyAPIPrefix),
 		DisabledPostStartHooks:      sets.NewString(),
+		PostStartHooks:              map[string]PostStartHookConfigEntry{},
 		HealthzChecks:               append([]healthz.HealthChecker{}, defaultHealthChecks...),
 		ReadyzChecks:                append([]healthz.HealthChecker{}, defaultHealthChecks...),
 		LivezChecks:                 append([]healthz.HealthChecker{}, defaultHealthChecks...),
@@ -389,6 +393,36 @@ func (c *Config) AddHealthChecks(healthChecks ...healthz.HealthChecker) {
 	}
 }
 
+// AddPostStartHook allows you to add a PostStartHook that will later be added to the server itself in a New call.
+// Name conflicts will cause an error.
+func (c *Config) AddPostStartHook(name string, hook PostStartHookFunc) error {
+	if len(name) == 0 {
+		return fmt.Errorf("missing name")
+	}
+	if hook == nil {
+		return fmt.Errorf("hook func may not be nil: %q", name)
+	}
+	if c.DisabledPostStartHooks.Has(name) {
+		klog.V(1).Infof("skipping %q because it was explicitly disabled", name)
+		return nil
+	}
+
+	if postStartHook, exists := c.PostStartHooks[name]; exists {
+		// this is programmer error, but it can be hard to debug
+		return fmt.Errorf("unable to add %q because it was already registered by: %s", name, postStartHook.originatingStack)
+	}
+	c.PostStartHooks[name] = PostStartHookConfigEntry{hook: hook, originatingStack: string(debug.Stack())}
+
+	return nil
+}
+
+// AddPostStartHookOrDie allows you to add a PostStartHook, but dies on failure.
+func (c *Config) AddPostStartHookOrDie(name string, hook PostStartHookFunc) {
+	if err := c.AddPostStartHook(name, hook); err != nil {
+		klog.Fatalf("Error registering PostStartHook %q: %v", name, err)
+	}
+}
+
 // Complete fills in any fields not set that are required to have valid data and can be derived
 // from other fields. If you're going to `ApplyOptions`, do that first. It's mutating the receiver.
 func (c *Config) Complete(informers informers.SharedInformerFactory) CompletedConfig {
@@ -550,6 +584,7 @@ func (c completedConfig) New(name string, delegationTarget DelegationTarget) (*G
 		}
 	}
 
+	// first add poststarthooks from delegated targets
 	for k, v := range delegationTarget.PostStartHooks() {
 		s.postStartHooks[k] = v
 	}
@@ -558,6 +593,13 @@ func (c completedConfig) New(name string, delegationTarget DelegationTarget) (*G
 		s.preShutdownHooks[k] = v
 	}
 
+	// add poststarthooks that were preconfigured.  Using the add method will give us an error if the same name has already been registered.
+	for name, preconfiguredPostStartHook := range c.PostStartHooks {
+		if err := s.AddPostStartHook(name, preconfiguredPostStartHook.hook); err != nil {
+			return nil, err
+		}
+	}
+
 	genericApiServerHookName := "generic-apiserver-start-informers"
 	if c.SharedInformerFactory != nil && !s.isPostStartHookRegistered(genericApiServerHookName) {
 		err := s.AddPostStartHook(genericApiServerHookName, func(context PostStartHookContext) error {
@@ -611,7 +653,6 @@ func DefaultBuildHandlerChain(apiHandler http.Handler, c *Config) http.Handler {
 	handler = genericfilters.WithTimeoutForNonLongRunningRequests(handler, c.LongRunningFunc, c.RequestTimeout)
 	handler = genericfilters.WithWaitGroup(handler, c.LongRunningFunc, c.HandlerChainWaitGroup)
 	handler = genericapifilters.WithRequestInfo(handler, c.RequestInfoResolver)
-	handler = genericapifilters.WithCacheControl(handler)
 	handler = genericfilters.WithPanicRecovery(handler)
 	return handler
 }

pkg/server/hooks.go

@@ -66,6 +66,13 @@ type postStartHookEntry struct {
 	done chan struct{}
 }
 
+type PostStartHookConfigEntry struct {
+	hook PostStartHookFunc
+	// originatingStack holds the stack that registered postStartHooks. This allows us to show a more helpful message
+	// for duplicate registration.
+	originatingStack string
+}
+
 type preShutdownHookEntry struct {
 	hook PreShutdownHookFunc
 }
@@ -76,9 +83,10 @@ func (s *GenericAPIServer) AddPostStartHook(name string, hook PostStartHookFunc)
 		return fmt.Errorf("missing name")
 	}
 	if hook == nil {
-		return nil
+		return fmt.Errorf("hook func may not be nil: %q", name)
 	}
 	if s.disabledPostStartHooks.Has(name) {
+		klog.V(1).Infof("skipping %q because it was explicitly disabled", name)
 		return nil
 	}