org.apache.twill.zookeeper

Class ZKOperations

java.lang.Object

org.apache.twill.zookeeper.ZKOperations

public final class ZKOperations
extends Object

Collection of helper methods for common operations that usually needed when interacting with ZooKeeper.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	ZKOperations.Callback<T> Represents a ZK operation updates callback.
static interface	ZKOperations.ChildrenCallback Interface for defining callback method to receive children nodes updates.
static interface	ZKOperations.DataCallback Interface for defining callback method to receive node data updates.

Method Summary

Modifier and Type	Method and Description
static OperationFuture<String>	createDeleteIfExists(ZKClient zkClient, String path, byte[] data, org.apache.zookeeper.CreateMode createMode, boolean createParent, org.apache.zookeeper.data.ACL... acls) Creates a ZK node of the given path.
static <V> OperationFuture<V>	ignoreError(OperationFuture<V> future, Class<? extends org.apache.zookeeper.KeeperException> exceptionType, V errorResult) Returns a new OperationFuture that the result will be the same as the given future, except that when the source future is having an exception matching the giving exception type, the errorResult will be set in to the returned OperationFuture.
static OperationFuture<String>	recursiveDelete(ZKClient zkClient, String path) Deletes the given path recursively.
static Cancellable	watchChildren(ZKClient zkClient, String path, ZKOperations.ChildrenCallback callback)
static Cancellable	watchData(ZKClient zkClient, String path, ZKOperations.DataCallback callback) Watch for data changes of the given path.
static com.google.common.util.concurrent.ListenableFuture<String>	watchDeleted(ZKClient zkClient, String path)
static void	watchDeleted(ZKClient zkClient, String path, com.google.common.util.concurrent.SettableFuture<String> completion)

Methods inherited from class java.lang.Object

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

Method Detail

watchData

public static Cancellable watchData(ZKClient zkClient,
                                    String path,
                                    ZKOperations.DataCallback callback)

Watch for data changes of the given path. The callback will be triggered whenever changes has been detected. Note that the callback won't see every single changes, as that's not the guarantee of ZooKeeper. If the node doesn't exists, it will watch for its creation then starts watching for data changes. When the node is deleted afterwards,

Parameters:

zkClient - The ZKClient for the operation

path - Path to watch

callback - Callback to be invoked when data changes is detected.

Returns:

A Cancellable to cancel the watch.

watchDeleted

public static com.google.common.util.concurrent.ListenableFuture<String> watchDeleted(ZKClient zkClient,
                                                                                      String path)

watchDeleted

public static void watchDeleted(ZKClient zkClient,
                                String path,
                                com.google.common.util.concurrent.SettableFuture<String> completion)

watchChildren

public static Cancellable watchChildren(ZKClient zkClient,
                                        String path,
                                        ZKOperations.ChildrenCallback callback)

ignoreError

public static <V> OperationFuture<V> ignoreError(OperationFuture<V> future,
                                                 Class<? extends org.apache.zookeeper.KeeperException> exceptionType,
                                                 V errorResult)

Returns a new OperationFuture that the result will be the same as the given future, except that when the source future is having an exception matching the giving exception type, the errorResult will be set in to the returned OperationFuture.

Type Parameters:

V - Type of the result.

Parameters:

future - The source future.

exceptionType - Type of KeeperException to be ignored.

errorResult - Object to be set into the resulting future on a matching exception.

Returns:

A new OperationFuture.

recursiveDelete

public static OperationFuture<String> recursiveDelete(ZKClient zkClient,
                                                      String path)

Deletes the given path recursively. The delete method will keep running until the given path is successfully removed, which means if there are new node created under the given path while deleting, they'll get deleted again. If there is KeeperException during the deletion other than KeeperException.NotEmptyException or KeeperException.NoNodeException, the exception would be reflected in the result future and deletion process will stop, leaving the given path with intermediate state.

Parameters:

path - The path to delete.

Returns:

An OperationFuture that will be completed when the given path is deleted or bailed due to exception.

createDeleteIfExists

public static OperationFuture<String> createDeleteIfExists(ZKClient zkClient,
                                                           String path,
                                                           @Nullable
                                                           byte[] data,
                                                           org.apache.zookeeper.CreateMode createMode,
                                                           boolean createParent,
                                                           org.apache.zookeeper.data.ACL... acls)

Creates a ZK node of the given path. If the node already exists, deletion of the node (recursively) will happen and the creation will be retried.