[从源码学设计]蚂蚁金服SOFARegistry之续约和驱逐
目录
0x00 摘要
SOFARegistry 是蚂蚁金服开源的一个生产级、高时效、高可用的服务注册中心。
本系列文章重点在于分析设计和架构，即利用多篇文章，从多个角度反推总结 DataServer 或者 SOFARegistry 的实现机制和架构思路，让大家借以学习阿里如何设计。
本文为第十五篇，介绍续约和剔除。
0x01 业务范畴
续约和剔除是服务注册与发现的重要功能，比如：
1.1 失效剔除
有些时候，我们的服务实例并不一定会正常下线，可能由于内存溢出，网络故障等原因使服务不能正常工作，而服务注册中心未收到”服务下线“的请求。
为了从服务列表中将这些无法提供服务的实例剔除。Server在启动的时候会创建一个定时任务，默认每隔一段时间（默认60s）将当前清单中，超时（默认为90s）没有续约的服务剔除出去。
1.2 服务续约
在注册完服务之后，服务提供者会维护一个心跳用来持续告诉 Server: "我还活着"。以防止 Server 的”剔除任务“将该服务实例从服务列表中排除出去。我们称该操作为服务续约（Renew）。
0x02 DatumLeaseManager
在 Data Server 端，DatumLeaseManager 实现了 “失效剔除” 和 “服务续约 “功能。
2.1 定义
DatumLeaseManager 的主要变量如下：
-
connectIdRenewTimestampMap 里面会维护每个服务最近一次发送心跳的时间，Eureka 里面也有类似的数据结构；
-
locksForConnectId ：为了每次只有一个线程操作；lock for connectId: every connectId allows only one task to be created；
具体定义如下：
public class DatumLeaseManager implements AfterWorkingProcess {
/** record the latest heartbeat time for each connectId, format: connectId -> lastRenewTimestamp */
private final Map<String, Long> connectIdRenewTimestampMap = new ConcurrentHashMap<>();
/** lock for connectId , format: connectId -> true */
private ConcurrentHashMap<String, Boolean> locksForConnectId = new ConcurrentHashMap();
private volatile boolean serverWorking = false;
private volatile boolean renewEnable = true;
private AsyncHashedWheelTimer datumAsyncHashedWheelTimer;
@Autowired
private DataServerConfig dataServerConfig;
@Autowired
private DisconnectEventHandler disconnectEventHandler;
@Autowired
private DatumCache datumCache;
@Autowired
private DataNodeStatus dataNodeStatus;
private ScheduledThreadPoolExecutor executorForHeartbeatLess;
private ScheduledFuture<?> futureForHeartbeatLess;
}
2.2 续约
2.2.1 数据结构
在DatumLeaseManager之中，主要是有如下数据结构对续约起作用。
private ConcurrentHashMap<String, Boolean> locksForConnectId = new ConcurrentHashMap();
private AsyncHashedWheelTimer datumAsyncHashedWheelTimer;
2.2.2 调用
在如下模块会调用到 review，这些都是 AbstractServerHandler。
public class PublishDataHandler extends AbstractServerHandler<PublishDataRequest>
public class DatumSnapshotHandler extends AbstractServerHandler<DatumSnapshotRequest>
public class RenewDatumHandler extends AbstractServerHandler<RenewDatumRequest> implements AfterWorkingProcess
public class UnPublishDataHandler extends AbstractServerHandler<UnPublishDataRequest>
2.2.3 续约
DatumLeaseManager 这里会记录最新的时间戳，然后启动scheduleEvictTask。
public void renew(String connectId) {
// record the renew timestamp
connectIdRenewTimestampMap.put(connectId, System.currentTimeMillis());
// try to trigger evict task
scheduleEvictTask(connectId, 0);
}
具体如下：
- 如果当前ConnectionId已经被锁定，则返回；
- 启动时间轮，加入一个定时操作，如果时间到，则：
- 释放当前ConnectionId对应的lock；
- 获取当前ConnectionId对应的上次续约时间，如果不存在，说明当前ConnectionId已经被移除，则返回；
- 如果当前状态是不可续约状态，则设置下次定时操作时间，因为If in a non-working state, cannot clean up because the renew request cannot be received at this time；
- 如果上次续约时间已经到期，则使用evict进行驱逐
- 如果没到期，则会调用 scheduleEvictTask(connectId, nextDelaySec); 设置下次操作
具体代码如下：
/**
* trigger evict task: if connectId expired, create ClientDisconnectEvent to cleanup datums bind to the connectId
* PS: every connectId allows only one task to be created
*/
private void scheduleEvictTask(String connectId, long delaySec) {
delaySec = (delaySec <= 0) ? dataServerConfig.getDatumTimeToLiveSec() : delaySec;
// lock for connectId: every connectId allows only one task to be created
Boolean ifAbsent = locksForConnectId.putIfAbsent(connectId, true);
if (ifAbsent != null) {
return;
}
datumAsyncHashedWheelTimer.newTimeout(_timeout -> {
boolean continued = true;
long nextDelaySec = 0;
try {
// release lock
locksForConnectId.remove(connectId);
// get lastRenewTime of this connectId
Long lastRenewTime = connectIdRenewTimestampMap.get(connectId);
if (lastRenewTime == null) {
// connectId is already clientOff
return;
}
/*
* 1. lastRenewTime expires, then:
* - build ClientOffEvent and hand it to DataChangeEventCenter.
