2 * ============LICENSE_START=======================================================
4 * ================================================================================
5 * Copyright (C) 2017 AT&T Intellectual Property. All rights reserved.
6 * Copyright (C) 2017 Amdocs
7 * ================================================================================
8 * Licensed under the Apache License, Version 2.0 (the "License");
9 * you may not use this file except in compliance with the License.
10 * You may obtain a copy of the License at
12 * http://www.apache.org/licenses/LICENSE-2.0
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 * ============LICENSE_END=========================================================
20 * ECOMP is a trademark and service mark of AT&T Intellectual Property.
23 package org.openecomp.appc.concurrent;
25 import java.util.ArrayList;
26 import java.util.Arrays;
27 import java.util.List;
28 import java.util.concurrent.TimeoutException;
30 import org.openecomp.appc.util.StringHelper;
33 * This class is used to synchronize signaling of status between threads.
35 * In complex multi-threaded applications it is often necessary to synchronize operations between threads. This is
36 * especially true in complex algorithms where processing dependencies exist between different threads and the
37 * synchronization of the operations of those threads is required. This class is a framework to enable multi-thread
38 * signaling and wait/post logic that makes the thread synchronization easier.
41 * Basically, in thread synchronization, one thread is the "waiter" and one or more other threads are the "notifiers".
42 * The notifiers send signals to the waiter to inform that thread that certain conditions are true, processing has been
43 * completed, or to inform the waiter of the state of the other thread(s). In the basic java framework, the waiter and
44 * notifier are simply using the wait/notify mechanism provided, which does not allow for different conditions, state,
45 * or "signals" to exist. The wait/notify mechanism, in combination with the object mutex, provides basic blocking and
46 * releasing of a thread's dispatching state.
49 * This class builds upon the java wait/notify mechanism and allows for "signals" to be defined. These signals are
50 * simply string constants that mean something to the waiter and notifier threads. Any number of signals may be defined,
51 * 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
52 * test if a signal has been received without blocking.
55 * Some operations are blocking operations. These stop the execution of the calling thread until the specified condition
56 * is true. These blocking methods are all named "wait...", such as {@link #waitFor(String...)} and
57 * {@link #waitForAny(String...)}. The thread making the call to these blocking methods MUST be the waiter thread (the
58 * thread registered with the signal object).
61 * Some operations are non-blocking. These operations allow for the testing or setting of signal conditions and do not
62 * block the caller. When calling these methods ({@link #isSignaled(String)}, {@link #signal(String)}, and
63 * {@link #setTimeout(long)} the waiter thread mutex will be held and may block the waiter thread for the duration of
70 * The thread must be the thread of the waiter that is waiting for the signals to be received. It is the recipient
71 * of the signaled condition. This allows any number of other threads to send signals to the recipient and have the
72 * recipient synchronize its operation with the receipt of the appropriate signal(s).
74 private Thread thread;
77 * The amount of time to wait for a signal to be receieved. Set to zero to wait forever.
79 private long timeout = 0L;
82 * The collection of all received signals. Note, this need not be a synchronized collection because it will always
83 * be accessed while holding the mutex of the thread, therefore it is implicitly synchronized.
85 private List<String> receivedSignals;
88 * A signal object must access a thread that is waiting for the receipt of the signal(s).
90 public Signal(Thread thread) {
92 receivedSignals = new ArrayList<String>();
96 * Checks the waiter to see if it has been signaled
99 * The signal to check for
100 * @return True if the signal has been received, false otherwise
102 public boolean isSignaled(String signal) {
103 synchronized (thread) {
104 return _signaled(signal);
109 * Sends the indicated signal to the waiter.
112 * The signal that is to be sent to the waiting thread and to notify it to process the signal.
114 public void signal(String signal) {
115 synchronized (thread) {
116 if (!_signaled(signal)) {
117 receivedSignals.add(signal);
124 * Blocks the waiting thread until all of the indicated signals have been received, or the wait times out.
127 * The signals to be received. The waiter is blocked forever or until all of the signals are received.
128 * @throws TimeoutException
129 * If the wait has timed out waiting for a response
131 public void waitFor(String... signals) throws TimeoutException {
132 long limit = System.currentTimeMillis() + timeout;
133 synchronized (thread) {
135 boolean complete = true;
136 for (String signal : signals) {
137 if (!_signaled(signal)) {
143 receivedSignals.removeAll(Arrays.asList(signals));
148 if (System.currentTimeMillis() > limit) {
149 throw new TimeoutException(String.format("Signals %s not received in the allotted timeout.",
150 StringHelper.asList(signals)));
155 thread.wait(timeout);
156 } catch (InterruptedException e) {
158 * Interrupted exceptions are ignored
166 * This method blocks the waiter until at least one of the indicated signals have been received.
169 * A list of signals, any one of which will satisfy the wait condition
170 * @return The signal that satisfied the wait
171 * @throws TimeoutException
172 * If none of the signals have been received within the allotted time
174 public String waitForAny(String... signals) throws TimeoutException {
175 long limit = System.currentTimeMillis() + timeout;
176 synchronized (thread) {
178 for (String signal : signals) {
179 if (!_signaled(signal)) {
180 receivedSignals.remove(signal);
186 if (System.currentTimeMillis() > limit) {
187 throw new TimeoutException(
188 String.format("One of signals \"%s\" not received in the allotted timeout.",
189 StringHelper.asList(signals)));
194 thread.wait(timeout);
195 } catch (InterruptedException e) {
197 * Interrupted exceptions are ignored
205 * This private method is used to handle the check for signaled status. Note that this method assumes the caller
206 * holds the thread mutex.
209 * The list of signals to check for
210 * @return True if any one of the signals has been received.
212 private boolean _signaled(String... signals) {
213 for (String signal : signals) {
214 if (receivedSignals.contains(signal)) {
222 * Sets the timeout value for waiting for signals to be received
226 public void setTimeout(long timeout) {
227 this.timeout = timeout;