Class AbstractService
- java.lang.Object
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- com.google.common.util.concurrent.AbstractService
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- All Implemented Interfaces:
Service
- Direct Known Subclasses:
AbstractIdleService.DelegateService
,AbstractScheduledService.ServiceDelegate
,ServiceManager.NoOpService
@Beta @GwtIncompatible public abstract class AbstractService extends java.lang.Object implements Service
Base class for implementing services that can handledoStart()
anddoStop()
requests, responding to them withnotifyStarted()
andnotifyStopped()
callbacks. Its subclasses must manage threads manually; considerAbstractExecutionThreadService
if you need only a single execution thread.- Since:
- 1.0
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Nested Class Summary
Nested Classes Modifier and Type Class 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.-
Nested classes/interfaces inherited from interface com.google.common.util.concurrent.Service
Service.Listener, Service.State
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Field Summary
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Constructor Summary
Constructors Modifier Constructor Description protected
AbstractService()
Constructor for use by subclasses.
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description void
addListener(Service.Listener listener, java.util.concurrent.Executor executor)
Registers aService.Listener
to be executed on the given executor.void
awaitRunning()
Waits for theService
to reach the running state.void
awaitRunning(long timeout, java.util.concurrent.TimeUnit unit)
Waits for theService
to reach the running state for no more than the given time.void
awaitTerminated()
Waits for theService
to reach the terminated state.void
awaitTerminated(long timeout, java.util.concurrent.TimeUnit unit)
Waits for theService
to reach a terminal state (eitherterminated
orfailed
) for no more than the given time.private void
checkCurrentState(Service.State expected)
Checks that the current state is equal to the expected state.protected abstract void
doStart()
This method is called bystartAsync()
to initiate service startup.protected abstract void
doStop()
This method should be used to initiate service shutdown.private void
executeListeners()
private void
failed(Service.State from, java.lang.Throwable cause)
java.lang.Throwable
failureCause()
Returns theThrowable
that caused this service to fail.boolean
isRunning()
Returnstrue
if this service is running.protected void
notifyFailed(java.lang.Throwable cause)
Invoke this method to transition the service to theService.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.private void
running()
Service
startAsync()
If the service state isService.State.NEW
, this initiates service startup and returns immediately.private void
starting()
Service.State
state()
Returns the lifecycle state of the service.Service
stopAsync()
private void
stopping(Service.State from)
private static ListenerCallQueue.Callback<Service.Listener>
stoppingCallback(Service.State from)
private void
terminated(Service.State from)
private static ListenerCallQueue.Callback<Service.Listener>
terminatedCallback(Service.State from)
java.lang.String
toString()
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Field Detail
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STARTING_CALLBACK
private static final ListenerCallQueue.Callback<Service.Listener> STARTING_CALLBACK
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RUNNING_CALLBACK
private static final ListenerCallQueue.Callback<Service.Listener> RUNNING_CALLBACK
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STOPPING_FROM_STARTING_CALLBACK
private static final ListenerCallQueue.Callback<Service.Listener> STOPPING_FROM_STARTING_CALLBACK
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STOPPING_FROM_RUNNING_CALLBACK
private static final ListenerCallQueue.Callback<Service.Listener> STOPPING_FROM_RUNNING_CALLBACK
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TERMINATED_FROM_NEW_CALLBACK
private static final ListenerCallQueue.Callback<Service.Listener> TERMINATED_FROM_NEW_CALLBACK
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TERMINATED_FROM_RUNNING_CALLBACK
private static final ListenerCallQueue.Callback<Service.Listener> TERMINATED_FROM_RUNNING_CALLBACK
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TERMINATED_FROM_STOPPING_CALLBACK
private static final ListenerCallQueue.Callback<Service.Listener> TERMINATED_FROM_STOPPING_CALLBACK
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monitor
private final Monitor monitor
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isStartable
private final Monitor.Guard isStartable
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isStoppable
private final Monitor.Guard isStoppable
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hasReachedRunning
private final Monitor.Guard hasReachedRunning
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isStopped
private final Monitor.Guard isStopped
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listeners
private final java.util.List<ListenerCallQueue<Service.Listener>> listeners
The listeners to notify during a state transition.
