@Beta @GwtIncompatible public abstract class AbstractService extends java.lang.Object implements Service
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.Modifier and Type | Class and Description |
---|---|
private class |
AbstractService.HasReachedRunningGuard |
private class |
AbstractService.IsStartableGuard |
private class |
AbstractService.IsStoppableGuard |
private class |
AbstractService.IsStoppedGuard |
private static class |
AbstractService.StateSnapshot
An immutable snapshot of the current state of the service.
|
Service.Listener, Service.State
Modifier and Type | Field and Description |
---|---|
private Monitor.Guard |
hasReachedRunning |
private Monitor.Guard |
isStartable |
private Monitor.Guard |
isStoppable |
private Monitor.Guard |
isStopped |
private ListenerCallQueue<Service.Listener> |
listeners
The listeners to notify during a state transition.
|
private Monitor |
monitor |
private static ListenerCallQueue.Event<Service.Listener> |
RUNNING_EVENT |
private AbstractService.StateSnapshot |
snapshot
The current state of the service.
|
private static ListenerCallQueue.Event<Service.Listener> |
STARTING_EVENT |
private static ListenerCallQueue.Event<Service.Listener> |
STOPPING_FROM_RUNNING_EVENT |
private static ListenerCallQueue.Event<Service.Listener> |
STOPPING_FROM_STARTING_EVENT |
private static ListenerCallQueue.Event<Service.Listener> |
TERMINATED_FROM_NEW_EVENT |
private static ListenerCallQueue.Event<Service.Listener> |
TERMINATED_FROM_RUNNING_EVENT |
private static ListenerCallQueue.Event<Service.Listener> |
TERMINATED_FROM_STOPPING_EVENT |
Modifier | Constructor and Description |
---|---|
protected |
AbstractService()
Constructor for use by subclasses.
|
Modifier and Type | Method and Description |
---|---|
void |
addListener(Service.Listener listener,
java.util.concurrent.Executor executor)
Registers a
Service.Listener to be executed on the given
executor. |
void |
awaitRunning()
Waits for the
Service to reach the running state. |
void |
awaitRunning(long timeout,
java.util.concurrent.TimeUnit unit)
Waits for the
Service to reach the running state for no more
than the given time. |
void |
awaitTerminated()
Waits for the
Service to reach the terminated state. |
void |
awaitTerminated(long timeout,
java.util.concurrent.TimeUnit unit)
Waits for the
Service to reach a terminal state (either terminated or failed ) for no more than the given time. |
private void |
checkCurrentState(Service.State expected)
Checks that the current state is equal to the expected state.
|
private void |
dispatchListenerEvents()
|
protected abstract void |
doStart()
This method is called by
startAsync() to initiate service startup. |
protected abstract void |
doStop()
This method should be used to initiate service shutdown.
|
private void |
enqueueFailedEvent(Service.State from,
java.lang.Throwable cause) |
private void |
enqueueRunningEvent() |
private void |
enqueueStartingEvent() |
private void |
enqueueStoppingEvent(Service.State from) |
private void |
enqueueTerminatedEvent(Service.State from) |
java.lang.Throwable |
failureCause()
Returns the
Throwable that caused this service to fail. |
boolean |
isRunning()
Returns
true if this service is running. |
protected void |
notifyFailed(java.lang.Throwable cause)
Invoke this method to transition the service to the
Service.State.FAILED . |
protected void |
notifyStarted()
Implementing classes should invoke this method once their service has started.
|
protected void |
notifyStopped()
Implementing classes should invoke this method once their service has stopped.
|
Service |
startAsync()
If the service state is
Service.State.NEW , this initiates service startup and returns
immediately. |
Service.State |
state()
Returns the lifecycle state of the service.
