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/*-
* ============LICENSE_START=======================================================
* Copyright (C) 2016-2018 Ericsson. All rights reserved.
* ================================================================================
* 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.
*
* SPDX-License-Identifier: Apache-2.0
* ============LICENSE_END=========================================================
*/
package org.onap.policy.apex.service.engine.event;
import java.util.AbstractMap.SimpleEntry;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import org.onap.policy.apex.core.infrastructure.threading.ThreadUtilities;
import org.onap.policy.apex.service.parameters.eventhandler.EventHandlerPeeredMode;
import org.slf4j.ext.XLogger;
import org.slf4j.ext.XLoggerFactory;
/**
* This class holds a cache of the synchronous events sent into Apex and that have not yet been replied to. It runs a thread to time out events that have not
* been replied to in the specified timeout.
*
* @author Liam Fallon (liam.fallon@ericsson.com)
*/
public class SynchronousEventCache extends PeeredReference implements Runnable {
// Get a reference to the logger
private static final XLogger LOGGER = XLoggerFactory.getXLogger(SynchronousEventCache.class);
// The default amount of time to wait for a synchronous event to be replied to is 1 second
private static final long DEFAULT_SYNCHRONOUS_EVENT_TIMEOUT = 1000;
// The timeout to wait between event polls in milliseconds and the time to wait for the thread to stop
private static final long OUTSTANDING_EVENT_POLL_TIMEOUT = 50;
private static final long CACHE_STOP_WAIT_INTERVAL = 10;
// The time in milliseconds to wait for the reply to a sent synchronous event
private long synchronousEventTimeout = DEFAULT_SYNCHRONOUS_EVENT_TIMEOUT;
// Map holding outstanding synchronous events
private final Map<Long, SimpleEntry<Long, Object>> toApexEventMap = new HashMap<Long, SimpleEntry<Long, Object>>();
// Map holding reply events
private final Map<Long, SimpleEntry<Long, Object>> fromApexEventMap = new HashMap<Long, SimpleEntry<Long, Object>>();
// The message listener thread and stopping flag
private final Thread synchronousEventCacheThread;
private boolean stopOrderedFlag = false;
/**
* Create a synchronous event cache that caches outstanding synchronous Apex events.
*
* @param peeredMode the peered mode for which to return the reference
* @param consumer the consumer that is populating the cache
* @param producer the producer that is emptying the cache
* @param synchronousEventTimeout the time in milliseconds to wait for the reply to a sent synchronous event
*/
public SynchronousEventCache(final EventHandlerPeeredMode peeredMode, final ApexEventConsumer consumer, final ApexEventProducer producer, final long synchronousEventTimeout) {
super(peeredMode, consumer, producer);
if (synchronousEventTimeout != 0) {
this.synchronousEventTimeout = synchronousEventTimeout;
}
else {
this.synchronousEventTimeout = DEFAULT_SYNCHRONOUS_EVENT_TIMEOUT;
}
// Start scanning the outstanding events
synchronousEventCacheThread = new Thread(this);
synchronousEventCacheThread.setDaemon(true);
synchronousEventCacheThread.start();
}
/**
* Gets the timeout value for synchronous events.
*
* @return the synchronous event timeout
*/
public long getSynchronousEventTimeout() {
return synchronousEventTimeout;
}
/**
* Cache a synchronized event sent into Apex in the event cache.
*
* @param executionId the execution ID that was assigned to the event
* @param event the apex event
*/
public void cacheSynchronizedEventToApex(final long executionId, final Object event) {
// Add the event to the map
synchronized (toApexEventMap) {
cacheSynchronizedEvent(toApexEventMap, executionId, event);
}
}
/**
* Remove the record of an event sent to Apex if it exists in the cache.
*
* @param executionId the execution ID of the event
* @return The removed event
*/
public Object removeCachedEventToApexIfExists(final long executionId) {
synchronized (toApexEventMap) {
return removeCachedEventIfExists(toApexEventMap, executionId);
}
}
/**
* Check if an event exists in the to apex cache.
*
* @param executionId the execution ID of the event
* @return true if the event exists, false otherwise
*/
public boolean existsEventToApex(final long executionId) {
synchronized (toApexEventMap) {
return toApexEventMap.containsKey(executionId);
}
}
/**
* Cache synchronized event received from Apex in the event cache.
*
* @param executionId the execution ID of the event
* @param event the apex event
*/
public void cacheSynchronizedEventFromApex(final long executionId, final Object event) {
// Add the event to the map
synchronized (fromApexEventMap) {
cacheSynchronizedEvent(fromApexEventMap, executionId, event);
}
}
/**
* Remove the record of an event received from Apex if it exists in the cache.
