Module dev.mccue.guava.concurrent
Package dev.mccue.guava.concurrent

Interface Service

All Known Implementing Classes:
AbstractExecutionThreadService, AbstractIdleService, AbstractScheduledService, AbstractService
@DoNotMock("Create an AbstractIdleService") public interface Service
An object with an operational state, plus asynchronous #startAsync() and #stopAsync() lifecycle methods to transition between states. Example services include webservers, RPC servers and timers.

The normal lifecycle of a service is:

  • State#NEW NEW ->
  • State#STARTING STARTING ->
  • State#RUNNING RUNNING ->
  • State#STOPPING STOPPING ->
  • State#TERMINATED TERMINATED

There are deviations from this if there are failures or if Service#stopAsync is called before the Service reaches the State#RUNNING RUNNING state. The set of legal transitions form a DAG, therefore every method of the listener will be called at most once. N.B. The State#FAILED and State#TERMINATED states are terminal states, once a service enters either of these states it cannot ever leave them.

Implementors of this interface are strongly encouraged to extend one of the abstract classes in this package which implement this interface and make the threading and state management easier.

Since:
9.0 (in 1.0 as dev.mccue.guava.base.Service)
Author:
Jesse Wilson, Luke Sandberg

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Interface
    Description
    static class 
    Service.Listener
    A listener for the various state changes that a Service goes through in its lifecycle.
    static enum 
    Service.State
    The lifecycle states of a service.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    addListener(Service.Listener listener, Executor executor)
    Registers a Listener to be Executor#execute executed on the given executor.
    void
    awaitRunning()
    Waits for the Service to reach the State#RUNNING running state.
    void
    awaitRunning(long timeout, TimeUnit unit)
    Waits for the Service to reach the State#RUNNING running state for no more than the given time.
    default void
    awaitRunning(Duration timeout)
    Waits for the Service to reach the State#RUNNING running state for no more than the given time.
    void
    awaitTerminated()
    Waits for the Service to reach the State#TERMINATED terminated state.
    void
    awaitTerminated(long timeout, TimeUnit unit)
    Waits for the Service to reach a terminal state (either Service.State#TERMINATED terminated or Service.State#FAILED failed) for no more than the given time.
    default void
    awaitTerminated(Duration timeout)
    Waits for the Service to reach a terminal state (either Service.State#TERMINATED terminated or Service.State#FAILED failed) for no more than the given time.
    Throwable
    failureCause()
    Returns the Throwable that caused this service to fail.
    boolean
    isRunning()
    Returns true if this service is State#RUNNING running.
    Service
    startAsync()
    If the service state is State#NEW, this initiates service startup and returns immediately.
    Service.State
    state()
    Returns the lifecycle state of the service.
    Service
    stopAsync()
    If the service is State#STARTING starting or State#RUNNING running, this initiates service shutdown and returns immediately.

  • Method Details

    • startAsync

      @CanIgnoreReturnValue Service startAsync()
      If the service state is State#NEW, this initiates service startup and returns immediately. A stopped service may not be restarted.
      Returns:
      this
      Throws:
      IllegalStateException - if the service is not State#NEW
      Since:
      15.0

    • isRunning

      boolean isRunning()
      Returns true if this service is State#RUNNING running.

    • state

      Service.State state()
      Returns the lifecycle state of the service.

    • stopAsync

      @CanIgnoreReturnValue Service stopAsync()
      If the service is State#STARTING starting or State#RUNNING running, this initiates service shutdown and returns immediately. If the service is State#NEW new, it is State#TERMINATED terminated without having been started nor stopped. If the service has already been stopped, this method returns immediately without taking action.
      Returns:
      this
      Since:
      15.0

    • awaitRunning

      void awaitRunning()
      Waits for the Service to reach the State#RUNNING running state.
      Throws:
      IllegalStateException - if the service reaches a state from which it is not possible to enter the State#RUNNING state. e.g. if the state is State#TERMINATED when this method is called then this will throw an IllegalStateException.
      Since:
      15.0

    • awaitRunning

      default void awaitRunning(Duration timeout) throws TimeoutException
      Waits for the Service to reach the State#RUNNING running state for no more than the given time.
      Parameters:
      timeout - the maximum time to wait
      Throws:
      TimeoutException - if the service has not reached the given state within the deadline
      IllegalStateException - if the service reaches a state from which it is not possible to enter the State#RUNNING RUNNING state. e.g. if the state is State#TERMINATED when this method is called then this will throw an IllegalStateException.
      Since:
      28.0

    • awaitRunning

      void awaitRunning(long timeout, TimeUnit unit) throws TimeoutException
      Waits for the Service to reach the State#RUNNING running state for no more than the given time.
      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
      IllegalStateException - if the service reaches a state from which it is not possible to enter the State#RUNNING RUNNING state. e.g. if the state is State#TERMINATED when this method is called then this will throw an IllegalStateException.
      Since:
      15.0

    • awaitTerminated

      void awaitTerminated()
      Waits for the Service to reach the State#TERMINATED terminated state.
      Throws:
      IllegalStateException - if the service State#FAILED fails.
      Since:
      15.0

    • awaitTerminated

      default void awaitTerminated(Duration timeout) throws TimeoutException
      Waits for the Service to reach a terminal state (either Service.State#TERMINATED terminated or Service.State#FAILED failed) for no more than the given time.
      Parameters:
      timeout - the maximum time to wait
      Throws:
      TimeoutException - if the service has not reached the given state within the deadline
      IllegalStateException - if the service State#FAILED fails.
      Since:
      28.0

    • awaitTerminated

      void awaitTerminated(long timeout, TimeUnit unit) throws TimeoutException
      Waits for the Service to reach a terminal state (either Service.State#TERMINATED terminated or Service.State#FAILED failed) for no more than the given time.
      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
      IllegalStateException - if the service State#FAILED fails.
      Since:
      15.0

    • failureCause

      Throwable failureCause()
      Returns the Throwable that caused this service to fail.
      Throws:
      IllegalStateException - if this service's state isn't State#FAILED FAILED.
      Since:
      14.0

    • addListener

      void addListener(Service.Listener listener, Executor executor)
      Registers a Listener to be Executor#execute 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.

      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