MetaRegionLocationCache (Apache HBase 1.7.2 API)

java.lang.Object
- org.apache.hadoop.hbase.zookeeper.ZooKeeperListener
- - org.apache.hadoop.hbase.master.MetaRegionLocationCache

```
@InterfaceAudience.Private
public class MetaRegionLocationCache
extends ZooKeeperListener
```
A cache of meta region location metadata. Registers a listener on ZK to track changes to the meta table znodes. Clients are expected to retry if the meta information is stale. This class is thread-safe (a single instance of this class can be shared by multiple threads without race conditions).

Field Summary
- Fields inherited from class org.apache.hadoop.hbase.zookeeper.ZooKeeperListener
  watcher

Constructor Summary

Constructors
Constructor and Description

MetaRegionLocationCache(ZooKeeperWatcher zkWatcher)

Constructors
Constructor and Description
`MetaRegionLocationCache(ZooKeeperWatcher zkWatcher)`

Method Summary

Methods
Modifier and Type	Method and Description
`List<HRegionLocation>`	`getMetaRegionLocations()`
`void`	`nodeChildrenChanged(String path)` Called when an existing node has a child node added or removed.
`void`	`nodeCreated(String path)` Called when a new node has been created.
`void`	`nodeDataChanged(String path)` Called when an existing node has changed data.
`void`	`nodeDeleted(String path)` Called when a node has been deleted

Methods inherited from class org.apache.hadoop.hbase.zookeeper.ZooKeeperListener
getWatcher

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

- Constructor Detail
  - MetaRegionLocationCache
```
public MetaRegionLocationCache(ZooKeeperWatcher zkWatcher)
```
- Method Detail
  - getMetaRegionLocations
```
public List<HRegionLocation> getMetaRegionLocations()
```
    Returns:
    Optional list of HRegionLocations for meta replica(s), null if the cache is empty.
  - nodeCreated
```
public void nodeCreated(String path)
```
    Description copied from class: ZooKeeperListener
    
    Called when a new node has been created.
    
    Overrides:
    
    nodeCreated in class ZooKeeperListener
    
    Parameters:
    path - full path of the new node
  - nodeDeleted
```
public void nodeDeleted(String path)
```
    Description copied from class: ZooKeeperListener
    
    Called when a node has been deleted
    
    Overrides:
    
    nodeDeleted in class ZooKeeperListener
    
    Parameters:
    path - full path of the deleted node
  - nodeDataChanged
```
public void nodeDataChanged(String path)
```
    Description copied from class: ZooKeeperListener
    
    Called when an existing node has changed data.
    
    Overrides:
    
    nodeDataChanged in class ZooKeeperListener
    
    Parameters:
    path - full path of the updated node
  - nodeChildrenChanged
```
public void nodeChildrenChanged(String path)
```
    Description copied from class: ZooKeeperListener
    
    Called when an existing node has a child node added or removed.
    
    Overrides:
    
    nodeChildrenChanged in class ZooKeeperListener
    
    Parameters:
    path - full path of the node whose children have changed

Class MetaRegionLocationCache

Field Summary

Fields inherited from class org.apache.hadoop.hbase.zookeeper.ZooKeeperListener

Constructor Summary

Method Summary

Methods inherited from class org.apache.hadoop.hbase.zookeeper.ZooKeeperListener

Methods inherited from class java.lang.Object

Constructor Detail

MetaRegionLocationCache

Method Detail

getMetaRegionLocations

nodeCreated

nodeDeleted

nodeDataChanged

nodeChildrenChanged