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server.go
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server.go
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/*
*
* Copyright 2020 gRPC 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 xds
import (
"context"
"errors"
"fmt"
"net"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc/grpclog"
"google.golang.org/grpc/internal"
"google.golang.org/grpc/internal/buffer"
"google.golang.org/grpc/internal/envconfig"
internalgrpclog "google.golang.org/grpc/internal/grpclog"
"google.golang.org/grpc/internal/grpcsync"
iresolver "google.golang.org/grpc/internal/resolver"
"google.golang.org/grpc/internal/transport"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/status"
"google.golang.org/grpc/xds/internal/server"
"google.golang.org/grpc/xds/internal/xdsclient"
"google.golang.org/grpc/xds/internal/xdsclient/bootstrap"
"google.golang.org/grpc/xds/internal/xdsclient/xdsresource"
)
const serverPrefix = "[xds-server %p] "
var (
// These new functions will be overridden in unit tests.
newXDSClient = func() (xdsclient.XDSClient, func(), error) {
return xdsclient.New()
}
newGRPCServer = func(opts ...grpc.ServerOption) grpcServer {
return grpc.NewServer(opts...)
}
grpcGetServerCreds = internal.GetServerCredentials.(func(*grpc.Server) credentials.TransportCredentials)
drainServerTransports = internal.DrainServerTransports.(func(*grpc.Server, string))
logger = grpclog.Component("xds")
)
// grpcServer contains methods from grpc.Server which are used by the
// GRPCServer type here. This is useful for overriding in unit tests.
type grpcServer interface {
RegisterService(*grpc.ServiceDesc, any)
Serve(net.Listener) error
Stop()
GracefulStop()
GetServiceInfo() map[string]grpc.ServiceInfo
}
// GRPCServer wraps a gRPC server and provides server-side xDS functionality, by
// communication with a management server using xDS APIs. It implements the
// grpc.ServiceRegistrar interface and can be passed to service registration
// functions in IDL generated code.
type GRPCServer struct {
gs grpcServer
quit *grpcsync.Event
logger *internalgrpclog.PrefixLogger
xdsCredsInUse bool
opts *serverOptions
xdsC xdsclient.XDSClient
xdsClientClose func()
}
// NewGRPCServer creates an xDS-enabled gRPC server using the passed in opts.
// The underlying gRPC server has no service registered and has not started to
// accept requests yet.
func NewGRPCServer(opts ...grpc.ServerOption) (*GRPCServer, error) {
newOpts := []grpc.ServerOption{
grpc.ChainUnaryInterceptor(xdsUnaryInterceptor),
grpc.ChainStreamInterceptor(xdsStreamInterceptor),
}
newOpts = append(newOpts, opts...)
s := &GRPCServer{
gs: newGRPCServer(newOpts...),
quit: grpcsync.NewEvent(),
}
s.handleServerOptions(opts)
// We type assert our underlying gRPC server to the real grpc.Server here
// before trying to retrieve the configured credentials. This approach
// avoids performing the same type assertion in the grpc package which
// provides the implementation for internal.GetServerCredentials, and allows
// us to use a fake gRPC server in tests.
if gs, ok := s.gs.(*grpc.Server); ok {
creds := grpcGetServerCreds(gs)
if xc, ok := creds.(interface{ UsesXDS() bool }); ok && xc.UsesXDS() {
s.xdsCredsInUse = true
}
}
// Initializing the xDS client upfront (instead of at serving time)
// simplifies the code by eliminating the need for a mutex to protect the
// xdsC and xdsClientClose fields.
newXDSClient := newXDSClient
if s.opts.bootstrapContentsForTesting != nil {
// Bootstrap file contents may be specified as a server option for tests.
newXDSClient = func() (xdsclient.XDSClient, func(), error) {
return xdsclient.NewWithBootstrapContentsForTesting(s.opts.bootstrapContentsForTesting)
}
}
xdsClient, xdsClientClose, err := newXDSClient()
if err != nil {
return nil, fmt.Errorf("xDS client creation failed: %v", err)
}
// Validate the bootstrap configuration for server specific fields.
