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前言
JGroups是一个开源的纯java编写的可靠的群组通讯工具。其工作模式基于IP多播，但可以在可靠性和群组成员管理上进行扩展。其结构上设计灵活，提供了一种灵活兼容多种协议的协议栈。
JGroups 多线程的方式实现了多个协议之间的协同工作，常见工作线程有心跳检测，诊断等等。
JGroups实现多机器之间的通信一般都会包含维护群组状态、群组通信协议、群组数据可靠性传输这样的一些主题。
JGroups群组的各个节点是存在"管理节点"的，至少可以说某个节点提供了在一段时间内维护状态信息和消息可靠性检测的功能(一般是最先启动的节点)。
目前Jboss、Ecache的分布式缓存是基于Groups通信。
若JGroups通信基于Udp，则可能需要开启机器上UDP相关的设置，比如Open udp。
温馨提示：JGroups各个协议相关的配置文件都可以从JGroups-x.x.x.Final.jar中找到。
JGroups 资料
http://www.jgroups.org/tutorial/index.html(官网)
http://sourceforge.net/projects/javagroups/(JGroups工程&讨论组(Discussion))
JGroups 入门示例
1,节点通信(tcp/ip,udp)方式.
2,通道和消息传送.
3,节点状态同步.
tcp/ip与udp协议
通常我们都知道tcp和udp最大的区别在于可靠性，tcp是基于可靠连接的传输，udp则属非连接，具体可参考百度百科(http://baike.baidu.com/view/1161229.htm?fr=aladdin)。
JGroups当中，udp是比较推荐的通信方式，其特点是不需要知道另一个节点的ip，通过多播网络发现就可以“找到”相应的节点，而tcp则需要在配置文件中固定配置。
示例代码(之后的测试基于tcp,因为不同机器的测试由于udp端口的问题未成功)
tcp配置文件network-tcp.xml
<!--
TCP based stack, with flow control and message bundling. This is usually used when IP
multicasting cannot be used in a network, e.g. because it is disabled (routers discard multicast).
Note that TCP.bind_addr and TCPPING.initial_hosts should be set, possibly via system properties, e.g.
-Djgroups.bind_addr=192.168.5.2 and -Djgroups.tcpping.initial_hosts=192.168.5.2[7800]
author: Bela Ban
-->
<config xmlns="urn:org:jgroups"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:org:jgroups http://www.jgroups.org/schema/JGroups-3.3.xsd">
<TCP bind_addr="192.168.19.112"
bind_port="7800"
loopback="false"
recv_buf_size="${tcp.recv_buf_size:5M}"
send_buf_size="${tcp.send_buf_size:640K}"
max_bundle_size="64K"
max_bundle_timeout="30"
use_send_queues="true"
sock_conn_timeout="300"
timer_type="new3"
timer.min_threads="4"
timer.max_threads="10"
timer.keep_alive_time="3000"
timer.queue_max_size="500"
thread_pool.enabled="true"
thread_pool.min_threads="1"
thread_pool.max_threads="10"
thread_pool.keep_alive_time="5000"
thread_pool.queue_enabled="false"
thread_pool.queue_max_size="100"
thread_pool.rejection_policy="discard"
oob_thread_pool.enabled="true"
oob_thread_pool.min_threads="1"
oob_thread_pool.max_threads="8"
oob_thread_pool.keep_alive_time="5000"
oob_thread_pool.queue_enabled="false"
oob_thread_pool.queue_max_size="100"
oob_thread_pool.rejection_policy="discard"/>
<TCPPING timeout="3000"
initial_hosts="${jgroups.tcpping.initial_hosts:192.168.19.112[7800],192.168.19.112[7801]}"
port_range="1"
num_initial_members="10"/>
<MERGE2 min_interval="10000"
max_interval="30000"/>
<FD_SOCK/>
<FD timeout="3000" max_tries="3" />
<VERIFY_SUSPECT timeout="1500" />
<BARRIER />
<pbcast.NAKACK2 use_mcast_xmit="false"
discard_delivered_msgs="true"/>
<UNICAST3 />
<pbcast.STABLE stability_delay="1000" desired_avg_gossip="50000"
max_bytes="4M"/>
<pbcast.GMS print_local_addr="true" join_timeout="3000"
view_bundling="true"/>
<MFC max_credits="2M"
min_threshold="0.4"/>
<FRAG2 frag_size="60K" />
<!--RSVP resend_interval="2000" timeout="10000"/-->
<pbcast.STATE_TRANSFER/>
</config>
udp配置文件network-udp.xml
