org.apache.hadoop.dfs
Class SecondaryNameNode

java.lang.Object
  org.apache.hadoop.dfs.SecondaryNameNode

All Implemented Interfaces:

Runnable, FSConstants

public class SecondaryNameNode
extends Object
implements FSConstants, Runnable

The Secondary NameNode is a helper to the primary NameNode. The Secondary is responsible for supporting periodic checkpoints of the HDFS metadata. The current design allows only one Secondary NameNode per HDFs cluster. The Secondary NameNode is a daemon that periodically wakes up (determined by the schedule specified in the configuration), triggers a periodic checkpoint and then goes back to sleep. The Secondary NameNode uses the ClientProtocol to talk to the primary NameNode.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.hadoop.dfs.FSConstants

FSConstants.CheckpointStates, FSConstants.DatanodeReportType, FSConstants.NodeType, FSConstants.SafeModeAction, FSConstants.StartupOption, FSConstants.UpgradeAction

Field Summary

static org.apache.commons.logging.Log

LOG

Fields inherited from interface org.apache.hadoop.dfs.FSConstants

BLOCK_INVALIDATE_CHUNK, BLOCKREPORT_INITIAL_DELAY, BLOCKREPORT_INTERVAL, BUFFER_SIZE, COMPLETE_SUCCESS, DATA_TRANSFER_VERSION, DEFAULT_BLOCK_SIZE, DEFAULT_DATA_SOCKET_SIZE, HEARTBEAT_INTERVAL, LAYOUT_VERSION, LEASE_HARDLIMIT_PERIOD, LEASE_SOFTLIMIT_PERIOD, MAX_PATH_DEPTH, MAX_PATH_LENGTH, MIN_BLOCKS_FOR_WRITE, OP_ACK, OP_BLOCKRECEIVED, OP_BLOCKREPORT, OP_CLIENT_ABANDONBLOCK, OP_CLIENT_ABANDONBLOCK_ACK, OP_CLIENT_ADDBLOCK, OP_CLIENT_ADDBLOCK_ACK, OP_CLIENT_COMPLETEFILE, OP_CLIENT_COMPLETEFILE_ACK, OP_CLIENT_DATANODE_HINTS, OP_CLIENT_DATANODE_HINTS_ACK, OP_CLIENT_DATANODEREPORT, OP_CLIENT_DATANODEREPORT_ACK, OP_CLIENT_DELETE, OP_CLIENT_DELETE_ACK, OP_CLIENT_EXISTS, OP_CLIENT_EXISTS_ACK, OP_CLIENT_ISDIR, OP_CLIENT_ISDIR_ACK, OP_CLIENT_LISTING, OP_CLIENT_LISTING_ACK, OP_CLIENT_MKDIRS, OP_CLIENT_MKDIRS_ACK, OP_CLIENT_OBTAINLOCK, OP_CLIENT_OBTAINLOCK_ACK, OP_CLIENT_OPEN, OP_CLIENT_OPEN_ACK, OP_CLIENT_RAWSTATS, OP_CLIENT_RAWSTATS_ACK, OP_CLIENT_RELEASELOCK, OP_CLIENT_RELEASELOCK_ACK, OP_CLIENT_RENAMETO, OP_CLIENT_RENAMETO_ACK, OP_CLIENT_RENEW_LEASE, OP_CLIENT_RENEW_LEASE_ACK, OP_CLIENT_STARTFILE, OP_CLIENT_STARTFILE_ACK, OP_CLIENT_TRYAGAIN, OP_COPY_BLOCK, OP_ERROR, OP_FAILURE, OP_HEARTBEAT, OP_INVALIDATE_BLOCKS, OP_READ_BLOCK, OP_READ_METADATA, OP_REPLACE_BLOCK, OP_STATUS_CHECKSUM_OK, OP_STATUS_ERROR, OP_STATUS_ERROR_CHECKSUM, OP_STATUS_ERROR_EXISTS, OP_STATUS_ERROR_INVALID, OP_STATUS_SUCCESS, OP_TRANSFERBLOCKS, OP_TRANSFERDATA, OP_WRITE_BLOCK, OPERATION_FAILED, READ_TIMEOUT, SIZE_OF_INTEGER, SMALL_BUFFER_SIZE, STILL_WAITING, WRITE_TIMEOUT, WRITE_TIMEOUT_EXTENSION

Method Summary

static void	main(String[] argv) main() has some simple utility methods.
void	run()
void	shutdown() Shut down this instance of the datanode.

Methods inherited from class java.lang.Object

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

Field Detail

LOG

public static final org.apache.commons.logging.Log LOG

Method Detail

shutdown

public void shutdown()

Shut down this instance of the datanode. Returns only after shutdown is complete.

run

public void run()

Specified by:

run in interface Runnable

main

public static void main(String[] argv)
                 throws Exception

main() has some simple utility methods.

Parameters:

argv - Command line parameters.

Throws:

Exception - if the filesystem does not exist.