Package org.apache.hadoop.hdfs.server.federation.fairness

Interface RouterRpcFairnessPolicyController

All Known Implementing Classes:

AbstractRouterRpcFairnessPolicyController, NoRouterRpcFairnessPolicyController, StaticRouterRpcFairnessPolicyController

@Private
@Evolving
public interface RouterRpcFairnessPolicyController

Interface to define handlers assignment for specific name services. This is needed to allow handlers provide a certain QoS for all name services configured. Implementations can choose to define any algorithm which would help maintain QoS. This is different when compared to FairCallQueue semantics as fairness has a separate context in router based federation. An implementation for example, could allocate a dedicated set of handlers per name service and allow handlers to continue making downstream name node calls if permissions are available, another implementation could use preemption semantics and dynamically increase or decrease handlers assigned per name service.

Method Summary

Modifier and Type	Method	Description
boolean	acquirePermit(java.lang.String nsId)	Request permission for a specific name service to continue the call and connect to downstream name node.
java.lang.String	getAvailableHandlerOnPerNs()	Returns the JSON string of the available handler for each name service.
int	getAvailablePermits(java.lang.String nsId)	Returns the available handler for each name service.
void	releasePermit(java.lang.String nsId)	Handler threads are expected to invoke this method that signals controller to release the resources allocated to the thread for the particular name service.
void	shutdown()	Shutdown steps to stop accepting new permission requests and clean-up.

Method Detail

acquirePermit

boolean acquirePermit(java.lang.String nsId)

Request permission for a specific name service to continue the call and connect to downstream name node. Controllers based on policies defined and allocations done at start-up through assignHandlersToNameservices, may provide a permission or reject the request by throwing exception.

Parameters:

nsId - NS id for which a permission to continue is requested.

Returns:

true or false based on whether permit is given.

releasePermit

void releasePermit(java.lang.String nsId)

Handler threads are expected to invoke this method that signals controller to release the resources allocated to the thread for the particular name service. This would mean permissions getting available for other handlers to request for this specific name service.

Parameters:

nsId - Name service id for which permission release request is made.

shutdown

void shutdown()

Shutdown steps to stop accepting new permission requests and clean-up.

getAvailableHandlerOnPerNs

java.lang.String getAvailableHandlerOnPerNs()

Returns the JSON string of the available handler for each name service.

Returns:

the JSON string of the available handler for each name service.

getAvailablePermits

int getAvailablePermits(java.lang.String nsId)

Returns the available handler for each name service.

Parameters:

nsId - name service id.

Returns:

the available handler for each name service.