org.apache.hadoop.hdfs.server.protocol

Interface NamenodeProtocol

All Known Subinterfaces:

NamenodeProtocols

All Known Implementing Classes:

NamenodeProtocolTranslatorPB

@InterfaceAudience.Private
public interface NamenodeProtocol

Protocol that a secondary NameNode uses to communicate with the NameNode. It's used to get part of the name node state

Field Summary

Fields

Modifier and Type	Field and Description
static int	ACT_CHECKPOINT
static int	ACT_SHUTDOWN
static int	ACT_UNKNOWN
static int	FATAL
static int	NOTIFY
static long	versionID Until version 6L, this class served as both the client interface to the NN AND the RPC protocol used to communicate with the NN.

Method Summary

Methods

Modifier and Type	Method and Description
void	endCheckpoint(NamenodeRegistration registration, CheckpointSignature sig) A request to the active name-node to finalize previously started checkpoint.
void	errorReport(NamenodeRegistration registration, int errorCode, String msg) Report to the active name-node an error occurred on a subordinate node.
ExportedBlockKeys	getBlockKeys() Get the current block keys
BlocksWithLocations	getBlocks(DatanodeInfo datanode, long size) Get a list of blocks belonging to datanode whose total size equals size.
RemoteEditLogManifest	getEditLogManifest(long sinceTxId) Return a structure containing details about all edit logs available to be fetched from the NameNode.
long	getMostRecentCheckpointTxId() Get the transaction ID of the most recent checkpoint.
long	getTransactionID()
NamenodeRegistration	registerSubordinateNamenode(NamenodeRegistration registration) Register a subordinate name-node like backup node.
CheckpointSignature	rollEditLog() Closes the current edit log and opens a new one.
NamenodeCommand	startCheckpoint(NamenodeRegistration registration) A request to the active name-node to start a checkpoint.
NamespaceInfo	versionRequest() Request name-node version and storage information.

Field Detail

versionID

static final long versionID

Until version 6L, this class served as both the client interface to the NN AND the RPC protocol used to communicate with the NN. This class is used by both the DFSClient and the NN server side to insulate from the protocol serialization. If you are adding/changing NN's interface then you need to change both this class and ALSO related protocol buffer wire protocol definition in NamenodeProtocol.proto. For more details on protocol buffer wire protocol, please see .../org/apache/hadoop/hdfs/protocolPB/overview.html 6: Switch to txid-based file naming for image and edits

See Also:

Constant Field Values

NOTIFY

static final int NOTIFY

See Also:

Constant Field Values

FATAL

static final int FATAL

See Also:

Constant Field Values

ACT_UNKNOWN

static final int ACT_UNKNOWN

See Also:

Constant Field Values

ACT_SHUTDOWN

static final int ACT_SHUTDOWN

See Also:

Constant Field Values

ACT_CHECKPOINT

static final int ACT_CHECKPOINT

See Also:

Constant Field Values

Method Detail

getBlocks

BlocksWithLocations getBlocks(DatanodeInfo datanode,
                            long size)
                              throws IOException

Get a list of blocks belonging to datanode whose total size equals size.

Parameters:

datanode - a data node

size - requested size

Returns:

a list of blocks & their locations

Throws:

IOException - if size is less than or equal to 0 or datanode does not exist

See Also:

Balancer

getBlockKeys

ExportedBlockKeys getBlockKeys()
                               throws IOException

Get the current block keys

Returns:

ExportedBlockKeys containing current block keys

Throws:

IOException

getTransactionID

long getTransactionID()
                      throws IOException

Returns:

The most recent transaction ID that has been synced to persistent storage, or applied from persistent storage in the case of a non-active node.

Throws:

IOException

getMostRecentCheckpointTxId

long getMostRecentCheckpointTxId()
                                 throws IOException

Get the transaction ID of the most recent checkpoint.

Throws:

IOException

rollEditLog

CheckpointSignature rollEditLog()
                                throws IOException

Closes the current edit log and opens a new one. The call fails if the file system is in SafeMode.

Returns:

a unique token to identify this transaction.

Throws:

IOException

versionRequest

NamespaceInfo versionRequest()
                             throws IOException

Request name-node version and storage information.

Returns:

NamespaceInfo identifying versions and storage information of the name-node

Throws:

IOException

errorReport

void errorReport(NamenodeRegistration registration,
               int errorCode,
               String msg)
                 throws IOException

Report to the active name-node an error occurred on a subordinate node. Depending on the error code the active node may decide to unregister the reporting node.

Parameters:

registration - requesting node.

errorCode - indicates the error

msg - free text description of the error

Throws:

IOException

registerSubordinateNamenode

NamenodeRegistration registerSubordinateNamenode(NamenodeRegistration registration)
                                                 throws IOException

Register a subordinate name-node like backup node.

Returns:

NamenodeRegistration of the node, which this node has just registered with.

Throws:

IOException

startCheckpoint

NamenodeCommand startCheckpoint(NamenodeRegistration registration)
                                throws IOException

A request to the active name-node to start a checkpoint. The name-node should decide whether to admit it or reject. The name-node also decides what should be done with the backup node image before and after the checkpoint.

Parameters:

registration - the requesting node

Returns:

CheckpointCommand if checkpoint is allowed.

Throws:

IOException

See Also:

CheckpointCommand, NamenodeCommand, ACT_SHUTDOWN

endCheckpoint

void endCheckpoint(NamenodeRegistration registration,
                 CheckpointSignature sig)
                   throws IOException

A request to the active name-node to finalize previously started checkpoint.

Parameters:

registration - the requesting node

sig - CheckpointSignature which identifies the checkpoint.

Throws:

IOException

getEditLogManifest

RemoteEditLogManifest getEditLogManifest(long sinceTxId)
                                         throws IOException

Return a structure containing details about all edit logs available to be fetched from the NameNode.

Parameters:

sinceTxId - return only logs that contain transactions >= sinceTxId

Throws:

IOException