接前一篇rpc框架之HA/负载均衡构架设计 继续，写了一个简单的thrift 连接池：
先做点准备工作：
package yjmyzz;
public class ServerInfo {
public String getHost() {
return host;
}
public void setHost(String host) {
this.host = host;
}
public int getPort() {
return port;
}
public void setPort(int port) {
this.port = port;
}
private String host;
private int port;
public ServerInfo(String host, int port) {
this.host = host;
this.port = port;
}
public String toString() {
return "host:" + host + ",port:" + port;
}
}
上面这个类，用来封装服务端的基本信息，主机名+端口号，连接时需要用到。
package yjmyzz;
import org.apache.thrift.transport.TTransport;
import java.text.SimpleDateFormat;
import java.util.Date;
public class TransfortWrapper {
private TTransport transport;
/**
* 是否正忙
*/
private boolean isBusy = false;
/**
* 是否已经挂
*/
private boolean isDead = false;
/**
* 最后使用时间
*/
private Date lastUseTime;
/**
* 服务端Server主机名或IP
*/
private String host;
/**
* 服务端Port
*/
private int port;
public TransfortWrapper(TTransport transport, String host, int port, boolean isOpen) {
this.lastUseTime = new Date();
this.transport = transport;
this.host = host;
this.port = port;
if (isOpen) {
try {
transport.open();
} catch (Exception e) {
//e.printStackTrace();
System.err.println(host + ":" + port + " " + e.getMessage());
isDead = true;
}
}
}
public TransfortWrapper(TTransport transport, String host, int port) {
this(transport, host, port, false);
}
public boolean isBusy() {
return isBusy;
}
public void setIsBusy(boolean isBusy) {
this.isBusy = isBusy;
}
public boolean isDead() {
return isDead;
}
public void setIsDead(boolean isDead) {
this.isDead = isDead;
}
public TTransport getTransport() {
return transport;
}
public void setTransport(TTransport transport) {
this.transport = transport;
}
/**
* 当前transport是否可用
*
* @return
*/
public boolean isAvailable() {
return !isBusy && !isDead && transport.isOpen();
}
public Date getLastUseTime() {
return lastUseTime;
}
public void setLastUseTime(Date lastUseTime) {
this.lastUseTime = lastUseTime;
}
public String getHost() {
return host;
}
public int getPort() {
return port;
}
public String toString() {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
return "hashCode:" + hashCode() + "," +
host + ":" + port + ",isBusy:" + isBusy + ",isDead:" + isDead + ",isOpen:" +
transport.isOpen() + ",isAvailable:" + isAvailable() + ",lastUseTime:" + format.format(lastUseTime);
}
}
这是对TTransport的封装，主要增加了一些辅助信息，直接看代码注释即可。
下面才是连接池的主要内容：
package yjmyzz;
import org.apache.thrift.transport.TSocket;
import org.apache.thrift.transport.TTransport;
import java.util.Date;
import java.util.List;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
/**
* Thrift连接池
*
* @author : 菩提树下的杨过(http://yjmyzz.cnblogs.com/)
* @version : 0.1 BETA
* @since : 2015-09-27（中秋）
*/
public class ThriftTransportPool {
Semaphore access = null;
TransfortWrapper[] pool = null;
int poolSize = 1;//连接池大小
int minSize = 1;//池中保持激活状态的最少连接个数
int maxIdleSecond = 300;//最大空闲时间（秒），超过该时间的空闲时间的连接将被关闭
int checkInvervalSecond = 60;//每隔多少秒，检测一次空闲连接（默认60秒）
List<ServerInfo> serverInfos;
boolean allowCheck = true;
Thread checkTread = null;
public int getCheckInvervalSecond() {
return checkInvervalSecond;
}
public void setCheckInvervalSecond(int checkInvervalSecond) {
this.checkInvervalSecond = checkInvervalSecond;
}
/**
* 连接池构造函数
*
* @param poolSize 连接池大小
* @param minSize 池中保持激活的最少连接数
* @param maxIdleSecond 单个连接最大空闲时间，超过此值的连接将被断开
* @param checkInvervalSecond 每隔多少秒检查一次空闲连接
* @param serverList 服务器列表
*/
public ThriftTransportPool(int poolSize, int minSize, int maxIdleSecond, int checkInvervalSecond, List<ServerInfo> serverList) {
if (poolSize <= 0) {
poolSize = 1;
}
if (minSize > poolSize) {
minSize = poolSize;
}
if (minSize <= 0) {
minSize = 0;
}
this.maxIdleSecond = maxIdleSecond;
this.minSize = minSize;
this.poolSize = poolSize;
this.serverInfos = serverList;
this.allowCheck = true;
this.checkInvervalSecond = checkInvervalSecond;
init();
check();
}
/**
* 连接池构造函数（默认最大空闲时间300秒）
*
* @param poolSize 连接池大小
* @param minSize 池中保持激活的最少连接数
* @param serverList 服务器列表
*/
public ThriftTransportPool(int poolSize, int minSize, List<ServerInfo> serverList) {
this(poolSize, minSize, 300, 60, serverList);
}
public ThriftTransportPool(int poolSize, List<ServerInfo> serverList) {
this(poolSize, 1, 300, 60, serverList);
