【Flume】flume中http监控类型的源码分析，度量信息分析，以及flume的事件总线

在flume1.5.2中，如果想要通过http方式的监控来获取flume相关度量值，通过在启动脚本后添加如下内容即可：

-Dflume.monitoring.type=http -Dflume.monitoring.port=34545

监控

-D的属性可以通过System.getProerties()直接获取得到，那么以上两个属性是通过方法loadMonitoring()来读取，该方法在flume入口中Application

 private void loadMonitoring() {
    Properties systemProps = System.getProperties();
    Set<String> keys = systemProps.stringPropertyNames();
    try {
      if (keys.contains(CONF_MONITOR_CLASS)) {
        String monitorType = systemProps.getProperty(CONF_MONITOR_CLASS);
        Class<? extends MonitorService> klass;
        try {
          //Is it a known type?
          klass = MonitoringType.valueOf(
                  monitorType.toUpperCase()).getMonitorClass();
        } catch (Exception e) {
          //Not a known type, use FQCN
          klass = (Class<? extends MonitorService>) Class.forName(monitorType);
        }
        this.monitorServer = klass.newInstance();
        Context context = new Context();
        for (String key : keys) {
          if (key.startsWith(CONF_MONITOR_PREFIX)) {
            context.put(key.substring(CONF_MONITOR_PREFIX.length()),
                    systemProps.getProperty(key));
          }
        }
        monitorServer.configure(context);
        monitorServer.start();
      }
    } catch (Exception e) {
      logger.warn("Error starting monitoring. "
              + "Monitoring might not be available.", e);
    }

  }

public void start() {
    jettyServer = new Server();
    //We can use Contexts etc if we have many urls to handle. For one url,
    //specifying a handler directly is the most efficient.
    SelectChannelConnector connector = new SelectChannelConnector();
    connector.setReuseAddress(true);
    connector.setPort(port);
    jettyServer.setConnectors(new Connector[] {connector});
    jettyServer.setHandler(new HTTPMetricsHandler());
    try {
      jettyServer.start();
      while (!jettyServer.isStarted()) {
        Thread.sleep(500);
      }
    } catch (Exception ex) {
      LOG.error("Error starting Jetty. JSON Metrics may not be available.", ex);
    }

看它的handle()方法

public void handle(String target,
            HttpServletRequest request,
            HttpServletResponse response,
            int dispatch) throws IOException, ServletException {
      // /metrics is the only place to pull metrics.
      //If we want to use any other url for something else, we should make sure
      //that for metrics only /metrics is used to prevent backward
      //compatibility issues.
      if(request.getMethod().equalsIgnoreCase("TRACE") || request.getMethod()
        .equalsIgnoreCase("OPTIONS")) {
        response.sendError(HttpServletResponse.SC_FORBIDDEN);
        response.flushBuffer();
        ((Request) request).setHandled(true);
        return;
      }
      if (target.equals("/")) {
        response.setContentType("text/html;charset=utf-8");
        response.setStatus(HttpServletResponse.SC_OK);
        response.getWriter().write("For Flume metrics please click"
                + " <a href = \"./metrics\"> here</a>.");
        response.flushBuffer();
        ((Request) request).setHandled(true);
        return;
      } else if (target.equalsIgnoreCase("/metrics")) {
        response.setContentType("application/json;charset=utf-8");
        response.setStatus(HttpServletResponse.SC_OK);
        Map<String, Map<String, String>> metricsMap = JMXPollUtil.getAllMBeans();
        String json = gson.toJson(metricsMap, mapType);
        response.getWriter().write(json);
        response.flushBuffer();
        ((Request) request).setHandled(true);
        return;
      }
      response.sendError(HttpServletResponse.SC_NOT_FOUND);
      response.flushBuffer();
      //Not handling the request returns a Not found error page.
    }

1、首先是禁止了TRACE和OPTIONS两种请求

TRACE- 回显服务器收到的请求，主要用于测试或诊断。
OPTIONS - 返回服务器针对特定资源所支持的HTTP请求方法。也可以利用向Web服务器发送‘*‘的请求来测试服务器的功能性。

2、如果你输入的地址是ip:port，没有输入后面的metrics，效果如下：

点击here就可以看到度量信息了

3、如果你输入了metrics请求，后面就是具体的处理逻辑了

Map<String, Map<String, String>> metricsMap = JMXPollUtil.getAllMBeans();

度量

现在来看看某一个度量信息是如何一步步被获取到的，以

OpenConnectionCount

为例

在类SourceCounter中

构造方法

public SourceCounter(String name) {
    super(MonitoredCounterGroup.Type.SOURCE, name, ATTRIBUTES);
  }

而该方法又被BasicSourceSemantics类的configure调用
在会上就回到了入口Application的loadMonitoring方法了，这一条链就通了

上面构造方法调用了父类构造方法

protected MonitoredCounterGroup(Type type, String name, String... attrs) {
    this.type = type;
    this.name = name;

    Map<String, AtomicLong> counterInitMap = new HashMap<String, AtomicLong>();

    // Initialize the counters
    for (String attribute : attrs) {
      counterInitMap.put(attribute, new AtomicLong(0L));
    }

    counterMap = Collections.unmodifiableMap(counterInitMap);

    startTime = new AtomicLong(0L);
    stopTime = new AtomicLong(0L);

