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Kubernetes Service Discovery for Hazelcast Discovery SPI
/*
* Copyright (c) 2008-2019, Hazelcast, Inc. 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.
*/
package com.hazelcast.util.scheduler;
import com.hazelcast.spi.TaskScheduler;
import com.hazelcast.util.Clock;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
/**
* Schedule execution of an entry for seconds later.
* This is similar to a scheduled executor service, but instead of scheduling
* a execution for a specific millisecond, this service will
* schedule it with second proximity. For example, if delayMillis is 600 ms,
* then the entry will be scheduled to execute in 1 second. If delayMillis is 2400,
* then the entry will be scheduled to execute in 3 seconds. Therefore, delayMillis is
* ceil-ed to the next second. It gives up exact time scheduling to gain
* the power of:
* a) bulk execution of all operations within the same second
* or
* b) being able to reschedule (postpone) execution.
*
* @param entry key type
* @param entry value type
*/
public final class SecondsBasedEntryTaskScheduler implements EntryTaskScheduler {
/**
* @see #ceilToSecond(long)
*/
public static final double FACTOR = 1000d;
private static final long INITIAL_TIME_MILLIS = Clock.currentTimeMillis();
private static final Comparator SCHEDULED_ENTRIES_COMPARATOR = new Comparator() {
@Override
public int compare(ScheduledEntry o1, ScheduledEntry o2) {
if (o1.getScheduleId() > o2.getScheduleId()) {
return 1;
} else if (o1.getScheduleId() < o2.getScheduleId()) {
return -1;
}
return 0;
}
};
/** Map from entry key to the scheduler responsible for this key */
private HashMap keys = new HashMap();
/** Map from second to the group of entries to be processed in this second */
private HashMap groups = new HashMap();
private final AtomicLong uniqueIdGenerator = new AtomicLong();
private final Object mutex = new Object();
private final TaskScheduler taskScheduler;
private final ScheduledEntryProcessor entryProcessor;
private final ScheduleType scheduleType;
SecondsBasedEntryTaskScheduler(TaskScheduler taskScheduler,
ScheduledEntryProcessor entryProcessor, ScheduleType scheduleType) {
this.taskScheduler = taskScheduler;
this.entryProcessor = entryProcessor;
this.scheduleType = scheduleType;
}
@Override
public boolean schedule(long delayMillis, K key, V value) {
int delaySeconds = ceilToSecond(delayMillis);
final int second = findRelativeSecond(delayMillis);
long id = uniqueIdGenerator.incrementAndGet();
synchronized (mutex) {
ScheduledEntry entry = new ScheduledEntry(key, value, delayMillis, delaySeconds, id);
PerKeyScheduler keyScheduler = keys.get(key);
if (keyScheduler == null) {
switch (scheduleType) {
case POSTPONE: keyScheduler = new PerKeyPostponeScheduler(key); break;
case FOR_EACH: keyScheduler = new PerKeyForEachScheduler(key); break;
default: throw new RuntimeException("Undefined schedule type.");
}
keys.put(key, keyScheduler);
}
ScheduledGroup group = groups.get(second);
if (group == null) {
Runnable groupExecutor = new Runnable() {
@Override
public void run() {
executeGroup(second);
}
};
ScheduledFuture executorFuture = taskScheduler.schedule(groupExecutor, delaySeconds, TimeUnit.SECONDS);
group = new ScheduledGroup(second, executorFuture);
groups.put(second, group);
}
return keyScheduler.schedule(entry, group);
}
}
private void executeGroup(int second) {
List> entries;
synchronized (mutex) {
ScheduledGroup group = groups.remove(second);
if (group == null) {
// group removed in meantime
return;
}
entries = new ArrayList>(group.listEntries());
for (ScheduledEntry entry : entries) {
keys.get(entry.getKey()).executed(entry);
}
}
Collections.sort(entries, SCHEDULED_ENTRIES_COMPARATOR);
entryProcessor.process(this, entries);
}
@Override
public ScheduledEntry get(K key) {
synchronized (mutex) {
PerKeyScheduler keyScheduler = keys.get(key);
return keyScheduler != null ? keyScheduler.get() : null;
}
}
@Override
public ScheduledEntry cancel(K key) {
synchronized (mutex) {
PerKeyScheduler keyScheduler = keys.get(key);
return keyScheduler != null ? keyScheduler.cancel() : null;
}
}
@Override
public int cancelIfExists(K key, V value) {
synchronized (mutex) {
PerKeyScheduler keyScheduler = keys.get(key);
return keyScheduler != null ? keyScheduler.cancelIfExists(value) : 0;
}
}
/**
* Decides how to schedule entries for a given key, and keeps track of what have been scheduled for the key.
*/
private abstract class PerKeyScheduler {
abstract boolean schedule(ScheduledEntry entry, ScheduledGroup group);
abstract ScheduledEntry get();
abstract ScheduledEntry cancel();
abstract int cancelIfExists(V value);
abstract void executed(ScheduledEntry entry);
}
/**
* Manages scheduling where there should be just one entry per key, and any subsequent scheduling request
* for this key just postpones the execution, according to the delay specified in new request.