<config xmlns="urn:org:jgroups"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:org:jgroups http://www.jgroups.org/schema/JGroups-3.5.xsd">
<UDP
mcast_addr="${jgroups.udp.mcast_addr:235.5.5.5}"
mcast_port="${jgroups.udp.mcast_port:45588}"
tos="8"
ucast_recv_buf_size="20M"
ucast_send_buf_size="640K"
mcast_recv_buf_size="25M"
mcast_send_buf_size="640K"
loopback="true"
max_bundle_size="64K"
max_bundle_timeout="30"
ip_ttl="${jgroups.udp.ip_ttl:2}"
enable_diagnostics="true"
thread_naming_pattern="cl"
timer_type="new"
timer.min_threads="4"
timer.max_threads="10"
timer.keep_alive_time="3000"
timer.queue_max_size="500"
thread_pool.enabled="true"
thread_pool.min_threads="2"
thread_pool.max_threads="8"
thread_pool.keep_alive_time="5000"
thread_pool.queue_enabled="true"
thread_pool.queue_max_size="10000"
thread_pool.rejection_policy="discard"
oob_thread_pool.enabled="true"
oob_thread_pool.min_threads="1"
oob_thread_pool.max_threads="8"
oob_thread_pool.keep_alive_time="5000"
oob_thread_pool.queue_enabled="false"
oob_thread_pool.queue_max_size="100"
oob_thread_pool.rejection_policy="Run"/>
<PING timeout="2000" num_initial_members="3"/>
<MERGE2 max_interval="30000" min_interval="10000"/>
<FD_SOCK/>
<FD_ALL/>
<VERIFY_SUSPECT timeout="1500" />
<BARRIER />
<pbcast.NAKACK use_mcast_xmit="true"
retransmit_timeout="300,600,1200"
discard_delivered_msgs="true"/>
<pbcast.STABLE stability_delay="1000"
desired_avg_gossip="50000"
max_bytes="4M"/>
<pbcast.GMS print_local_addr="true"
print_physical_addrs="true"
join_timeout="3000"
view_bundling="true"
max_join_attempts="3"/>
<UFC max_credits="2M" min_threshold="0.4"/>
<MFC max_credits="2M" min_threshold="0.4"/>
<FRAG2 frag_size="60K" />
<pbcast.STATE_TRANSFER />
</config>
数据节点Node.java
package org.wit.ff;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReentrantLock;
import org.apache.log4j.Logger;
import org.jgroups.Address;
import org.jgroups.JChannel;
import org.jgroups.Message;
import org.jgroups.ReceiverAdapter;
import org.jgroups.View;
import org.jgroups.util.Util;
/**
*
* <pre>
* 节点.
* </pre>
*
* @author F.Fang
* @version $Id: CacheNode.java, v 0.1 2014年10月17日 上午5:27:11 F.Fang Exp $
*/
public class Node extends ReceiverAdapter {
private final static Logger LOG = Logger.getLogger(Node.class);
/**
* 配置文件.
*/
private static final String CONFIG_XML = "network-tcp.xml";
/**
* 集群名称.
*/
private static final String CLUSTER_NAME = "FF";
/**
* 节点通道.
*/
private JChannel channel = null;
/**
* 以此作为节点间初始化的同步数据.
*/
private Map<String, String> cacheData = new HashMap<String, String>();
private ReentrantLock lock = new ReentrantLock();
public Node() {
InputStream is = this.getClass().getClassLoader().getResourceAsStream(CONFIG_XML);
try {
channel = new JChannel(is);
channel.setReceiver(this);
channel.connect(CLUSTER_NAME);
channel.getState(null,50000);
} catch (Exception e) {
LOG.error("启动节点异常!", e);
// 最好是自定义RuntimeException!
throw new RuntimeException("启动节点异常!", e);
}
}
/**
*
* <pre>
* 发送消息给目标地址.
* </pre>
*
* @param dest
* 为空表示发给所有节点.
* @param textMsg
* 消息.