* - It will not be scheduled next time, so terminated.
* 2. lastRenewTime not expires, then:
* - trigger the next schedule
*/
boolean isExpired =
System.currentTimeMillis() - lastRenewTime > dataServerConfig.getDatumTimeToLiveSec() * 1000L;
if (!isRenewEnable()) {
nextDelaySec = dataServerConfig.getDatumTimeToLiveSec();
} else if (isExpired) {
int ownPubSize = getOwnPubSize(connectId);
if (ownPubSize > 0) {
evict(connectId);
}
connectIdRenewTimestampMap.remove(connectId, lastRenewTime);
continued = false;
} else {
nextDelaySec = dataServerConfig.getDatumTimeToLiveSec()
- (System.currentTimeMillis() - lastRenewTime) / 1000L;
nextDelaySec = nextDelaySec <= 0 ? 1 : nextDelaySec;
}
}
if (continued) {
scheduleEvictTask(connectId, nextDelaySec);
}
}, delaySec, TimeUnit.SECONDS);
}
2.2.4 图示
具体如下图所示
+------------------+ +-------------------------------------------+
|PublishDataHandler| | DatumLeaseManager |
+--------+---------+ | |
| | newTimeout |
| | +----------------------> |
doHandle | ^ + |
| | | | |
| renew | +-----------+--------------+ | |
| +--------------> | | AsyncHashedWheelTimer | | |
| | +-----+-----+--------------+ | |
| | | ^ | |
| | | | scheduleEvictTask | |
| | evict | + v |
| | | <----------------------+ |
| +-------------------------------------------+
| |
| |
| |
| |
v v
或者如下图所示：
+------------------+ +-------------------+ +------------------------+
|PublishDataHandler| | DatumLeaseManager | | AsyncHashedWheelTimer |
+--------+---------+ +--------+----------+ +-----------+------------+
| | new |
doHandle +------------------------> |
| renew | |
+-------------------> | |
| | |
| | |
| scheduleEvictTask |
| | |
| | newTimeout |
| +----------> +------------------------> |
| | | |
| | | |
| | | |
| | | No +
| | | <---------------+ if (ownPubSize > 0)
| | | +
| | v |
| +--+ scheduleEvictTask | Yes
| + v
| | evict
| | |
v v v
2.3 驱逐
2.3.1 数据结构
在DatumLeaseManager之中，主要是有如下数据结构对续约起作用。
private ScheduledThreadPoolExecutor executorForHeartbeatLess;
private ScheduledFuture<?> futureForHeartbeatLess;
有两个调用途径，这样在数据变化时，就会看看是否可以驱逐：
- 启动时调用；
- 显式调用；
2.3.2 显式调用
LocalDataServerChangeEventHandler 类中，调用了datumLeaseManager.reset()，随之调用了 evict。
@Override
public void doHandle(LocalDataServerChangeEvent localDataServerChangeEvent) {
isChanged.set(true);
// Better change to Listener pattern
localDataServerCleanHandler.reset();
datumLeaseManager.reset();
events.offer(localDataServerChangeEvent);
}
DatumLeaseManager的reset调用了scheduleEvictTaskForHeartbeatLess启动了驱逐线程。
public synchronized void reset() {
if (futureForHeartbeatLess != null) {
futureForHeartbeatLess.cancel(false);
}
scheduleEvictTaskForHeartbeatLess();
}
2.3.3 启动调用
启动时候，会启动驱逐线程。
@PostConstruct
public void init() {
......
