org.apache.drill.exec.coord.zk

Class ZookeeperClient

java.lang.Object

org.apache.drill.exec.coord.zk.ZookeeperClient

All Implemented Interfaces:

AutoCloseable

public class ZookeeperClient
extends Object
implements AutoCloseable

A namespace aware Zookeeper client. The implementation only operates under the given namespace and is safe to use. Note that instance of this class holds onto resources that must be released via #close().

Constructor Summary

Constructors

Constructor and Description
ZookeeperClient(org.apache.curator.framework.CuratorFramework curator, String root, org.apache.zookeeper.CreateMode mode)

Method Summary

Modifier and Type	Method and Description
void	close()
void	create(String path) Creates the given path without placing any data in.
void	delete(String path) Deletes the given node residing at the given path
Iterator<Map.Entry<String,byte[]>>	entries() Returns an iterator of (key, value) pairs residing under root path.
byte[]	get(String path) Returns a value corresponding to the given path if path exists in the cache, null otherwise.
byte[]	get(String path, boolean consistent) Returns the value corresponding to the given key, null otherwise.
byte[]	get(String path, boolean consistent, DataChangeVersion version) Returns the value corresponding to the given key, null otherwise.
byte[]	get(String path, DataChangeVersion version) Returns the value corresponding to the given key, null otherwise.
org.apache.curator.framework.recipes.cache.PathChildrenCache	getCache()
org.apache.zookeeper.CreateMode	getMode()
String	getRoot()
boolean	hasPath(String path) Returns true if path exists in the cache, false otherwise.
boolean	hasPath(String path, boolean consistent) Returns true if path exists, false otherwise.
boolean	hasPath(String path, boolean consistent, DataChangeVersion version) Checks if the given path exists.
void	put(String path, byte[] data) Puts the given byte sequence into the given path.
void	put(String path, byte[] data, DataChangeVersion version) Puts the given byte sequence into the given path.
byte[]	putIfAbsent(String path, byte[] data) Puts the given byte sequence into the given path if path is does not exist.
void	start() Starts the client.

Methods inherited from class java.lang.Object

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

Constructor Detail

ZookeeperClient

public ZookeeperClient(org.apache.curator.framework.CuratorFramework curator,
                       String root,
                       org.apache.zookeeper.CreateMode mode)

Method Detail

start

public void start()
           throws Exception

Starts the client. This call ensures the creation of the root path.

Throws:

Exception - if cache fails to start or root path creation fails.

See Also:

close()

getCache

public org.apache.curator.framework.recipes.cache.PathChildrenCache getCache()

getRoot

public String getRoot()

getMode

public org.apache.zookeeper.CreateMode getMode()

hasPath

public boolean hasPath(String path)

Returns true if path exists in the cache, false otherwise. Note that calls to this method are eventually consistent.

Parameters:

path - path to check

Returns:

true if path exists, false otherwise

hasPath

public boolean hasPath(String path,
                       boolean consistent)

Returns true if path exists, false otherwise. If consistent flag is set to true, check is done directly is made against Zookeeper directly, else check is done against local cache.

Parameters:

path - path to check

consistent - whether the check should be consistent

Returns:

true if path exists, false otherwise

hasPath

public boolean hasPath(String path,
                       boolean consistent,
                       DataChangeVersion version)

Checks if the given path exists. If the flag consistent is set, the check is consistent as it is made against Zookeeper directly. Otherwise, the check is eventually consistent. If consistency flag is set to true and version holder is not null, passes version holder to get data change version. Data change version is retrieved from Stat object, it increases each time znode data change is performed. Link to Zookeeper documentation - https://zookeeper.apache.org/doc/r3.2.2/zookeeperProgrammers.html#sc_zkDataModel_znodes

Parameters:

path - path to check

consistent - whether the check should be consistent

version - version holder

Returns:

true if path exists, false otherwise

get

public byte[] get(String path)

Returns a value corresponding to the given path if path exists in the cache, null otherwise. Note that calls to this method are eventually consistent.

Parameters:

path - target path

get

public byte[] get(String path,
                  boolean consistent)

Returns the value corresponding to the given key, null otherwise. If the flag consistent is set, the check is consistent as it is made against Zookeeper directly. Otherwise, the check is eventually consistent.

Parameters:

path - target path

consistent - consistency flag

get

public byte[] get(String path,
                  DataChangeVersion version)

Returns the value corresponding to the given key, null otherwise. The check is consistent as it is made against Zookeeper directly. Passes version holder to get data change version.

Parameters:

path - target path

version - version holder

get

public byte[] get(String path,
                  boolean consistent,
                  DataChangeVersion version)

Returns the value corresponding to the given key, null otherwise. If the flag consistent is set, the check is consistent as it is made against Zookeeper directly. Otherwise, the check is eventually consistent. If consistency flag is set to true and version holder is not null, passes version holder to get data change version. Data change version is retrieved from Stat object, it increases each time znode data change is performed. Link to Zookeeper documentation - https://zookeeper.apache.org/doc/r3.2.2/zookeeperProgrammers.html#sc_zkDataModel_znodes

Parameters:

path - target path

consistent - consistency check

version - version holder

create

public void create(String path)

Creates the given path without placing any data in.

Parameters:

path - target path

put

public void put(String path,
                byte[] data)

Puts the given byte sequence into the given path. If path does not exists, this call creates it.

Parameters:

path - target path

data - data to store

put

public void put(String path,
                byte[] data,
                DataChangeVersion version)

Puts the given byte sequence into the given path. If path does not exists, this call creates it. If version holder is not null and path already exists, passes given version for comparison. Zookeeper maintains stat structure that holds version number which increases each time znode data change is performed. If we pass version that doesn't match the actual version of the data, the update will fail KeeperException.BadVersionException. We catch such exception and re-throw it as VersionMismatchException. Link to documentation - https://zookeeper.apache.org/doc/r3.2.2/zookeeperProgrammers.html#sc_zkDataModel_znodes

Parameters:

path - target path

data - data to store

version - version holder

putIfAbsent

public byte[] putIfAbsent(String path,
                          byte[] data)

Puts the given byte sequence into the given path if path is does not exist.

Parameters:

path - target path

data - data to store

Returns:

null if path was created, else data stored for the given path

delete

public void delete(String path)

Deletes the given node residing at the given path

Parameters:

path - target path to delete

entries

public Iterator<Map.Entry<String,byte[]>> entries()

Returns an iterator of (key, value) pairs residing under root path.

close

public void close()
           throws Exception

Specified by:

close in interface AutoCloseable

Throws:

Exception