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

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.