motan源码分析十一：部分特性_motan workerqueuesize-优快云博客

本文介绍了Motan RPC框架的关键特性，包括requestid生成机制、限流策略、客户端故障处理及多注册中心支持等内容。

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本章将描述motan部分的特性并对源码进行分析。

1.requestid的维护，使用了当前时间左移20位，再和一个自增变量组合

public class RequestIdGenerator {
    protected static final AtomicLong offset = new AtomicLong(0);
    protected static final int BITS = 20;
    protected static final long MAX_COUNT_PER_MILLIS = 1 << BITS;


    /**
     * 获取 requestId
     * 
     * @return
     */
    public static long getRequestId() {
        long currentTime = System.currentTimeMillis();
        long count = offset.incrementAndGet();
        while(count >= MAX_COUNT_PER_MILLIS){
            synchronized (RequestIdGenerator.class){
                if(offset.get() >= MAX_COUNT_PER_MILLIS){
                    offset.set(0);
                }
            }
            count = offset.incrementAndGet();
        }
        return (currentTime << BITS) + count;
    }

    public static long getRequestIdFromClient() {
        // TODO 上下文 requestid
        return 0;

    }

}

2.限流，motan支持简单的限流，是利用filter来实现的

@SpiMeta(name
 = "active")

@Activation(sequence
 = 1)

public class ActiveLimitFilter implements Filter
 {

    @Override

    public Response
 filter(Caller<?> caller, Request request) {

        int maxAcvitivyCount
 = caller.getUrl().getIntParameter(URLParamType.actives.getName(), URLParamType.actives.getIntValue());

        if (maxAcvitivyCount
 > 0)
 {

            int activeCount
 = RpcStats.getServiceStat(caller.getUrl()).getActiveCount();

            if (activeCount
 >= maxAcvitivyCount) {

                throw new MotanServiceException(String.format("Request(%s)
 active count exceed the limit (%s), referer:%s",
 request,

                        maxAcvitivyCount,
 caller.getUrl()), MotanErrorMsgConstant.SERVICE_REJECT);

            }

        }

        long startTime
 = System.currentTimeMillis();

        RpcStats.beforeCall(caller.getUrl(),
 request);

        try {

            Response
 rs = caller.call(request);

            RpcStats.afterCall(caller.getUrl(),
 request, true,
 System.currentTimeMillis() - startTime);

            return rs;

        } catch (RuntimeException
 re) {

            RpcStats.afterCall(caller.getUrl(),
 request, false,
 System.currentTimeMillis() - startTime);

            throw re;

        }

    }

}

3.对于连续失败的client进行不可用操作

    void incrErrorCount() {
        long count = errorCount.incrementAndGet();

        // 如果节点是可用状态，同时当前连续失败的次数超过限制maxClientConnection次，那么把该节点标示为不可用
        if (count >= maxClientConnection && state.isAliveState()) {
            synchronized (this) {
                count = errorCount.longValue();

                if (count >= maxClientConnection && state.isAliveState()) {
                    LoggerUtil.error("NettyClient unavailable Error: url=" + url.getIdentity() + " "
                            + url.getServerPortStr());
                    state = ChannelState.UNALIVE;
                }
            }
        }
    }

    void resetErrorCount() {
        errorCount.set(0);

        if (state.isAliveState()) {
            return;
        }

        synchronized (this) {
            if (state.isAliveState()) {
                return;
            }

            // 如果节点是unalive才进行设置，而如果是 close 或者 uninit，那么直接忽略
            if (state.isUnAliveState()) {
                long count = errorCount.longValue();

                // 过程中有其他并发更新errorCount的，因此这里需要进行一次判断
                if (count < maxClientConnection) {
                    state = ChannelState.ALIVE;
                    LoggerUtil.info("NettyClient recover available: url=" + url.getIdentity() + " "
                            + url.getServerPortStr());
                }
            }
        }
    }

4.支持多注册中心，因此cluster的refer集合是所有注册中心包含服务器的集合，如果同一个服务器在不同的注册中心注册，则cluster中当作两个服务器

5.服务端的采用boss线程池+工作线程池+业务线程池的处理方式

private final static ChannelFactory
 channelFactory = new NioServerSocketChannelFactory(//boss线程池和工作线程池，主要负责接收消息

        Executors.newCachedThreadPool(new DefaultThreadFactory("nettyServerBoss", true)),

        Executors.newCachedThreadPool(new DefaultThreadFactory("nettyServerWorker", true)));

    private StandardThreadExecutor
 standardThreadExecutor = null;//业务线程池，负责具体的业务处理

    standardThreadExecutor
 = (standardThreadExecutor != null &&
 !standardThreadExecutor.isShutdown()) ? standardThreadExecutor

            : new StandardThreadExecutor(minWorkerThread,
 maxWorkerThread, workerQueueSize,

                    new DefaultThreadFactory("NettyServer-" +
 url.getServerPortStr(), true));

    standardThreadExecutor.prestartAllCoreThreads();

   final NettyChannelHandler
 handler = new NettyChannelHandler(NettyServer.this,
 messageHandler,

            standardThreadExecutor);//handler使用业务线程池今天处理具体的业务