dispatcher: migrate to SubConn.Shutdown and deprecate Addresses

See https://github.com/grpc/grpc-go/pull/6471/files and https://github.com/grpc/grpc-go/pull/6493/files

broker/protocol/dispatcher.go

@@ -141,6 +141,9 @@ func (d *dispatcher) updateSubConnState(sc balancer.SubConn, state balancer.SubC
 	})
 }
 
+// This method has been deprecated but may still be in use. See https://github.com/grpc/grpc-go/pull/6481
+// For updates to the logic, apply them to `updateSubConnState` instead which has been integrated with the new
+// StateListener interface
 func (d *dispatcher) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) {
   d.updateSubConnState(sc, state)
 }
@@ -301,10 +304,10 @@ func (d *dispatcher) sweep() {
 	d.mu.Unlock()
 
 	for _, sc := range toSweep {
-		// RemoveSubConn begins SubConn shutdown. We expect to see a
+		// SubConn.Shutdown begins a shutdown. We expect to see a
 		// HandleSubConnStateChange with connectivity.Shutdown, at which
 		// point we'll de-index it.
-		d.cc.RemoveSubConn(sc)
+		sc.Shutdown()
 	}
 }
 

broker/protocol/dispatcher_test.go

@@ -72,7 +72,7 @@ func (s *DispatcherSuite) TestDispatchCases(c *gc.C) {
 
 	// Case: Specific remote peer is dispatched to.
 	ctx = WithDispatchRoute(context.Background(),
-		buildRouteFixture(), ProcessSpec_ID{Zone: "remote", Suffix: "primary"})
+	buildRouteFixture(), ProcessSpec_ID{Zone: "remote", Suffix: "primary"})
 
 	result, err = disp.Pick(balancer.PickInfo{Ctx: ctx})
 	c.Check(err, gc.Equals, balancer.ErrNoSubConnAvailable)
@@ -130,7 +130,7 @@ func (s *DispatcherSuite) TestDispatchCases(c *gc.C) {
 	mockSubConn{Name: "remote.addr", disp: disp}.UpdateState(balancer.SubConnState{ConnectivityState: connectivity.TransientFailure})
 
 	ctx = WithDispatchRoute(context.Background(),
-		buildRouteFixture(), ProcessSpec_ID{Zone: "remote", Suffix: "primary"})
+	buildRouteFixture(), ProcessSpec_ID{Zone: "remote", Suffix: "primary"})
 
 	_, err = disp.Pick(balancer.PickInfo{Ctx: ctx})
 	c.Check(err, gc.Equals, balancer.ErrTransientFailure)
@@ -253,7 +253,7 @@ func (s mockSubConn) UpdateAddresses([]resolver.Address) { panic("deprecated") }
 func (s mockSubConn) UpdateState(state balancer.SubConnState)  { s.disp.updateSubConnState(s, state) }
 func (s mockSubConn) Connect()                           {}
 func (s mockSubConn) GetOrBuildProducer(balancer.ProducerBuilder) (balancer.Producer, func()) {
-  return nil, func() {}
+	return nil, func() {}
 }
 func (s mockSubConn) Shutdown()                          {
 	var c = s.disp.cc.(*mockClientConn)
@@ -266,12 +266,12 @@ func (c *mockClientConn) NewSubConn(a []resolver.Address, _ balancer.NewSubConnO
 	return sc, c.err
 }
 
-func (c *mockClientConn) UpdateAddresses(balancer.SubConn, []resolver.Address) {}
+func (c *mockClientConn) UpdateAddresses(balancer.SubConn, []resolver.Address) { panic("deprecated") }
 func (c *mockClientConn) UpdateState(balancer.State)                           {}
 func (c *mockClientConn) ResolveNow(resolver.ResolveNowOptions)                {}
 func (c *mockClientConn) Target() string                                       { return "default.addr" }
-func (c *mockClientConn) RemoveSubConn(balancer.SubConn) {
-	panic("deprecated")
+func (c *mockClientConn) RemoveSubConn(sc balancer.SubConn) {
+	sc.Shutdown()
 }
 
 type mockRouter struct{ invalidated string }