executorForHeartbeatLess = new ScheduledThreadPoolExecutor(1, threadFactoryBuilder
.setNameFormat("Registry-DatumLeaseManager-ExecutorForHeartbeatLess").build());
scheduleEvictTaskForHeartbeatLess();
}
2.3.4 驱逐
具体驱逐是通过启动了一个定时线程 EvictTaskForHeartbeatLess 来完成。
private void scheduleEvictTaskForHeartbeatLess() {
futureForHeartbeatLess = executorForHeartbeatLess.scheduleWithFixedDelay(
new EvictTaskForHeartbeatLess(), dataServerConfig.getDatumTimeToLiveSec(),
dataServerConfig.getDatumTimeToLiveSec(), TimeUnit.SECONDS);
}
当时间端到达之后，会从datumCache获取目前所有connectionId，然后遍历connectionID，看看上次时间戳是否到期，如果到期就驱逐。
/**
* evict own connectIds with heartbeat less
*/
private class EvictTaskForHeartbeatLess implements Runnable {
@Override
public void run() {
// If in a non-working state, cannot clean up because the renew request cannot be received at this time.
if (!isRenewEnable()) {
return;
}
Set<String> allConnectIds = datumCache.getAllConnectIds();
for (String connectId : allConnectIds) {
Long timestamp = connectIdRenewTimestampMap.get(connectId);
// no heartbeat
if (timestamp == null) {
int ownPubSize = getOwnPubSize(connectId);
if (ownPubSize > 0) {
evict(connectId);
}
}
}
}
}
这里调用
private void evict(String connectId) {
disconnectEventHandler.receive(new ClientDisconnectEvent(connectId, System
.currentTimeMillis(), 0));
}
具体如下图：
+--------------------------------------------------+
| DatumLeaseManager |
| |
| |
| EvictTaskForHeartbeatLess.run |
| |
| +----------------------------------------------+ |
| | | |
| | | | |
| | | | |
| | v | |
| | | |
| | allConnectIds = datumCache.getAllConnectIds()| |
| | | |
| | | | |
| | | for (allConnectIds) | |
| | v | |
| | | |
| | connectIdRenewTimestampMap | |
| | | |
| | | | |
| | | no heartbeat | |
| | v | |
| | | |
| | evict | |
| | | |
| +----------------------------------------------+ |
+--------------------------------------------------+
2.3.5 驱逐处理业务
2.3.5.1 转发驱逐消息
驱逐消息需要转发出来，就对应到 DisconnectEventHandler . receive 这里，就是 EVENT_QUEUE.add(event);
public class DisconnectEventHandler implements InitializingBean, AfterWorkingProcess {
/**
* a DelayQueue that contains client disconnect events
*/
private final DelayQueue<DisconnectEvent> EVENT_QUEUE = new DelayQueue<>();
@Autowired
private SessionServerConnectionFactory sessionServerConnectionFactory;
@Autowired
private DataChangeEventCenter dataChangeEventCenter;
@Autowired
private DataNodeStatus dataNodeStatus;
private static final BlockingQueue<DisconnectEvent> noWorkQueue = new LinkedBlockingQueue<>();
public void receive(DisconnectEvent event) {
if (dataNodeStatus.getStatus() != LocalServerStatusEnum.WORKING) {
noWorkQueue.add(event);
return;
}
EVENT_QUEUE.add(event);
}
}
在 afterPropertiesSet 中会启动一个 Thread，循环从 EVENT_QUEUE 之中取出消息，然后处理，具体就是：
- 从 sessionServerConnectionFactory 之中移除对应的 Connection；
- 给 dataChangeEventCenter 发一个 ClientChangeEvent 通知；
具体如下：
@Override
public void afterPropertiesSet() {
Executor executor = ExecutorFactory
.newSingleThreadExecutor(DisconnectEventHandler.class.getSimpleName());
executor.execute(() -> {
while (true) {
try {
DisconnectEvent disconnectEvent = EVENT_QUEUE.take();
if (disconnectEvent.getType() == DisconnectTypeEnum.SESSION_SERVER) {
SessionServerDisconnectEvent event = (SessionServerDisconnectEvent) disconnectEvent;
String processId = event.getProcessId();
//check processId confirm remove,and not be registered again when delay time
String sessionServerHost = event.getSessionServerHost();
if (sessionServerConnectionFactory
.removeProcessIfMatch(processId,sessionServerHost)) {
Set<String> connectIds = sessionServerConnectionFactory
.removeConnectIds(processId);
if (connectIds != null && !connectIds.isEmpty()) {
for (String connectId : connectIds) {
unPub(connectId, event.getRegisterTimestamp());
}
}
}
} else {
ClientDisconnectEvent event = (ClientDisconnectEvent) disconnectEvent;
unPub(event.getConnectId(), event.getRegisterTimestamp());
}
}
}
});
}
/**
*
* @param connectId
* @param registerTimestamp
