org.apache.hadoop.service
Interface Service

All Superinterfaces:
Closeable
All Known Implementing Classes:
AbstractLivelinessMonitor, AbstractService, AMRMClient, AMRMClientAsync, AsyncDispatcher, CompositeService, HistoryFileManager, NMClient, NMClientAsync, YarnClient

@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface Service
extends Closeable

Service LifeCycle.


Method Summary
 void close()
          A version of stop() that is designed to be usable in Java7 closure clauses.
 Map<String,String> getBlockers()
          Get the blockers on a service -remote dependencies that are stopping the service from being live.
 Configuration getConfig()
          Get the configuration of this service.
 Throwable getFailureCause()
          Get the first exception raised during the service failure.
 org.apache.hadoop.service.Service.STATE getFailureState()
          Get the state in which the failure in getFailureCause() occurred.
 List<LifecycleEvent> getLifecycleHistory()
          Get a snapshot of the lifecycle history; it is a static list
 String getName()
          Get the name of this service.
 org.apache.hadoop.service.Service.STATE getServiceState()
          Get the current service state
 long getStartTime()
          Get the service start time
 void init(Configuration config)
          Initialize the service.
 boolean isInState(org.apache.hadoop.service.Service.STATE state)
          Query to see if the service is in a specific state.
 void registerServiceListener(ServiceStateChangeListener listener)
          Register a listener to the service state change events.
 void start()
          Start the service.
 void stop()
          Stop the service.
 void unregisterServiceListener(ServiceStateChangeListener listener)
          Unregister a previously registered listener of the service state change events.
 boolean waitForServiceToStop(long timeout)
          Block waiting for the service to stop; uses the termination notification object to do so.
 

Method Detail

init

void init(Configuration config)
Initialize the service. The transition MUST be from Service.STATE.NOTINITED to Service.STATE.INITED unless the operation failed and an exception was raised, in which case stop() MUST be invoked and the service enter the state Service.STATE.STOPPED.

Parameters:
config - the configuration of the service
Throws:
RuntimeException - on any failure during the operation

start

void start()
Start the service. The transition MUST be from Service.STATE.INITED to Service.STATE.STARTED unless the operation failed and an exception was raised, in which case stop() MUST be invoked and the service enter the state Service.STATE.STOPPED.

Throws:
RuntimeException - on any failure during the operation

stop

void stop()
Stop the service. This MUST be a no-op if the service is already in the Service.STATE.STOPPED state. It SHOULD be a best-effort attempt to stop all parts of the service. The implementation must be designed to complete regardless of the service state, including the initialized/uninitialized state of all its internal fields.

Throws:
RuntimeException - on any failure during the stop operation

close

void close()
           throws IOException
A version of stop() that is designed to be usable in Java7 closure clauses. Implementation classes MUST relay this directly to stop()

Specified by:
close in interface Closeable
Throws:
IOException - never
RuntimeException - on any failure during the stop operation

registerServiceListener

void registerServiceListener(ServiceStateChangeListener listener)
Register a listener to the service state change events. If the supplied listener is already listening to this service, this method is a no-op.

Parameters:
listener - a new listener

unregisterServiceListener

void unregisterServiceListener(ServiceStateChangeListener listener)
Unregister a previously registered listener of the service state change events. No-op if the listener is already unregistered.

Parameters:
listener - the listener to unregister.

getName

String getName()
Get the name of this service.

Returns:
the service name

getConfig

Configuration getConfig()
Get the configuration of this service. This is normally not a clone and may be manipulated, though there are no guarantees as to what the consequences of such actions may be

Returns:
the current configuration, unless a specific implentation chooses otherwise.

getServiceState

org.apache.hadoop.service.Service.STATE getServiceState()
Get the current service state

Returns:
the state of the service

getStartTime

long getStartTime()
Get the service start time

Returns:
the start time of the service. This will be zero if the service has not yet been started.

isInState

boolean isInState(org.apache.hadoop.service.Service.STATE state)
Query to see if the service is in a specific state. In a multi-threaded system, the state may not hold for very long.

Parameters:
state - the expected state
Returns:
true if, at the time of invocation, the service was in that state.

getFailureCause

Throwable getFailureCause()
Get the first exception raised during the service failure. If null, no exception was logged

Returns:
the failure logged during a transition to the stopped state

getFailureState

org.apache.hadoop.service.Service.STATE getFailureState()
Get the state in which the failure in getFailureCause() occurred.

Returns:
the state or null if there was no failure

waitForServiceToStop

boolean waitForServiceToStop(long timeout)
Block waiting for the service to stop; uses the termination notification object to do so. This method will only return after all the service stop actions have been executed (to success or failure), or the timeout elapsed This method can be called before the service is inited or started; this is to eliminate any race condition with the service stopping before this event occurs.

Parameters:
timeout - timeout in milliseconds. A value of zero means "forever"
Returns:
true iff the service stopped in the time period

getLifecycleHistory

List<LifecycleEvent> getLifecycleHistory()
Get a snapshot of the lifecycle history; it is a static list

Returns:
a possibly empty but never null list of lifecycle events.

getBlockers

Map<String,String> getBlockers()
Get the blockers on a service -remote dependencies that are stopping the service from being live.

Returns:
a (snapshotted) map of blocker name->description values


Copyright © 2013 Apache Software Foundation. All Rights Reserved.