/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package cache;
import com.google.common.collect.Lists;
import org.apache.curator.utils.CloseableUtils;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.ChildData;
import org.apache.curator.framework.recipes.cache.PathChildrenCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.test.TestingServer;
import org.apache.curator.utils.ZKPaths;
import discovery.ExampleServer;
import org.apache.zookeeper.KeeperException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.List;
/**
* An example of the PathChildrenCache. The example "harness" is a command processor
* that allows adding/updating/removed nodes in a path. A PathChildrenCache keeps a
* cache of these changes and outputs when updates occurs.
*/
public class PathCacheExample
{
private static final String PATH = "/example/cache";
public static void main(String[] args) throws Exception
{
TestingServer server = new TestingServer();
CuratorFramework client = null;
PathChildrenCache cache = null;
try
{
client = CuratorFrameworkFactory.newClient(server.getConnectString(), new ExponentialBackoffRetry(1000, 3));
client.start();
// in this example we will cache data. Notice that this is optional.
cache = new PathChildrenCache(client, PATH, true);
cache.start();
processCommands(client, cache);
}
finally
{
CloseableUtils.closeQuietly(cache);
CloseableUtils.closeQuietly(client);
CloseableUtils.closeQuietly(server);
}
}
private static void addListener(PathChildrenCache cache)
{
// a PathChildrenCacheListener is optional. Here, it's used just to log changes
PathChildrenCacheListener listener = new PathChildrenCacheListener()
{
@Override
public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception
{
switch ( event.getType() )
{
case CHILD_ADDED:
{
System.out.println("Node added: " + ZKPaths.getNodeFromPath(event.getData().getPath()));
break;
}
case CHILD_UPDATED:
{
System.out.println("Node changed: " + ZKPaths.getNodeFromPath(event.getData().getPath()));
break;
}
case CHILD_REMOVED:
{
System.out.println("Node removed: " + ZKPaths.getNodeFromPath(event.getData().getPath()));
break;
}
}
}
};
cache.getListenable().addListener(listener);
}
private static void processCommands(CuratorFramework client, PathChildrenCache cache) throws Exception
{
// More scaffolding that does a simple command line processor
printHelp();
List<ExampleServer> servers = Lists.newArrayList();
try
{
addListener(cache);
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
boolean done = false;
while ( !done )
{
System.out.print("> ");
String line = in.readLine();
if ( line == null )
{
break;
}
String command = line.trim();
String[] parts = command.split("\\s");
if ( parts.length == 0 )
{
continue;
}
String operation = parts[0];
String args[] = Arrays.copyOfRange(parts, 1, parts.length);
if ( operation.equalsIgnoreCase("help") || operation.equalsIgnoreCase("?") )
{
printHelp();
}
else if ( operation.equalsIgnoreCase("q") || operation.equalsIgnoreCase("quit") )
{
done = true;
}
else if ( operation.equals("set") )
{
setValue(client, command, args);
}
else if ( operation.equals("remove") )
{
remove(client, command, args);
}
else if ( operation.equals("list") )
{
list(cache);
}
Thread.sleep(1000); // just to allow the console output to catch up
}
}
finally
{
for ( ExampleServer server : servers )
{
CloseableUtils.closeQuietly(server);
}
}
}
private static void list(PathChildrenCache cache)
{
if ( cache.getCurrentData().size() == 0 )
{
System.out.println("* empty *");
}
else
{
for ( ChildData data : cache.getCurrentData() )
{
System.out.println(data.getPath() + " = " + new String(data.getData()));
}
}
}
private static void remove(CuratorFramework client, String command, String[] args) throws Exception
{
if ( args.length != 1 )
{
System.err.println("syntax error (expected remove <path>): " + command);
return;
}
String name = args[0];
if ( name.contains("/") )
{
System.err.println("Invalid node name" + name);
return;
}
String path = ZKPaths.makePath(PATH, name);
try
{
client.delete().forPath(path);
}
catch ( KeeperException.NoNodeException e )
{
// ignore
}
}
private static void setValue(CuratorFramework client, String command, String[] args) throws Exception
{
if ( args.length != 2 )
{
System.err.println("syntax error (expected set <path> <value>): " + command);
return;
}
String name = args[0];
if ( name.contains("/") )
{
System.err.println("Invalid node name" + name);
return;
}
String path = ZKPaths.makePath(PATH, name);
byte[] bytes = args[1].getBytes();
try
{
client.setData().forPath(path, bytes);
}
catch ( KeeperException.NoNodeException e )
{
client.create().creatingParentsIfNeeded().forPath(path, bytes);
}
}
private static void printHelp()
{
System.out.println("An example of using PathChildrenCache. This example is driven by entering commands at the prompt:\n");
System.out.println("set <name> <value>: Adds or updates a node with the given name");
System.out.println("remove <name>: Deletes the node with the given name");
System.out.println("list: List the nodes/values in the cache");
System.out.println("quit: Quit the example");
System.out.println();
}
}