// Listener resource name template is mandatory on the server side.
cfg := xdsClient.BootstrapConfig()
if cfg.ServerListenerResourceNameTemplate == "" {
xdsClientClose()
return nil, errors.New("missing server_listener_resource_name_template in the bootstrap configuration")
}
// If xds credentials were specified by the user, but bootstrap configs do
// not contain any certificate provider configuration, it is better to fail
// right now rather than failing when attempting to create certificate
// providers after receiving an LDS response with security configuration.
if s.xdsCredsInUse {
if len(cfg.CertProviderConfigs) == 0 {
xdsClientClose()
return nil, fmt.Errorf("xds credentials are passed to the user, but certificate_providers config is missing in the bootstrap configuration")
}
}
s.xdsC = xdsClient
s.xdsClientClose = xdsClientClose
s.logger = internalgrpclog.NewPrefixLogger(logger, fmt.Sprintf(serverPrefix, s))
s.logger.Infof("Created xds.GRPCServer")
s.logger.Infof("xDS credentials in use: %v", s.xdsCredsInUse)
return s, nil
}
// handleServerOptions iterates through the list of server options passed in by
// the user, and handles the xDS server specific options.
func (s *GRPCServer) handleServerOptions(opts []grpc.ServerOption) {
so := s.defaultServerOptions()
for _, opt := range opts {
if o, ok := opt.(*serverOption); ok {
o.apply(so)
}
}
s.opts = so
}
func (s *GRPCServer) defaultServerOptions() *serverOptions {
return &serverOptions{
// A default serving mode change callback which simply logs at the
// default-visible log level. This will be used if the application does not
// register a mode change callback.
//
// Note that this means that `s.opts.modeCallback` will never be nil and can
// safely be invoked directly from `handleServingModeChanges`.
modeCallback: s.loggingServerModeChangeCallback,
}
}
func (s *GRPCServer) loggingServerModeChangeCallback(addr net.Addr, args ServingModeChangeArgs) {
switch args.Mode {
case connectivity.ServingModeServing:
s.logger.Errorf("Listener %q entering mode: %q", addr.String(), args.Mode)
case connectivity.ServingModeNotServing:
s.logger.Errorf("Listener %q entering mode: %q due to error: %v", addr.String(), args.Mode, args.Err)
}
}
// RegisterService registers a service and its implementation to the underlying
// gRPC server. It is called from the IDL generated code. This must be called
// before invoking Serve.
func (s *GRPCServer) RegisterService(sd *grpc.ServiceDesc, ss any) {
s.gs.RegisterService(sd, ss)
}
// GetServiceInfo returns a map from service names to ServiceInfo.
// Service names include the package names, in the form of <package>.<service>.
func (s *GRPCServer) GetServiceInfo() map[string]grpc.ServiceInfo {
return s.gs.GetServiceInfo()
}
// Serve gets the underlying gRPC server to accept incoming connections on the
// listener lis, which is expected to be listening on a TCP port.
//
// A connection to the management server, to receive xDS configuration, is
// initiated here.
//
// Serve will return a non-nil error unless Stop or GracefulStop is called.
func (s *GRPCServer) Serve(lis net.Listener) error {
s.logger.Infof("Serve() passed a net.Listener on %s", lis.Addr().String())
if _, ok := lis.Addr().(*net.TCPAddr); !ok {
return fmt.Errorf("xds: GRPCServer expects listener to return a net.TCPAddr. Got %T", lis.Addr())
}
if s.quit.HasFired() {
return grpc.ErrServerStopped
}
// The server listener resource name template from the bootstrap
// configuration contains a template for the name of the Listener resource
// to subscribe to for a gRPC server. If the token `%s` is present in the
// string, it will be replaced with the server's listening "IP:port" (e.g.,
// "0.0.0.0:8080", "[::]:8080").
cfg := s.xdsC.BootstrapConfig()
name := bootstrap.PopulateResourceTemplate(cfg.ServerListenerResourceNameTemplate, lis.Addr().String())
modeUpdateCh := buffer.NewUnbounded()
go func() {
s.handleServingModeChanges(modeUpdateCh)
}()
// Create a listenerWrapper which handles all functionality required by
// this particular instance of Serve().
lw, goodUpdateCh := server.NewListenerWrapper(server.ListenerWrapperParams{
Listener: lis,
ListenerResourceName: name,
XDSCredsInUse: s.xdsCredsInUse,
XDSClient: s.xdsC,
ModeCallback: func(addr net.Addr, mode connectivity.ServingMode, err error) {
modeUpdateCh.Put(&modeChangeArgs{
addr: addr,
mode: mode,
err: err,
})
},
DrainCallback: func(addr net.Addr) {
if gs, ok := s.gs.(*grpc.Server); ok {
drainServerTransports(gs, addr.String())
}
},
})
// Block until a good LDS response is received or the server is stopped.
select {
case <-s.quit.Done():
// Since the listener has not yet been handed over to gs.Serve(), we
// need to explicitly close the listener. Cancellation of the xDS watch
// is handled by the listenerWrapper.
lw.Close()
modeUpdateCh.Close()
return nil
case <-goodUpdateCh:
}
return s.gs.Serve(lw)
}
// modeChangeArgs wraps argument required for invoking mode change callback.
type modeChangeArgs struct {
addr net.Addr
mode connectivity.ServingMode
err error
}
// handleServingModeChanges runs as a separate goroutine, spawned from Serve().
