org.apache.druid.java.util.common.lifecycle

Class Lifecycle

java.lang.Object

org.apache.druid.java.util.common.lifecycle.Lifecycle

public class Lifecycle
extends Object

A manager of object Lifecycles. This object has methods for registering objects that should be started and stopped. The Lifecycle allows for four stages: Lifecycle.Stage.INIT, Lifecycle.Stage.NORMAL, Lifecycle.Stage.SERVER, and Lifecycle.Stage.ANNOUNCEMENTS. Things added at Lifecycle.Stage.INIT will be started first (in the order that they are added to the Lifecycle instance) and then things added at Lifecycle.Stage.NORMAL, then Lifecycle.Stage.SERVER, and finally, Lifecycle.Stage.ANNOUNCEMENTS will be started. The close operation goes in reverse order, starting with the last thing added at Lifecycle.Stage.ANNOUNCEMENTS and working backwards. Conceptually, the stages have the following purposes: - Lifecycle.Stage.INIT: Currently, this stage is used exclusively for log4j initialization, since almost everything needs logging and it should be the last thing to shutdown. Any sort of bootstrapping object that provides something that should be initialized before nearly all other Lifecycle objects could also belong here (if it doesn't need logging during start or stop). - Lifecycle.Stage.NORMAL: This is the default stage. Most objects will probably make the most sense to be registered at this level, with the exception of any form of server or service announcements - Lifecycle.Stage.SERVER: This lifecycle stage is intended for all 'server' objects, for example, org.apache.druid.server.initialization.jetty.JettyServerModule, but any sort of 'server' that expects most (or some specific) Lifecycle objects to be initialized by the time it starts, and still available at the time it stops can logically live in this stage. - Lifecycle.Stage.ANNOUNCEMENTS: Any object which announces to a cluster this servers location belongs in this stage. By being last, we can be sure that all servers are initialized before we advertise the endpoint locations, and also can be sure that we un-announce these advertisements prior to the Stage.SERVER objects stop. There are two sets of methods to add things to the Lifecycle. One set that will just add instances and enforce that start() has not been called yet. The other set will add instances and, if the lifecycle is already started, start them.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	Lifecycle.Handler
static class	Lifecycle.Stage

Constructor Summary

Constructors

Constructor and Description
Lifecycle()
Lifecycle(String name)

Method Summary

Modifier and Type	Method and Description
<T extends Closeable> T	addCloseableInstance(T o) Adds a Closeable instance to the lifecycle at Lifecycle.Stage.NORMAL stage, doesn't try to call any "start" method on it, use addStartCloseInstance(Object) instead if you need the latter behaviour.
void	addHandler(Lifecycle.Handler handler) Adds a handler to the Lifecycle at the Stage.NORMAL stage.
void	addHandler(Lifecycle.Handler handler, Lifecycle.Stage stage) Adds a handler to the Lifecycle.
<T> T	addManagedInstance(T o) Adds a "managed" instance (annotated with LifecycleStart and LifecycleStop) to the Lifecycle at Stage.NORMAL.
<T> T	addManagedInstance(T o, Lifecycle.Stage stage) Adds a "managed" instance (annotated with LifecycleStart and LifecycleStop) to the Lifecycle.
void	addMaybeStartHandler(Lifecycle.Handler handler) Adds a handler to the Lifecycle at the Stage.NORMAL stage and starts it if the lifecycle has already been started.
void	addMaybeStartHandler(Lifecycle.Handler handler, Lifecycle.Stage stage) Adds a handler to the Lifecycle and starts it if the lifecycle has already been started.
<T> T	addMaybeStartManagedInstance(T o) Adds a "managed" instance (annotated with LifecycleStart and LifecycleStop) to the Lifecycle at Stage.NORMAL and starts it if the lifecycle has already been started.
<T> T	addMaybeStartManagedInstance(T o, Lifecycle.Stage stage) Adds a "managed" instance (annotated with LifecycleStart and LifecycleStop) to the Lifecycle and starts it if the lifecycle has already been started.
<T> T	addMaybeStartStartCloseInstance(T o) Adds an instance with a start() and/or close() method to the Lifecycle at Stage.NORMAL and starts it if the lifecycle has already been started.
<T> T	addMaybeStartStartCloseInstance(T o, Lifecycle.Stage stage) Adds an instance with a start() and/or close() method to the Lifecycle and starts it if the lifecycle has already been started.
<T> T	addStartCloseInstance(T o) Adds an instance with a start() and/or close() method to the Lifecycle at Stage.NORMAL.
<T> T	addStartCloseInstance(T o, Lifecycle.Stage stage) Adds an instance with a start() and/or close() method to the Lifecycle.
void	ensureShutdownHook()
void	join()
void	start()
void	stop()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Lifecycle

public Lifecycle()

Lifecycle

public Lifecycle(String name)

Method Detail

addManagedInstance

public <T> T addManagedInstance(T o)

