Gemfire 6.5 缓存之服务器管理模式分析

GemFire 客服端/服务器 缓存模式能提供动态的服务器连接池管理，均衡和有条件的服务器加载，逻辑的服务器组管理，以及对高效性服务器的自动失效备援。

和以往旧版本的GemFire相比，在分布式系统的连接管理中，旧版本是采用DistributedSystem类进行连接管理。最新版本提供了CacheServer 和 CacheClient类实现客户端/服务器模式。以下是一个简单的例子：

服务器配置：
1.Server.xml

<?xml version="1.0"?>

<!-- Server.xml
     Configures a cache to serve caching clients at port 40405.
     The example region also is configured with a loader. 
-->

<!DOCTYPE cache PUBLIC
  "-//GemStone Systems, Inc.//GemFire Declarative Caching 6.5//EN"
  "http://www.gemstone.com/dtd/cache6_5.dtd">
<cache>
    <cache-server port="40404"/>
    <region name="exampleRegion">
      <region-attributes refid="REPLICATE">
        <cache-loader>
          <class-name>quickstart.SimpleCacheLoader</class-name>
        </cache-loader>
      </region-attributes>
    </region>
</cache>

2.服务器在这里使用的是GemFire cacheserver 进程。

客户端配置：

1. Client.xml

<client-cache>
	<pool name="client" subscription-enabled="true">
		<server host="localhost" port="40404" />
	</pool>

	<region name="exampleRegion">
		<region-attributes refid="CACHING_PROXY">
			<cache-listener>
				<class-name>quickstart.SimpleCacheListener</class-name>
			</cache-listener>
		</region-attributes>
	</region>
</client-cache>

2. ClientWorker.java，该类用于往cache中get和put数据。

public class ClientWorker {

	public static final String EXAMPLE_REGION_NAME = "exampleRegion";

	public static void main(String[] args) throws Exception {

		System.out.println("Connecting to the distributed system and creating the cache.");
		// Create the cache which causes the cache-xml-file to be parsed
		ClientCache cache = new ClientCacheFactory()
                  .set("name", "ClientWorker")
                  .set("cache-xml-file", "xml/Client.xml")
                  .create();

		// Get the exampleRegion
		Region<String, String> exampleRegion = cache.getRegion(EXAMPLE_REGION_NAME);
		System.out.println("Example region \"" + exampleRegion.getFullPath() + "\" created in cache.");
		System.out.println();
		System.out.println("Getting three values from the cache server.");
		System.out.println("This will cause the server's loader to run, which will add the values");
		System.out.println("to the server cache and return them to me. The values will also be");
		System.out.println("forwarded to any other client that has subscribed to the region.");

		// Get three values from the cache
		for (int count = 0; count < 3; count++) {
			String key = "key" + count;
			System.out.println("Getting key " + key);
			exampleRegion.get(key);
		}

		System.out.println("Note the other client's region listener in response to these gets.");
		System.out.println("Press Enter to continue.");
		BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
		bufferedReader.readLine();

		System.out.println("Changing the data in my cache - all destroys and updates are forwarded");
		System.out.println("through the server to other clients. Invalidations are not forwarded.");

		// Update one value in the cache
		System.out.println("Putting new value for key0");
		exampleRegion.put("key0", "ClientValue0");

		// Invalidate one entry in the cache
		System.out.println("Invalidating key1");
		exampleRegion.invalidate("key1");

		// Destroy one entry in the cache
		System.out.println("Destroying key2");
		exampleRegion.destroy("key2");

		// Close the cache and disconnect from GemFire distributed system
		System.out.println("Closing the cache and disconnecting.");
		cache.close();

		System.out.println("In the other session, please hit Enter in the Consumer client");
		System.out.println("and then stop the cacheserver with 'cacheserver stop'.");
	}
}

3. ClientConsumer.java，模拟从server端获取数据。

public class ClientConsumer {

	public static final String USAGE = "Usage: java ClientConsumer <register-interest-type>\n"
			+ "  register-interest-type may be one of the following:\n"
			+ "    all-keys    Register interest in all keys on the server\n"
			+ "    keyset      Register interest in a set of keys on the server\n"
			+ "    regex       Register interest in keys on the server matching a regular expression\n";

	public static final String EXAMPLE_REGION_NAME = "exampleRegion";

	private static enum RegisterInterestType {
		ALL_KEYS, KEYSET, REGEX
	}

	public static void main(String[] args) throws Exception {

		if (args.length != 1) {
			System.out.println(USAGE);
			System.exit(1);
		}

		RegisterInterestType registerInterestType;
		if (args[0].equals("all-keys")) {
			registerInterestType = RegisterInterestType.ALL_KEYS;
		} else if (args[0].equals("keyset")) {
			registerInterestType = RegisterInterestType.KEYSET;
		} else if (args[0].equals("regex")) {
			registerInterestType = RegisterInterestType.REGEX;
		} else {
			registerInterestType = null;
			System.out.println(USAGE);
			System.exit(2);
		}

