internal/grpcsync: move CallbackSerializer from xdsclient/internal to here (#6153)

internal/grpcsync/callback_serializer.go

@@ -16,7 +16,7 @@
  *
  */
 
-package xdsclient
+package grpcsync
 
 import (
 	"context"
@@ -24,22 +24,22 @@ import (
 	"google.golang.org/grpc/internal/buffer"
 )
 
-// callbackSerializer provides a mechanism to schedule callbacks in a
+// CallbackSerializer provides a mechanism to schedule callbacks in a
 // synchronized manner. It provides a FIFO guarantee on the order of execution
 // of scheduled callbacks. New callbacks can be scheduled by invoking the
 // Schedule() method.
 //
 // This type is safe for concurrent access.
-type callbackSerializer struct {
+type CallbackSerializer struct {
 	callbacks *buffer.Unbounded
 }
 
-// newCallbackSerializer returns a new callbackSerializer instance. The provided
+// NewCallbackSerializer returns a new CallbackSerializer instance. The provided
 // context will be passed to the scheduled callbacks. Users should cancel the
-// provided context to shutdown the callbackSerializer. It is guaranteed that no
+// provided context to shutdown the CallbackSerializer. It is guaranteed that no
 // callbacks will be executed once this context is canceled.
-func newCallbackSerializer(ctx context.Context) *callbackSerializer {
-	t := &callbackSerializer{callbacks: buffer.NewUnbounded()}
+func NewCallbackSerializer(ctx context.Context) *CallbackSerializer {
+	t := &CallbackSerializer{callbacks: buffer.NewUnbounded()}
 	go t.run(ctx)
 	return t
 }
@@ -48,11 +48,11 @@ func newCallbackSerializer(ctx context.Context) *callbackSerializer {
 //
 // Callbacks are expected to honor the context when performing any blocking
 // operations, and should return early when the context is canceled.
-func (t *callbackSerializer) Schedule(f func(ctx context.Context)) {
+func (t *CallbackSerializer) Schedule(f func(ctx context.Context)) {
 	t.callbacks.Put(f)
 }
 
-func (t *callbackSerializer) run(ctx context.Context) {
+func (t *CallbackSerializer) run(ctx context.Context) {
 	for ctx.Err() == nil {
 		select {
 		case <-ctx.Done():

internal/grpcsync/callback_serializer_test.go

@@ -16,7 +16,7 @@
  *
  */
 
-package xdsclient
+package grpcsync
 
 import (
 	"context"
@@ -28,11 +28,16 @@ import (
 	"github.com/google/go-cmp/cmp"
 )
 
+const (
+	defaultTestTimeout      = 5 * time.Second
+	defaultTestShortTimeout = 10 * time.Millisecond // For events expected to *not* happen.
+)
+
 // TestCallbackSerializer_Schedule_FIFO verifies that callbacks are executed in
 // the same order in which they were scheduled.
 func (s) TestCallbackSerializer_Schedule_FIFO(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
-	cs := newCallbackSerializer(ctx)
+	cs := NewCallbackSerializer(ctx)
 	defer cancel()
 
 	// We have two channels, one to record the order of scheduling, and the
@@ -100,7 +105,7 @@ func (s) TestCallbackSerializer_Schedule_FIFO(t *testing.T) {
 // scheduled callbacks get executed.
 func (s) TestCallbackSerializer_Schedule_Concurrent(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
-	cs := newCallbackSerializer(ctx)
+	cs := NewCallbackSerializer(ctx)
 	defer cancel()
 
 	// Schedule callbacks concurrently by calling Schedule() from goroutines.
@@ -136,7 +141,7 @@ func (s) TestCallbackSerializer_Schedule_Concurrent(t *testing.T) {
 // are not executed once Close() returns.
 func (s) TestCallbackSerializer_Schedule_Close(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
-	cs := newCallbackSerializer(ctx)
+	cs := NewCallbackSerializer(ctx)
 
 	// Schedule a callback which blocks until the context passed to it is
 	// canceled. It also closes a couple of channels to signal that it started

xds/internal/xdsclient/authority.go

@@ -26,6 +26,7 @@ import (
 	"time"
 
 	"google.golang.org/grpc/internal/grpclog"
+	"google.golang.org/grpc/internal/grpcsync"
 	"google.golang.org/grpc/xds/internal/xdsclient/bootstrap"
 	"google.golang.org/grpc/xds/internal/xdsclient/load"
 	"google.golang.org/grpc/xds/internal/xdsclient/transport"
@@ -65,7 +66,7 @@ type authority struct {
 	serverCfg          *bootstrap.ServerConfig       // Server config for this authority
 	bootstrapCfg       *bootstrap.Config             // Full bootstrap configuration
 	refCount           int                           // Reference count of watches referring to this authority
-	serializer         *callbackSerializer           // Callback serializer for invoking watch callbacks
+	serializer         *grpcsync.CallbackSerializer  // Callback serializer for invoking watch callbacks
 	resourceTypeGetter func(string) xdsresource.Type // ResourceType registry lookup
 	transport          *transport.Transport          // Underlying xDS transport to the management server
 	watchExpiryTimeout time.Duration                 // Resource watch expiry timeout
@@ -99,7 +100,7 @@ type authorityArgs struct {
 	// the second case.
 	serverCfg          *bootstrap.ServerConfig
 	bootstrapCfg       *bootstrap.Config
-	serializer         *callbackSerializer
+	serializer         *grpcsync.CallbackSerializer
 	resourceTypeGetter func(string) xdsresource.Type
 	watchExpiryTimeout time.Duration
 	logger             *grpclog.PrefixLogger

xds/internal/xdsclient/authority_test.go

@@ -25,6 +25,7 @@ import (
 	"time"
 
 	"github.com/google/uuid"
+	"google.golang.org/grpc/internal/grpcsync"
 	"google.golang.org/grpc/internal/testutils/xds/e2e"
 	"google.golang.org/grpc/xds/internal"
 	"google.golang.org/grpc/xds/internal/testutils"
@@ -69,7 +70,7 @@ func setupTest(ctx context.Context, t *testing.T, opts e2e.ManagementServerOptio
 		bootstrapCfg: &bootstrap.Config{
 			NodeProto: &v3corepb.Node{Id: nodeID},
 		},
-		serializer:         newCallbackSerializer(ctx),
+		serializer:         grpcsync.NewCallbackSerializer(ctx),
 		resourceTypeGetter: rtRegistry.get,
 		watchExpiryTimeout: watchExpiryTimeout,
 		logger:             nil,

xds/internal/xdsclient/client_new.go

@@ -69,7 +69,7 @@ func newWithConfig(config *bootstrap.Config, watchExpiryTimeout time.Duration, i
 		done:               grpcsync.NewEvent(),
 		config:             config,
 		watchExpiryTimeout: watchExpiryTimeout,
-		serializer:         newCallbackSerializer(ctx),
+		serializer:         grpcsync.NewCallbackSerializer(ctx),
 		serializerClose:    cancel,
 		resourceTypes:      newResourceTypeRegistry(),
 		authorities:        make(map[string]*authority),

xds/internal/xdsclient/clientimpl.go

@@ -37,7 +37,7 @@ type clientImpl struct {
 	config             *bootstrap.Config
 	logger             *grpclog.PrefixLogger
 	watchExpiryTimeout time.Duration
-	serializer         *callbackSerializer
+	serializer         *grpcsync.CallbackSerializer
 	serializerClose    func()
 	resourceTypes      *resourceTypeRegistry