* @see ScheduleType#POSTPONE
*/
private final class PerKeyPostponeScheduler extends PerKeyScheduler {
final K key;
Long id;
ScheduledGroup group;
PerKeyPostponeScheduler(K key) {
this.key = key;
}
boolean schedule(ScheduledEntry newEntry, ScheduledGroup newGroup) {
if (newGroup == group) {
// no reschedule if in the same second
return false;
}
if (group != null) {
// unschedule previous entry
group.removeEntry(id);
}
id = newEntry.getScheduleId();
group = newGroup;
newGroup.addEntry(id, newEntry);
return true;
}
ScheduledEntry get() {
return group.getEntry(id);
}
ScheduledEntry cancel() {
ScheduledEntry entry = group.removeEntry(id);
keys.remove(key);
return entry;
}
int cancelIfExists(V value) {
ScheduledEntry entry = group.getEntry(id);
if (areEqual(entry.getValue(), value)) {
group.removeEntry(id);
keys.remove(key);
return 1;
}
return 0;
}
void executed(ScheduledEntry entry) {
assert entry.getScheduleId() == id;
// no need to remove entry from group, whole group is being executed and will be removed
keys.remove(key);
}
}
/**
* Manages scheduling where each scheduled entry for given key should be executed when its time comes.
* @see ScheduleType#FOR_EACH
*/
private final class PerKeyForEachScheduler extends PerKeyScheduler {
final K key;
final Map idToGroupMap = new HashMap();
PerKeyForEachScheduler(K key) {
this.key = key;
}
boolean schedule(ScheduledEntry entry, ScheduledGroup group) {
Long id = entry.getScheduleId();
idToGroupMap.put(id, group);
group.addEntry(id, entry);
return true;
}
ScheduledEntry get() {
ScheduledEntry entry = null;
for (Map.Entry idToGroup : idToGroupMap.entrySet()) {
Long id = idToGroup.getKey();
ScheduledGroup group = idToGroup.getValue();
entry = group.getEntry(id);
}
assert entry != null;
return entry;
}
ScheduledEntry cancel() {
ScheduledEntry entry = null;
for (Map.Entry idToGroup : idToGroupMap.entrySet()) {
Long id = idToGroup.getKey();
ScheduledGroup group = idToGroup.getValue();
entry = group.removeEntry(id);
}
keys.remove(key);
assert entry != null;
return entry;
}
int cancelIfExists(V value) {
int cancelled = 0;
Iterator> iterator = idToGroupMap.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry idToGroup = iterator.next();
Long id = idToGroup.getKey();
ScheduledGroup group = idToGroup.getValue();
ScheduledEntry entry = group.getEntry(id);
if (areEqual(entry.getValue(), value)) {
group.removeEntry(id);
iterator.remove();
cancelled++;
}
}
if (idToGroupMap.isEmpty()) {
keys.remove(key);
}
return cancelled;
}
void executed(ScheduledEntry entry) {
idToGroupMap.remove(entry.getScheduleId());
// no need to remove entry from group, whole group is being executed and will be removed
if (idToGroupMap.isEmpty()) {
keys.remove(key);
}
}
}
/**
* Group of entries scheduled for execution in the same second.
*/
private final class ScheduledGroup {
final int second;
final ScheduledFuture executor;
final Map> idToEntryMap = new HashMap>();
private ScheduledGroup(int second, ScheduledFuture executor) {
this.second = second;
this.executor = executor;
}
private void addEntry(Long id, ScheduledEntry entry) {
idToEntryMap.put(id, entry);
}
private ScheduledEntry getEntry(Long id) {
return idToEntryMap.get(id);
}
private Collection> listEntries() {
return idToEntryMap.values();
}
private int countEntries() {
return idToEntryMap.size();
}
private ScheduledEntry removeEntry(Long id) {
ScheduledEntry entry = idToEntryMap.remove(id);
if (idToEntryMap.isEmpty()) {
executor.cancel(false);
groups.remove(second);
}
return entry;
}
}
@Override
public void cancelAll() {
synchronized (mutex) {
for (ScheduledGroup group : groups.values()) {
group.executor.cancel(false);
}
groups.clear();
keys.clear();
}
}
@Override
public String toString() {
return "EntryTaskScheduler{"
+ "numberOfEntries="
+ size()
+ ", numberOfKeys="
+ keys.size()
+ ", numberOfGroups="
+ groups.size()
+ '}';
}
/**
* Returns number of scheduled entries.
*/
// exposed for testing
int size() {
synchronized (mutex) {
int size = 0;
for (ScheduledGroup group : groups.values()) {
size += group.countEntries();
}
return size;
}
}
/**
* Returns {@code true} if there are no scheduled entries.
*/
// exposed for testing
public boolean isEmpty() {
synchronized (mutex) {
// check every collection for emptiness to make sure no memory is leaking
return groups.isEmpty() && keys.isEmpty();
}
}
/**
* Returns the duration in seconds between the time this class was loaded and now+{@code delayMillis}
*/
// exposed for testing
static int findRelativeSecond(long delayMillis) {
long now = Clock.currentTimeMillis();
long d = (now + delayMillis - INITIAL_TIME_MILLIS);
return ceilToSecond(d);
}
private static int ceilToSecond(long delayMillis) {
return (int) Math.ceil(delayMillis / FACTOR);
}
private static boolean areEqual(Object a, Object b) {
return (a == b) || (a != null && a.equals(b));
}
}