1 /* 2 * Copyright 2016 The gRPC Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package io.grpc.internal; 18 19 import static com.google.common.base.Preconditions.checkNotNull; 20 21 import io.grpc.ConnectivityState; 22 import io.grpc.ManagedChannel; 23 import java.util.ArrayList; 24 import java.util.concurrent.Executor; 25 import javax.annotation.Nonnull; 26 import javax.annotation.concurrent.NotThreadSafe; 27 28 /** 29 * Manages connectivity states of the channel. Used for {@link ManagedChannel#getState} to read the 30 * current state of the channel, for {@link ManagedChannel#notifyWhenStateChanged} to add 31 * listeners to state change events, and for {@link io.grpc.LoadBalancer.Helper#updateBalancingState 32 * LoadBalancer.Helper#updateBalancingState} to update the state and run the {@link #gotoState}s. 33 */ 34 @NotThreadSafe 35 final class ConnectivityStateManager { 36 private ArrayList<Listener> listeners = new ArrayList<>(); 37 38 private volatile ConnectivityState state = ConnectivityState.IDLE; 39 40 /** 41 * Adds a listener for state change event. 42 * 43 * <p>The {@code executor} must be one that can run RPC call listeners. 44 */ notifyWhenStateChanged(Runnable callback, Executor executor, ConnectivityState source)45 void notifyWhenStateChanged(Runnable callback, Executor executor, ConnectivityState source) { 46 checkNotNull(callback, "callback"); 47 checkNotNull(executor, "executor"); 48 checkNotNull(source, "source"); 49 50 Listener stateChangeListener = new Listener(callback, executor); 51 if (state != source) { 52 stateChangeListener.runInExecutor(); 53 } else { 54 listeners.add(stateChangeListener); 55 } 56 } 57 58 /** 59 * Connectivity state is changed to the specified value. Will trigger some notifications that have 60 * been registered earlier by {@link ManagedChannel#notifyWhenStateChanged}. 61 */ gotoState(@onnull ConnectivityState newState)62 void gotoState(@Nonnull ConnectivityState newState) { 63 checkNotNull(newState, "newState"); 64 if (state != newState && state != ConnectivityState.SHUTDOWN) { 65 state = newState; 66 if (listeners.isEmpty()) { 67 return; 68 } 69 // Swap out callback list before calling them, because a callback may register new callbacks, 70 // if run in direct executor, can cause ConcurrentModificationException. 71 ArrayList<Listener> savedListeners = listeners; 72 listeners = new ArrayList<>(); 73 for (Listener listener : savedListeners) { 74 listener.runInExecutor(); 75 } 76 } 77 } 78 79 /** 80 * Gets the current connectivity state of the channel. This method is threadsafe. 81 */ getState()82 ConnectivityState getState() { 83 ConnectivityState stateCopy = state; 84 if (stateCopy == null) { 85 throw new UnsupportedOperationException("Channel state API is not implemented"); 86 } 87 return stateCopy; 88 } 89 90 private static final class Listener { 91 final Runnable callback; 92 final Executor executor; 93 Listener(Runnable callback, Executor executor)94 Listener(Runnable callback, Executor executor) { 95 this.callback = callback; 96 this.executor = executor; 97 } 98 runInExecutor()99 void runInExecutor() { 100 executor.execute(callback); 101 } 102 } 103 } 104