Package org.apache.hadoop.service

Interface Service

All Superinterfaces:
AutoCloseable, Closeable
All Known Subinterfaces:
DNSOperations, LaunchableService, RegistryOperations
All Known Implementing Classes:
AbstractLaunchableService, AbstractLivelinessMonitor, AbstractService, AddingCompositeService, AHSClient, AMRMClient, AMRMClientAsync, AppAdminClient, AsyncDispatcher, CompositeService, org.apache.hadoop.registry.client.impl.zk.CuratorService, HistoryFileManager, NMClient, NMClientAsync, RegistryOperationsClient, RegistryOperationsService, ServiceClient, SharedCacheClient, TimelineClient, TimelineReaderClient, TimelineReaderClientImpl, YarnClient
@Public @Evolving public interface Service extends Closeable
Service LifeCycle.

  • Method Details

    • 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 AutoCloseable
      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

      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(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

      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