Package org.apache.hadoop.hdfs.server.namenode

Class SecondaryNameNode

java.lang.Object

org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode

All Implemented Interfaces:

Runnable, SecondaryNameNodeInfoMXBean, VersionInfoMXBean

@Private
public class SecondaryNameNode
extends Object
implements Runnable, SecondaryNameNodeInfoMXBean

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 NamenodeProtocol to talk to the primary NameNode.

Field Summary

Fields

Modifier and Type	Field	Description
static final org.slf4j.Logger	LOG

Constructor Summary

Constructors

Constructor	Description
SecondaryNameNode(org.apache.hadoop.conf.Configuration conf)	Create a connection to the primary namenode.
SecondaryNameNode(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode.CommandLineOpts commandLineOpts)

Method Summary

Modifier and Type	Method	Description
boolean	doCheckpoint()	Create a new checkpoint
void	doWork()
String[]	getCheckpointDirectories()
String[]	getCheckpointEditlogDirectories()
String	getCompileInfo()
FSNamesystem	getFSNamesystem()
String	getHostAndPort()	Gets the host and port colon separated.
static InetSocketAddress	getHttpAddress(org.apache.hadoop.conf.Configuration conf)
long	getLastCheckpointDeltaMs()
long	getLastCheckpointTime()
String	getSoftwareVersion()
long	getStartTime()
boolean	isSecurityEnabled()	Gets if security is enabled.
static void	main(String[] argv)	main() has some simple utility methods.
void	run()
void	shutdown()	Shut down this instance of the secondary namenode.
void	startCheckpointThread()
void	startInfoServer()	Start the web server.
String	toString()

Methods inherited from class java.lang.Object

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

Field Details

LOG

public static final org.slf4j.Logger LOG

Constructor Details

SecondaryNameNode

public SecondaryNameNode(org.apache.hadoop.conf.Configuration conf)
                  throws IOException

Create a connection to the primary namenode.

Throws:

IOException

SecondaryNameNode

public SecondaryNameNode(org.apache.hadoop.conf.Configuration conf,
 org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode.CommandLineOpts commandLineOpts)
                  throws IOException

Throws:

IOException

Method Details

toString

public String toString()

Overrides:

toString in class Object

getFSNamesystem

@VisibleForTesting
public FSNamesystem getFSNamesystem()

getHttpAddress

public static InetSocketAddress getHttpAddress(org.apache.hadoop.conf.Configuration conf)

shutdown

public void shutdown()

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

run

public void run()

Specified by:

run in interface Runnable

doWork

public void doWork()

startInfoServer

@VisibleForTesting
public void startInfoServer()
                     throws IOException

Start the web server.

Throws:

IOException

doCheckpoint

@VisibleForTesting
public boolean doCheckpoint()
                     throws IOException

Create a new checkpoint

Returns:

if the image is fetched from primary or not

Throws:

IOException

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.

startCheckpointThread

public void startCheckpointThread()

getHostAndPort

public String getHostAndPort()

Description copied from interface: SecondaryNameNodeInfoMXBean

Gets the host and port colon separated.

Specified by:

getHostAndPort in interface SecondaryNameNodeInfoMXBean

isSecurityEnabled

public boolean isSecurityEnabled()

Description copied from interface: SecondaryNameNodeInfoMXBean

Gets if security is enabled.

Specified by:

isSecurityEnabled in interface SecondaryNameNodeInfoMXBean

Returns:

true, if security is enabled.

getStartTime

public long getStartTime()

Specified by:

getStartTime in interface SecondaryNameNodeInfoMXBean

Returns:

the timestamp of when the SNN starts

getLastCheckpointTime

public long getLastCheckpointTime()

Specified by:

getLastCheckpointTime in interface SecondaryNameNodeInfoMXBean

Returns:

the timestamp of the last checkpoint

getLastCheckpointDeltaMs

public long getLastCheckpointDeltaMs()

Specified by:

getLastCheckpointDeltaMs in interface SecondaryNameNodeInfoMXBean

Returns:

the number of msec since the last checkpoint, or -1 if no checkpoint has been done yet.

getCheckpointDirectories

public String[] getCheckpointDirectories()

Specified by:

getCheckpointDirectories in interface SecondaryNameNodeInfoMXBean

Returns:

the directories that store the checkpoint images

getCheckpointEditlogDirectories

public String[] getCheckpointEditlogDirectories()

Specified by:

getCheckpointEditlogDirectories in interface SecondaryNameNodeInfoMXBean

Returns:

the directories that store the edit logs

getCompileInfo

public String getCompileInfo()

Specified by:

getCompileInfo in interface VersionInfoMXBean

Returns:

the compilation information which contains date, user and branch

getSoftwareVersion

public String getSoftwareVersion()

Specified by:

getSoftwareVersion in interface VersionInfoMXBean

Returns:

the software version