		// Subscribe to the indicated key set
		System.out.println("Connecting to the distributed system and creating the cache.");
		// Create the cache which causes the cache-xml-file to be parsed
		ClientCache cache = new ClientCacheFactory()
                  .set("name", "ClientConsumer")
                  .set("cache-xml-file", "xml/Client.xml")
                  .create();

		// Get the exampleRegion which is a subregion of /root
		Region<String,?> exampleRegion = cache.getRegion(EXAMPLE_REGION_NAME);
		System.out.println("Example region \"" + exampleRegion.getFullPath() + "\" created in cache. ");

		switch (registerInterestType) {
		case ALL_KEYS:
			System.out.println("Asking the server to send me all data additions, updates, and destroys. ");
			exampleRegion.registerInterest("ALL_KEYS");
			break;
		case KEYSET:
			System.out.println("Asking the server to send me events for data with these keys: 'key0', 'key1'");
			exampleRegion.registerInterest("key0");
			exampleRegion.registerInterest("key1");
			break;
		case REGEX:
			System.out.println("Asking the server to register interest in keys matching this");
			System.out.println("regular expression: 'k.*2'");
			exampleRegion.registerInterestRegex("k.*2");
			break;
		default:
			// Can't happen
			throw new RuntimeException();
		}

		System.out.println("The data region has a listener that reports all changes to standard out.");
		System.out.println();
		System.out.println("Please run the worker client in another session. It will update the");
		System.out.println("cache and the server will forward the updates to me. Note the listener");
		System.out.println("output in this session.");
		System.out.println();
		System.out.println("When the other client finishes, hit Enter to exit this program.");

		BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
		bufferedReader.readLine();

		System.out.println("Closing the cache and disconnecting.");
		cache.close();
	}
}

4. SimpleCacheLoader.java，如果该Region在服务器端没有数据，将自动加载数据。

public class SimpleCacheLoader implements CacheLoader<String,String>, Declarable {
  
  public String load(LoaderHelper<String,String> helper) {
    String key = helper.getKey();
    System.out.println("    Loader called to retrieve value for " + key);
    
    // Create a value using the suffix number of the key (key1, key2, etc.)
    return "LoadedValue" + (Integer.parseInt(key.substring(3)));
  }
  
  public void close() {
    // do nothing
  }
  
  public void init(Properties props) {
    // do nothing
  }
}

5. SimpleCacheListener.java，一个异步的监听器用于监听本地缓存的变化。

public class SimpleCacheListener<K,V> extends CacheListenerAdapter<K,V> implements Declarable {

  public void afterCreate(EntryEvent<K,V> e) {
    System.out.println("    Received afterCreate event for entry: " +
      e.getKey() + ", " + e.getNewValue());
  }
  
  public void afterUpdate(EntryEvent<K,V> e) {
    System.out.println("    Received afterUpdate event for entry: " +
      e.getKey() + ", " + e.getNewValue());
  }
  
  public void afterDestroy(EntryEvent<K,V> e) {
    System.out.println("    Received afterDestroy event for entry: " +
      e.getKey());
  }

  public void afterInvalidate(EntryEvent<K,V> e) {
    System.out.println("    Received afterInvalidate event for entry: " +
      e.getKey());
  }

  public void afterRegionLive(RegionEvent e) {
    System.out.println("    Received afterRegionLive event, sent to durable clients after \nthe server has finished replaying stored events.  ");
  }

  public void init(Properties props) {
    // do nothing
  }

}

启动步骤：
1. 启动GemFire cacheserver：

cacheserver start cache-xml-file=xml/Server.xml

2. 启动customer client：

java quickstart.ClientConsumer all-keys

3. 启动ClientWorker：

java quickstart.ClientWorker

4. 当所有客户端退出后，停止cacheserver：

cacheserver stop

本文摘自：http://community.gemstone.com/display/gemfire/Server-Managed+Caching+Example