2 * ============LICENSE_START=======================================================
3 * feature-active-standby-management
4 * ================================================================================
5 * Copyright (C) 2017-2019 AT&T Intellectual Property. All rights reserved.
6 * ================================================================================
7 * Licensed under the Apache License, Version 2.0 (the "License");
8 * you may not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
11 * http://www.apache.org/licenses/LICENSE-2.0
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 * ============LICENSE_END=========================================================
21 package org.onap.policy.drools.activestandby;
24 * Per MultiSite_v1-10.ppt:
26 * Extends the StateChangeNotifier class and overwrites the abstract handleStateChange() method to get state changes
27 * and do the following:
29 * When the Standby Status changes (from providingservice) to hotstandby or coldstandby,
30 * the Active/Standby selection algorithm must stand down if the PDP-D is currently the lead/active node
31 * and allow another PDP-D to take over. It must also call lock on all engines in the engine management.
33 * When the Standby Status changes from (hotstandby) to coldstandby, the Active/Standby algorithm must NOT assume
34 * the active/lead role.
36 * When the Standby Status changes (from coldstandby or providingservice) to hotstandby,
37 * the Active/Standby algorithm may assume the active/lead role if the active/lead fails.
39 * When the Standby Status changes to providingservice (from hotstandby or coldstandby) call unlock on all
40 * engines in the engine management layer.
42 import java.util.Date;
43 import java.util.Timer;
44 import java.util.TimerTask;
46 import org.onap.policy.common.im.StateChangeNotifier;
47 import org.onap.policy.common.im.StateManagement;
48 import org.onap.policy.drools.system.PolicyEngine;
49 import org.slf4j.Logger;
50 import org.slf4j.LoggerFactory;
55 * Originally, there was a "StandbyStateChangeNotifier" that belonged to policy-core, and this class's
56 * handleStateChange() method used to take care of invoking conn.standDownPdp().
58 * But testing revealed that when a state change to hot standby
59 * occurred from a demote() operation, first the PMStandbyStateChangeNotifier.handleStateChange() method
60 * would be invoked and then the StandbyStateChangeNotifier.handleStateChange() method would be invoked,
61 * and this ordering was creating the following problem:
63 * When PMStandbyStateChangeNotifier.handleStateChange() was invoked it would take a long time to finish,
64 * because it would result in SingleThreadedUebTopicSource.stop() being invoked, which can potentially do a
65 * 5 second sleep for each controller being stopped.
67 * Meanwhile, as these controller stoppages and their associated sleeps were occurring, the election handler
68 * would discover the demoted PDP in hotstandby (but still designated!) and promote it, resulting in the
69 * standbyStatus going from hotstandby to providingservice. So then, by the time that
70 * PMStandbyStateChangeNotifier.handleStateChange() finished its work and
71 * StandbyStateChangeNotifier.handleStateChange() started executing, the standbyStatus was no longer hotstandby
72 * (as effected by the demote), but providingservice (as reset by the election handling logic) and
73 * conn.standDownPdp() would not get called!
75 * To fix this bug, we consolidated StandbyStateChangeNotifier and PMStandbyStateChangeNotifier,
76 * with the standDownPdp() always
77 * being invoked prior to the TopicEndpoint.manager.lock(). In this way, when the election handling logic is invoked
78 * during the controller stoppages, the PDP is in hotstandby and the standdown occurs.
81 public class PmStandbyStateChangeNotifier extends StateChangeNotifier {
82 // get an instance of logger
83 private static final Logger logger = LoggerFactory.getLogger(PmStandbyStateChangeNotifier.class);
84 private Timer delayActivateTimer;
85 private int pdpUpdateInterval;
86 private boolean isWaitingForActivation;
87 private long startTimeWaitingForActivationMs;
88 private long waitInterval;
89 private boolean isNowActivating;
90 private String previousStandbyStatus;
91 public static final String NONE = "none";
92 public static final String UNSUPPORTED = "unsupported";
93 public static final String HOTSTANDBY_OR_COLDSTANDBY = "hotstandby_or_coldstandby";
99 public PmStandbyStateChangeNotifier() {
101 Integer.parseInt(ActiveStandbyProperties.getProperty(ActiveStandbyProperties.PDP_UPDATE_INTERVAL));
102 isWaitingForActivation = false;
103 startTimeWaitingForActivationMs = new Date().getTime();
104 // delay the activate so the DesignatedWaiter can run twice - give it an extra 2 seconds
105 waitInterval = 2 * pdpUpdateInterval + 2000L;
106 isNowActivating = false;
107 previousStandbyStatus = PmStandbyStateChangeNotifier.NONE;
111 public void handleStateChange() {
113 * A note on synchronization: This method is not synchronized because the caller,
114 * stateManagememt, has synchronize all of its methods. Only one stateManagement operation
115 * can occur at a time. Thus, only one handleStateChange() call will ever be made at a time.
