ZooKeeperWatcher (Hortonworks Data Platform Apache HBase Java API Reference)

java.lang.Object
- org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher

All Implemented Interfaces:

Closeable, AutoCloseable, Abortable
```
@InterfaceAudience.Private
public class ZooKeeperWatcher
extends Object
implements Abortable, Closeable
```
Acts as the single ZooKeeper Watcher. One instance of this is instantiated for each Master, RegionServer, and client process.
This is the only class that implements Watcher. Other internal classes which need to be notified of ZooKeeper events must register with the local instance of this watcher via registerListener(org.apache.hadoop.hbase.zookeeper.ZooKeeperListener).
This class also holds and manages the connection to ZooKeeper. Code to deal with connection related events and exceptions are handled here.

Field Summary

Fields
Modifier and Type	Field and Description
`protected Abortable`	`abortable`
`String`	`assignmentZNode`
`String`	`backupMasterAddressesZNode`
`String`	`balancerZNode`
`String`	`baseZNode`
`String`	`clusterIdZNode`
`String`	`clusterStateZNode`
`static ArrayList<ACL>`	`CREATOR_ALL_AND_WORLD_READABLE`
`String`	`drainingZNode`
`static String`	`META_ZNODE_PREFIX`
`static String`	`namespaceZNode`
`String`	`recoveringRegionsZNode`
`String`	`rsZNode`
`CountDownLatch`	`saslLatch`
`String`	`splitLogZNode`
`String`	`tableLockZNode`
`String`	`tableZNode`