// It reads a channel on to which mode change arguments are pushed, and in turn
// invokes the user registered callback. It also calls an internal method on the
// underlying grpc.Server to gracefully close existing connections, if the
// listener moved to a "not-serving" mode.
func (s *GRPCServer) handleServingModeChanges(updateCh *buffer.Unbounded) {
for {
select {
case <-s.quit.Done():
return
case u, ok := <-updateCh.Get():
if !ok {
return
}
updateCh.Load()
args := u.(*modeChangeArgs)
if args.mode == connectivity.ServingModeNotServing {
// We type assert our underlying gRPC server to the real
// grpc.Server here before trying to initiate the drain
// operation. This approach avoids performing the same type
// assertion in the grpc package which provides the
// implementation for internal.GetServerCredentials, and allows
// us to use a fake gRPC server in tests.
if gs, ok := s.gs.(*grpc.Server); ok {
drainServerTransports(gs, args.addr.String())
}
}
// The XdsServer API will allow applications to register a "serving state"
// callback to be invoked when the server begins serving and when the
// server encounters errors that force it to be "not serving". If "not
// serving", the callback must be provided error information, for
// debugging use by developers - A36.
s.opts.modeCallback(args.addr, ServingModeChangeArgs{
Mode: args.mode,
Err: args.err,
})
}
}
}
// Stop stops the underlying gRPC server. It immediately closes all open
// connections. It cancels all active RPCs on the server side and the
// corresponding pending RPCs on the client side will get notified by connection
// errors.
func (s *GRPCServer) Stop() {
s.quit.Fire()
s.gs.Stop()
if s.xdsC != nil {
s.xdsClientClose()
}
}
// GracefulStop stops the underlying gRPC server gracefully. It stops the server
// from accepting new connections and RPCs and blocks until all the pending RPCs
// are finished.
func (s *GRPCServer) GracefulStop() {
s.quit.Fire()
s.gs.GracefulStop()
if s.xdsC != nil {
s.xdsClientClose()
}
}
// routeAndProcess routes the incoming RPC to a configured route in the route
// table and also processes the RPC by running the incoming RPC through any HTTP
// Filters configured.
func routeAndProcess(ctx context.Context) error {
conn := transport.GetConnection(ctx)
cw, ok := conn.(interface {
VirtualHosts() []xdsresource.VirtualHostWithInterceptors
})
if !ok {
return errors.New("missing virtual hosts in incoming context")
}
mn, ok := grpc.Method(ctx)
if !ok {
return errors.New("missing method name in incoming context")
}
md, ok := metadata.FromIncomingContext(ctx)
if !ok {
return errors.New("missing metadata in incoming context")
}
// A41 added logic to the core grpc implementation to guarantee that once
// the RPC gets to this point, there will be a single, unambiguous authority
// present in the header map.
authority := md.Get(":authority")
vh := xdsresource.FindBestMatchingVirtualHostServer(authority[0], cw.VirtualHosts())
if vh == nil {
return status.Error(codes.Unavailable, "the incoming RPC did not match a configured Virtual Host")
}
var rwi *xdsresource.RouteWithInterceptors
rpcInfo := iresolver.RPCInfo{
Context: ctx,
Method: mn,
}
for _, r := range vh.Routes {
if r.M.Match(rpcInfo) {
// "NonForwardingAction is expected for all Routes used on server-side; a route with an inappropriate action causes
// RPCs matching that route to fail with UNAVAILABLE." - A36
if r.ActionType != xdsresource.RouteActionNonForwardingAction {
return status.Error(codes.Unavailable, "the incoming RPC matched to a route that was not of action type non forwarding")
}
rwi = &r
break
}
}
if rwi == nil {
return status.Error(codes.Unavailable, "the incoming RPC did not match a configured Route")
}
for _, interceptor := range rwi.Interceptors {
if err := interceptor.AllowRPC(ctx); err != nil {
return status.Errorf(codes.PermissionDenied, "Incoming RPC is not allowed: %v", err)
}
}
return nil
}
// xdsUnaryInterceptor is the unary interceptor added to the gRPC server to
// perform any xDS specific functionality on unary RPCs.
func xdsUnaryInterceptor(ctx context.Context, req any, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp any, err error) {
if envconfig.XDSRBAC {
if err := routeAndProcess(ctx); err != nil {
return nil, err
}
}
return handler(ctx, req)
}
// xdsStreamInterceptor is the stream interceptor added to the gRPC server to
// perform any xDS specific functionality on streaming RPCs.
func xdsStreamInterceptor(srv any, ss grpc.ServerStream, _ *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
if envconfig.XDSRBAC {
if err := routeAndProcess(ss.Context()); err != nil {
return err
}
}
return handler(srv, ss)
}