*/
public void sendMsg(Address dest, Object textMsg) {
Message msg = new Message(dest, null, textMsg);
try {
channel.send(msg);
} catch (Exception e) {
LOG.error("消息发送失败!", e);
// 应自定异常,最好是自定义Exception类型!
throw new RuntimeException("消息发送失败!", e);
}
}
@Override
public void getState(OutputStream output) throws Exception {
//cacheData过大可能会造成节点的状态同步时间过长.
lock.lock();
try {
Util.objectToStream(state, new DataOutputStream(output));
}catch(Exception e){
throw e;
}finally{
lock.unlock();
}
}
@Override
public void receive(Message msg) {
//当前节点不接收自己发送到通道当中的消息.
if (msg.getSrc().equals(channel.getAddress())) {
return;
}
LOG.info(msg.getObject());
}
@Override
public void setState(InputStream input) throws Exception {
lock.lock();
try {
@SuppressWarnings("unchecked")
Map<String, String> cacheData = (Map<String, String>) Util.objectFromStream(new DataInputStream(input));
this.cacheData.putAll(cacheData);
} catch (Exception e) {
LOG.error("从主节点同步状态到当前节点发生异常!", e);
} finally {
lock.unlock();
}
}
@Override
public void viewAccepted(View view) {
LOG.info("当前成员[" + this.channel.getAddressAsString() + "]");
LOG.info(view.getCreator());
LOG.info(view.getMembers());
LOG.info("当前节点数据:" + cacheData);
}
/**
*
* <pre>
* 提供一个简单的初始化数据的方法.
* </pre>
*
*/
public void addData(String key,String val){
if(key!=null&&!key.isEmpty()){
cacheData.put(key, val);
}
}
}
实例节点1 Node1.java
package org.wit.ff;
import java.util.Scanner;
import java.util.concurrent.TimeUnit;
import org.wit.ff.Node;
/**
*
* <pre>
* tcp模式下:
* 如果是同一台机器测试,请注意在
* TCPPING 元素下修改 initial_hosts的配置端口:
* 例如:"${jgroups.tcpping.initial_hosts:192.168.19.100[7800],192.168.19.100[7801]}
* 如果是多台机器测试,请注意在
* TCPPING 元素下修改 initial_hosts的ip,端口随意:
* 例如:"${jgroups.tcpping.initial_hosts:192.168.19.100[7800],192.168.19.178[7800]}
*
* udp模式下:
* 同一台机器的不同端口(端口是动态的)可通信.
* 不同机器之间的ip多播可能会受到一些因素限制而造成节点之间无法彼此发现.
* </pre>
*
* @author F.Fang
* @version $Id: Node1.java, v 0.1 2014年10月15日 上午5:31:32 F.Fang Exp $
*/
public class Node1 {
public static void main(String[] args) {
Node node = new Node();
node.addData("hello", "world");
try {
TimeUnit.SECONDS.sleep(5);
} catch (InterruptedException e) {
e.printStackTrace();
}
// 使用控制台发送消息给Node2.
Scanner scanner = new Scanner(System.in);
while(true){
String text = scanner.next();
if("exit".equals(text)){
break;
}
node.sendMsg(null,"hello "+text+",node2!");
}
}
}
实例节点2 Node2.java
package org.wit.ff;
import java.util.Scanner;
import java.util.concurrent.TimeUnit;
/**
*
* <pre>
* tcp模式下:
* 如果是同一台机器测试,请注意在
* TCPPING 元素下修改 initial_hosts的配置端口:
* 例如:"${jgroups.tcpping.initial_hosts:192.168.19.100[7800],192.168.19.100[7801]}
* 如果是多台机器测试,请注意在
* TCPPING 元素下修改 initial_hosts的ip,端口随意:
* 例如:"${jgroups.tcpping.initial_hosts:192.168.19.100[7800],192.168.19.178[7800]}
*
* @author F.Fang
* @version $Id: Node2.java, v 0.1 2014年10月15日 上午5:31:44 F.Fang Exp $
*/
public class Node2 {
public static void main(String[] args) {
Node node = new Node();
try {
TimeUnit.SECONDS.sleep(5);
} catch (InterruptedException e) {
e.printStackTrace();
}
// 使用控制台发送消息给Node1.
