1 /* 2 * Copyright (C) 2006 Google Inc. 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 com.google.common.util.concurrent; 18 19 import static com.google.common.base.Preconditions.checkArgument; 20 import static com.google.common.base.Preconditions.checkNotNull; 21 import com.google.common.base.Throwables; 22 import com.google.common.collect.Sets; 23 24 import java.lang.reflect.InvocationHandler; 25 import java.lang.reflect.InvocationTargetException; 26 import java.lang.reflect.Method; 27 import java.lang.reflect.Proxy; 28 import java.util.Set; 29 import java.util.concurrent.Callable; 30 import java.util.concurrent.ExecutionException; 31 import java.util.concurrent.ExecutorService; 32 import java.util.concurrent.Executors; 33 import java.util.concurrent.Future; 34 import java.util.concurrent.TimeUnit; 35 import java.util.concurrent.TimeoutException; 36 37 /** 38 * A TimeLimiter that runs method calls in the background using an 39 * {@link ExecutorService}. If the time limit expires for a given method call, 40 * the thread running the call will be interrupted. 41 * 42 * @author Kevin Bourrillion 43 * @since 2009.09.15 <b>tentative</b> 44 */ 45 public class SimpleTimeLimiter implements TimeLimiter { 46 47 private final ExecutorService executor; 48 49 /** 50 * Constructs a TimeLimiter instance using the given executor service to 51 * execute proxied method calls. 52 * <p> 53 * <b>Warning:</b> using a bounded executor 54 * may be counterproductive! If the thread pool fills up, any time callers 55 * spend waiting for a thread may count toward their time limit, and in 56 * this case the call may even time out before the target method is ever 57 * invoked. 58 * 59 * @param executor the ExecutorService that will execute the method calls on 60 * the target objects; for example, a {@link 61 * java.util.concurrent.Executors#newCachedThreadPool()}. 62 */ 63 public SimpleTimeLimiter(ExecutorService executor) { 64 checkNotNull(executor); 65 this.executor = executor; 66 } 67 68 /** 69 * Constructs a TimeLimiter instance using a {@link 70 * java.util.concurrent.Executors#newCachedThreadPool()} to execute proxied 71 * method calls. 72 * 73 * <p><b>Warning:</b> using a bounded executor may be counterproductive! If 74 * the thread pool fills up, any time callers spend waiting for a thread may 75 * count toward their time limit, and in this case the call may even time out 76 * before the target method is ever invoked. 77 */ 78 public SimpleTimeLimiter() { 79 this(Executors.newCachedThreadPool()); 80 } 81 82 public <T> T newProxy(final T target, Class<T> interfaceType, 83 final long timeoutDuration, final TimeUnit timeoutUnit) { 84 checkNotNull(target); 85 checkNotNull(interfaceType); 86 checkNotNull(timeoutUnit); 87 checkArgument(timeoutDuration > 0, "bad timeout: " + timeoutDuration); 88 checkArgument(interfaceType.isInterface(), 89 "interfaceType must be an interface type"); 90 91 final Set<Method> interruptibleMethods 92 = findInterruptibleMethods(interfaceType); 93 94 InvocationHandler handler = new InvocationHandler() { 95 public Object invoke(Object obj, final Method method, final Object[] args) 96 throws Throwable { 97 Callable<Object> callable = new Callable<Object>() { 98 public Object call() throws Exception { 99 try { 100 return method.invoke(target, args); 101 } catch (InvocationTargetException e) { 102 Throwables.throwCause(e, false); 103 throw new AssertionError("can't get here"); 104 } 105 } 106 }; 107 return callWithTimeout(callable, timeoutDuration, timeoutUnit, 108 interruptibleMethods.contains(method)); 109 } 110 }; 111 return newProxy(interfaceType, handler); 112 } 113 114 // TODO: should this actually throw only ExecutionException? 115 public <T> T callWithTimeout(Callable<T> callable, long timeoutDuration, 116 TimeUnit timeoutUnit, boolean amInterruptible) throws Exception { 117 checkNotNull(callable); 118 checkNotNull(timeoutUnit); 119 checkArgument(timeoutDuration > 0, "bad timeout: " + timeoutDuration); 120 Future<T> future = executor.submit(callable); 121 try { 122 if (amInterruptible) { 123 try { 124 return future.get(timeoutDuration, timeoutUnit); 125 } catch (InterruptedException e) { 126 future.cancel(true); 127 throw e; 128 } 129 } else { 130 Future<T> uninterruptible = Futures.makeUninterruptible(future); 131 return uninterruptible.get(timeoutDuration, timeoutUnit); 132 } 133 } catch (ExecutionException e) { 134 throw Throwables.throwCause(e, true); 135 } catch (TimeoutException e) { 136 future.cancel(true); 137 throw new UncheckedTimeoutException(e); 138 } 139 } 140 141 private static Set<Method> findInterruptibleMethods(Class<?> interfaceType) { 142 Set<Method> set = Sets.newHashSet(); 143 for (Method m : interfaceType.getMethods()) { 144 if (declaresInterruptedEx(m)) { 145 set.add(m); 146 } 147 } 148 return set; 149 } 150 151 private static boolean declaresInterruptedEx(Method method) { 152 for (Class<?> exType : method.getExceptionTypes()) { 153 // debate: == or isAssignableFrom? 154 if (exType == InterruptedException.class) { 155 return true; 156 } 157 } 158 return false; 159 } 160 161 // TODO: replace with version in common.reflect if and when that gets open-sourced 162 private static <T> T newProxy( 163 Class<T> interfaceType, InvocationHandler handler) { 164 Object object = Proxy.newProxyInstance( 165 interfaceType.getClassLoader(), new Class<?>[] { interfaceType }, handler); 166 return interfaceType.cast(object); 167 } 168 } 169
