org.apache.hadoop.util

Class ShutdownHookManager

java.lang.Object

org.apache.hadoop.util.ShutdownHookManager

public class ShutdownHookManager
extends Object

The ShutdownHookManager enables running shutdownHook in a deterministic order, higher priority first.

The JVM runs ShutdownHooks in a non-deterministic order or in parallel. This class registers a single JVM shutdownHook and run all the shutdownHooks registered to it (to this class) in order based on their priority.

Method Summary

Modifier and Type	Method and Description
void	addShutdownHook(Runnable shutdownHook, int priority) Adds a shutdownHook with a priority, the higher the priority the earlier will run.
static ShutdownHookManager	get() Return ShutdownHookManager singleton.
boolean	hasShutdownHook(Runnable shutdownHook) Indicates if a shutdownHook is registered or not.
boolean	isShutdownInProgress() Indicates if shutdown is in progress or not.
boolean	removeShutdownHook(Runnable shutdownHook) Removes a shutdownHook.

Methods inherited from class java.lang.Object

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

Method Detail

get

public static ShutdownHookManager get()

Return ShutdownHookManager singleton.

Returns:

ShutdownHookManager singleton.

addShutdownHook

public void addShutdownHook(Runnable shutdownHook,
                            int priority)

Adds a shutdownHook with a priority, the higher the priority the earlier will run. ShutdownHooks with same priority run in a non-deterministic order.

Parameters:

shutdownHook - shutdownHook Runnable

priority - priority of the shutdownHook.

removeShutdownHook

public boolean removeShutdownHook(Runnable shutdownHook)

Removes a shutdownHook.

Parameters:

shutdownHook - shutdownHook to remove.

Returns:

TRUE if the shutdownHook was registered and removed, FALSE otherwise.

hasShutdownHook

public boolean hasShutdownHook(Runnable shutdownHook)

Indicates if a shutdownHook is registered or not.

Parameters:

shutdownHook - shutdownHook to check if registered.

Returns:

TRUE/FALSE depending if the shutdownHook is is registered.

isShutdownInProgress

public boolean isShutdownInProgress()

Indicates if shutdown is in progress or not.

Returns:

TRUE if the shutdown is in progress, otherwise FALSE.