强制DataNode向NameNode上报blocks

内容简介：强制DataNode向NameNode上报blocks

正常情况下，什么时候上报blocks，是由NameNode通过回复心跳响应的方式触发的。

一次机房搬迁中，原机房hadoop版本为2.7.2，新机房版本为2.8.0，采用先扩容再缩容的方式搬迁。由于新旧机房机型不同和磁盘数不同，操作过程搞混过hdfs-site.xml，因为两种不同的机型，hdfs-site.xml不便做到相同，导致了NameNode报大量“missing block”。

然而依据NameNode所报信息，在DataNode能找到那些被标记为“missing”的blocks。修复配置问题后，“missing block”并没有消失。结合DataNode源代码，估计是因为DataNode没有向NameNode上报blocks。

结合DataNode的源代码，发现了HDFS自带的工具triggerBlockReport，它可以强制指定的DataNode向NameNode上报块，使用方法为：

hdfs dfsadmin -triggerBlockReport datanode_host:ipc_port

如：hdfs dfsadmin -triggerBlockReport 192.168.31.35:50020

正常情况下NameNode启动时，会要求DataNode上报一次blocks（通过fullBlockReportLeaseId值来控制），相关源代码如下：

DataNode相关代码（BPServiceActor.java）：

private void offerService() throws Exception {

HeartbeatResponse resp = sendHeartBeat(requestBlockReportLease); // 向NameNode发向心跳

long fullBlockReportLeaseId = resp.getFullBlockReportLeaseId(); // 心跳响应

boolean forceFullBr = scheduler.forceFullBlockReport.getAndSet(false); // triggerBlockReport强制上报仅一次有效

if (forceFullBr) {

LOG.info("Forcing a full block report to " + nnAddr);

}

if ((fullBlockReportLeaseId != 0) || forceFullBr) {

cmds = blockReport(fullBlockReportLeaseId);

fullBlockReportLeaseId = 0;

}

}

// NameNode相关代码（FSNamesystem.java）：

/**

* The given node has reported in.  This method should:

* 1) Record the heartbeat, so the datanode isn't timed out

* 2) Adjust usage stats for future block allocation

* 

* If a substantial amount of time passed since the last datanode 

* heartbeat then request an immediate block report.  

* 

* @return an array of datanode commands 

* @throws IOException

*/

HeartbeatResponse handleHeartbeat(DatanodeRegistration nodeReg,

StorageReport[] reports, long cacheCapacity, long cacheUsed,

int xceiverCount, int xmitsInProgress, int failedVolumes,

VolumeFailureSummary volumeFailureSummary,

boolean requestFullBlockReportLease) throws IOException {

readLock();

try {

//get datanode commands

final int maxTransfer = blockManager.getMaxReplicationStreams() - xmitsInProgress;

DatanodeCommand[] cmds = blockManager.getDatanodeManager().handleHeartbeat(

nodeReg, reports, blockPoolId, cacheCapacity, cacheUsed,

xceiverCount, maxTransfer, failedVolumes, volumeFailureSummary);

long fullBlockReportLeaseId = 0;

if (requestFullBlockReportLease) {

fullBlockReportLeaseId =  blockManager.requestBlockReportLeaseId(nodeReg);

}

//create ha status

final NNHAStatusHeartbeat haState = new NNHAStatusHeartbeat(

haContext.getState().getServiceState(),

getFSImage().getCorrectLastAppliedOrWrittenTxId());

return new HeartbeatResponse(cmds, haState, rollingUpgradeInfo, fullBlockReportLeaseId);

} finally {

readUnlock("handleHeartbeat");

}

}

以上所述就是小编给大家介绍的《强制DataNode向NameNode上报blocks》，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对 码农网 的支持！

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