ZooKeeper - Hadoop: The Definitive Guide - page 760

vert the string value to a byte array, for which we just use the getBytes() method with
a UTF-8 encoding.
To illustrate the use of the ActiveKeyValueStore , consider a ConfigUpdater
class that updates a configuration property with a value. The listing appears in
Example 21-6 .
Example 21-6. An application that updates a property in ZooKeeper at random times
public class ConfigUpdater {
public static final String PATH = "/config" ;
private ActiveKeyValueStore store ;
private Random random = new Random ();
public ConfigUpdater ( String hosts ) throws IOException ,
InterruptedException {
store = new ActiveKeyValueStore ();
store . connect ( hosts );
}
public void run () throws InterruptedException , KeeperException {
while ( true ) {
String value = random . nextInt ( 100 ) + "" ;
store . write ( PATH , value );
System . out . printf ( "Set %s to %s\n" , PATH , value );
TimeUnit . SECONDS . sleep ( random . nextInt ( 10 ));
}
}
public static void main ( String [] args ) throws Exception {
ConfigUpdater configUpdater = new ConfigUpdater ( args [ 0 ]);
configUpdater . run ();
}
}
The program is simple. A ConfigUpdater has an ActiveKeyValueStore that
connects to ZooKeeper in the ConfigUpdater 's constructor. The run() method loops
forever, updating the /config znode at random times with random values.
Next, let's look at how to read the /config configuration property. First, we add a read
method to ActiveKeyValueStore :
public String read ( String path , Watcher watcher ) throws
InterruptedException ,