JobTracker无任务时处理心跳流程
HeartBeat格式：{restarted=true，initialContact=true，acceptNewTasks=true，responseId=-1，
status=TaskTrackerStatus {failures=0，trackerName="tracker_server3:localhost.localdomain/127.0.0.1:57441"(id=2249) ，taskReports=[], maxReduceTasks=2, lastSeen=0, httpPort=50060, host="server3"(id=2243),
healthStatus=TaskTrackerStatus$TaskTrackerHealthStatus { lastReported=0,isNodeHealthy=true, healthReport="" (id=2261)}
resStatus=TaskTrackerStatus$ResourceStatus {availablePhysicalMemory=601034752, availableSpace=32463671296,availableVirtualMemory=2705653760, cpuFrequency=2195079,cpuUsage=-1.0,cumulativeCpuTime=1227000 , mapSlotMemorySizeOnTT=-1, numProcessors=1,reduceSlotMemorySizeOnTT=-1, totalPhysicalMemory=1044144128,totalVirtualMemory=3158065152}
}
}
判断是否应该接受：(inHostsList(status)&& !inExcludedHostsList(status))
主要调用方法:
public synchronized HeartbeatResponse heartbeat(TaskTrackerStatus status, boolean restarted, boolean initialContact, boolean acceptNewTasks， short responseId)
private synchronized boolean process Heartbeat(TaskTrackerStatus trackerStatus,
boolean initialContact,long timeStamp) throws UnknownHostException
private boolean updateTaskTrackerStatus(String trackerName, TaskTrackerStatus status)
private void addNewTracker(TaskTracker taskTracker) throws UnknownHostException
public Node resolveAndAddToTopology(String name) throws UnknownHostException
private Node addHostToNodeMapping(String host, StringnetworkLoc)
void updateTaskStatuses(TaskTrackerStatus status)
private void updateNodeHealthStatus(TaskTrackerStatus trackerStatus, long timeStamp)
synchronized List＜Task＞ getSetupAndCleanupTasks(TaskTrackerStatus taskTracker) throws IOException
public synchronized ClusterStatus getClusterStatus(boolean detailed)
private synchronized List＜TaskTrackerAction＞ getTasksToKill(String taskTracker)
private List＜TaskTrackerAction＞ getJobsForCleanup(String taskTracker)
private synchronized List＜TaskTrackerAction＞ getTasksToSave(TaskTrackerStatust ts )
public int getNextHeartbeatInterval()
private void removeMarkedTasks(String taskTracker)
void org.apache.hadoop.mapred.JobTracker.FaultyTrackersInfo.markTrackerHealthy(StringhostName)
boolean org.apache.hadoop.mapred.JobTracker.FaultyTrackersInfo.isBlacklisted(StringhostName)
void org.apache.hadoop.mapred.JobTracker.FaultyTrackersInfo.setNodeHealthStatus(StringhostName, boolean isHealthy, Stringreason, long timeStamp)
List＜String＞ org.apache.hadoop.net.CachedDNSToSwitchMapping.resolve(List＜String＞ names)
void org.apache.hadoop.net.CachedDNSToSwitchMapping.cacheResolvedHosts(List＜String＞ uncachedHosts, List＜String＞ resolvedHosts)
List＜String＞ org.apache.hadoop.net.CachedDNSToSwitchMapping.getCachedHosts(List＜String＞ names)
List＜Task＞ org.apache.hadoop.mapred.JobQueueTaskScheduler.assignTasks(TaskTrackertaskTracker) throws IOException
1、Server3的TaskTracker首次启动后HeartBeat
从FaultyTrackersInfo.potentiallyFaultyTrackers移除，看是否应该从Graylist或 Blacklist移除
从trackerToHeartbeatResponseMap拿出上一次的HeartbeatResponse，为null
从taskTrackers拿出上一次的TaskTracker.TaskTrackerStatus,为null，
更新JobTracker的成员totalMaps=0、totalReduces=0、occupiedMapSlots=0、occupiedReduceSlots=0，
从FaultyTrackersInfo.potentiallyFaultyTrackers查看是否在黑名单中，更新totalMapTaskCapacity=2、totalReduceTaskCapacity=2。
加入taskTrackers此时内容为：
{tracker_server3:localhost.localdomain/127.0.0.1:43336=org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker@4fd86469}
加入uniqueHostsMap此时其内容为：
{server3=1}
加入trackerExpiryQueue，此时其内容为：
[org.apache.hadoop.mapred.TaskTrackerStatus@4e048dc6]
加入dnsToSwitchMapping.cache，内容为
{10.1.1.103=/default-rack}
加入clusterMap，内容为：
Number of racks: 1
Expected number of leaves:1
/default-rack/server3
加入hostnameToNodeMap，内容为：
{server3=/default-rack/server3}
加入nodesAtMaxLevel，内容为：
[/default-rack]
加入hostnameToTaskTracker，内容为
{server3=[org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker@4fd86469]}
检查status.getTaskReports()，若不为空，则更新expireLaunchingTasks、trackerToJobsToCleanup、trackerToTasksToCleanup、taskidToTIPMap
responseId加1，从jobs、jobQueueJobInProgressListener、trackerToTaskMap、trackerToTasksToCleanup、trackerToJobsToCleanup、taskidToTIPMap取出Job和Task，生成TaskTrackerAction（此时为空）