Constructor Summary

Constructors
Constructor and Description
`ZooKeeperWatcher(Configuration conf, String identifier, Abortable abortable)` Instantiate a ZooKeeper connection and watcher.
`ZooKeeperWatcher(Configuration conf, String identifier, Abortable abortable, boolean canCreateBaseZNode)` Instantiate a ZooKeeper connection and watcher.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`abort(String why, Throwable e)` Abort the server or client.
`void`	`checkAndSetZNodeAcls()` On master start, we check the znode ACLs under the root directory and set the ACLs properly if needed.
`void`	`close()` Close the connection to ZooKeeper.
`String`	`getBaseZNode()`
`Configuration`	`getConfiguration()`
`List<ZooKeeperListener>`	`getListeners()` Get a copy of current registered listeners
`String`	`getMasterAddressZNode()`
`int`	`getMetaReplicaIdFromZnode(String znode)` Parse the meta replicaId from the passed znode
`List<String>`	`getMetaReplicaNodes()` Get the znodes corresponding to the meta replicas from ZK
`int`	`getNumberOfListeners()`
`String`	`getQuorum()` Get the quorum address of this instance.
`RecoverableZooKeeper`	`getRecoverableZooKeeper()` Get the connection to ZooKeeper.
`String`	`getRegionNormalizerZNode()`
`String`	`getZNodeForReplica(int replicaId)` Get the znode string corresponding to a replicaId
`void`	`interruptedException(InterruptedException ie)` Handles InterruptedExceptions in client calls.
`boolean`	`isAborted()` Check if the server or client was aborted.
`boolean`	`isAnyMetaReplicaZnode(String node)` Is the znode of any meta replica
`boolean`	`isClientReadable(String node)` Returns whether the znode is supposed to be readable by the client and DOES NOT contain sensitive information (world readable).
`boolean`	`isDefaultMetaReplicaZnode(String node)` Is it the default meta replica's znode
`void`	`keeperException(KeeperException ke)` Handles KeeperExceptions in client calls.
`String`	`prefix(String str)` Adds this instance's identifier as a prefix to the passed `str`
`void`	`process(WatchedEvent event)` Method called from ZooKeeper for events and connection status.
`void`	`reconnectAfterExpiration()`
`void`	`registerListener(ZooKeeperListener listener)` Register the specified listener to receive ZooKeeper events.
`void`	`registerListenerFirst(ZooKeeperListener listener)` Register the specified listener to receive ZooKeeper events and add it as the first in the list of current listeners.
`void`	`sync(String path)` Forces a synchronization of this ZooKeeper client connection.
`String`	`toString()`
`void`	`unregisterAllListeners()` Clean all existing listeners
`void`	`unregisterListener(ZooKeeperListener listener)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - abortable
```
protected Abortable abortable
```
  - saslLatch
```
public CountDownLatch saslLatch
```
  - baseZNode
```
public String baseZNode
```
  - rsZNode
```
public String rsZNode
```
  - drainingZNode
```
public String drainingZNode
```
  - backupMasterAddressesZNode
```
public String backupMasterAddressesZNode
```
  - clusterStateZNode
```
public String clusterStateZNode
```
  - assignmentZNode
```
public String assignmentZNode
```
  - tableZNode
```
public String tableZNode
```
  - clusterIdZNode
```
public String clusterIdZNode
```
  - splitLogZNode
```
public String splitLogZNode
```
  - balancerZNode
```
public String balancerZNode
```
  - tableLockZNode
```
public String tableLockZNode
```
  - recoveringRegionsZNode
```
public String recoveringRegionsZNode
```
  - namespaceZNode
```
public static String namespaceZNode
```
  - CREATOR_ALL_AND_WORLD_READABLE
```
public static final ArrayList<ACL> CREATOR_ALL_AND_WORLD_READABLE
```
  - META_ZNODE_PREFIX
```
public static final String META_ZNODE_PREFIX
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - ZooKeeperWatcher
```
public ZooKeeperWatcher(Configuration conf,
                        String identifier,
                        Abortable abortable)
                 throws ZooKeeperConnectionException,
                        IOException
```
    Instantiate a ZooKeeper connection and watcher.
    
    Parameters:
    
    identifier - string that is passed to RecoverableZookeeper to be used as identifier for this instance. Use null for default.
    
    Throws:
    
    IOException
    
    ZooKeeperConnectionException
  - ZooKeeperWatcher
```
public ZooKeeperWatcher(Configuration conf,
                        String identifier,
                        Abortable abortable,
                        boolean canCreateBaseZNode)
                 throws IOException,
                        ZooKeeperConnectionException
```
    Instantiate a ZooKeeper connection and watcher.
    
    Parameters:
    
    conf -
    
    identifier - string that is passed to RecoverableZookeeper to be used as identifier for this instance. Use null for default.
    
    abortable - Can be null if there is on error there is no host to abort: e.g. client context.
    
    canCreateBaseZNode -
    
    Throws:
    
    IOException
    
    ZooKeeperConnectionException
- Method Detail
  - isClientReadable
```
public boolean isClientReadable(String node)
```
    Returns whether the znode is supposed to be readable by the client and DOES NOT contain sensitive information (world readable).
  - checkAndSetZNodeAcls
```
public void checkAndSetZNodeAcls()
```
    On master start, we check the znode ACLs under the root directory and set the ACLs properly if needed. If the cluster goes from an unsecure setup to a secure setup, this step is needed so that the existing znodes created with open permissions are now changed with restrictive perms.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - prefix
```
public String prefix(String str)
```
    Adds this instance's identifier as a prefix to the passed str
    
    Parameters:
    
    str - String to amend.
    
    Returns:
    
    A new string with this instance's identifier as prefix: e.g. if passed 'hello world', the returned string could be
  - isAnyMetaReplicaZnode
```
public boolean isAnyMetaReplicaZnode(String node)
```
    Is the znode of any meta replica
    
    Parameters:
    
    node -
    
    Returns:
    
    true or false
  - isDefaultMetaReplicaZnode
```
public boolean isDefaultMetaReplicaZnode(String node)
```
    Is it the default meta replica's znode
    
