Package org.apache.hadoop.ha

Interface HAServiceProtocol

@Public
@Evolving
public interface HAServiceProtocol

Protocol interface that provides High Availability related primitives to monitor and fail-over the service. This interface could be used by HA frameworks to manage the service.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	HAServiceProtocol.HAServiceState	An HA service may be in active or standby state.
static class	HAServiceProtocol.RequestSource
static class	HAServiceProtocol.StateChangeRequestInfo	Information describing the source for a request to change state.

Field Summary

Fields

Modifier and Type	Field	Description
static long	versionID	Initial version of the protocol

Method Summary

Modifier and Type	Method	Description
HAServiceStatus	getServiceStatus()	Return the current status of the service.
void	monitorHealth()	Monitor the health of service.
void	transitionToActive(HAServiceProtocol.StateChangeRequestInfo reqInfo)	Request service to transition to active state.
void	transitionToObserver(HAServiceProtocol.StateChangeRequestInfo reqInfo)	Request service to transition to observer state.
void	transitionToStandby(HAServiceProtocol.StateChangeRequestInfo reqInfo)	Request service to transition to standby state.

Field Detail

versionID

static final long versionID

Initial version of the protocol

See Also:

Constant Field Values

Method Detail

monitorHealth

void monitorHealth()
            throws HealthCheckFailedException,
                   AccessControlException,
                   java.io.IOException

Monitor the health of service. This periodically called by the HA frameworks to monitor the health of the service. Service is expected to perform checks to ensure it is functional. If the service is not healthy due to failure or partial failure, it is expected to throw HealthCheckFailedException. The definition of service not healthy is left to the service. Note that when health check of an Active service fails, failover to standby may be done.

Throws:

HealthCheckFailedException - if the health check of a service fails.

AccessControlException - if access is denied.

java.io.IOException - if other errors happen

transitionToActive

void transitionToActive(HAServiceProtocol.StateChangeRequestInfo reqInfo)
                 throws ServiceFailedException,
                        AccessControlException,
                        java.io.IOException

Request service to transition to active state. No operation, if the service is already in active state.

Parameters:

reqInfo - reqInfo.

Throws:

ServiceFailedException - if transition from standby to active fails.

AccessControlException - if access is denied.

java.io.IOException - if other errors happen

transitionToStandby

void transitionToStandby(HAServiceProtocol.StateChangeRequestInfo reqInfo)
                  throws ServiceFailedException,
                         AccessControlException,
                         java.io.IOException

Request service to transition to standby state. No operation, if the service is already in standby state.

Parameters:

reqInfo - reqInfo.

Throws:

ServiceFailedException - if transition from active to standby fails.

AccessControlException - if access is denied.

java.io.IOException - if other errors happen

transitionToObserver

void transitionToObserver(HAServiceProtocol.StateChangeRequestInfo reqInfo)
                   throws ServiceFailedException,
                          AccessControlException,
                          java.io.IOException

Request service to transition to observer state. No operation, if the service is already in observer state.

Parameters:

reqInfo - reqInfo.

Throws:

ServiceFailedException - if transition from standby to observer fails.

AccessControlException - if access is denied.

java.io.IOException - if other errors happen

getServiceStatus

HAServiceStatus getServiceStatus()
                          throws AccessControlException,
                                 java.io.IOException

Return the current status of the service. The status indicates the current state (e.g ACTIVE/STANDBY) as well as some additional information.

Returns:

HAServiceStatus.

Throws:

AccessControlException - if access is denied.

java.io.IOException - if other errors happen

See Also:

HAServiceStatus