Package org.apache.hadoop.hbase.master

Class ActiveMasterManager

java.lang.Object

org.apache.hadoop.hbase.zookeeper.ZKListener

org.apache.hadoop.hbase.master.ActiveMasterManager

@Private
public class ActiveMasterManager
extends ZKListener

Handles everything on master-side related to master election. Keeps track of currently active master and registered backup masters.

Listens and responds to ZooKeeper notifications on the master znodes, both nodeCreated and nodeDeleted.

Contains blocking methods which will hold up backup masters, waiting for the active master to fail.

This class is instantiated in the HMaster constructor and the method #blockUntilBecomingActiveMaster() is called to wait until becoming the active master of the cluster.

Field Summary

Fields

Modifier and Type	Field	Description
(package private) ServerName	activeMasterServerName
private org.apache.hbase.thirdparty.com.google.common.collect.ImmutableList<ServerName>	backupMasters
(package private) final AtomicBoolean	clusterHasActiveMaster
(package private) final AtomicBoolean	clusterShutDown
(package private) int	infoPort
private static final org.slf4j.Logger	LOG
(package private) final Server	master
(package private) final ServerName	sn

Fields inherited from class org.apache.hadoop.hbase.zookeeper.ZKListener

watcher

Constructor Summary

Constructors

Constructor	Description
ActiveMasterManager(ZKWatcher watcher, ServerName sn, Server master)

Method Summary

Modifier and Type	Method	Description
(package private) boolean	blockUntilBecomingActiveMaster(int checkInterval, TaskGroup startupTaskGroup)	Block until becoming the active master.
private void	fetchAndSetActiveMasterServerName()	Fetches the active master's ServerName from zookeeper.
int	getActiveMasterInfoPort()
Optional<ServerName>	getActiveMasterServerName()
int	getBackupMasterInfoPort(ServerName sn)
List<ServerName>	getBackupMasters()	Returns list of registered backup masters.
(package private) void	handle(String path)
private void	handleMasterNodeChange()	Handle a change in the master node.
(package private) boolean	hasActiveMaster()	Returns True if cluster has an active master.
void	nodeChildrenChanged(String path)	Called when an existing node has a child node added or removed.
void	nodeCreated(String path)	Called when a new node has been created.
void	nodeDeleted(String path)	Called when a node has been deleted
void	setInfoPort(int infoPort)
void	stop()
private void	updateBackupMasters()

Methods inherited from class org.apache.hadoop.hbase.zookeeper.ZKListener

getWatcher, nodeDataChanged

Methods inherited from class java.lang.Object

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

Field Details

LOG

private static final org.slf4j.Logger LOG

clusterHasActiveMaster

final AtomicBoolean clusterHasActiveMaster

clusterShutDown

final AtomicBoolean clusterShutDown

infoPort

int infoPort

sn

final ServerName sn

master

final Server master

activeMasterServerName

volatile ServerName activeMasterServerName

backupMasters

private volatile org.apache.hbase.thirdparty.com.google.common.collect.ImmutableList<ServerName> backupMasters

Constructor Details

ActiveMasterManager

ActiveMasterManager(ZKWatcher watcher,
 ServerName sn,
 Server master)
             throws InterruptedIOException

Parameters:

watcher - ZK watcher

sn - ServerName

master - In an instance of a Master.

Throws:

InterruptedIOException

Method Details

setInfoPort

public void setInfoPort(int infoPort)

nodeCreated

public void nodeCreated(String path)

Description copied from class: ZKListener

Called when a new node has been created.

Overrides:

nodeCreated in class ZKListener

Parameters:

path - full path of the new node

nodeChildrenChanged

public void nodeChildrenChanged(String path)

Description copied from class: ZKListener

Called when an existing node has a child node added or removed.

Overrides:

nodeChildrenChanged in class ZKListener

Parameters:

path - full path of the node whose children have changed

nodeDeleted

public void nodeDeleted(String path)

Description copied from class: ZKListener

Called when a node has been deleted

Overrides:

nodeDeleted in class ZKListener

Parameters:

path - full path of the deleted node

handle

void handle(String path)

updateBackupMasters

private void updateBackupMasters()
                          throws InterruptedIOException

Throws:

InterruptedIOException

fetchAndSetActiveMasterServerName

private void fetchAndSetActiveMasterServerName()

Fetches the active master's ServerName from zookeeper.

getActiveMasterServerName

public Optional<ServerName> getActiveMasterServerName()

getActiveMasterInfoPort

public int getActiveMasterInfoPort()

getBackupMasterInfoPort

public int getBackupMasterInfoPort(ServerName sn)

handleMasterNodeChange

private void handleMasterNodeChange()

Handle a change in the master node. Doesn't matter whether this was called from a nodeCreated or nodeDeleted event because there are no guarantees that the current state of the master node matches the event at the time of our next ZK request.

Uses the watchAndCheckExists method which watches the master address node regardless of whether it exists or not. If it does exist (there is an active master), it returns true. Otherwise it returns false.

A watcher is set which guarantees that this method will get called again if there is another change in the master node.

blockUntilBecomingActiveMaster

boolean blockUntilBecomingActiveMaster(int checkInterval,
 TaskGroup startupTaskGroup)

Block until becoming the active master. Method blocks until there is not another active master and our attempt to become the new active master is successful. This also makes sure that we are watching the master znode so will be notified if another master dies.

Parameters:

checkInterval - the interval to check if the master is stopped

startupTaskGroup - the task group for master startup to track the progress

Returns:

True if no issue becoming active master else false if another master was running or if some other problem (zookeeper, stop flag has been set on this Master)

hasActiveMaster

boolean hasActiveMaster()

Returns True if cluster has an active master.

stop

public void stop()

getBackupMasters

public List<ServerName> getBackupMasters()

Returns list of registered backup masters.