Package org.apache.hadoop.hdfs.server.protocol

Class BlockCommand

java.lang.Object

org.apache.hadoop.hdfs.server.protocol.ServerCommand

org.apache.hadoop.hdfs.server.protocol.DatanodeCommand

org.apache.hadoop.hdfs.server.protocol.BlockCommand

@Private
@Evolving
public class BlockCommand
extends DatanodeCommand

A BlockCommand is an instruction to a datanode regarding some blocks under its control. It tells the DataNode to either invalidate a set of indicated blocks, or to copy a set of indicated blocks to another DataNode.

Field Summary

Fields

Modifier and Type	Field	Description
static final long	NO_ACK	This constant is used to indicate that the block deletion does not need explicit ACK from the datanode.

Constructor Summary

Constructors

Constructor	Description
BlockCommand(int action, String poolId, List<DatanodeDescriptor.BlockTargetPair> blocktargetlist)	Create BlockCommand for transferring blocks to another datanode
BlockCommand(int action, String poolId, org.apache.hadoop.hdfs.protocol.Block[] blocks)	Create BlockCommand for the given action
BlockCommand(int action, String poolId, org.apache.hadoop.hdfs.protocol.Block[] blocks, org.apache.hadoop.hdfs.protocol.DatanodeInfo[][] targets, org.apache.hadoop.fs.StorageType[][] targetStorageTypes, String[][] targetStorageIDs)	Create BlockCommand for the given action

Method Summary

Modifier and Type	Method	Description
String	getBlockPoolId()
org.apache.hadoop.hdfs.protocol.Block[]	getBlocks()
org.apache.hadoop.hdfs.protocol.DatanodeInfo[][]	getTargets()
String[][]	getTargetStorageIDs()
org.apache.hadoop.fs.StorageType[][]	getTargetStorageTypes()

Methods inherited from class org.apache.hadoop.hdfs.server.protocol.ServerCommand

getAction, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

NO_ACK

public static final long NO_ACK

This constant is used to indicate that the block deletion does not need explicit ACK from the datanode. When a block is put into the list of blocks to be deleted, it's size is set to this constant. We assume that no block would actually have this size. Otherwise, we would miss ACKs for blocks with such size. Positive number is used for compatibility reasons.

See Also:

• Constant Field Values

Constructor Details

BlockCommand

public BlockCommand(int action,
 String poolId,
 List<DatanodeDescriptor.BlockTargetPair> blocktargetlist)

Create BlockCommand for transferring blocks to another datanode

Parameters:

blocktargetlist - blocks to be transferred

BlockCommand

public BlockCommand(int action,
 String poolId,
 org.apache.hadoop.hdfs.protocol.Block[] blocks)

Create BlockCommand for the given action

Parameters:

blocks - blocks related to the action

BlockCommand

public BlockCommand(int action,
 String poolId,
 org.apache.hadoop.hdfs.protocol.Block[] blocks,
 org.apache.hadoop.hdfs.protocol.DatanodeInfo[][] targets,
 org.apache.hadoop.fs.StorageType[][] targetStorageTypes,
 String[][] targetStorageIDs)

Create BlockCommand for the given action

Parameters:

blocks - blocks related to the action

Method Details

getBlockPoolId

public String getBlockPoolId()

getBlocks

public org.apache.hadoop.hdfs.protocol.Block[] getBlocks()

getTargets

public org.apache.hadoop.hdfs.protocol.DatanodeInfo[][] getTargets()

getTargetStorageTypes

public org.apache.hadoop.fs.StorageType[][] getTargetStorageTypes()

getTargetStorageIDs

public String[][] getTargetStorageIDs()