117 logger.debug("handleStateChange: Entering, message={}, standbyStatus={}", super.getMessage(),
118 super.getStateManagement().getStandbyStatus());
119 String standbyStatus = super.getStateManagement().getStandbyStatus();
120 String pdpId = ActiveStandbyProperties.getProperty(ActiveStandbyProperties.NODE_NAME);
122 logger.debug("handleStateChange: previousStandbyStatus = {}; standbyStatus = {}",
123 previousStandbyStatus, standbyStatus);
125 if (standbyStatus == null || standbyStatus.equals(StateManagement.NULL_VALUE)) {
126 logger.debug("handleStateChange: standbyStatus is null; standing down PDP={}", pdpId);
127 if (previousStandbyStatus.equals(StateManagement.NULL_VALUE)) {
128 // We were just here and did this successfully
129 logger.debug("handleStateChange: "
130 + "Is returning because standbyStatus is null and was previously 'null'; PDP={}",
134 isWaitingForActivation = false;
136 logger.debug("handleStateChange: null: cancelling delayActivationTimer.");
138 // Only want to lock the endpoints, not the controllers.
139 getPolicyEngineManager().deactivate();
140 // The operation was fully successful, but you cannot assign it a real null value
141 // because later we might try to execute previousStandbyStatus.equals() and get
142 // a null pointer exception.
143 previousStandbyStatus = StateManagement.NULL_VALUE;
144 } catch (Exception e) {
145 logger.warn("handleStateChange: standbyStatus == null caught exception: ", e);
147 } else if (standbyStatus.equals(StateManagement.HOT_STANDBY)
148 || standbyStatus.equals(StateManagement.COLD_STANDBY)) {
149 logger.debug("handleStateChange: standbyStatus={}; standing down PDP={}", standbyStatus, pdpId);
150 if (previousStandbyStatus.equals(PmStandbyStateChangeNotifier.HOTSTANDBY_OR_COLDSTANDBY)) {
151 // We were just here and did this successfully
152 logger.debug("handleStateChange: Is returning because standbyStatus is {}"
153 + " and was previously {}; PDP= {}", standbyStatus, previousStandbyStatus, pdpId);
156 isWaitingForActivation = false;
158 logger.debug("handleStateChange: HOT_STNDBY || COLD_STANDBY: cancelling delayActivationTimer.");
160 // Only want to lock the endpoints, not the controllers.
161 getPolicyEngineManager().deactivate();
162 // The operation was fully successful
163 previousStandbyStatus = PmStandbyStateChangeNotifier.HOTSTANDBY_OR_COLDSTANDBY;
164 } catch (Exception e) {
165 logger.warn("handleStateChange: standbyStatus = {} caught exception: {}", standbyStatus, e.getMessage(),
169 } else if (standbyStatus.equals(StateManagement.PROVIDING_SERVICE)) {
170 logger.debug("handleStateChange: standbyStatus= {} scheduling activation of PDP={}", standbyStatus,
172 if (previousStandbyStatus.equals(StateManagement.PROVIDING_SERVICE)) {
173 // We were just here and did this successfully
174 logger.debug("handleStateChange: Is returning because standbyStatus is {}"
175 + "and was previously {}; PDP={}", standbyStatus, previousStandbyStatus, pdpId);
179 // UnLock all the endpoints
180 logger.debug("handleStateChange: standbyStatus={}; controllers must be unlocked.", standbyStatus);
182 * Only endpoints should be unlocked. Controllers have not been locked. Because,
183 * sometimes, it is possible for more than one PDP-D to become active (race
184 * conditions) we need to delay the activation of the topic endpoint interfaces to
185 * give the election algorithm time to resolve the conflict.
