@Beta @GwtIncompatible public interface Service
startAsync()
and stopAsync()
lifecycle methods to transition between states. Example services include
webservers, RPC servers and timers.
The normal lifecycle of a service is:
There are deviations from this if there are failures or if stopAsync()
is called
before the Service
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. The Service.State.FAILED
and Service.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.
com.google.common.base.Service
)Modifier and Type | Interface and Description |
---|---|
static class |
Service.Listener
A listener for the various state changes that a
Service goes through in its lifecycle. |
static class |
Service.State
The lifecycle states of a service.
|
Modifier and Type | Method and Description |
---|---|
void |
addListener(Service.Listener listener,
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,
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,
TimeUnit unit)
Waits for the
Service to reach a terminal state (either terminated or 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 running. |
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()
|
@CanIgnoreReturnValue Service startAsync()
Service.State.NEW
, this initiates service startup and returns
immediately. A stopped service may not be restarted.IllegalStateException
- if the service is not Service.State.NEW
Service.State state()
@CanIgnoreReturnValue Service stopAsync()
void awaitRunning()
Service
to reach the running state.IllegalStateException
- if the service reaches a state from which it is not possible to
enter the Service.State.RUNNING
state. e.g. if the state
is State#TERMINATED
when this method is called then this will throw an IllegalStateException.void awaitRunning(long timeout, TimeUnit unit) throws TimeoutException
Service
to reach the running state for no more
than the given time.timeout
- the maximum time to waitunit
- the time unit of the timeout argumentTimeoutException
- if the service has not reached the given state within the deadlineIllegalStateException
- if the service reaches a state from which it is not possible to
enter the RUNNING
state. e.g. if the state
is State#TERMINATED
when this method is called then this will throw an IllegalStateException.void awaitTerminated()
Service
to reach the terminated state.IllegalStateException
- if the service fails.void awaitTerminated(long timeout, TimeUnit unit) throws TimeoutException
Service
to reach a terminal state (either terminated
or failed
) for no more than the given time.timeout
- the maximum time to waitunit
- the time unit of the timeout argumentTimeoutException
- if the service has not reached the given state within the deadlineIllegalStateException
- if the service fails.Throwable failureCause()
Throwable
that caused this service to fail.IllegalStateException
- if this service's state isn't FAILED.void addListener(Service.Listener listener, Executor executor)
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.
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()
.Copyright © 2010–2019. All rights reserved.