Package org.apache.hadoop.service

Class AbstractService

java.lang.Object
org.apache.hadoop.service.AbstractService
All Implemented Interfaces:
Closeable, AutoCloseable, Service
Direct Known Subclasses:
AbstractLaunchableService, AbstractLivelinessMonitor, AHSClient, AMRMClient, AMRMClientAsync, AsyncDispatcher, CompositeService, HistoryFileManager, NMClient, NMClientAsync, SharedCacheClient, YarnClient
@Public @Evolving public abstract class AbstractService extends Object implements Service
This is the base implementation class for services.

  • Constructor Details

    • AbstractService

      public AbstractService(String name)
      Construct the service.
      Parameters:
      name - service name

  • Method Details

    • getServiceState

      public final Service.STATE getServiceState()
      Description copied from interface: Service
      Get the current service state
      Specified by:
      getServiceState in interface Service
      Returns:
      the state of the service

    • getFailureCause

      public final Throwable getFailureCause()
      Description copied from interface: Service
      Get the first exception raised during the service failure. If null, no exception was logged
      Specified by:
      getFailureCause in interface Service
      Returns:
      the failure logged during a transition to the stopped state

    • getFailureState

      public Service.STATE getFailureState()
      Description copied from interface: Service
      Get the state in which the failure in Service.getFailureCause() occurred.
      Specified by:
      getFailureState in interface Service
      Returns:
      the state or null if there was no failure

    • setConfig

      protected void setConfig(Configuration conf)
      Set the configuration for this service. This method is called during init(Configuration) and should only be needed if for some reason a service implementation needs to override that initial setting -for example replacing it with a new subclass of Configuration
      Parameters:
      conf - new configuration.

    • init

      public void init(Configuration conf)
      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 Service.stop() MUST be invoked and the service enter the state Service.STATE.STOPPED. This invokes serviceInit(org.apache.hadoop.conf.Configuration)
      Specified by:
      init in interface Service
      Parameters:
      conf - the configuration of the service. This must not be null
      Throws:
      ServiceStateException - if the configuration was null, the state change not permitted, or something else went wrong

    • start

      public 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 Service.stop() MUST be invoked and the service enter the state Service.STATE.STOPPED.
      Specified by:
      start in interface Service
      Throws:
      ServiceStateException - if the current service state does not permit this action

    • stop

      public 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.
      Specified by:
      stop in interface Service

    • close

      public final void close() throws IOException
      Relay to stop()
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Specified by:
      close in interface Service
      Throws:
      IOException - raised on errors performing I/O.

    • noteFailure

      protected final void noteFailure(Exception exception)
      Failure handling: record the exception that triggered it -if there was not one already. Services are free to call this themselves.
      Parameters:
      exception - the exception

    • waitForServiceToStop

      public final boolean waitForServiceToStop(long timeout)
      Description copied from interface: Service
      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.
      Specified by:
      waitForServiceToStop in interface Service
      Parameters:
      timeout - timeout in milliseconds. A value of zero means "forever"
      Returns:
      true iff the service stopped in the time period

    • serviceInit

      protected void serviceInit(Configuration conf) throws Exception
      All initialization code needed by a service. This method will only ever be called once during the lifecycle of a specific service instance. Implementations do not need to be synchronized as the logic in init(Configuration) prevents re-entrancy. The base implementation checks to see if the subclass has created a new configuration instance, and if so, updates the base class value
      Parameters:
      conf - configuration
      Throws:
      Exception - on a failure -these will be caught, possibly wrapped, and will trigger a service stop

    • serviceStart

      protected void serviceStart() throws Exception
      Actions called during the INITED to STARTED transition. This method will only ever be called once during the lifecycle of a specific service instance. Implementations do not need to be synchronized as the logic in start() prevents re-entrancy.
      Throws:
      Exception - if needed -these will be caught, wrapped, and trigger a service stop

    • serviceStop

      protected void serviceStop() throws Exception
      Actions called during the transition to the STOPPED state. This method will only ever be called once during the lifecycle of a specific service instance. Implementations do not need to be synchronized as the logic in stop() prevents re-entrancy. Implementations MUST write this to be robust against failures, including checks for null references -and for the first failure to not stop other attempts to shut down parts of the service.
      Throws:
      Exception - if needed -these will be caught and logged.

    • registerServiceListener

      public void registerServiceListener(ServiceStateChangeListener l)
      Description copied from interface: Service
      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.
      Specified by:
      registerServiceListener in interface Service
      Parameters:
      l - a new listener

    • unregisterServiceListener

      public void unregisterServiceListener(ServiceStateChangeListener l)
      Description copied from interface: Service
      Unregister a previously registered listener of the service state change events. No-op if the listener is already unregistered.
      Specified by:
      unregisterServiceListener in interface Service
      Parameters:
      l - the listener to unregister.

    • registerGlobalListener

      public static void registerGlobalListener(ServiceStateChangeListener l)
      Register a global listener, which receives notifications from the state change events of all services in the JVM
      Parameters:
      l - listener

    • unregisterGlobalListener

      public static boolean unregisterGlobalListener(ServiceStateChangeListener l)
      unregister a global listener.
      Parameters:
      l - listener to unregister
      Returns:
      true if the listener was found (and then deleted)

    • getName

      public String getName()
      Description copied from interface: Service
      Get the name of this service.
      Specified by:
      getName in interface Service
      Returns:
      the service name

    • getConfig

      public Configuration getConfig()
      Description copied from interface: Service
      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
      Specified by:
      getConfig in interface Service
      Returns:
      the current configuration, unless a specific implentation chooses otherwise.

    • getStartTime

      public long getStartTime()
      Description copied from interface: Service
      Get the service start time
      Specified by:
      getStartTime in interface Service
      Returns:
      the start time of the service. This will be zero if the service has not yet been started.

    • getLifecycleHistory

      public List<LifecycleEvent> getLifecycleHistory()
      Description copied from interface: Service
      Get a snapshot of the lifecycle history; it is a static list
      Specified by:
      getLifecycleHistory in interface Service
      Returns:
      a possibly empty but never null list of lifecycle events.

    • isInState

      public final boolean isInState(Service.STATE expected)
      Description copied from interface: Service
      Query to see if the service is in a specific state. In a multi-threaded system, the state may not hold for very long.
      Specified by:
      isInState in interface Service
      Parameters:
      expected - the expected state
      Returns:
      true if, at the time of invocation, the service was in that state.

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • putBlocker

      protected void putBlocker(String name, String details)
      Put a blocker to the blocker map -replacing any with the same name.
      Parameters:
      name - blocker name
      details - any specifics on the block. This must be non-null.

    • removeBlocker

      public void removeBlocker(String name)
      Remove a blocker from the blocker map - this is a no-op if the blocker is not present
      Parameters:
      name - the name of the blocker

    • getBlockers

      public Map<String,String> getBlockers()
      Description copied from interface: Service
      Get the blockers on a service -remote dependencies that are stopping the service from being live.
      Specified by:
      getBlockers in interface Service
      Returns:
      a (snapshotted) map of blocker name->description values