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- 从命名空间删除文件
- 将相应的数据块加到InvalidateBlocks中
- ReplicationMonitor监控线程
- 心跳生成删除命令
- 心跳处理删除命令
- 异步单独开启线程删除磁盘数据
- 向namenode汇报删除的块
客户端删除文件
先来一段简单的代码,用java的api删除hdfs的 文件
代码语言：javascript复制 Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
Path p = new Path("hdfs://127.0.0.1:9000/demo021.txt");
fs.delete(p,true);
fs.close();// 释放资源
System.out.println("删除成功.....");
namenode删除文件
客户端通过ClientProtocol.delete(String, boolean)方法来删除文件,最终实现是NameNodeRpcServer.delete(String, boolean)方法.
之后调用了FSNamesystem的delete来删除namesystem中的相应的文件.,这里总共分为两步,第一步,从namespace删除相应的文件信息并收集删除的文件的数据块.第二步,将收集到的待删除的数据块加到blockmanage的invalidateBlocks中,等待datanode下次心跳的时候生成删除命令发给datanode,然后删除具体的数据块.
代码语言：javascript复制
boolean delete(String src, boolean recursive, boolean logRetryCache)
throws IOException {
waitForLoadingFSImage();
BlocksMapUpdateInfo toRemovedBlocks = null;
writeLock();
boolean ret = false;
try {
//检查是否有写的权限
checkOperation(OperationCategory.WRITE);
//检查是否处于安全模式
checkNameNodeSafeMode("Cannot delete " src);
//从命名空间删除相应的文件
toRemovedBlocks = FSDirDeleteOp.delete(
this, src, recursive, logRetryCache);
ret = toRemovedBlocks != null;
} catch (AccessControlException e) {
logAuditEvent(false, "delete", src);
throw e;
} finally {
writeUnlock();
}
//将删除操作记录到editlog中
getEditLog().logSync();
if (toRemovedBlocks != null) {
//删除数据块操作
removeBlocks(toRemovedBlocks); // Incremental deletion of blocks
}
logAuditEvent(true, "delete", src);
return ret;
}
从命名空间删除文件
通过工具类FSDirDeleteOp的静态方法delete来删除文件,并且收集该文件的要删除的block.
最终通过FSDirDeleteOp类的unprotectedDelete(FSDirectory, INodesInPath, BlocksMapUpdateInfo, List, long)方法来执行删除操作.之所以叫做unprotectedDelet,是因为这个时候删除只是将该文件从命名空间中删除,并没有真正的写入editlog.
删除过程分为以下几个步骤: 1.检查文件是否存在 2,修改快照记录 3.从namespace中移除文件,也就是FSDirectory记录的INodeDirectory 类型的rootDir中删除; 4.设置父文件夹的最后修改时间 5更新删除的记录数 6 收集要删除的block
代码语言：javascript复制
/**
* Delete a path from the name space
* Update the count at each ancestor directory with quota
* @param iip the inodes resolved from the path
* @param collectedBlocks blocks collected from the deleted path
* @param removedINodes inodes that should be removed from inodeMap
* @param mtime the time the inode is removed
* @return the number of inodes deleted; 0 if no inodes are deleted.
*/
private static long unprotectedDelete(
FSDirectory fsd, INodesInPath iip, BlocksMapUpdateInfo collectedBlocks,
List<INode> removedINodes, long mtime) {
assert fsd.hasWriteLock();
// check if target node exists
//检查是否存在
INode targetNode = iip.getLastINode();
if (targetNode == null) {
return -1;
}
//修改快照
// record modification
final int latestSnapshot = iip.getLatestSnapshotId();
targetNode.recordModification(latestSnapshot);
//最核心的代码,从命名空间删除
// Remove the node from the namespace
long removed = fsd.removeLastINode(iip);
if (removed == -1) {
return -1;
}
//设置父文件夹的最后修改时间
// set the parent's modification time
final INodeDirectory parent = targetNode.getParent();
parent.updateModificationTime(mtime, latestSnapshot);
//更新记录数
fsd.updateCountForDelete(targetNode, iip);
if (removed == 0) {
return 0;
}
//收集要删除的block
// collect block and update quota
if (!targetNode.isInLatestSnapshot(latestSnapshot)) {
//收集INodeFile中的blocks变量存放的block信息
targetNode.destroyAndCollectBlocks(fsd.getBlockStoragePolicySuite(),
collectedBlocks, removedINodes);
} else {
QuotaCounts counts = targetNode.cleanSubtree(
fsd.getBlockStoragePolicySuite(), CURRENT_STATE_ID,
latestSnapshot, collectedBlocks, removedINodes);
removed = counts.getNameSpace();
fsd.updateCountNoQuotaCheck(iip, iip.length() -1, counts.negation());
}
if (NameNode.stateChangeLog.isDebugEnabled()) {
NameNode.stateChangeLog.debug("DIR* FSDirectory.unprotectedDelete: "
iip.getPath() " is removed");
}
return removed;
}
}
将相应的数据块加到InvalidateBlocks中
FSNamesystem的removeBlocks循环刚才收集到的blocks,然后调用blockManager的removeBlock来处理要删除的数据块.
