2 * ============LICENSE_START=======================================================
4 * ================================================================================
5 * Copyright (C) 2017-2018 AT&T Intellectual Property. All rights reserved.
6 * ================================================================================
7 * Copyright (C) 2017 Amdocs
8 * =============================================================================
9 * Licensed under the Apache License, Version 2.0 (the "License");
10 * you may not use this file except in compliance with the License.
11 * You may obtain a copy of the License at
13 * http://www.apache.org/licenses/LICENSE-2.0
15 * Unless required by applicable law or agreed to in writing, software
16 * distributed under the License is distributed on an "AS IS" BASIS,
17 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
18 * See the License for the specific language governing permissions and
19 * limitations under the License.
21 * ============LICENSE_END=========================================================
24 package org.onap.appc.concurrent;
26 import java.util.ArrayList;
27 import java.util.Arrays;
28 import java.util.List;
29 import java.util.concurrent.TimeoutException;
31 import org.onap.appc.util.StringHelper;
34 * This class is used to synchronize signaling of status between threads.
36 * In complex multi-threaded applications it is often necessary to synchronize operations between threads. This is
37 * especially true in complex algorithms where processing dependencies exist between different threads and the
38 * synchronization of the operations of those threads is required. This class is a framework to enable multi-thread
39 * signaling and wait/post logic that makes the thread synchronization easier.
42 * Basically, in thread synchronization, one thread is the "waiter" and one or more other threads are the "notifiers".
43 * The notifiers send signals to the waiter to inform that thread that certain conditions are true, processing has been
44 * completed, or to inform the waiter of the state of the other thread(s). In the basic java framework, the waiter and
45 * notifier are simply using the wait/notify mechanism provided, which does not allow for different conditions, state,
46 * or "signals" to exist. The wait/notify mechanism, in combination with the object mutex, provides basic blocking and
47 * releasing of a thread's dispatching state.
50 * This class builds upon the java wait/notify mechanism and allows for "signals" to be defined. These signals are
51 * simply string constants that mean something to the waiter and notifier threads. Any number of signals may be defined,
52 * 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
53 * test if a signal has been received without blocking.
56 * Some operations are blocking operations. These stop the execution of the calling thread until the specified condition
57 * is true. These blocking methods are all named "wait...", such as {@link #waitFor(String...)} and
58 * {@link #waitForAny(String...)}. The thread making the call to these blocking methods MUST be the waiter thread (the
59 * thread registered with the signal object).
62 * Some operations are non-blocking. These operations allow for the testing or setting of signal conditions and do not
63 * block the caller. When calling these methods ({@link #isSignaled(String)}, {@link #signal(String)}, and
64 * {@link #setTimeout(long)} the waiter thread mutex will be held and may block the waiter thread for the duration of
71 * The thread must be the thread of the waiter that is waiting for the signals to be received. It is the recipient
72 * of the signaled condition. This allows any number of other threads to send signals to the recipient and have the
73 * recipient synchronize its operation with the receipt of the appropriate signal(s).
75 private Thread thread;
78 * The amount of time to wait for a signal to be receieved. Set to zero to wait forever.
80 private long timeout = 0L;
83 * The collection of all received signals. Note, this need not be a synchronized collection because it will always
84 * be accessed while holding the mutex of the thread, therefore it is implicitly synchronized.
86 private List<String> receivedSignals;
89 * A signal object must access a thread that is waiting for the receipt of the signal(s).
91 public Signal(Thread thread) {
93 receivedSignals = new ArrayList<String>();
97 * Checks the waiter to see if it has been signaled
100 * The signal to check for
101 * @return True if the signal has been received, false otherwise
103 public boolean isSignaled(String signal) {
104 synchronized (thread) {
105 return _signaled(signal);
110 * Sends the indicated signal to the waiter.
113 * The signal that is to be sent to the waiting thread and to notify it to process the signal.
115 public void signal(String signal) {
116 synchronized (thread) {
117 if (!_signaled(signal)) {
118 receivedSignals.add(signal);
125 * Blocks the waiting thread until all of the indicated signals have been received, or the wait times out.
128 * The signals to be received. The waiter is blocked forever or until all of the signals are received.
129 * @throws TimeoutException
130 * If the wait has timed out waiting for a response
132 public void waitFor(String... signals) throws TimeoutException {
133 long limit = System.currentTimeMillis() + timeout;
134 synchronized (thread) {
136 boolean complete = true;
137 for (String signal : signals) {
138 if (!_signaled(signal)) {
144 receivedSignals.removeAll(Arrays.asList(signals));
149 if (System.currentTimeMillis() > limit) {
150 throw new TimeoutException(String.format("Signals %s not received in the allotted timeout.",
151 StringHelper.asList(signals)));
156 thread.wait(timeout);
157 } catch (InterruptedException e) {
159 * Interrupted exceptions are ignored
167 * This method blocks the waiter until at least one of the indicated signals have been received.
170 * A list of signals, any one of which will satisfy the wait condition
171 * @return The signal that satisfied the wait
172 * @throws TimeoutException
173 * If none of the signals have been received within the allotted time
175 public String waitForAny(String... signals) throws TimeoutException {
176 long limit = System.currentTimeMillis() + timeout;
177 synchronized (thread) {
179 for (String signal : signals) {
180 if (!_signaled(signal)) {
181 receivedSignals.remove(signal);
187 if (System.currentTimeMillis() > limit) {
188 throw new TimeoutException(
189 String.format("One of signals \"%s\" not received in the allotted timeout.",
190 StringHelper.asList(signals)));
195 thread.wait(timeout);
196 } catch (InterruptedException e) {
198 * Interrupted exceptions are ignored
206 * This private method is used to handle the check for signaled status. Note that this method assumes the caller
207 * holds the thread mutex.
210 * The list of signals to check for
211 * @return True if any one of the signals has been received.
213 private boolean _signaled(String... signals) {
214 for (String signal : signals) {
215 if (receivedSignals.contains(signal)) {
223 * Sets the timeout value for waiting for signals to be received
227 public void setTimeout(long timeout) {
228 this.timeout = timeout;