src/com/google/common/util/concurrent/TimeLimiter.java

/*
 * Copyright (C) 2006 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.util.concurrent;

import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;

/**
 * Produces proxies that impose a time limit on method
 * calls to the proxied object.  For example, to return the value of
 * {@code target.someMethod()}, but substitute {@code DEFAULT_VALUE} if this
 * method call takes over 50 ms, you can use this code:
 * <pre>
 *   TimeLimiter limiter = . . .;
 *   TargetType proxy = limiter.newProxy(
 *       target, TargetType.class, 50, TimeUnit.MILLISECONDS);
 *   try {
 *     return proxy.someMethod();
 *   } catch (UncheckedTimeoutException e) {
 *     return DEFAULT_VALUE;
 *   }
 * </pre>
 * Please see {@code SimpleTimeLimiterTest} for more usage examples.
 *
 * @author Kevin Bourrillion
 * @since 2009.09.15 <b>tentative</b>
 */
public interface TimeLimiter {

  /**
   * Returns an instance of {@code interfaceType} that delegates all method
   * calls to the {@code target} object, enforcing the specified time limit on
   * each call.  This time-limited delegation is also performed for calls to
   * {@link Object#equals}, {@link Object#hashCode}, and
   * {@link Object#toString}.
   * <p>
   * If the target method call finishes before the limit is reached, the return
   * value or exception is propagated to the caller exactly as-is. If, on the
   * other hand, the time limit is reached, the proxy will attempt to abort the
   * call to the target, and will throw an {@link UncheckedTimeoutException} to
   * the caller.
   * <p>
   * It is important to note that the primary purpose of the proxy object is to
   * return control to the caller when the timeout elapses; aborting the target
   * method call is of secondary concern.  The particular nature and strength
   * of the guarantees made by the proxy is implementation-dependent.  However,
   * it is important that each of the methods on the target object behaves
   * appropriately when its thread is interrupted.
   *
   * @param target the object to proxy
   * @param interfaceType the interface you wish the returned proxy to
   *     implement
   * @param timeoutDuration with timeoutUnit, the maximum length of time that
   *     callers are willing to wait on each method call to the proxy
   * @param timeoutUnit with timeoutDuration, the maximum length of time that
   *     callers are willing to wait on each method call to the proxy
   * @return a time-limiting proxy
   * @throws IllegalArgumentException if {@code interfaceType} is a regular
   *     class, enum, or annotation type, rather than an interface
   */
  <T> T newProxy(T target, Class<T> interfaceType,
     long timeoutDuration, TimeUnit timeoutUnit);

  /**
   * Invokes a specified Callable, timing out after the specified time limit.
   * If the target method call finished before the limit is reached, the return
   * value or exception is propagated to the caller exactly as-is.  If, on the
   * other hand, the time limit is reached, we attempt to abort the call to the
   * target, and throw an {@link UncheckedTimeoutException} to the caller.
   * <p>
   * <b>Warning:</b> The future of this method is in doubt.  It may be nuked, or
   * changed significantly.
   *
   * @param callable the Callable to execute
   * @param timeoutDuration with timeoutUnit, the maximum length of time to wait
   * @param timeoutUnit with timeoutDuration, the maximum length of time to wait
   * @param interruptible whether to respond to thread interruption by aborting
   *     the operation and throwing InterruptedException; if false, the
   *     operation is allowed to complete or time out, and the current thread's
   *     interrupt status is re-asserted.
   * @return the result returned by the Callable
   * @throws InterruptedException if {@code interruptible} is true and our
   *     thread is interrupted during execution
   * @throws UncheckedTimeoutException if the time limit is reached
   * @throws Exception
   */
  <T> T callWithTimeout(Callable<T> callable, long timeoutDuration,
      TimeUnit timeoutUnit, boolean interruptible) throws Exception;
}