Class ServiceManager
- java.lang.Object
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- com.google.common.util.concurrent.ServiceManager
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@GwtIncompatible public final class ServiceManager extends Object
A manager for monitoring and controlling a set of services. This class provides methods for starting, stopping and inspecting a collection of services. Additionally, users can monitor state transitions with the listener mechanism.While it is recommended that service lifecycles be managed via this class, state transitions initiated via other mechanisms do not impact the correctness of its methods. For example, if the services are started by some mechanism besides
startAsync()
, the listeners will be invoked when appropriate andawaitHealthy()
will still work as expected.Here is a simple example of how to use a
ServiceManager
to start a server.class Server { public static void main(String[] args) { Set<Service> services = ...; ServiceManager manager = new ServiceManager(services); manager.addListener(new Listener() { public void stopped() {} public void healthy() { // Services have been initialized and are healthy, start accepting requests... } public void failure(Service service) { // Something failed, at this point we could log it, notify a load balancer, or take // some other action. For now we will just exit. System.exit(1); } }, MoreExecutors.directExecutor()); Runtime.getRuntime().addShutdownHook(new Thread() { public void run() { // Give the services 5 seconds to stop to ensure that we are responsive to shutdown // requests. try { manager.stopAsync().awaitStopped(5, TimeUnit.SECONDS); } catch (TimeoutException timeout) { // stopping timed out } } }); manager.startAsync(); // start all the services asynchronously } }
This class uses the ServiceManager's methods to start all of its services, to respond to service failure and to ensure that when the JVM is shutting down all the services are stopped.
- Since:
- 14.0
- Author:
- Luke Sandberg
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
ServiceManager.Listener
A listener for the aggregate state changes of the services that are under management.
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Constructor Summary
Constructors Constructor Description ServiceManager(Iterable<? extends Service> services)
Constructs a new instance for managing the given services.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
addListener(ServiceManager.Listener listener, Executor executor)
Registers aServiceManager.Listener
to be executed on the given executor.void
awaitHealthy()
Waits for theServiceManager
to become healthy.void
awaitHealthy(long timeout, TimeUnit unit)
Waits for theServiceManager
to become healthy for no more than the given time.void
awaitHealthy(Duration timeout)
Waits for theServiceManager
to become healthy for no more than the given time.void
awaitStopped()
Waits for the all the services to reach a terminal state.void
awaitStopped(long timeout, TimeUnit unit)
Waits for the all the services to reach a terminal state for no more than the given time.void
awaitStopped(Duration timeout)
Waits for the all the services to reach a terminal state for no more than the given time.boolean
isHealthy()
Returns true if all services are currently in the running state.ImmutableSetMultimap<Service.State,Service>
servicesByState()
Provides a snapshot of the current state of all the services under management.ServiceManager
startAsync()
Initiates service startup on all the services being managed.ImmutableMap<Service,Duration>
startupDurations()
Returns the service load times.ImmutableMap<Service,Long>
startupTimes()
Returns the service load times.ServiceManager
stopAsync()
Initiates service shutdown if necessary on all the services being managed.String
toString()
Returns a string representation of the object.
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Constructor Detail
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ServiceManager
public ServiceManager(Iterable<? extends Service> services)
Constructs a new instance for managing the given services.- Parameters:
services
- The services to manage- Throws:
IllegalArgumentException
- if not all services are new or if there are any duplicate services.
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Method Detail
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addListener
public void addListener(ServiceManager.Listener listener, Executor executor)
Registers aServiceManager.Listener
to be executed on the given executor. The listener will not have previous state changes replayed, so it is suggested that listeners are added before any of the managed services are started.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.When selecting an executor, note that
directExecutor
is dangerous in some cases. See the discussion in theListenableFuture.addListener
documentation.- Parameters:
listener
- the listener to run when the manager changes stateexecutor
- the executor in which the listeners callback methods will be run.
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startAsync
@CanIgnoreReturnValue public ServiceManager startAsync()
Initiates service startup on all the services being managed. It is only valid to call this method if all of the services are new.- Returns:
- this
- Throws:
IllegalStateException
- if any of the Services are notnew
when the method is called.
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awaitHealthy
public void awaitHealthy()
Waits for theServiceManager
to become healthy. The manager will become healthy after all the component services have reached the running state.- Throws:
IllegalStateException
- if the service manager reaches a state from which it cannot become healthy.
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awaitHealthy
public void awaitHealthy(Duration timeout) throws TimeoutException
Waits for theServiceManager
to become healthy for no more than the given time. The manager will become healthy after all the component services have reached the running state.- Parameters:
timeout
- the maximum time to wait- Throws:
TimeoutException
- if not all of the services have finished starting within the deadlineIllegalStateException
- if the service manager reaches a state from which it cannot become healthy.- Since:
- 28.0
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awaitHealthy
public void awaitHealthy(long timeout, TimeUnit unit) throws TimeoutException
Waits for theServiceManager
to become healthy for no more than the given time. The manager will become healthy after all the component services have reached the running state.- Parameters:
timeout
- the maximum time to waitunit
- the time unit of the timeout argument- Throws:
TimeoutException
- if not all of the services have finished starting within the deadlineIllegalStateException
- if the service manager reaches a state from which it cannot become healthy.
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stopAsync
@CanIgnoreReturnValue public ServiceManager stopAsync()
Initiates service shutdown if necessary on all the services being managed.- Returns:
- this
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awaitStopped
public void awaitStopped()
Waits for the all the services to reach a terminal state. After this method returns all services will either be terminated or failed.
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awaitStopped
public void awaitStopped(Duration timeout) throws TimeoutException
Waits for the all the services to reach a terminal state for no more than the given time. After this method returns all services will either be terminated or failed.- Parameters:
timeout
- the maximum time to wait- Throws:
TimeoutException
- if not all of the services have stopped within the deadline- Since:
- 28.0
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awaitStopped
public void awaitStopped(long timeout, TimeUnit unit) throws TimeoutException
Waits for the all the services to reach a terminal state for no more than the given time. After this method returns all services will either be terminated or failed.- Parameters:
timeout
- the maximum time to waitunit
- the time unit of the timeout argument- Throws:
TimeoutException
- if not all of the services have stopped within the deadline
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isHealthy
public boolean isHealthy()
Returns true if all services are currently in the running state.Users who want more detailed information should use the
servicesByState()
method to get detailed information about which services are not running.
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servicesByState
public ImmutableSetMultimap<Service.State,Service> servicesByState()
Provides a snapshot of the current state of all the services under management.N.B. This snapshot is guaranteed to be consistent, i.e. the set of states returned will correspond to a point in time view of the services.
- Since:
- 29.0 (present with return type
ImmutableMultimap
since 14.0)
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startupTimes
public ImmutableMap<Service,Long> startupTimes()
Returns the service load times. This value will only return startup times for services that have finished starting.- Returns:
- Map of services and their corresponding startup time in millis, the map entries will be ordered by startup time.
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startupDurations
public ImmutableMap<Service,Duration> startupDurations()
Returns the service load times. This value will only return startup times for services that have finished starting.- Returns:
- Map of services and their corresponding startup time, the map entries will be ordered by startup time.
- Since:
- 31.0
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toString
public String toString()
Description copied from class:java.lang.Object
Returns a string representation of the object. In general, thetoString
method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.The
toString
method for classObject
returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@
', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:getClass().getName() + '@' + Integer.toHexString(hashCode())
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