|
Service |
stopAsync()
|
private static ListenerCallQueue.Event<Service.Listener> |
stoppingEvent(Service.State from) |
private static ListenerCallQueue.Event<Service.Listener> |
terminatedEvent(Service.State from) |
java.lang.String |
toString() |
private static final ListenerCallQueue.Event<Service.Listener> STARTING_EVENT
private static final ListenerCallQueue.Event<Service.Listener> RUNNING_EVENT
private static final ListenerCallQueue.Event<Service.Listener> STOPPING_FROM_STARTING_EVENT
private static final ListenerCallQueue.Event<Service.Listener> STOPPING_FROM_RUNNING_EVENT
private static final ListenerCallQueue.Event<Service.Listener> TERMINATED_FROM_NEW_EVENT
private static final ListenerCallQueue.Event<Service.Listener> TERMINATED_FROM_RUNNING_EVENT
private static final ListenerCallQueue.Event<Service.Listener> TERMINATED_FROM_STOPPING_EVENT
private final Monitor monitor
private final Monitor.Guard isStartable
private final Monitor.Guard isStoppable
private final Monitor.Guard hasReachedRunning
private final Monitor.Guard isStopped
private final ListenerCallQueue<Service.Listener> listeners
private volatile AbstractService.StateSnapshot snapshot
state()
, failureCause()
and notably toString()
can be run
without grabbing the lock.
To update this field correctly the lock must be held to guarantee that the state is consistent.
private static ListenerCallQueue.Event<Service.Listener> terminatedEvent(Service.State from)
private static ListenerCallQueue.Event<Service.Listener> stoppingEvent(Service.State from)
protected abstract void doStart()
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.
protected abstract void doStop()
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.
public final Service startAsync()
Service
Service.State.NEW
, this initiates service startup and returns
immediately. A stopped service may not be restarted.startAsync
in interface Service
public final Service stopAsync()
Service
public final void awaitRunning()
Service
Service
to reach the running state.awaitRunning
in interface Service
public final void awaitRunning(long timeout, java.util.concurrent.TimeUnit unit) throws java.util.concurrent.TimeoutException
Service
Service
to reach the running state for no more
than the given time.awaitRunning
in interface Service
timeout
- the maximum time to waitunit
- the time unit of the timeout argumentjava.util.concurrent.TimeoutException
- if the service has not reached the given state within the deadlinepublic final void awaitTerminated()
Service
Service
to reach the terminated state.awaitTerminated
in interface Service
public final void awaitTerminated(long timeout, java.util.concurrent.TimeUnit unit) throws java.util.concurrent.TimeoutException
Service
Service
to reach a terminal state (either terminated
or failed
) for no more than the given time.awaitTerminated
in interface Service
timeout
- the maximum time to waitunit
- the time unit of the timeout argumentjava.util.concurrent.TimeoutException
- if the service has not reached the given state within the deadlineprivate void checkCurrentState(Service.State expected)
protected final void notifyStarted()
Service.State.STARTING
to Service.State.RUNNING
.java.lang.IllegalStateException
- if the service is not Service.State.STARTING
.protected final void notifyStopped()
Service.State.STOPPING
to Service.State.TERMINATED
.java.lang.IllegalStateException
- if the service is neither Service.State.STOPPING
nor Service.State.RUNNING
.protected final void notifyFailed(java.lang.Throwable cause)
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.public final boolean isRunning()
Service
true
if this service is running.public final Service.State state()
Service
public final java.lang.Throwable failureCause()
Service
Throwable
that caused this service to fail.failureCause
in interface Service
public final void addListener(Service.Listener listener, java.util.concurrent.Executor executor)
Service
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.
addListener
in interface Service
listener
- the listener to run when the service changes state is completeexecutor
- 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()
.public java.lang.String toString()
toString
in class java.lang.Object
private void dispatchListenerEvents()
private void enqueueStartingEvent()
private void enqueueRunningEvent()
private void enqueueStoppingEvent(Service.State from)
private void enqueueTerminatedEvent(Service.State from)
private void enqueueFailedEvent(Service.State from, java.lang.Throwable cause)