*
* @param executionId the execution ID of the event
* @return The removed event
*/
public Object removeCachedEventFromApexIfExists(final long executionId) {
synchronized (fromApexEventMap) {
return removeCachedEventIfExists(fromApexEventMap, executionId);
}
}
/**
* Check if an event exists in the from apex cache.
*
* @param executionId the execution ID of the event
* @return true if the event exists, false otherwise
*/
public boolean existsEventFromApex(final long executionId) {
synchronized (fromApexEventMap) {
return fromApexEventMap.containsKey(executionId);
}
}
/*
* (non-Javadoc)
*
* @see java.lang.Runnable#run()
*/
@Override
public void run() {
LOGGER.entry();
// Periodic scan of outstanding events
while (synchronousEventCacheThread.isAlive() && !stopOrderedFlag) {
ThreadUtilities.sleep(OUTSTANDING_EVENT_POLL_TIMEOUT);
// Check for timeouts on events
synchronized (toApexEventMap) {
timeoutEventsOnCache(toApexEventMap);
}
synchronized (fromApexEventMap) {
timeoutEventsOnCache(fromApexEventMap);
}
}
LOGGER.exit();
}
/**
* Stops the scanning thread and clears the cache.
*/
public synchronized void stop() {
LOGGER.entry();
stopOrderedFlag = true;
while (synchronousEventCacheThread.isAlive()) {
ThreadUtilities.sleep(CACHE_STOP_WAIT_INTERVAL);
}
// Check if there are any unprocessed events
if (!toApexEventMap.isEmpty()) {
LOGGER.warn(toApexEventMap.size() + " synchronous events dropped due to system shutdown");
}
toApexEventMap.clear();
LOGGER.exit();
}
/**
* Cache a synchronized event sent in an event cache.
* @param eventCacheMap the map to cache the event on
* @param executionId the execution ID of the event
* @param event the event to cache
*/
private void cacheSynchronizedEvent(final Map<Long, SimpleEntry<Long, Object>> eventCacheMap, final long executionId, final Object event) {
LOGGER.entry("Adding event with execution ID: " + executionId);
// Check if the event is already in the cache
if (eventCacheMap.containsKey(executionId)) {
// If there was no sent event then the event timed out or some unexpected event was received
final String errorMessage = "an event with ID " + executionId
+ " already exists in the synchronous event cache, execution IDs must be unique in the system";
LOGGER.warn(errorMessage);
throw new ApexEventRuntimeException(errorMessage);
}
// Add the event to the map
eventCacheMap.put(executionId, new SimpleEntry<Long, Object>(System.currentTimeMillis(), event));
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("event has been cached:" + event);
}
LOGGER.exit("Added: " + executionId);
}
/**
* Remove the record of an event if it exists in the cache.
*
* @param eventCacheMap the map to remove the event from
* @param executionId the execution ID of the event
* @return The removed event
*/
private Object removeCachedEventIfExists(final Map<Long, SimpleEntry<Long, Object>> eventCacheMap, final long executionId) {
LOGGER.entry("Removing: " + executionId);
final SimpleEntry<Long, Object> removedEventEntry = eventCacheMap.remove(executionId);
if (removedEventEntry != null) {
LOGGER.exit("Removed: " + executionId);
return removedEventEntry.getValue();
}
else {
// The event may not be one of the events in our cache, so we just ignore removal failures
return null;
}
}
/**
* Time out events on an event cache map. Events that have a timeout longer than the configured timeout are timed out.
* @param eventCacheMap the event cache to operate on
*/
private void timeoutEventsOnCache(final Map<Long, SimpleEntry<Long, Object>> eventCacheMap) {
// Use a set to keep track of the events that have timed out
final Set<Long> timedOutEventSet = new HashSet<>();
for (final Entry<Long, SimpleEntry<Long, Object>> cachedEventEntry : eventCacheMap.entrySet()) {
// The amount of time we are waiting for the event reply
final long eventWaitTime = System.currentTimeMillis() - cachedEventEntry.getValue().getKey();
// Have we a timeout?
if (eventWaitTime > synchronousEventTimeout) {
timedOutEventSet.add(cachedEventEntry.getKey());
}
}
// Remove timed out events from the map
for (final long timedoutEventExecutionID : timedOutEventSet) {
// Remove the map entry and issue a warning
final SimpleEntry<Long, Object> timedOutEventEntry = eventCacheMap.remove(timedoutEventExecutionID);
LOGGER.warn("synchronous event timed out, reply not received in " + synchronousEventTimeout + " milliseconds on event "
+ timedOutEventEntry.getValue());
}
}
}
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