+++ /dev/null
-/*-
- * ============LICENSE_START=======================================================
- * ONAP : APPC
- * ================================================================================
- * Copyright (C) 2017-2018 AT&T Intellectual Property. All rights reserved.
- * ================================================================================
- * Copyright (C) 2017 Amdocs
- * =============================================================================
- * 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.
- *
- * ============LICENSE_END=========================================================
- */
-
-package org.onap.appc.concurrent;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
-import java.util.concurrent.TimeoutException;
-
-import org.onap.appc.util.StringHelper;
-
-/**
- * This class is used to synchronize signaling of status between threads.
- * <p>
- * In complex multi-threaded applications it is often necessary to synchronize operations between threads. This is
- * especially true in complex algorithms where processing dependencies exist between different threads and the
- * synchronization of the operations of those threads is required. This class is a framework to enable multi-thread
- * signaling and wait/post logic that makes the thread synchronization easier.
- * </p>
- * <p>
- * Basically, in thread synchronization, one thread is the "waiter" and one or more other threads are the "notifiers".
- * The notifiers send signals to the waiter to inform that thread that certain conditions are true, processing has been
- * completed, or to inform the waiter of the state of the other thread(s). In the basic java framework, the waiter and
- * notifier are simply using the wait/notify mechanism provided, which does not allow for different conditions, state,
- * or "signals" to exist. The wait/notify mechanism, in combination with the object mutex, provides basic blocking and
- * releasing of a thread's dispatching state.
- * </p>
- * <p>
- * This class builds upon the java wait/notify mechanism and allows for "signals" to be defined. These signals are
- * simply string constants that mean something to the waiter and notifier threads. Any number of signals may be defined,
- * and it is possible to wait for more than one signal to be received, wait for any one of a set to be received, or to
- * test if a signal has been received without blocking.
- * </p>
- * <p>
- * Some operations are blocking operations. These stop the execution of the calling thread until the specified condition
- * is true. These blocking methods are all named "wait...", such as {@link #waitFor(String...)} and
- * {@link #waitForAny(String...)}. The thread making the call to these blocking methods MUST be the waiter thread (the
- * thread registered with the signal object).
- * </p>
- * <p>
- * Some operations are non-blocking. These operations allow for the testing or setting of signal conditions and do not
- * block the caller. When calling these methods ({@link #isSignaled(String)}, {@link #signal(String)}, and
- * {@link #setTimeout(long)} the waiter thread mutex will be held and may block the waiter thread for the duration of
- * the method call.
- * </p>
- */
-public class Signal {
-
- /**
- * The thread must be the thread of the waiter that is waiting for the signals to be received. It is the recipient
- * of the signaled condition. This allows any number of other threads to send signals to the recipient and have the
- * recipient synchronize its operation with the receipt of the appropriate signal(s).
- */
- private Thread thread;
-
- /**
- * The amount of time to wait for a signal to be receieved. Set to zero to wait forever.
- */
- private long timeout = 0L;
-
- /**
- * The collection of all received signals. Note, this need not be a synchronized collection because it will always
- * be accessed while holding the mutex of the thread, therefore it is implicitly synchronized.
- */
- private List<String> receivedSignals;
-
- /**
- * A signal object must access a thread that is waiting for the receipt of the signal(s).
- */
- public Signal(Thread thread) {
- this.thread = thread;
- receivedSignals = new ArrayList<String>();
- }
-
- /**
- * Checks the waiter to see if it has been signaled
- *
- * @param signal
- * The signal to check for
- * @return True if the signal has been received, false otherwise
- */
- public boolean isSignaled(String signal) {
- synchronized (thread) {
- return _signaled(signal);
- }
- }
-
- /**
- * Sends the indicated signal to the waiter.
- *
- * @param signal
- * The signal that is to be sent to the waiting thread and to notify it to process the signal.
- */
- public void signal(String signal) {
- synchronized (thread) {
- if (!_signaled(signal)) {
- receivedSignals.add(signal);
- }
- thread.notify();
- }
- }
-
- /**
- * Blocks the waiting thread until all of the indicated signals have been received, or the wait times out.
- *
- * @param signals
- * The signals to be received. The waiter is blocked forever or until all of the signals are received.
- * @throws TimeoutException
- * If the wait has timed out waiting for a response
- */
- public void waitFor(String... signals) throws TimeoutException {
- long limit = System.currentTimeMillis() + timeout;
- synchronized (thread) {
- while (true) {
- boolean complete = true;
- for (String signal : signals) {
- if (!_signaled(signal)) {
- complete = false;
- }
- }
-
- if (complete) {
- receivedSignals.removeAll(Arrays.asList(signals));
- return;
- }
-
- if (timeout > 0) {
- if (System.currentTimeMillis() > limit) {
- throw new TimeoutException(String.format("Signals %s not received in the allotted timeout.",
- StringHelper.asList(signals)));
- }
- }
-
- try {
- thread.wait(timeout);
- } catch (InterruptedException e) {
- /*
- * Interrupted exceptions are ignored
- */
- }
- }
- }
- }
-
- /**
- * This method blocks the waiter until at least one of the indicated signals have been received.
- *
- * @param signals
- * A list of signals, any one of which will satisfy the wait condition
- * @return The signal that satisfied the wait
- * @throws TimeoutException
- * If none of the signals have been received within the allotted time
- */
- public String waitForAny(String... signals) throws TimeoutException {
- long limit = System.currentTimeMillis() + timeout;
- synchronized (thread) {
- while (true) {
- for (String signal : signals) {
- if (!_signaled(signal)) {
- receivedSignals.remove(signal);
- return signal;
- }
- }
-
- if (timeout > 0) {
- if (System.currentTimeMillis() > limit) {
- throw new TimeoutException(
- String.format("One of signals \"%s\" not received in the allotted timeout.",
- StringHelper.asList(signals)));
- }
- }
-
- try {
- thread.wait(timeout);
- } catch (InterruptedException e) {
- /*
- * Interrupted exceptions are ignored
- */
- }
- }
- }
- }
-
- /**
- * This private method is used to handle the check for signaled status. Note that this method assumes the caller
- * holds the thread mutex.
- *
- * @param signals
- * The list of signals to check for
- * @return True if any one of the signals has been received.
- */
- private boolean _signaled(String... signals) {
- for (String signal : signals) {
- if (receivedSignals.contains(signal)) {
- return true;
- }
- }
- return false;
- }
-
- /**
- * Sets the timeout value for waiting for signals to be received
- *
- * @param timeout
- */
- public void setTimeout(long timeout) {
- this.timeout = timeout;
- }
-}
Code Review / appc.git / blobdiff