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snapshot
private volatile AbstractService.StateSnapshot snapshot
The current state of the service. This should be written with the lock held but can be read without it because it is an immutable object in a volatile field. This is desirable so that methods likestate()
,failureCause()
and notablytoString()
can be run without grabbing the lock.To update this field correctly the lock must be held to guarantee that the state is consistent.
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Method Detail
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terminatedCallback
private static ListenerCallQueue.Callback<Service.Listener> terminatedCallback(Service.State from)
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stoppingCallback
private static ListenerCallQueue.Callback<Service.Listener> stoppingCallback(Service.State from)
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doStart
protected abstract void doStart()
This method is called bystartAsync()
to initiate service startup. The invocation of this method should cause a call tonotifyStarted()
, either during this method's run, or after it has returned. If startup fails, the invocation should cause a call tonotifyFailed(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.
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doStop
protected abstract void doStop()
This method should be used to initiate service shutdown. The invocation of this method should cause a call tonotifyStopped()
, either during this method's run, or after it has returned. If shutdown fails, the invocation should cause a call tonotifyFailed(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.
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startAsync
public final Service startAsync()
Description copied from interface:Service
If the service state isService.State.NEW
, this initiates service startup and returns immediately. A stopped service may not be restarted.- Specified by:
startAsync
in interfaceService
- Returns:
- this
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stopAsync
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.
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awaitRunning
public final void awaitRunning()
Description copied from interface:Service
Waits for theService
to reach the running state.- Specified by:
awaitRunning
in interfaceService
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awaitRunning
public final void awaitRunning(long timeout, java.util.concurrent.TimeUnit unit) throws java.util.concurrent.TimeoutException
Description copied from interface:Service
Waits for theService
to reach the running state for no more than the given time.- Specified by:
awaitRunning
in interfaceService
- Parameters:
timeout
- the maximum time to waitunit
- the time unit of the timeout argument- Throws:
java.util.concurrent.TimeoutException
- if the service has not reached the given state within the deadline
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awaitTerminated
public final void awaitTerminated()
Description copied from interface:Service
Waits for theService
to reach the terminated state.- Specified by:
awaitTerminated
in interfaceService
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awaitTerminated
public final void awaitTerminated(long timeout, java.util.concurrent.TimeUnit unit) throws java.util.concurrent.TimeoutException
Description copied from interface:Service
Waits for theService
to reach a terminal state (eitherterminated
orfailed
) for no more than the given time.- Specified by:
awaitTerminated
in interfaceService
- Parameters:
timeout
- the maximum time to waitunit
- the time unit of the timeout argument- Throws:
java.util.concurrent.TimeoutException
- if the service has not reached the given state within the deadline
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checkCurrentState
private void checkCurrentState(Service.State expected)
Checks that the current state is equal to the expected state.
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notifyStarted
protected final void notifyStarted()
Implementing classes should invoke this method once their service has started. It will cause the service to transition fromService.State.STARTING
toService.State.RUNNING
.- Throws:
java.lang.IllegalStateException
- if the service is notService.State.STARTING
.
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notifyStopped
protected final void notifyStopped()
Implementing classes should invoke this method once their service has stopped. It will cause the service to transition fromService.State.STOPPING
toService.State.TERMINATED
.- Throws:
java.lang.IllegalStateException
- if the service is neitherService.State.STOPPING
norService.State.RUNNING
.
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notifyFailed
protected final void notifyFailed(java.lang.Throwable cause)
Invoke this method to transition the service to theService.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.
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isRunning
public final boolean isRunning()
Description copied from interface:Service
Returnstrue
if this service is running.
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state
public final Service.State state()
Description copied from interface:Service
Returns the lifecycle state of the service.
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failureCause
public final java.lang.Throwable failureCause()
Description copied from interface:Service
Returns theThrowable
that caused this service to fail.- Specified by:
failureCause
in interfaceService
- Since:
- 14.0
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addListener
public final void addListener(Service.Listener listener, java.util.concurrent.Executor executor)
Description copied from interface:Service
Registers aService.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., aRejectedExecutionException
) will be caught and logged.- Specified by:
addListener
in interfaceService
- Parameters:
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, considerMoreExecutors.directExecutor()
.- Since:
- 13.0
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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executeListeners
private void executeListeners()
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starting
private void starting()
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running
private void running()
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stopping
private void stopping(Service.State from)
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terminated
private void terminated(Service.State from)
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failed
private void failed(Service.State from, java.lang.Throwable cause)
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