187 logger.debug("handleStateChange: PROVIDING_SERVICE isWaitingForActivation= {}",
188 isWaitingForActivation);
190 // Delay activation for 2*pdpUpdateInterval+2000 ms in case of an election handler
192 // You could have multiple election handlers thinking they can take over.
194 // First let's check that the timer has not died
195 if (isWaitingForActivation) {
196 logger.debug("handleStateChange: PROVIDING_SERVICE isWaitingForActivation = {}",
197 isWaitingForActivation);
198 long now = new Date().getTime();
199 long waitTimeMs = now - startTimeWaitingForActivationMs;
200 if (waitTimeMs > 3 * waitInterval) {
201 logger.debug("handleStateChange: PROVIDING_SERVICE looks like the activation wait timer "
202 + "may be hung, waitTimeMs = {} and allowable waitInterval = {}"
203 + " Checking whether it is currently in activation. isNowActivating = {}",
204 waitTimeMs, waitInterval, isNowActivating);
205 // Now check that it is not currently executing an activation
206 if (!isNowActivating) {
207 logger.debug("handleStateChange: PROVIDING_SERVICE looks like the activation "
208 + "wait timer died");
209 // This will assure the timer is cancelled and rescheduled.
210 isWaitingForActivation = false;
216 if (!isWaitingForActivation) {
217 // Just in case there is an old timer hanging around
218 logger.debug("handleStateChange: PROVIDING_SERVICE cancelling delayActivationTimer.");
220 delayActivateTimer = makeTimer();
221 // delay the activate so the DesignatedWaiter can run twice
222 delayActivateTimer.schedule(new DelayActivateClass(), waitInterval);
223 isWaitingForActivation = true;
224 startTimeWaitingForActivationMs = new Date().getTime();
225 logger.debug("handleStateChange: PROVIDING_SERVICE scheduling delayActivationTimer in {} ms",
228 logger.debug("handleStateChange: PROVIDING_SERVICE delayActivationTimer is "
229 + "waiting for activation.");
232 } catch (Exception e) {
233 logger.warn("handleStateChange: PROVIDING_SERVICE standbyStatus == providingservice caught exception: ",
238 logger.error("handleStateChange: Unsupported standbyStatus={}; standing down PDP={}", standbyStatus, pdpId);
239 if (previousStandbyStatus.equals(PmStandbyStateChangeNotifier.UNSUPPORTED)) {
240 // We were just here and did this successfully
241 logger.debug("handleStateChange: Is returning because standbyStatus is "
242 + "UNSUPPORTED and was previously {}; PDP={}", previousStandbyStatus, pdpId);
245 // Only want to lock the endpoints, not the controllers.
246 isWaitingForActivation = false;
248 logger.debug("handleStateChange: unsupported standbystatus: cancelling delayActivationTimer.");
250 getPolicyEngineManager().deactivate();
251 // We know the standbystatus is unsupported
252 previousStandbyStatus = PmStandbyStateChangeNotifier.UNSUPPORTED;
253 } catch (Exception e) {
254 logger.warn("handleStateChange: Unsupported standbyStatus = {} " + "caught exception: {} ",
255 standbyStatus, e.getMessage(), e);
258 logger.debug("handleStateChange: Exiting");
261 private void cancelTimer() {
262 if (delayActivateTimer != null) {
263 delayActivateTimer.cancel();
267 private class DelayActivateClass extends TimerTask {
269 private Object delayActivateLock = new Object();
274 isNowActivating = true;
276 logger.debug("DelayActivateClass.run: entry");
277 synchronized (delayActivateLock) {
278 getPolicyEngineManager().activate();
279 // The state change fully succeeded
280 previousStandbyStatus = StateManagement.PROVIDING_SERVICE;
281 // We want to set this to false here because the activate call can take a while
282 isWaitingForActivation = false;
283 isNowActivating = false;
285 logger.debug("DelayActivateClass.run.exit");
286 } catch (Exception e) {
287 isWaitingForActivation = false;
288 isNowActivating = false;
289 logger.warn("DelayActivateClass.run: caught an unexpected exception "
290 + "calling PolicyEngine.manager.activate: ", e);
295 public String getPreviousStandbyStatus() {
296 return previousStandbyStatus;
299 // these may be overridden by junit tests
301 protected PolicyEngine getPolicyEngineManager() {
302 return PolicyEngine.manager;
305 protected Timer makeTimer() {