*/
private void unPub(String connectId, long registerTimestamp) {
dataChangeEventCenter.onChange(new ClientChangeEvent(connectId, dataServerConfig
.getLocalDataCenter(), registerTimestamp));
}
如下图所示
+--------------------------------------------------+
| DatumLeaseManager |
| |
| |
| EvictTaskForHeartbeatLess.run |
| |
| +----------------------------------------------+ |
| | | |
| | | | |
| | | | |
| | v | |
| | | |
| | allConnectIds = datumCache.getAllConnectIds()| |
| | | |
| | | | |
| | | for (allConnectIds) | | +------------------------+
| | v | | | |
| | | | | DisconnectEventHandler |
| | connectIdRenewTimestampMap | | | |
| | | | | +-------------+ |
| | | | | | | noWorkQueue | |
| | | no heartbeat | | | +-------------+ |
| | v | | receive | |
| | | | | +--------------+ |
| | evict +---------------------------------> | EVENT_QUEUE | |
| | | | | +--------------+ |
| +----------------------------------------------+ | +------------------------+
+--------------------------------------------------+
2.3.5.1 DataChangeEventCenter 转发
逻辑然后来到了 DataChangeEventCenter，这里也是起到转发作用。
public class DataChangeEventCenter {
/**
* queues of DataChangeEvent
*/
private DataChangeEventQueue[] dataChangeEventQueues;
/**
* receive changed publisher, then wrap it into the DataChangeEvent and put it into dataChangeEventQueue
*
* @param publisher
* @param dataCenter
*/
public void onChange(Publisher publisher, String dataCenter) {
int idx = hash(publisher.getDataInfoId());
Datum datum = new Datum(publisher, dataCenter);
if (publisher instanceof UnPublisher) {
datum.setContainsUnPub(true);
}
if (publisher.getPublishType() != PublishType.TEMPORARY) {
dataChangeEventQueues[idx].onChange(new DataChangeEvent(DataChangeTypeEnum.MERGE,
DataSourceTypeEnum.PUB, datum));
} else {
dataChangeEventQueues[idx].onChange(new DataChangeEvent(DataChangeTypeEnum.MERGE,
DataSourceTypeEnum.PUB_TEMP, datum));
}
}
}
2.3.5.2 DataChangeEventQueue 处理
具体业务是 DataChangeEventQueue 完成的，就是调用 addTempChangeData 与 handleDatum 处理对应数据，就是处理这些需要驱逐的数据。
当event被取出之后，会根据 DataChangeScopeEnum.DATUM 的不同，会做不同的处理。
- 如果是DataChangeScopeEnum.DATUM，则判断dataChangeEvent.getSourceType()；
- 如果是 DataSourceTypeEnum.PUB_TEMP，则addTempChangeData，就是往CHANGE_QUEUE添加ChangeData；
- 如果不是，则handleDatum；
- 如果是DataChangeScopeEnum.CLIENT，则handleClientOff((ClientChangeEvent) event);
- 如果是DataChangeScopeEnum.SNAPSHOT，则handleSnapshot((DatumSnapshotEvent) event)；
具体参见前文 从源码学设计]蚂蚁金服SOFARegistry之消息总线异步处理
+--------------------------------------------------+
| DatumLeaseManager |
| |
| |
| EvictTaskForHeartbeatLess.run |
| |
| +----------------------------------------------+ |
| | | |
| | | | |
| | | | |
| | v | |
| | | |
| | allConnectIds = datumCache.getAllConnectIds()| |
| | | |
| | | | |
| | | for (allConnectIds) | | +------------------------+
| | v | | | |
| | | | | DisconnectEventHandler |
| | connectIdRenewTimestampMap | | | |
| | | | | +-------------+ |
| | | | | | | noWorkQueue | |
| | | no heartbeat | | | +-------------+ |
| | v | | receive | |
| | | | | +--------------+ |
| | evict +---------------------------------> | EVENT_QUEUE | |
| | | | | +--------------+ |
| +----------------------------------------------+ | +------------------------+
+--------------------------------------------------+ |
|
+----------------------+ | onChange
| DataChangeEventQueue | v
| | +--------+------------------+
| | | DataChangeEventCenter |
| +------------+ | | |
| | eventQueue | | add DataChangeEvent | |
| +------------+ | | +-----------------------+ |
| | <-----------------------------+ | | dataChangeEventQueues | |
| addTempChangeData | | +-----------------------+ |
| | +---------------------------+
| handleDatum |
| |
+----------------------+
0xFF 参考
蚂蚁金服服务注册中心如何实现 DataServer 平滑扩缩容
蚂蚁金服服务注册中心 SOFARegistry 解析 | 服务发现优化之路
服务注册中心 Session 存储策略 | SOFARegistry 解析
海量数据下的注册中心 - SOFARegistry 架构介绍
服务注册中心数据分片和同步方案详解 | SOFARegistry 解析
蚂蚁金服开源通信框架SOFABolt解析之超时控制机制及心跳机制
蚂蚁金服服务注册中心数据一致性方案分析 | SOFARegistry 解析