Adds a "managed" instance (annotated with LifecycleStart and LifecycleStop) to the Lifecycle at Stage.NORMAL. If the lifecycle has already been started, it throws an ISE

Parameters:

o - The object to add to the lifecycle

Throws:

ISE - addHandler(Handler, Stage)

addManagedInstance

public <T> T addManagedInstance(T o,
                                Lifecycle.Stage stage)

Adds a "managed" instance (annotated with LifecycleStart and LifecycleStop) to the Lifecycle. If the lifecycle has already been started, it throws an ISE

Parameters:

o - The object to add to the lifecycle

stage - The stage to add the lifecycle at

Throws:

ISE - addHandler(Handler, Stage)

addStartCloseInstance

public <T> T addStartCloseInstance(T o)

Adds an instance with a start() and/or close() method to the Lifecycle at Stage.NORMAL. If the lifecycle has already been started, it throws an ISE

Parameters:

o - The object to add to the lifecycle

Throws:

ISE - addHandler(Handler, Stage)

addStartCloseInstance

public <T> T addStartCloseInstance(T o,
                                   Lifecycle.Stage stage)

Adds an instance with a start() and/or close() method to the Lifecycle. If the lifecycle has already been started, it throws an ISE

Parameters:

o - The object to add to the lifecycle

stage - The stage to add the lifecycle at

Throws:

ISE - addHandler(Handler, Stage)

addHandler

public void addHandler(Lifecycle.Handler handler)

Adds a handler to the Lifecycle at the Stage.NORMAL stage. If the lifecycle has already been started, it throws an ISE

Parameters:

handler - The hander to add to the lifecycle

Throws:

ISE - addHandler(Handler, Stage)

addHandler

public void addHandler(Lifecycle.Handler handler,
                       Lifecycle.Stage stage)

Adds a handler to the Lifecycle. If the lifecycle has already been started, it throws an ISE

Parameters:

handler - The hander to add to the lifecycle

stage - The stage to add the lifecycle at

Throws:

ISE - indicates that the lifecycle has already been started and thus cannot be added to

addMaybeStartManagedInstance

public <T> T addMaybeStartManagedInstance(T o)
                                   throws Exception

Adds a "managed" instance (annotated with LifecycleStart and LifecycleStop) to the Lifecycle at Stage.NORMAL and starts it if the lifecycle has already been started.

Parameters:

o - The object to add to the lifecycle

Throws:

Exception - addMaybeStartHandler(Handler, Stage)

addMaybeStartManagedInstance

public <T> T addMaybeStartManagedInstance(T o,
                                          Lifecycle.Stage stage)
                                   throws Exception

Adds a "managed" instance (annotated with LifecycleStart and LifecycleStop) to the Lifecycle and starts it if the lifecycle has already been started.

Parameters:

o - The object to add to the lifecycle

stage - The stage to add the lifecycle at

Throws:

Exception - addMaybeStartHandler(Handler, Stage)

addMaybeStartStartCloseInstance

public <T> T addMaybeStartStartCloseInstance(T o)
                                      throws Exception

Adds an instance with a start() and/or close() method to the Lifecycle at Stage.NORMAL and starts it if the lifecycle has already been started.

Parameters:

o - The object to add to the lifecycle

Throws:

Exception - addMaybeStartHandler(Handler, Stage)

addMaybeStartStartCloseInstance

public <T> T addMaybeStartStartCloseInstance(T o,
                                             Lifecycle.Stage stage)
                                      throws Exception

Adds an instance with a start() and/or close() method to the Lifecycle and starts it if the lifecycle has already been started.

Parameters:

o - The object to add to the lifecycle

stage - The stage to add the lifecycle at

Throws:

Exception - addMaybeStartHandler(Handler, Stage)

addCloseableInstance

public <T extends Closeable> T addCloseableInstance(T o)

Adds a Closeable instance to the lifecycle at Lifecycle.Stage.NORMAL stage, doesn't try to call any "start" method on it, use addStartCloseInstance(Object) instead if you need the latter behaviour.

addMaybeStartHandler

public void addMaybeStartHandler(Lifecycle.Handler handler)
                          throws Exception

Adds a handler to the Lifecycle at the Stage.NORMAL stage and starts it if the lifecycle has already been started.

Parameters:

handler - The hander to add to the lifecycle

Throws:

Exception - addMaybeStartHandler(Handler, Stage)

addMaybeStartHandler

public void addMaybeStartHandler(Lifecycle.Handler handler,
                                 Lifecycle.Stage stage)
                          throws Exception

Adds a handler to the Lifecycle and starts it if the lifecycle has already been started.

Parameters:

handler - The hander to add to the lifecycle

stage - The stage to add the lifecycle at

Throws:

Exception - an exception thrown from handler.start(). If an exception is thrown, the handler is *not* added

start

public void start()
           throws Exception

Throws:

Exception

stop

public void stop()

ensureShutdownHook

public void ensureShutdownHook()

join

public void join()
          throws InterruptedException

Throws:

InterruptedException