在blockManager的removeBlock中,首先获取到相应的block对应的DatanodeDescriptor,然后将其加到invalidateBlocks里面,然后从blocksMap,corruptReplicas,pendingReplications ,neededReplications 中删除相应的block.
代码语言：javascript复制 public void removeBlock(Block block) {
assert namesystem.hasWriteLock();
// No need to ACK blocks that are being removed entirely
// from the namespace, since the removal of the associated
// file already removes them from the block map below.
block.setNumBytes(BlockCommand.NO_ACK);
addToInvalidates(block); //加到invalidateBlocks中
removeBlockFromMap(block);//从blocksMap删除
// Remove the block from pendingReplications and neededReplications
pendingReplications.remove(block);
neededReplications.remove(block, UnderReplicatedBlocks.LEVEL);
if (postponedMisreplicatedBlocks.remove(block)) {
postponedMisreplicatedBlocksCount.decrementAndGet();
}
}
ReplicationMonitor监控线程
BlockManage里面有一个ReplicationMonitor线程,不断的计算块的副本信息和无效的块信息,以便生成相应的命令,等下次心跳的时候传给datanode.在这里我们只是看下相应的删除的方法.
通过run方法我们找到计算无效的块信息的方法computeInvalidateWork,在这里会循环invalidateBlocks中的所有datanode,然后循环调用invalidateWorkForOneNode方法一个一个的datanode来处理.
在invalidateWorkForOneNode中,首先将相应的datanode从invalidateBlocks中删除,然后调用invalidateBlocks.invalidateWork将该DatanodeDescriptor相应的无效的块加到DatanodeDescriptor类中LightWeightHashSet类型的变量invalidateBlocks中,等待下次心跳生成删除命令.
心跳生成删除命令
具体生成删除相关命令的代码在以下方法中,DatanodeManager.handleHeartbeat(DatanodeRegistration, StorageReport[], String, long, long, int, int, int, VolumeFailureSummary).
代码语言：javascript复制 //check block invalidation
Block[] blks = nodeinfo.getInvalidateBlocks(blockInvalidateLimit);
if (blks != null) {
cmds.add(new BlockCommand(DatanodeProtocol.DNA_INVALIDATE,
blockPoolId, blks));
}有关hdfs心跳相关的信息请参考 http://blog.csdn.net/zhangjun5965/article/details/75579238
datanode删除相应的block并汇报
心跳处理删除命令
datanode方面是通过BPServiceActor的offerService方法进行心跳相关的操作,报告心跳之后,会依次处理从namenode接收的命令,最终处理的方法落在BPOfferService.processCommandFromActive(DatanodeCommand, BPServiceActor)方法上.
在这个方法中,通过switch来判断传过来的是哪种命令,来分别进行处理,删除数据块对应的是DatanodeProtocol.DNA_INVALIDATE,最终进入了FsDatasetImpl.invalidate(String, Block[])方法来从磁盘删除具体的数据块.
异步单独开启线程删除磁盘数据
具体的操作方法是调用了asyncDiskService.deleteAsync异步的开启线程删除数据块,以便提高效率.
代码语言：javascript复制 // Delete the block asynchronously to make sure we can do it fast enough.
