有个线程，AzkabanWebServer-QueueProcessor-Thread.
下面分析下这个线程到底干嘛的！！！
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stop in azkaban.executor.ExecutorManager$QueueProcessorThread.run
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public void run() {
// Loops till QueueProcessorThread is shutdown
while (!shutdown) { // 一直循环
synchronized (this) { //
try {
// start processing queue if active, other wait for
// sometime
if (isActive) {
// 开始处理任务
processQueuedFlows(activeExecutorRefreshWindowInMilisec,
activeExecutorRefreshWindowInFlows);
}
wait(QUEUE_PROCESSOR_WAIT_IN_MS);// 等待1秒
} catch (Exception e) {
logger.error("QueueProcessorThread Interrupted. Probably to shut down.", e);
}
}
}
}
所以接下来要看这个processQueuedFlows干嘛的？
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// process flow with current snapshot of activeExecutors
selectExecutorAndDispatchFlow(reference, exflow, new HashSet<Executor>(activeExecutors));
从这里来看，就是把任务分发到具体的executor上，
不过这个函数其实还做了其它的事情！那就是executor的存活监控
// if we have dispatched more than maxContinuousFlowProcessed or
// It has been more then activeExecutorsRefreshWindow millisec
// since we
// refreshed
// 满足上面的条件就探测executor的存活性
if (currentTime - lastExecutorRefreshTime > activeExecutorsRefreshWindow
|| currentContinuousFlowProcessed >= maxContinuousFlowProcessed) {
// Refresh executorInfo for all activeExecutors
refreshExecutors();
lastExecutorRefreshTime = currentTime;
currentContinuousFlowProcessed = 0;
}
所以接下来，我们来看看refreshExecutors的代码实现！
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jdb azkaban.webapp.AzkabanWebServer -conf /root/azkb/azkaban_3.0.0_debug/conf
stop in azkaban.executor.ExecutorManager.refreshExecutors
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其中刷新周期
azkProps.getLong(AZKABAN_ACTIVE_EXECUTOR_REFRESH_IN_MS, 50000),
private static final String AZKABAN_ACTIVE_EXECUTOR_REFRESH_IN_MS = "azkaban.activeexecutor.refresh.milisecinterval";
默认为50秒刷1次更新请求
其实是通过一个线程池来跑的，
Future<String> fetchExecutionInfo = executorInforRefresherService.submit(new Callable<String>() {
@Override
public String call() throws Exception {
return callExecutorForJsonString(executor.getHost(), executor.getPort(), "/serverStatistics",
null);
}
});
那么，这个线程池的个数呢？
executorInforRefresherService = Executors
.newFixedThreadPool(azkProps.getInt(AZKABAN_EXECUTORINFO_REFRESH_MAX_THREADS, 5));
private static final String AZKABAN_EXECUTORINFO_REFRESH_MAX_THREADS = "azkaban.executorinfo.refresh.maxThreads";
默认就是5个了，好，回来看怎么执行！
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发出HTTP请求 /serverStatistics
然后结果更新到executor,所以重点就是 /serverStatistics在executor中的执行过程！
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root.addServlet(new ServletHolder(new ServerStatisticsServlet()), "/serverStatistics");
jdb azkaban.execapp.AzkabanExecutorServer -conf /root/azkb/azkaban_3.0.0_debug/conf
stop in azkaban.execapp.ServerStatisticsServlet.doGet
stop in azkaban.execapp.ServerStatisticsServlet.populateStatistics
run
其实就是生成本地的信息汇总
1）
fillRemainingMemoryPercent(stats);
azkaban.execapp.ServerStatisticsServlet.fillRemainingMemoryPercent
2）
fillRemainingFlowCapacityAndLastDispatchedTime(stats);
stop in azkaban.execapp.ServerStatisticsServlet.fillRemainingFlowCapacityAndLastDispatchedTime
3）
fillCpuUsage(stats);
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其实就是返回这3种信息
对于web server来说，5秒内拿到返回内容后，更新本地消息
public void setExecutorInfo(ExecutorInfo info) {
this.cachedExecutorStats = info;
this.lastStatsUpdatedTime = new Date();
}
以此来作为存活监控！