Class AbstractService

java.lang.Object
com.google.common.util.concurrent.AbstractService
All Implemented Interfaces:
Service
@GwtIncompatible public abstract class AbstractService extends Object implements Service
Base class for implementing services that can handle doStart() and doStop() requests, responding to them with notifyStarted() and notifyStopped() callbacks. Its subclasses must manage threads manually; consider AbstractExecutionThreadService if you need only a single execution thread.
Since:
1.0
Author:
Jesse Wilson, Luke Sandberg

  • Constructor Details

    • AbstractService

      protected AbstractService()
      Constructor for use by subclasses.

  • Method Details

    • doStart

      @ForOverride protected abstract void doStart()
      This method is called by startAsync() to initiate service startup. The invocation of this method should cause a call to notifyStarted(), either during this method's run, or after it has returned. If startup fails, the invocation should cause a call to notifyFailed(Throwable) instead.

      This method should return promptly; prefer to do work on a different thread where it is convenient. It is invoked exactly once on service startup, even when startAsync() is called multiple times.

    • doStop

      @ForOverride protected abstract void doStop()
      This method should be used to initiate service shutdown. The invocation of this method should cause a call to notifyStopped(), either during this method's run, or after it has returned. If shutdown fails, the invocation should cause a call to notifyFailed(Throwable) instead.

      This method should return promptly; prefer to do work on a different thread where it is convenient. It is invoked exactly once on service shutdown, even when stopAsync() is called multiple times.

      If stopAsync() is called on a Service.State.STARTING service, this method is not invoked immediately. Instead, it will be deferred until after the service is Service.State.RUNNING. Services that need to cancel startup work can override doCancelStart().

    • doCancelStart

      @ForOverride protected void doCancelStart()
      This method is called by stopAsync() when the service is still starting (i.e. startAsync() has been called but notifyStarted() has not). Subclasses can override the method to cancel pending work and then call notifyStopped() to stop the service.

      This method should return promptly; prefer to do work on a different thread where it is convenient. It is invoked exactly once on service shutdown, even when stopAsync() is called multiple times.

      When this method is called state() will return Service.State.STOPPING, which is the external state observable by the caller of stopAsync().

      Since:
      27.0

    • startAsync

      @CanIgnoreReturnValue public final Service startAsync()
      Description copied from interface: Service
      If the service state is Service.State.NEW, this initiates service startup and returns immediately. A stopped service may not be restarted.
      Specified by:
      startAsync in interface Service
      Returns:
      this

    • stopAsync

      @CanIgnoreReturnValue public final Service stopAsync()
      Description copied from interface: Service
      If the service is starting or running, this initiates service shutdown and returns immediately. If the service is new, it is terminated without having been started nor stopped. If the service has already been stopped, this method returns immediately without taking action.
      Specified by:
      stopAsync in interface Service
      Returns:
      this

    • awaitRunning

      public final void awaitRunning()
      Description copied from interface: Service
      Waits for the Service to reach the running state.
      Specified by:
      awaitRunning in interface Service

    • awaitRunning

      public final void awaitRunning(long timeout, TimeUnit unit) throws TimeoutException
      Description copied from interface: Service
      Waits for the Service to reach the running state for no more than the given time.
      Specified by:
      awaitRunning in interface Service
      Parameters:
      timeout - the maximum time to wait
      unit - the time unit of the timeout argument
      Throws:
      TimeoutException - if the service has not reached the given state within the deadline

    • awaitTerminated

      public final void awaitTerminated()
      Description copied from interface: Service
      Waits for the Service to reach the terminated state.
      Specified by:
      awaitTerminated in interface Service

    • awaitTerminated

      public final void awaitTerminated(long timeout, TimeUnit unit) throws TimeoutException
      Description copied from interface: Service
      Waits for the Service to reach a terminal state (either terminated or failed) for no more than the given time.
      Specified by:
      awaitTerminated in interface Service
      Parameters:
      timeout - the maximum time to wait
      unit - the time unit of the timeout argument
      Throws:
      TimeoutException - if the service has not reached the given state within the deadline

    • notifyStarted

      protected final void notifyStarted()
      Implementing classes should invoke this method once their service has started. It will cause the service to transition from Service.State.STARTING to Service.State.RUNNING.
      Throws:
      IllegalStateException - if the service is not Service.State.STARTING.

    • notifyStopped

      protected final void notifyStopped()
      Implementing classes should invoke this method once their service has stopped. It will cause the service to transition from Service.State.STARTING or Service.State.STOPPING to Service.State.TERMINATED.
      Throws:
      IllegalStateException - if the service is not one of Service.State.STOPPING, Service.State.STARTING, or Service.State.RUNNING.

    • notifyFailed

      protected final void notifyFailed(Throwable cause)
      Invoke this method to transition the service to the Service.State.FAILED. The service will not be stopped if it is running. Invoke this method when a service has failed critically or otherwise cannot be started nor stopped.

    • isRunning

      public final boolean isRunning()
      Description copied from interface: Service
      Returns true if this service is running.
      Specified by:
      isRunning in interface Service

    • state

      public final Service.State state()
      Description copied from interface: Service
      Returns the lifecycle state of the service.
      Specified by:
      state in interface Service

    • failureCause

      public final Throwable failureCause()
      Description copied from interface: Service
      Returns the Throwable that caused this service to fail.
      Specified by:
      failureCause in interface Service
      Since:
      14.0

    • addListener

      public final void addListener(Service.Listener listener, Executor executor)
      Description copied from interface: Service
      Registers a Service.Listener to be executed on the given executor. The listener will have the corresponding transition method called whenever the service changes state. The listener will not have previous state changes replayed, so it is suggested that listeners are added before the service starts.

      addListener guarantees execution ordering across calls to a given listener but not across calls to multiple listeners. Specifically, a given listener will have its callbacks invoked in the same order as the underlying service enters those states. Additionally, at most one of the listener's callbacks will execute at once. However, multiple listeners' callbacks may execute concurrently, and listeners may execute in an order different from the one in which they were registered.

      RuntimeExceptions thrown by a listener will be caught and logged. Any exception thrown during Executor.execute (e.g., a RejectedExecutionException) will be caught and logged.

      Specified by:
      addListener in interface Service
      Parameters:
      listener - the listener to run when the service changes state is complete
      executor - the executor in which the listeners callback methods will be run. For fast, lightweight listeners that would be safe to execute in any thread, consider MoreExecutors.directExecutor().
      Since:
      13.0

    • toString

      public String toString()
      Overrides:
      toString in class Object