001    /*
002     * Copyright (C) 2006 The Guava Authors
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package com.google.common.util.concurrent;
018    
019    import com.google.common.annotations.Beta;
020    
021    import java.util.concurrent.Callable;
022    import java.util.concurrent.TimeUnit;
023    
024    /**
025     * Produces proxies that impose a time limit on method
026     * calls to the proxied object.  For example, to return the value of
027     * {@code target.someMethod()}, but substitute {@code DEFAULT_VALUE} if this
028     * method call takes over 50 ms, you can use this code:
029     * <pre>
030     *   TimeLimiter limiter = . . .;
031     *   TargetType proxy = limiter.newProxy(
032     *       target, TargetType.class, 50, TimeUnit.MILLISECONDS);
033     *   try {
034     *     return proxy.someMethod();
035     *   } catch (UncheckedTimeoutException e) {
036     *     return DEFAULT_VALUE;
037     *   }
038     * </pre>
039     * Please see {@code SimpleTimeLimiterTest} for more usage examples.
040     *
041     * @author Kevin Bourrillion
042     * @since 1
043     */
044    @Beta
045    public interface TimeLimiter {
046    
047      /**
048       * Returns an instance of {@code interfaceType} that delegates all method
049       * calls to the {@code target} object, enforcing the specified time limit on
050       * each call.  This time-limited delegation is also performed for calls to
051       * {@link Object#equals}, {@link Object#hashCode}, and
052       * {@link Object#toString}.
053       * <p>
054       * If the target method call finishes before the limit is reached, the return
055       * value or exception is propagated to the caller exactly as-is. If, on the
056       * other hand, the time limit is reached, the proxy will attempt to abort the
057       * call to the target, and will throw an {@link UncheckedTimeoutException} to
058       * the caller.
059       * <p>
060       * It is important to note that the primary purpose of the proxy object is to
061       * return control to the caller when the timeout elapses; aborting the target
062       * method call is of secondary concern.  The particular nature and strength
063       * of the guarantees made by the proxy is implementation-dependent.  However,
064       * it is important that each of the methods on the target object behaves
065       * appropriately when its thread is interrupted.
066       *
067       * @param target the object to proxy
068       * @param interfaceType the interface you wish the returned proxy to
069       *     implement
070       * @param timeoutDuration with timeoutUnit, the maximum length of time that
071       *     callers are willing to wait on each method call to the proxy
072       * @param timeoutUnit with timeoutDuration, the maximum length of time that
073       *     callers are willing to wait on each method call to the proxy
074       * @return a time-limiting proxy
075       * @throws IllegalArgumentException if {@code interfaceType} is a regular
076       *     class, enum, or annotation type, rather than an interface
077       */
078      <T> T newProxy(T target, Class<T> interfaceType,
079         long timeoutDuration, TimeUnit timeoutUnit);
080    
081      /**
082       * Invokes a specified Callable, timing out after the specified time limit.
083       * If the target method call finished before the limit is reached, the return
084       * value or exception is propagated to the caller exactly as-is.  If, on the
085       * other hand, the time limit is reached, we attempt to abort the call to the
086       * target, and throw an {@link UncheckedTimeoutException} to the caller.
087       * <p>
088       * <b>Warning:</b> The future of this method is in doubt.  It may be nuked, or
089       * changed significantly.
090       *
091       * @param callable the Callable to execute
092       * @param timeoutDuration with timeoutUnit, the maximum length of time to wait
093       * @param timeoutUnit with timeoutDuration, the maximum length of time to wait
094       * @param interruptible whether to respond to thread interruption by aborting
095       *     the operation and throwing InterruptedException; if false, the
096       *     operation is allowed to complete or time out, and the current thread's
097       *     interrupt status is re-asserted.
098       * @return the result returned by the Callable
099       * @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    }