1/*
2 * Copyright (C) 2006 The Guava 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
17package com.google.common.util.concurrent;
18
19import com.google.common.annotations.Beta;
20
21import java.util.concurrent.Callable;
22import java.util.concurrent.TimeUnit;
23
24/**
25 * Produces proxies that impose a time limit on method
26 * calls to the proxied object.  For example, to return the value of
27 * {@code target.someMethod()}, but substitute {@code DEFAULT_VALUE} if this
28 * method call takes over 50 ms, you can use this code:
29 * <pre>
30 *   TimeLimiter limiter = . . .;
31 *   TargetType proxy = limiter.newProxy(
32 *       target, TargetType.class, 50, TimeUnit.MILLISECONDS);
33 *   try {
34 *     return proxy.someMethod();
35 *   } catch (UncheckedTimeoutException e) {
36 *     return DEFAULT_VALUE;
37 *   }
38 * </pre>
39 * <p>Please see {@code SimpleTimeLimiterTest} for more usage examples.
40 *
41 * @author Kevin Bourrillion
42 * @since 1.0
43 */
44@Beta
45public interface TimeLimiter {
46
47  /**
48   * Returns an instance of {@code interfaceType} that delegates all method
49   * calls to the {@code target} object, enforcing the specified time limit on
50   * each call.  This time-limited delegation is also performed for calls to
51   * {@link Object#equals}, {@link Object#hashCode}, and
52   * {@link Object#toString}.
53   * <p>
54   * If the target method call finishes before the limit is reached, the return
55   * value or exception is propagated to the caller exactly as-is. If, on the
56   * other hand, the time limit is reached, the proxy will attempt to abort the
57   * call to the target, and will throw an {@link UncheckedTimeoutException} to
58   * the caller.
59   * <p>
60   * It is important to note that the primary purpose of the proxy object is to
61   * return control to the caller when the timeout elapses; aborting the target
62   * method call is of secondary concern.  The particular nature and strength
63   * of the guarantees made by the proxy is implementation-dependent.  However,
64   * it is important that each of the methods on the target object behaves
65   * appropriately when its thread is interrupted.
66   *
67   * @param target the object to proxy
68   * @param interfaceType the interface you wish the returned proxy to
69   *     implement
70   * @param timeoutDuration with timeoutUnit, the maximum length of time that
71   *     callers are willing to wait on each method call to the proxy
72   * @param timeoutUnit with timeoutDuration, the maximum length of time that
73   *     callers are willing to wait on each method call to the proxy
74   * @return a time-limiting proxy
75   * @throws IllegalArgumentException if {@code interfaceType} is a regular
76   *     class, enum, or annotation type, rather than an interface
77   */
78  <T> T newProxy(T target, Class<T> interfaceType,
79      long timeoutDuration, TimeUnit timeoutUnit);
80
81  /**
82   * Invokes a specified Callable, timing out after the specified time limit.
83   * If the target method call finished before the limit is reached, the return
84   * value or exception is propagated to the caller exactly as-is.  If, on the
85   * other hand, the time limit is reached, we attempt to abort the call to the
86   * target, and throw an {@link UncheckedTimeoutException} to the caller.
87   * <p>
88   * <b>Warning:</b> The future of this method is in doubt.  It may be nuked, or
89   * changed significantly.
90   *
91   * @param callable the Callable to execute
92   * @param timeoutDuration with timeoutUnit, the maximum length of time to wait
93   * @param timeoutUnit with timeoutDuration, the maximum length of time to wait
94   * @param interruptible whether to respond to thread interruption by aborting
95   *     the operation and throwing InterruptedException; if false, the
96   *     operation is allowed to complete or time out, and the current thread's
97   *     interrupt status is re-asserted.
98   * @return the result returned by the Callable
99   * @throws InterruptedException if {@code interruptible} is true and our
100   *     thread is interrupted during execution
101   * @throws UncheckedTimeoutException if the time limit is reached
102   * @throws Exception
103   */
104  <T> T callWithTimeout(Callable<T> callable, long timeoutDuration,
105      TimeUnit timeoutUnit, boolean interruptible) throws Exception;
106}
107