    Parameters:
    
    node -
    
    Returns:
    
    true or false
  - getMetaReplicaNodes
```
public List<String> getMetaReplicaNodes()
                                 throws KeeperException
```
    Get the znodes corresponding to the meta replicas from ZK
    
    Returns:
    
    list of znodes
    
    Throws:
    
    KeeperException
  - getZNodeForReplica
```
public String getZNodeForReplica(int replicaId)
```
    Get the znode string corresponding to a replicaId
    
    Parameters:
    
    replicaId -
    
    Returns:
    
    znode
  - getMetaReplicaIdFromZnode
```
public int getMetaReplicaIdFromZnode(String znode)
```
    Parse the meta replicaId from the passed znode
    
    Parameters:
    
    znode -
    
    Returns:
    
    replicaId
  - registerListener
```
public void registerListener(ZooKeeperListener listener)
```
    Register the specified listener to receive ZooKeeper events.
    
    Parameters:
    
    listener -
  - registerListenerFirst
```
public void registerListenerFirst(ZooKeeperListener listener)
```
    Register the specified listener to receive ZooKeeper events and add it as the first in the list of current listeners.
    
    Parameters:
    
    listener -
  - unregisterListener
```
public void unregisterListener(ZooKeeperListener listener)
```
  - unregisterAllListeners
```
public void unregisterAllListeners()
```
    Clean all existing listeners
  - getListeners
```
public List<ZooKeeperListener> getListeners()
```
    Get a copy of current registered listeners
  - getNumberOfListeners
```
public int getNumberOfListeners()
```
    Returns:
    
    The number of currently registered listeners
  - getRecoverableZooKeeper
```
public RecoverableZooKeeper getRecoverableZooKeeper()
```
    Get the connection to ZooKeeper.
    
    Returns:
    
    connection reference to zookeeper
  - reconnectAfterExpiration
```
public void reconnectAfterExpiration()
                              throws IOException,
                                     KeeperException,
                                     InterruptedException
```
    Throws:
    
    IOException
    
    KeeperException
    
    InterruptedException
  - getQuorum
```
public String getQuorum()
```
    Get the quorum address of this instance.
    
    Returns:
    
    quorum string of this zookeeper connection instance
  - getBaseZNode
```
public String getBaseZNode()
```
    Returns:
    
    the base znode of this zookeeper connection instance.
  - process
```
public void process(WatchedEvent event)
```
    Method called from ZooKeeper for events and connection status.
    Valid events are passed along to listeners. Connection status changes are dealt with locally.
  - sync
```
public void sync(String path)
          throws KeeperException
```
    Forces a synchronization of this ZooKeeper client connection.
    Executing this method before running other methods will ensure that the subsequent operations are up-to-date and consistent as of the time that the sync is complete.
    This is used for compareAndSwap type operations where we need to read the data of an existing node and delete or transition that node, utilizing the previously read version and data. We want to ensure that the version read is up-to-date from when we begin the operation.
    
    Throws:
    
    KeeperException
  - keeperException
```
public void keeperException(KeeperException ke)
                     throws KeeperException
```
    Handles KeeperExceptions in client calls.
    This may be temporary but for now this gives one place to deal with these.
    TODO: Currently this method rethrows the exception to let the caller handle
    
    Parameters:
    
    ke -
    
    Throws:
    
    KeeperException
  - interruptedException
```
public void interruptedException(InterruptedException ie)
```
    Handles InterruptedExceptions in client calls.
    This may be temporary but for now this gives one place to deal with these.
    TODO: Currently, this method does nothing. Is this ever expected to happen? Do we abort or can we let it run? Maybe this should be logged as WARN? It shouldn't happen?
    
    Parameters:
    
    ie -
  - close
```
public void close()
```
    Close the connection to ZooKeeper.
    
    Specified by:
    
    close in interface Closeable
    
    Specified by:
    
    close in interface AutoCloseable
    
    Throws:
    
    InterruptedException
  - getConfiguration
```
public Configuration getConfiguration()
```
  - abort
```
public void abort(String why,
                  Throwable e)
```
    Description copied from interface: Abortable
    
    Abort the server or client.
    
    Specified by:
    
    abort in interface Abortable
    
    Parameters:
    
    why - Why we're aborting.
    
    e - Throwable that caused abort. Can be null.
  - isAborted
```
public boolean isAborted()
```
    Description copied from interface: Abortable
    
    Check if the server or client was aborted.
    
    Specified by:
    
    isAborted in interface Abortable
    
    Returns:
    
    true if the server or client was aborted, false otherwise
  - getMasterAddressZNode
```
public String getMasterAddressZNode()
```
    Returns:
    
    Path to the currently active master.
  - getRegionNormalizerZNode
```
public String getRegionNormalizerZNode()
```
    Returns:
    
    ZooKeeper znode for region normalizer state

Class ZooKeeperWatcher

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

abortable

saslLatch

baseZNode

rsZNode

drainingZNode

backupMasterAddressesZNode

clusterStateZNode

assignmentZNode

tableZNode

clusterIdZNode

splitLogZNode

balancerZNode

tableLockZNode

recoveringRegionsZNode

namespaceZNode

CREATOR_ALL_AND_WORLD_READABLE

META_ZNODE_PREFIX

Constructor Detail

ZooKeeperWatcher

ZooKeeperWatcher

Method Detail

isClientReadable

checkAndSetZNodeAcls

toString

prefix

isAnyMetaReplicaZnode

isDefaultMetaReplicaZnode

getMetaReplicaNodes

getZNodeForReplica

getMetaReplicaIdFromZnode

registerListener

registerListenerFirst

unregisterListener

unregisterAllListeners

getListeners

getNumberOfListeners

getRecoverableZooKeeper

reconnectAfterExpiration

getQuorum

getBaseZNode

process

sync

keeperException

interruptedException

close

getConfiguration

abort

isAborted

getMasterAddressZNode

getRegionNormalizerZNode