  }

在整个SourceCounter类中，我们看到有很多increment,add,get的方法，那么这些方法什么时候被调用呢？

我们看一个具体的AvroSource类

public Status append(AvroFlumeEvent avroEvent) {
    logger.debug("Avro source {}: Received avro event: {}", getName(),
        avroEvent);
    sourceCounter.incrementAppendReceivedCount();
    sourceCounter.incrementEventReceivedCount();

    Event event = EventBuilder.withBody(avroEvent.getBody().array(),
        toStringMap(avroEvent.getHeaders()));

    try {
      getChannelProcessor().processEvent(event);
    } catch (ChannelException ex) {
      logger.warn("Avro source " + getName() + ": Unable to process event. " +
          "Exception follows.", ex);
      return Status.FAILED;
    }

    sourceCounter.incrementAppendAcceptedCount();
    sourceCounter.incrementEventAcceptedCount();

    return Status.OK;
  }

各个属性都是在组件运行过程，实时的去赋值的。

{
    "SOURCE.r1": {
        "OpenConnectionCount": "0",                         当前有效的连接数
        "Type": "SOURCE",                                        组件类型
        "AppendBatchAcceptedCount": "0",                source端刚刚追加放入channel的批量数
        "AppendBatchReceivedCount": "0",                source端刚刚追加的批量的数量，比如一批100，该度量为2，就是source端收到了200个events
        "EventAcceptedCount": "10",                          source端目前成功放入channel的event数量
        "StopTime": "0",
        "AppendReceivedCount": "0",                         source端刚刚追加的目前收到的event数量
        "StartTime": "1422502242340",                      source组件启动的时间
        "EventReceivedCount": "10",                          source端已经收到的event数量
        "AppendAcceptedCount": "0"                          source端刚刚追加放入channel的event数量
    },
    "SOURCE.r2": {
        "OpenConnectionCount": "0",
        "Type": "SOURCE",
        "AppendBatchAcceptedCount": "0",
        "AppendBatchReceivedCount": "0",
        "EventAcceptedCount": "10",
        "StopTime": "0",
        "AppendReceivedCount": "0",
        "StartTime": "1422502242341",
        "EventReceivedCount": "10",
        "AppendAcceptedCount": "0"
    },
    "CHANNEL.c1": {
        "EventPutSuccessCount": "20",                   成功放入通道的event数量
        "ChannelFillPercentage": "0.0",                    通道使用比例
        "Type": "CHANNEL",
        "StopTime": "0",
        "EventPutAttemptCount": "20",                     正在放进通道的event数量
        "ChannelSize": "0",
        "StartTime": "1422502242328",
        "EventTakeSuccessCount": "20",                从通道中成功取出event的数量
        "ChannelCapacity": "10000000",
        "EventTakeAttemptCount": "2105"              正在从通道中取event的数量
    },
    "SINK.k1": {
        "BatchCompleteCount": "0",                        成功完成输出的批量事件个数
        "ConnectionFailedCount": "0",                     sink端连接失败的次数
        "EventDrainAttemptCount": "20",                 试图消耗的事件数量，从通道中拿来消耗
        "ConnectionCreatedCount": "1",                  sink端连接数
        "Type": "SINK",
        "BatchEmptyCount": "1042",                       批量取空的次数
        "ConnectionClosedCount": "0",                   连接关闭的次数
        "EventDrainSuccessCount": "20",               成功处理的event数量
        "StopTime": "0",
        "StartTime": "1422502242340",
        "BatchUnderflowCount": "1"                        内部event正处在批量处理过程中的batch数量，比如两个batch，内部都有event正在处理，就等于2
    },
    "SINK.k2": {
        "BatchCompleteCount": "0",
        "ConnectionFailedCount": "0",
        "EventDrainAttemptCount": "0",
        "ConnectionCreatedCount": "1",
        "Type": "SINK",
        "BatchEmptyCount": "1042",
        "ConnectionClosedCount": "0",
        "EventDrainSuccessCount": "0",
        "StopTime": "0",
        "StartTime": "1422502243048",
        "BatchUnderflowCount": "0"
    }
}

事件总线

以上是监控相关的度量信息，那么回到本文的一开始，loadMonitoring方法，我们来看看它的调用过程，分析下eventBus相关内容

if(reload) {
        EventBus eventBus = new EventBus(agentName + "-event-bus");
        PollingPropertiesFileConfigurationProvider configurationProvider =
            new PollingPropertiesFileConfigurationProvider(agentName,
                configurationFile, eventBus, 30);
        components.add(configurationProvider);
        application = new Application(components);
        eventBus.register(application);
      } else {
        PropertiesFileConfigurationProvider configurationProvider =
            new PropertiesFileConfigurationProvider(agentName,
                configurationFile);
        application = new Application();
        application.handleConfigurationEvent(configurationProvider.getConfiguration());
      }

eventBus是一个事件总线

EventBus的代码：

    public void register(Object object) {
        Multimap<Class<?>, EventHandler> methodsInListener =
                finder.findAllHandlers(object);
        handlersByType.putAll(methodsInListener);
    }

在EventBus进行register时，会通过一个finder找到register的object中被标注了@Subscribe的方法。并且按照EventType进行分类，放在handlersByType里。这样当EventBus的post新的Event时，就可以根据EventType调用相应的EventHandler。

@Subscribe
  public synchronized void handleConfigurationEvent(MaterializedConfiguration conf) {
    stopAllComponents();
    startAllComponents(conf);
  }

关于事件总线的详细介绍，请参考： http://blog.csdn.net/kiwi_coder/article/details/9338721