[从源码学设计]蚂蚁金服SOFARegistry之续约和驱逐

[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解析之连接管理剖析

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

蚂蚁金服开源通信框架 SOFABolt 协议框架解析

蚂蚁金服服务注册中心数据一致性方案分析 | SOFARegistry 解析

蚂蚁通信框架实践

sofa-bolt 远程调用

sofa-bolt学习

SOFABolt 设计总结 - 优雅简洁的设计之道

SofaBolt源码分析-服务启动到消息处理

SOFABolt 源码分析

SOFABolt 源码分析9 - UserProcessor 自定义处理器的设计

SOFARegistry 介绍

SOFABolt 源码分析13 - Connection 事件处理机制的设计

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