Interface Service
-
- All Known Implementing Classes:
AbstractExecutionThreadService
,AbstractIdleService
,AbstractScheduledService
,AbstractService
,ForwardingService
@Beta public interface Service
An object with an operational state, plus asynchronousstartAsync()
andstopAsync()
lifecycle methods to transition between states. Example services include webservers, RPC servers and timers.The normal lifecycle of a service is:
- NEW ->
- STARTING ->
- RUNNING ->
- STOPPING ->
- TERMINATED
There are deviations from this if there are failures or if
stopAsync()
is called before theService
reaches the RUNNING state. The set of legal transitions form a DAG, therefore every method of the listener will be called at most once. N.B. TheService.State.FAILED
andService.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
com.google.common.base.Service
)
-
-
Nested Class Summary
Nested Classes Modifier and Type Interface Description static class
Service.Listener
A listener for the various state changes that aService
goes through in its lifecycle.static class
Service.State
The lifecycle states of a service.
-
Method Summary
All Methods Instance Methods Abstract Methods Deprecated 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.java.lang.Throwable
failureCause()
Returns theThrowable
that caused this service to fail.boolean
isRunning()
Returnstrue
if this service is running.ListenableFuture<Service.State>
start()
Deprecated.UsestartAsync()
instead of this method to start theService
or use aService.Listener
to asynchronously wait for service startup.Service.State
startAndWait()
Deprecated.UsestartAsync()
andawaitRunning()
instead of this method.Service
startAsync()
If the service state isService.State.NEW
, this initiates service startup and returns immediately.Service.State
state()
Returns the lifecycle state of the service.ListenableFuture<Service.State>
stop()
Deprecated.UsestopAsync()
instead of this method to initiate service shutdown or use a serviceService.Listener
to asynchronously wait for service shutdown.Service.State
stopAndWait()
Deprecated.UsestopAsync()
andawaitTerminated()
instead of this method.Service
stopAsync()
-
-
-
Method Detail
-
start
@Deprecated ListenableFuture<Service.State> start()
Deprecated.UsestartAsync()
instead of this method to start theService
or use aService.Listener
to asynchronously wait for service startup.If the service state isService.State.NEW
, this initiates service startup and returns immediately. If the service has already been started, this method returns immediately without taking action. A stopped service may not be restarted.- Returns:
- a future for the startup result, regardless of whether this call initiated startup.
Calling
Future.get()
will block until the service has finished starting, and returns one ofService.State.RUNNING
,Service.State.STOPPING
orService.State.TERMINATED
. If the service fails to start,Future.get()
will throw anExecutionException
, and the service's state will beService.State.FAILED
. If it has already finished starting,Future.get()
returns immediately. Cancelling this future has no effect on the service.
-
startAndWait
@Deprecated Service.State startAndWait()
Deprecated.UsestartAsync()
andawaitRunning()
instead of this method.Initiates service startup (if necessary), returning once the service has finished starting. Unlike callingstart().get()
, this method throws no checked exceptions, and it cannot be interrupted.- Returns:
- the state of the service when startup finished.
- Throws:
UncheckedExecutionException
- if startup failed
-
startAsync
Service startAsync()
If the service state isService.State.NEW
, this initiates service startup and returns immediately. A stopped service may not be restarted.- Returns:
- this
- Throws:
java.lang.IllegalStateException
- if the service is notService.State.NEW
- Since:
- 15.0
-
isRunning
boolean isRunning()
Returnstrue
if this service is running.
-
state
Service.State state()
Returns the lifecycle state of the service.
-
stop
@Deprecated ListenableFuture<Service.State> stop()
Deprecated.UsestopAsync()
instead of this method to initiate service shutdown or use a serviceService.Listener
to asynchronously wait for service shutdown.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.- Returns:
- a future for the shutdown result, regardless of whether this call initiated shutdown.
Calling
Future.get()
will block until the service has finished shutting down, and either returnsService.State.TERMINATED
or throws anExecutionException
. If it has already finished stopping,Future.get()
returns immediately. Cancelling this future has no effect on the service.
-
stopAndWait
@Deprecated Service.State stopAndWait()
Deprecated.UsestopAsync()
andawaitTerminated()
instead of this method.Initiates service shutdown (if necessary), returning once the service has finished stopping. If this isService.State.STARTING
, startup will be cancelled. If this isService.State.NEW
, it isterminated
without having been started nor stopped. Unlike callingstop().get()
, this method throws no checked exceptions.- Returns:
- the state of the service when shutdown finished.
- Throws:
UncheckedExecutionException
- if the service has failed or fails during shutdown
-
stopAsync
Service stopAsync()
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.- Returns:
- this
- Since:
- 15.0
-
awaitRunning
void awaitRunning()
Waits for theService
to reach the running state.- Throws:
java.lang.IllegalStateException
- if the service reaches a state from which it is not possible to enter theService.State.RUNNING
state. e.g. if thestate
isState#TERMINATED
when this method is called then this will throw an IllegalStateException.- Since:
- 15.0
-
awaitRunning
void awaitRunning(long timeout, java.util.concurrent.TimeUnit unit) throws java.util.concurrent.TimeoutException
Waits for theService
to reach the running state for no more than the given time.- 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 deadlinejava.lang.IllegalStateException
- if the service reaches a state from which it is not possible to enter theRUNNING
state. e.g. if thestate
isState#TERMINATED
when this method is called then this will throw an IllegalStateException.- Since:
- 15.0
-
awaitTerminated
void awaitTerminated()
Waits for theService
to reach the terminated state.- Throws:
java.lang.IllegalStateException
- if the service fails.- Since:
- 15.0
-
awaitTerminated
void awaitTerminated(long timeout, java.util.concurrent.TimeUnit unit) throws java.util.concurrent.TimeoutException
Waits for theService
to reach a terminal state (eitherterminated
orfailed
) for no more than the given time.- 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 deadlinejava.lang.IllegalStateException
- if the service fails.- Since:
- 15.0
-
failureCause
java.lang.Throwable failureCause()
Returns theThrowable
that caused this service to fail.- Throws:
java.lang.IllegalStateException
- if this service's state isn't FAILED.- Since:
- 14.0
-
addListener
void addListener(Service.Listener listener, java.util.concurrent.Executor executor)
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.There is no guaranteed ordering of execution of listeners, but any listener added through this method is guaranteed to be called whenever there is a state change.
Exceptions thrown by a listener will be propagated up to the executor. Any exception thrown during
Executor.execute
(e.g., aRejectedExecutionException
or an exception thrown by inline execution) will be caught and logged.- 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.sameThreadExecutor()
.- Since:
- 13.0
-
-