Scanner scanner = new Scanner(System.in);
while (true) {
String text = scanner.next();
if ("exit".equals(text)) {
break;
}
node.sendMsg(null,"hello " + text + ",node1!");
}
}
}
测试Case
启动Node1，Node1平稳后启动Node2。
Node1运行信息如下：
DEBUG Configurator - set property TCP.diagnostics_addr to default value /ff0e:0:0:0:0:0:75:75
-------------------------------------------------------------------
GMS: address=DSH07fFang-18185, cluster=FF, physical address=192.168.19.112:7800
-------------------------------------------------------------------
DEBUG NAKACK2 -
[DSH07fFang-18185 setDigest()]
existing digest: []
new digest: DSH07fFang-18185: [0 (0)]
resulting digest: DSH07fFang-18185: [0 (0)]
DEBUG GMS - DSH07fFang-18185: installing view [DSH07fFang-18185|0] (1) [DSH07fFang-18185]
DEBUG STABLE - resuming message garbage collection
DEBUG FD_SOCK - VIEW_CHANGE received: [DSH07fFang-18185]
INFO Node - 当前成员[DSH07fFang-18185]
INFO Node - DSH07fFang-18185
INFO Node - [DSH07fFang-18185]
INFO Node - 当前节点数据:{}
DEBUG STABLE - resuming message garbage collection
DEBUG GMS - created cluster (first member). My view is [DSH07fFang-18185|0], impl is org.jgroups.protocols.pbcast.CoordGmsImpl
DEBUG STABLE - suspending message garbage collection
DEBUG STABLE - DSH07fFang-18185: resume task started, max_suspend_time=33000
DEBUG GMS - DSH07fFang-18185: installing view [DSH07fFang-18185|1] (2) [DSH07fFang-18185, DSH07fFang-2882]
DEBUG FD_SOCK - VIEW_CHANGE received: [DSH07fFang-18185, DSH07fFang-2882]
INFO Node - 当前成员[DSH07fFang-18185]
INFO Node - DSH07fFang-18185
INFO Node - [DSH07fFang-18185, DSH07fFang-2882]
INFO Node - 当前节点数据:{hello=world}
DEBUG FD_SOCK - ping_dest is DSH07fFang-2882, pingable_mbrs=[DSH07fFang-18185, DSH07fFang-2882]
DEBUG STABLE - resuming message garbage collection
DEBUG FD - DSH07fFang-18185: sending are-you-alive msg to DSH07fFang-2882
DEBUG FD - DSH07fFang-18185: sending are-you-alive msg to DSH07fFang-2882
DEBUG FD - DSH07fFang-18185: sending are-you-alive msg to DSH07fFang-2882
DEBUG FD - DSH07fFang-18185: sending are-you-alive msg to DSH07fFang-2882
DEBUG FD - DSH07fFang-18185: sending are-you-alive msg to DSH07fFang-2882
DEBUG FD - DSH07fFang-18185: sending are-you-alive msg to DSH07fFang-2882
主要包括ip通信信息、状态、心跳等等。
Node2运行消息如下：
DEBUG Configurator - set property TCP.diagnostics_addr to default value /ff0e:0:0:0:0:0:75:75
-------------------------------------------------------------------
GMS: address=DSH07fFang-2882, cluster=FF, physical address=192.168.19.112:7801
-------------------------------------------------------------------
DEBUG GMS - DSH07fFang-2882: sending JOIN(DSH07fFang-2882) to DSH07fFang-18185
DEBUG NAKACK2 -
[DSH07fFang-2882 setDigest()]
existing digest: []
new digest: DSH07fFang-18185: [0 (0)], DSH07fFang-2882: [0 (0)]
resulting digest: DSH07fFang-18185: [0 (0)], DSH07fFang-2882: [0 (0)]
DEBUG GMS - DSH07fFang-2882: installing view [DSH07fFang-18185|1] (2) [DSH07fFang-18185, DSH07fFang-2882]
DEBUG FD_SOCK - VIEW_CHANGE received: [DSH07fFang-18185, DSH07fFang-2882]
INFO Node - 当前成员[DSH07fFang-2882]
INFO Node - DSH07fFang-18185
INFO Node - [DSH07fFang-18185, DSH07fFang-2882]
INFO Node - 当前节点数据:{hello=world}
DEBUG FD_SOCK - ping_dest is DSH07fFang-18185, pingable_mbrs=[DSH07fFang-18185, DSH07fFang-2882] DEBUG FD - DSH07fFang-2882: sending are-you-alive msg to DSH07fFang-18185 DEBUG FD - DSH07fFang-2882: sending are-you-alive msg to DSH07fFang-18185
节点之间存在通信和状态同步，可以通过控制台输入发送消息的命令观察节点变化。
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原文地址：http://www.cnblogs.com/softidea/p/5196828.html