// It's ok to unlink the block file before the uncache operation
// finishes.
try {
asyncDiskService.deleteAsync(v.obtainReference(), f,
FsDatasetUtil.getMetaFile(f, invalidBlks[i].getGenerationStamp()),
new ExtendedBlock(bpid, invalidBlks[i]),
dataStorage.getTrashDirectoryForBlockFile(bpid, f));
} catch (ClosedChannelException e) {
LOG.warn("Volume " v " is closed, ignore the deletion task for "
"block " invalidBlks[i]);
}多线程删除具体是开启了一个ReplicaFileDeleteTask线程来做删除的操作,这个方法会先删除数据块信息和meta信息,删除之后调用 datanode.notifyNamenodeDeletedBlock(block, volume.getStorageID());向namenode报告最近删除的数据块. 但是这个时候并不是将这些信息直接发给namenode,而是要删除的blocks和其对应的DatanodeStorage生成ReceivedDeletedBlockInfo对象存在了BPServiceActor的Map<DatanodeStorage, PerStoragePendingIncrementalBR>类型的map的变量pendingIncrementalBRperStorage中,等下次心跳的时候,由BPServiceActor来处理.
向namenode汇报删除的块
在BPServiceActor的心跳处理方法offerService中,会通过 reportReceivedDeletedBlocks();读取pendingIncrementalBRperStorage变量中的blocks信息,向namenode汇报刚刚删除的数据块信息.
代码语言：javascript复制 if (sendImmediateIBR ||
(startTime - lastDeletedReport > dnConf.deleteReportInterval)) {
reportReceivedDeletedBlocks();
lastDeletedReport = startTime;
}
最终通过datanode和namenode之间的协议DatanodeProtocol.blockReceivedAndDeleted(DatanodeRegistration, String, StorageReceivedDeletedBlocks[])来向namenode报告刚才删除的数据块.
namenode处理删除block的汇报
namenode处理最近删除的块的方法是在NameNodeRpcServer中的方法blockReceivedAndDeleted中,通过跟踪代码,最终到了BlockManager.removeStoredBlock(Block, DatanodeDescriptor)中.
首先从blocksMap中移除相应的块信息,然后判断是否是因为datanode挂掉而导致的block被移除,并做相应的处理,然后从excessReplicateMap,corruptReplicas队列中将其移除.
代码语言：javascript复制 /**
* Modify (block-->datanode) map. Possibly generate replication tasks, if the
* removed block is still valid.
*/
public void removeStoredBlock(Block block, DatanodeDescriptor node) {
blockLog.debug("BLOCK* removeStoredBlock: {} from {}", block, node);
assert (namesystem.hasWriteLock());
{
//从blocksMap移除
if (!blocksMap.removeNode(block, node)) {
blockLog.debug("BLOCK* removeStoredBlock: {} has already been"
" removed from node {}", block, node);
return;
}
//判断是否是因为datanode失败而移除的数据块,如果block仍然有效,检查副本是不是必要的,在这种情况下,需要将block加到待复制的block列表中.
// It's possible that the block was removed because of a datanode
// failure. If the block is still valid, check if replication is
// necessary. In that case, put block on a possibly-will-
// be-replicated list.
//
BlockCollection bc = blocksMap.getBlockCollection(block);
if (bc != null) {
namesystem.decrementSafeBlockCount(block);
updateNeededReplications(block, -1, 0);
}
//
// We've removed a block from a node, so it's definitely no longer
// in "excess" there.
//从excessReplicateMap移除
LightWeightLinkedSet<Block> excessBlocks = excessReplicateMap.get(node
.getDatanodeUuid());
if (excessBlocks != null) {
if (excessBlocks.remove(block)) {
excessBlocksCount.decrementAndGet();
blockLog.debug("BLOCK* removeStoredBlock: {} is removed from "
"excessBlocks", block);
if (excessBlocks.size() == 0) {
excessReplicateMap.remove(node.getDatanodeUuid());
}
}
}
//从corruptReplicas移除
// Remove the replica from corruptReplicas
corruptReplicas.removeFromCorruptReplicasMap(block, node);
}
}总结
上述只是基于hadoop2.7.3源码自己的一些学习笔记,如有不对的地方,还请见谅。
