Package org.apache.hadoop.util

Class ShutdownHookManager

java.lang.Object

org.apache.hadoop.util.ShutdownHookManager

@Public
@Evolving
public final 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. Unless a hook was registered with a shutdown explicitly set through addShutdownHook(Runnable, int, long, TimeUnit), the shutdown time allocated to it is set by the configuration option CommonConfigurationKeysPublic.SERVICE_SHUTDOWN_TIMEOUT in core-site.xml, with a default value of CommonConfigurationKeysPublic.SERVICE_SHUTDOWN_TIMEOUT_DEFAULT seconds.

Field Summary

Fields

Modifier and Type	Field	Description
static final TimeUnit	TIME_UNIT_DEFAULT	The default time unit used: seconds.
static final long	TIMEOUT_MINIMUM	Minimum shutdown timeout: 1L second(s).

Method Summary

Modifier and Type	Method	Description
void	addShutdownHook(Runnable shutdownHook, int priority)	Adds a shutdownHook with a priority, the higher the priority the earlier will run.
void	addShutdownHook(Runnable shutdownHook, int priority, long timeout, TimeUnit unit)	Adds a shutdownHook with a priority and timeout the higher the priority the earlier will run.
void	clearShutdownHooks()	clear all registered shutdownHooks.
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

Field Details

TIMEOUT_MINIMUM

public static final long TIMEOUT_MINIMUM

Minimum shutdown timeout: 1L second(s).

See Also:

• Constant Field Values

TIME_UNIT_DEFAULT

public static final TimeUnit TIME_UNIT_DEFAULT

The default time unit used: seconds.

Method Details

get

@Public
public static ShutdownHookManager get()

Return ShutdownHookManager singleton.

Returns:

ShutdownHookManager singleton.

addShutdownHook

@Public
@Stable
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.

addShutdownHook

@Public
@Stable
public void addShutdownHook(Runnable shutdownHook,
 int priority,
 long timeout,
 TimeUnit unit)

Adds a shutdownHook with a priority and timeout the higher the priority the earlier will run. ShutdownHooks with same priority run in a non-deterministic order. The shutdown hook will be terminated if it has not been finished in the specified period of time.

Parameters:

shutdownHook - shutdownHook Runnable

priority - priority of the shutdownHook

timeout - timeout of the shutdownHook

unit - unit of the timeout TimeUnit

removeShutdownHook

@Public
@Stable
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
@Stable
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
@Stable
public boolean isShutdownInProgress()

Indicates if shutdown is in progress or not.

Returns:

TRUE if the shutdown is in progress, otherwise FALSE.

clearShutdownHooks

@Public
@Stable
public void clearShutdownHooks()

clear all registered shutdownHooks.