rls: control channel implementation (grpc#5046)

Author: easwars

balancer/rls/internal/balancer.go

@@ -19,183 +19,36 @@
 package rls
 
 import (
-	"sync"
-
-	"google.golang.org/grpc"
 	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/grpclog"
-	"google.golang.org/grpc/internal/grpcsync"
 )
 
 var (
 	_ balancer.Balancer = (*rlsBalancer)(nil)
 
-	// For overriding in tests.
-	newRLSClientFunc = newRLSClient
-	logger           = grpclog.Component("rls")
+	logger = grpclog.Component("rls")
 )
 
 // rlsBalancer implements the RLS LB policy.
-type rlsBalancer struct {
-	done *grpcsync.Event
-	cc   balancer.ClientConn
-	opts balancer.BuildOptions
-
-	// Mutex protects all the state maintained by the LB policy.
-	// TODO(easwars): Once we add the cache, we will also have another lock for
-	// the cache alone.
-	mu    sync.Mutex
-	lbCfg *lbConfig        // Most recently received service config.
-	rlsCC *grpc.ClientConn // ClientConn to the RLS server.
-	rlsC  *rlsClient       // RLS client wrapper.
-
-	ccUpdateCh chan *balancer.ClientConnState
-}
-
-// run is a long running goroutine which handles all the updates that the
-// balancer wishes to handle. The appropriate updateHandler will push the update
-// on to a channel that this goroutine will select on, thereby the handling of
-// the update will happen asynchronously.
-func (lb *rlsBalancer) run() {
-	for {
-		// TODO(easwars): Handle other updates like subConn state changes, RLS
-		// responses from the server etc.
-		select {
-		case u := <-lb.ccUpdateCh:
-			lb.handleClientConnUpdate(u)
-		case <-lb.done.Done():
-			return
-		}
-	}
-}
-
-// handleClientConnUpdate handles updates to the service config.
-// If the RLS server name or the RLS RPC timeout changes, it updates the control
-// channel accordingly.
-// TODO(easwars): Handle updates to other fields in the service config.
-func (lb *rlsBalancer) handleClientConnUpdate(ccs *balancer.ClientConnState) {
-	logger.Infof("rls: service config: %+v", ccs.BalancerConfig)
-	lb.mu.Lock()
-	defer lb.mu.Unlock()
-
-	if lb.done.HasFired() {
-		logger.Warning("rls: received service config after balancer close")
-		return
-	}
-
-	newCfg := ccs.BalancerConfig.(*lbConfig)
-	if lb.lbCfg.Equal(newCfg) {
-		logger.Info("rls: new service config matches existing config")
-		return
-	}
-
-	lb.updateControlChannel(newCfg)
-	lb.lbCfg = newCfg
-}
+type rlsBalancer struct{}
 
-// UpdateClientConnState pushes the received ClientConnState update on the
-// update channel which will be processed asynchronously by the run goroutine.
-// Implements balancer.Balancer interface.
 func (lb *rlsBalancer) UpdateClientConnState(ccs balancer.ClientConnState) error {
-	select {
-	case lb.ccUpdateCh <- &ccs:
-	case <-lb.done.Done():
-	}
+	logger.Fatal("rls: UpdateClientConnState is not yet unimplemented")
 	return nil
 }
 
-// ResolverErr implements balancer.Balancer interface.
 func (lb *rlsBalancer) ResolverError(error) {
-	// ResolverError is called by gRPC when the name resolver reports an error.
-	// TODO(easwars): How do we handle this?
 	logger.Fatal("rls: ResolverError is not yet unimplemented")
 }
 
-// UpdateSubConnState implements balancer.Balancer interface.
 func (lb *rlsBalancer) UpdateSubConnState(_ balancer.SubConn, _ balancer.SubConnState) {
 	logger.Fatal("rls: UpdateSubConnState is not yet implemented")
 }
 
-// Cleans up the resources allocated by the LB policy including the clientConn
-// to the RLS server.
-// Implements balancer.Balancer.
 func (lb *rlsBalancer) Close() {
-	lb.mu.Lock()
-	defer lb.mu.Unlock()
-
-	lb.done.Fire()
-	if lb.rlsCC != nil {
-		lb.rlsCC.Close()
-	}
+	logger.Fatal("rls: Close is not yet implemented")
 }
 
 func (lb *rlsBalancer) ExitIdle() {
-	// TODO: are we 100% sure this should be a nop?
-}
-
-// updateControlChannel updates the RLS client if required.
-// Caller must hold lb.mu.
-func (lb *rlsBalancer) updateControlChannel(newCfg *lbConfig) {
-	oldCfg := lb.lbCfg
-	if newCfg.lookupService == oldCfg.lookupService && newCfg.lookupServiceTimeout == oldCfg.lookupServiceTimeout {
-		return
-	}
-
-	// Use RPC timeout from new config, if different from existing one.
-	timeout := oldCfg.lookupServiceTimeout
-	if timeout != newCfg.lookupServiceTimeout {
-		timeout = newCfg.lookupServiceTimeout
-	}
-
-	if newCfg.lookupService == oldCfg.lookupService {
-		// This is the case where only the timeout has changed. We will continue
-		// to use the existing clientConn. but will create a new rlsClient with
-		// the new timeout.
-		lb.rlsC = newRLSClientFunc(lb.rlsCC, lb.opts.Target.Endpoint, timeout)
-		return
-	}
-
-	// This is the case where the RLS server name has changed. We need to create
-	// a new clientConn and close the old one.
-	var dopts []grpc.DialOption
-	if dialer := lb.opts.Dialer; dialer != nil {
-		dopts = append(dopts, grpc.WithContextDialer(dialer))
-	}
-	dopts = append(dopts, dialCreds(lb.opts))
-
-	cc, err := grpc.Dial(newCfg.lookupService, dopts...)
-	if err != nil {
-		logger.Errorf("rls: dialRLS(%s, %v): %v", newCfg.lookupService, lb.opts, err)
-		// An error from a non-blocking dial indicates something serious. We
-		// should continue to use the old control channel if one exists, and
-		// return so that the rest of the config updates can be processes.
-		return
-	}
-	if lb.rlsCC != nil {
-		lb.rlsCC.Close()
-	}
-	lb.rlsCC = cc
-	lb.rlsC = newRLSClientFunc(cc, lb.opts.Target.Endpoint, timeout)
-}
-
-func dialCreds(opts balancer.BuildOptions) grpc.DialOption {
-	// The control channel should use the same authority as that of the parent
-	// channel. This ensures that the identify of the RLS server and that of the
-	// backend is the same, so if the RLS config is injected by an attacker, it
-	// cannot cause leakage of private information contained in headers set by
-	// the application.
-	server := opts.Target.Authority
-	switch {
-	case opts.DialCreds != nil:
-		if err := opts.DialCreds.OverrideServerName(server); err != nil {
-			logger.Warningf("rls: OverrideServerName(%s) = (%v), using Insecure", server, err)
-			return grpc.WithInsecure()
-		}
-		return grpc.WithTransportCredentials(opts.DialCreds)
-	case opts.CredsBundle != nil:
-		return grpc.WithTransportCredentials(opts.CredsBundle.TransportCredentials())
-	default:
-		logger.Warning("rls: no credentials available, using Insecure")
-		return grpc.WithInsecure()
-	}
+	logger.Fatal("rls: ExitIdle is not yet implemented")
 }