Package org.apache.accumulo.server.conf.util

Class TransformToken

java.lang.Object

org.apache.accumulo.server.conf.util.TransformToken

public class TransformToken
extends Object

Provides a token used in property conversion. The token is used to limit the number of processes that try to create a property node and transform the legacy property format to the 2.1 encoded properties. Processes do not queue for a token (using a sequential node) - processes should look for the token to exist, and if present wait and then periodically re-check for the property node to be created by the process that created / has the token.

Features

• Uses ephemeral node that will be removed if transform process terminates without completing
• Watcher not necessary - the existence of the node and uuid in data sufficient to detect changes.

Field Summary

Fields

Modifier and Type	Field	Description
static String	TRANSFORM_TOKEN

Method Summary

Modifier and Type	Method	Description
static TransformToken	createToken(@NonNull String path, ZooReaderWriter zrw)	Create a lock node in ZooKeeper using an ephemeral node.
boolean	equals(Object o)
boolean	getTokenOwnership()	Create and try to establish ownership (hold the token).
int	hashCode()
boolean	haveTokenOwnership()	Return the token ownership status
void	releaseToken()	If the token was created by this instance, the uuid of this instance and the uuid stored in the ZooKeeper data will match.
String	toString()
boolean	validateToken()	Verify ownership is still valid while holding the token.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

TRANSFORM_TOKEN

public static final String TRANSFORM_TOKEN

See Also:

Constant Field Values

Method Detail

createToken

public static TransformToken createToken(@NonNull String path,
                                         ZooReaderWriter zrw)

Create a lock node in ZooKeeper using an ephemeral node. Will not throw and exception except on an interrupt. If the lock node is created, the returned lock will be locked. If another lock already exists, the lock is unlocked and the caller can decide to either wait for the resource to be created by the thread that created the lock, or try calling to lock to succeed

Parameters:

path - the parent node of the legacy properties and the associated property children nodes.

zrw - a ZooReaderWriter

Returns:

an TransformLock instance.

Throws:

IllegalStateException - is the lock creation fails due to an underlying ZooKeeper exception.

getTokenOwnership

public boolean getTokenOwnership()

Create and try to establish ownership (hold the token). Token ownership can be tested with haveTokenOwnership

Returns:

true if able to get ownership, false otherwise.

haveTokenOwnership

public boolean haveTokenOwnership()

Return the token ownership status

Returns:

true if this instance has ownership of the token, false otherwise.

validateToken

public boolean validateToken()

Verify ownership is still valid while holding the token.

Returns:

true if token is still owned, false otherwise

releaseToken

public void releaseToken()

If the token was created by this instance, the uuid of this instance and the uuid stored in the ZooKeeper data will match.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object