2 * ============LICENSE_START=======================================================
4 * ================================================================================
5 * Copyright (C) 2017 AT&T Intellectual Property. All rights
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=========================================================
22 package org.openecomp.appc.concurrent;
24 import java.util.ArrayList;
25 import java.util.Arrays;
26 import java.util.List;
27 import java.util.concurrent.TimeoutException;
29 import org.openecomp.appc.util.StringHelper;
32 * This class is used to synchronize signaling of status between threads.
34 * In complex multi-threaded applications it is often necessary to synchronize operations between threads. This is
35 * especially true in complex algorithms where processing dependencies exist between different threads and the
36 * synchronization of the operations of those threads is required. This class is a framework to enable multi-thread
37 * signaling and wait/post logic that makes the thread synchronization easier.
40 * Basically, in thread synchronization, one thread is the "waiter" and one or more other threads are the "notifiers".
41 * The notifiers send signals to the waiter to inform that thread that certain conditions are true, processing has been
42 * completed, or to inform the waiter of the state of the other thread(s). In the basic java framework, the waiter and
43 * notifier are simply using the wait/notify mechanism provided, which does not allow for different conditions, state,
44 * or "signals" to exist. The wait/notify mechanism, in combination with the object mutex, provides basic blocking and
45 * releasing of a thread's dispatching state.
48 * This class builds upon the java wait/notify mechanism and allows for "signals" to be defined. These signals are
49 * simply string constants that mean something to the waiter and notifier threads. Any number of signals may be defined,
50 * 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
51 * test if a signal has been received without blocking.
54 * Some operations are blocking operations. These stop the execution of the calling thread until the specified condition
55 * is true. These blocking methods are all named "wait...", such as {@link #waitFor(String...)} and
56 * {@link #waitForAny(String...)}. The thread making the call to these blocking methods MUST be the waiter thread (the
57 * thread registered with the signal object).
60 * Some operations are non-blocking. These operations allow for the testing or setting of signal conditions and do not
61 * block the caller. When calling these methods ({@link #isSignaled(String)}, {@link #signal(String)}, and
62 * {@link #setTimeout(long)} the waiter thread mutex will be held and may block the waiter thread for the duration of
69 * The thread must be the thread of the waiter that is waiting for the signals to be received. It is the recipient
70 * of the signaled condition. This allows any number of other threads to send signals to the recipient and have the
71 * recipient synchronize its operation with the receipt of the appropriate signal(s).
73 private Thread thread;
76 * The amount of time to wait for a signal to be receieved. Set to zero to wait forever.
78 private long timeout = 0L;
81 * The collection of all received signals. Note, this need not be a synchronized collection because it will always
82 * be accessed while holding the mutex of the thread, therefore it is implicitly synchronized.
84 private List<String> receivedSignals;
87 * A signal object must access a thread that is waiting for the receipt of the signal(s).
89 public Signal(Thread thread) {
91 receivedSignals = new ArrayList<String>();
95 * Checks the waiter to see if it has been signaled
98 * The signal to check for
99 * @return True if the signal has been received, false otherwise
101 public boolean isSignaled(String signal) {
102 synchronized (thread) {
103 return _signaled(signal);
108 * Sends the indicated signal to the waiter.
111 * The signal that is to be sent to the waiting thread and to notify it to process the signal.
113 public void signal(String signal) {
114 synchronized (thread) {
115 if (!_signaled(signal)) {
116 receivedSignals.add(signal);
123 * Blocks the waiting thread until all of the indicated signals have been received, or the wait times out.
126 * The signals to be received. The waiter is blocked forever or until all of the signals are received.
127 * @throws TimeoutException
128 * If the wait has timed out waiting for a response
130 public void waitFor(String... signals) throws TimeoutException {
131 long limit = System.currentTimeMillis() + timeout;
132 synchronized (thread) {
134 boolean complete = true;
135 for (String signal : signals) {
136 if (!_signaled(signal)) {
142 receivedSignals.removeAll(Arrays.asList(signals));
147 if (System.currentTimeMillis() > limit) {
148 throw new TimeoutException(String.format("Signals %s not received in the allotted timeout.",
149 StringHelper.asList(signals)));
154 thread.wait(timeout);
155 } catch (InterruptedException e) {
157 * Interrupted exceptions are ignored
165 * This method blocks the waiter until at least one of the indicated signals have been received.
168 * A list of signals, any one of which will satisfy the wait condition
169 * @return The signal that satisfied the wait
170 * @throws TimeoutException
171 * If none of the signals have been received within the allotted time
173 public String waitForAny(String... signals) throws TimeoutException {
174 long limit = System.currentTimeMillis() + timeout;
175 synchronized (thread) {
177 for (String signal : signals) {
178 if (!_signaled(signal)) {
179 receivedSignals.remove(signal);
185 if (System.currentTimeMillis() > limit) {
186 throw new TimeoutException(
187 String.format("One of signals \"%s\" not received in the allotted timeout.",
188 StringHelper.asList(signals)));
193 thread.wait(timeout);
194 } catch (InterruptedException e) {
196 * Interrupted exceptions are ignored
204 * This private method is used to handle the check for signaled status. Note that this method assumes the caller
205 * holds the thread mutex.
208 * The list of signals to check for
209 * @return True if any one of the signals has been received.
211 private boolean _signaled(String... signals) {
212 for (String signal : signals) {
213 if (receivedSignals.contains(signal)) {
221 * Sets the timeout value for waiting for signals to be received
225 public void setTimeout(long timeout) {
226 this.timeout = timeout;