org.apache.hadoop.hdfs.server.namenode.ha

Class HAState

java.lang.Object

org.apache.hadoop.hdfs.server.namenode.ha.HAState

Direct Known Subclasses:

ActiveState, BackupState, StandbyState

@InterfaceAudience.Private
public abstract class HAState
extends Object

Namenode base state to implement state machine pattern.

Field Summary

Fields

Modifier and Type	Field and Description
protected HAServiceProtocol.HAServiceState	state

Constructor Summary

Constructors

Constructor and Description
HAState(HAServiceProtocol.HAServiceState state) Constructor

Method Summary

Methods

Modifier and Type	Method and Description
abstract void	checkOperation(HAContext context, NameNode.OperationCategory op) Check if an operation is supported in a given state.
abstract void	enterState(HAContext context) Method to be overridden by subclasses to perform steps necessary for entering a state.
abstract void	exitState(HAContext context) Method to be overridden by subclasses to perform steps necessary for exiting a state.
HAServiceProtocol.HAServiceState	getServiceState()
void	prepareToEnterState(HAContext context) Method to be overridden by subclasses to prepare to enter a state.
void	prepareToExitState(HAContext context) Method to be overridden by subclasses to prepare to exit a state.
void	setState(HAContext context, HAState s) Move from the existing state to a new state
protected void	setStateInternal(HAContext context, HAState s) Internal method to transition the state of a given namenode to a new state.
abstract boolean	shouldPopulateReplQueues()
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

state

protected final HAServiceProtocol.HAServiceState state

Constructor Detail

HAState

public HAState(HAServiceProtocol.HAServiceState state)

Constructor

Parameters:

name - Name of the state.

Method Detail

getServiceState

public HAServiceProtocol.HAServiceState getServiceState()

Returns:

the generic service state

setStateInternal

protected final void setStateInternal(HAContext context,
                    HAState s)
                               throws ServiceFailedException

Internal method to transition the state of a given namenode to a new state.

Parameters:

nn - Namenode

s - new state

Throws:

ServiceFailedException - on failure to transition to new state.

prepareToEnterState

public void prepareToEnterState(HAContext context)
                         throws ServiceFailedException

Method to be overridden by subclasses to prepare to enter a state. This method is called without the context being locked, and after prepareToExitState(HAContext) has been called for the previous state, but before exitState(HAContext) has been called for the previous state.

Parameters:

context - HA context

Throws:

ServiceFailedException - on precondition failure

enterState

public abstract void enterState(HAContext context)
                         throws ServiceFailedException

Method to be overridden by subclasses to perform steps necessary for entering a state.

Parameters:

context - HA context

Throws:

ServiceFailedException - on failure to enter the state.

prepareToExitState

public void prepareToExitState(HAContext context)
                        throws ServiceFailedException

Method to be overridden by subclasses to prepare to exit a state. This method is called without the context being locked. This is used by the standby state to cancel any checkpoints that are going on. It can also be used to check any preconditions for the state transition. This method should not make any destructuve changes to the state (eg stopping threads) since prepareToEnterState(HAContext) may subsequently cancel the state transition.

Parameters:

context - HA context

Throws:

ServiceFailedException - on precondition failure

exitState

public abstract void exitState(HAContext context)
                        throws ServiceFailedException

Method to be overridden by subclasses to perform steps necessary for exiting a state.

Parameters:

context - HA context

Throws:

ServiceFailedException - on failure to enter the state.

setState

public void setState(HAContext context,
            HAState s)
              throws ServiceFailedException

Move from the existing state to a new state

Parameters:

context - HA context

s - new state

Throws:

ServiceFailedException - on failure to transition to new state.

checkOperation

public abstract void checkOperation(HAContext context,
                  NameNode.OperationCategory op)
                             throws StandbyException

Check if an operation is supported in a given state.

Parameters:

context - HA context

op - Type of the operation.

Throws:

UnsupportedActionException - if a given type of operation is not supported in this state.

StandbyException

shouldPopulateReplQueues

public abstract boolean shouldPopulateReplQueues()

toString

public String toString()

Overrides:

toString in class Object

Returns:

String representation of the service state.