取得nextInterval
生成HeartbeatResponse，内容：
{actions=[],conf=null,heartbeatInterval=240000,recoveredJobs=[],responseId=0}
加入trackerToHeartbeatResponseMap，内容为
{tracker_server3:localhost.localdomain/127.0.0.1:43336=org.apache.hadoop.mapred.HeartbeatResponse@25a78661}
发送HeartbeatResponse给客户端
2、Server2的TaskTracker首次启动后HeartBeat
同样先从potentiallyFaultyTrackers移除，看是否应该从Graylist或 Blacklist移除
从FaultyTrackersInfo.trackerToHeartbeatResponseMap拿出上一次的HeartbeatResponse，为null
从taskTrackers拿出上一次的TaskTracker.TaskTrackerStatus,为null，
更新JobTracker的成员totalMaps=0、totalReduces=0、occupiedMapSlots=0、occupiedReduceSlots=0、totalMapTaskCapacity=4、totalReduceTaskCapacity=4。
加入taskTrackers此时内容为：
{tracker_server2:localhost.localdomain/127.0.0.1:34381=org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker@412eb15f,tracker_server3:localhost.localdomain/127.0.0.1:45605=org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker@2634d0e2}
加入uniqueHostsMap此时其内容为：
{server2=1, server3=1}
加入trackerExpiryQueue，此时其内容为：
[org.apache.hadoop.mapred.TaskTrackerStatus@4444ad54,org.apache.hadoop.mapred.TaskTrackerStatus@2ea31991]
加入dnsToSwitchMapping.cache，内容为
{10.1.1.102=/default-rack,10.1.1.103=/default-rack}
加入clusterMap，内容为：
Number of racks: 1
Expected number of leaves:2
/default-rack/server3
/default-rack/server2
加入hostnameToNodeMap，内容为：
{server2=/default-rack/server2,server3=/default-rack/server3}
加入nodesAtMaxLevel，内容为：
[/default-rack]
加入hostnameToTaskTracker，内容为
{server2=[org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker@412eb15f],server3=[org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker@2634d0e2]}
检查status.getTaskReports()，若不为空，则更新expireLaunchingTasks、trackerToJobsToCleanup、trackerToTasksToCleanup、taskidToTIPMap
responseId加1，从jobs、jobQueueJobInProgressListener、trackerToTaskMap、trackerToTasksToCleanup、trackerToJobsToCleanup、taskidToTIPMap取出Job和Task，生成TaskTrackerAction（此时为空）
取得nextInterval
生成HeartbeatResponse，内容：
{actions=[],conf=null,heartbeatInterval=240000,recoveredJobs=[],responseId=0}
加入trackerToHeartbeatResponseMap，内容为
{tracker_server2:localhost.localdomain/127.0.0.1:34381=org.apache.hadoop.mapred.HeartbeatResponse@2f4dd8ae,tracker_server3:localhost.localdomain/127.0.0.1:45605=org.apache.hadoop.mapred.HeartbeatResponse@16bd1f19}
发送HeartbeatResponse给客户端
3. Server3再次HeartBeat
从potentiallyFaultyTrackers移除，看是否应该从Blacklist移除
从FaultyTrackersInfo.trackerToHeartbeatResponseMap取得上次HeartbeatResponse，为
org.apache.hadoop.mapred.HeartbeatResponse@16bd1f19
判断上一次的ResponseId是否与这次接收的ResponseId相同。
更新JobTracker的成员totalMaps、totalReduces、occupiedMapSlots、occupiedReduceSlots、totalMapTaskCapacity、totalReduceTaskCapacity，先从taskTrackers拿出上一次的TaskTracker.TaskTrackerStatus还原更新，然后用这一次的TaskTrackerStatus更新，其中要从FaultyTrackersInfo.potentiallyFaultyTrackers查看是否在黑名单中。
更新taskTrackers此时内容为： {tracker_server2:localhost.localdomain/127.0.0.1:52688=org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker@1cdc471a,tracker_server3:localhost.localdomain/127.0.0.1:40286=org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker@665755f5}
检查status.getTaskReports()，若不为空，则更新expireLaunchingTasks、trackerToJobsToCleanup、trackerToTasksToCleanup、taskidToTIPMap
responseId加1，从jobs、jobQueueJobInProgressListener、trackerToTaskMap、trackerToTasksToCleanup、trackerToJobsToCleanup、taskidToTIPMap取出Job和Task，生成TaskTrackerAction（此时为空）
取得nextInterval
生成HeartbeatResponse，内容：
{actions=[],conf=null,heartbeatInterval=240000,recoveredJobs=[],responseId=1}
更新trackerToHeartbeatResponseMap，内容为
{tracker_server2:localhost.localdomain/127.0.0.1:52688=org.apache.hadoop.mapred.HeartbeatResponse@1500df0b,tracker_server3:localhost.localdomain/127.0.0.1:40286=org.apache.hadoop.mapred.HeartbeatResponse@6c3355f2}
发送HeartbeatResponse给客户端
4. ExpireTrackers移除过期
从trackerExpiryQueue取出一个 TaskTrackerStatus，根据LastSeen判断是否清除或更新，
从taskTrackers取出TaskTracker.TaskTrackerStatus，继续判断LastSeen。
若不需清除有则更新trackerExpiryQueue。
若需清除从trackerExpiryQueue清除，从trackerToJobsToCleanup、trackerToTasksToCleanup、recoveredTrackers、trackerToTaskMap清除
还原更新totalMaps、totalReduces、occupiedMapSlots、occupiedReduceSlots、totalMapTaskCapacity、totalReduceTaskCapacity。
从taskTrackers、uniqueHostsMap、hostnameToTaskTracker移除