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

Class StandbyState

java.lang.Object

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

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

@Private
public class StandbyState
extends HAState

Namenode standby state. In this state the namenode acts as warm standby and keeps the following updated:

• Namespace by getting the edits.
• Block location information by receiving block reports and blocks received from the datanodes.

It does not handle read/write/checkpoint operations.

Field Summary

Fields inherited from class org.apache.hadoop.hdfs.server.namenode.ha.HAState

state

Constructor Summary

Constructors

Constructor	Description
StandbyState()
StandbyState(boolean isObserver)

Method Summary

Modifier and Type	Method	Description
void	checkOperation(HAContext context, NameNode.OperationCategory op)	Check if an operation is supported in a given state.
void	enterState(HAContext context)	Method to be overridden by subclasses to perform steps necessary for entering a state.
void	exitState(HAContext context)	Method to be overridden by subclasses to perform steps necessary for exiting 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
boolean	shouldPopulateReplQueues()
java.lang.String	toString()

Methods inherited from class org.apache.hadoop.hdfs.server.namenode.ha.HAState

getLastHATransitionTime, getServiceState, prepareToEnterState, setStateInternal

Methods inherited from class java.lang.Object

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

Constructor Detail

StandbyState

public StandbyState()

StandbyState

public StandbyState(boolean isObserver)

Method Detail

setState

public void setState(HAContext context,
                     HAState s)
              throws org.apache.hadoop.ha.ServiceFailedException

Description copied from class: HAState

Move from the existing state to a new state

Overrides:

setState in class HAState

Parameters:

context - HA context

s - new state

Throws:

org.apache.hadoop.ha.ServiceFailedException - on failure to transition to new state.

enterState

public void enterState(HAContext context)
                throws org.apache.hadoop.ha.ServiceFailedException

Description copied from class: HAState

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

Specified by:

enterState in class HAState

Parameters:

context - HA context

Throws:

org.apache.hadoop.ha.ServiceFailedException - on failure to enter the state.

prepareToExitState

public void prepareToExitState(HAContext context)
                        throws org.apache.hadoop.ha.ServiceFailedException

Description copied from class: HAState

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 destructive changes to the state (eg stopping threads) since HAState.prepareToEnterState(HAContext) may subsequently cancel the state transition.

Overrides:

prepareToExitState in class HAState

Parameters:

context - HA context

Throws:

org.apache.hadoop.ha.ServiceFailedException - on precondition failure

exitState

public void exitState(HAContext context)
               throws org.apache.hadoop.ha.ServiceFailedException

Description copied from class: HAState

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

Specified by:

exitState in class HAState

Parameters:

context - HA context

Throws:

org.apache.hadoop.ha.ServiceFailedException - on failure to enter the state.

checkOperation

public void checkOperation(HAContext context,
                           NameNode.OperationCategory op)
                    throws org.apache.hadoop.ipc.StandbyException

Description copied from class: HAState

Check if an operation is supported in a given state.

Specified by:

checkOperation in class HAState

Parameters:

context - HA context

op - Type of the operation.

Throws:

org.apache.hadoop.ipc.StandbyException - if a given type of operation is not supported in standby state

shouldPopulateReplQueues

public boolean shouldPopulateReplQueues()

Specified by:

shouldPopulateReplQueues in class HAState

toString

public java.lang.String toString()

Overrides:

toString in class HAState

Returns:

String representation of the service state.