}
public ThriftTransportPool(List<ServerInfo> serverList) {
this(serverList.size(), 1, 300, 60, serverList);
}
/**
* 检查空闲连接
*/
private void check() {
checkTread =
new Thread(new Runnable() {
public void run() {
while (allowCheck) {
//System.out.println("--------------");
System.out.println("开始检测空闲连接...");
for (int i = 0; i < pool.length; i++) {
//if (pool[i] == null) {
// System.out.println("pool[" + i + "]为null");
//}
//if (pool[i].getTransport() == null) {
// System.out.println("pool[" + i + "].getTransport()为null");
//}
if (pool[i].isAvailable() && pool[i].getLastUseTime() != null) {
long idleTime = new Date().getTime() - pool[i].getLastUseTime().getTime();
//超过空闲阀值的连接，主动断开，以减少资源消耗
if (idleTime > maxIdleSecond * 1000) {
if (getActiveCount() > minSize) {
pool[i].getTransport().close();
pool[i].setIsBusy(false);
System.out.println(pool[i].hashCode() + "," + pool[i].getHost() + ":" + pool[i].getPort() + " 超过空闲时间阀值被断开！");
}
}
}
}
System.out.println("当前活动连接数：" + getActiveCount());
try {
Thread.sleep(checkInvervalSecond * 1000);
} catch (Exception e) {
e.printStackTrace();
}
}
}
});
checkTread.start();
}
/**
* 连接池初始化
*/
private void init() {
access = new Semaphore(poolSize);
pool = new TransfortWrapper[poolSize];
for (int i = 0; i < pool.length; i++) {
int j = i % serverInfos.size();
TSocket socket = new TSocket(serverInfos.get(j).getHost(),
serverInfos.get(j).getPort());
if (i < minSize) {
pool[i] = new TransfortWrapper(socket, serverInfos.get(j).getHost(), serverInfos.get(j).getPort(), true);
} else {
pool[i] = new TransfortWrapper(socket, serverInfos.get(j).getHost(), serverInfos.get(j).getPort());
}
}
}
/**
* 从池中取一个可用连接
* @return
*/
public TTransport get() {
try {
if (access.tryAcquire(3, TimeUnit.SECONDS)) {
synchronized (this) {
for (int i = 0; i < pool.length; i++) {
if (pool[i].isAvailable()) {
pool[i].setIsBusy(true);
pool[i].setLastUseTime(new Date());
return pool[i].getTransport();
}
}
//尝试激活更多连接
for (int i = 0; i < pool.length; i++) {
if (!pool[i].isBusy() && !pool[i].isDead()
&& !pool[i].getTransport().isOpen()) {
try {
pool[i].getTransport().open();
pool[i].setIsBusy(true);
pool[i].setLastUseTime(new Date());
return pool[i].getTransport();
} catch (Exception e) {
//e.printStackTrace();
System.err.println(pool[i].getHost() + ":" + pool[i].getPort() + " " + e.getMessage());
pool[i].setIsDead(true);
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException("can not get available client");
}
throw new RuntimeException("all client is too busy");
}
/**
* 客户端调用完成后，必须手动调用此方法，将TTransport恢复为可用状态
*
* @param client
*/
public void release(TTransport client) {
boolean released = false;
synchronized (this) {
for (int i = 0; i < pool.length; i++) {
if (client == pool[i].getTransport() && pool[i].isBusy()) {
pool[i].setIsBusy(false);
released = true;
break;
}
}
}
if (released) {
access.release();
}
}
public void destory() {
if (pool != null) {
for (int i = 0; i < pool.length; i++) {
pool[i].getTransport().close();
}
}
allowCheck = false;
checkTread = null;
System.out.print("连接池被销毁！");
}
/**
* 获取当前已经激活的连接数
*
* @return
*/
public int getActiveCount() {
int result = 0;
for (int i = 0; i < pool.length; i++) {
if (!pool[i].isDead() && pool[i].getTransport().isOpen()) {
result += 1;
}
}
return result;
}
/**
* 获取当前繁忙状态的连接数
*
* @return
*/
public int getBusyCount() {
int result = 0;
for (int i = 0; i < pool.length; i++) {
if (!pool[i].isDead() && pool[i].isBusy()) {
result += 1;
}
}
return result;
}
/**
* 获取当前已"挂"掉连接数
*
* @return
*/
public int getDeadCount() {
int result = 0;
for (int i = 0; i < pool.length; i++) {
if (pool[i].isDead()) {
result += 1;
}
}
return result;
}
public String toString() {
return "poolsize:" + pool.length +
",minSize:" + minSize +
",maxIdleSecond:" + maxIdleSecond +
",checkInvervalSecond:" + checkInvervalSecond +
",active:" + getActiveCount() +
",busy:" + getBusyCount() +
",dead:" + getDeadCount();
}
public String getWrapperInfo(TTransport client) {
for (int i = 0; i < pool.length; i++) {
if (pool[i].getTransport() == client) {
return pool[i].toString();
}
}
return "";
}
}
主要思路：
1.构造器里，传入 连接池大小，最小连接数，连接最大空闲时间，空间连接检测时间间隔，服务端列表等基本信息
2.然后调用init方法进行初始化，初始化时把pool[]数组填满，不过在填充的时候，要根据minsize决定激活多少连接（换句话讲，连接实例都都建好了，只是连不连的问题)，另外初始化的时候，还要考虑到某个服务器宕机的可能，如果服务端挂了，将对应的实例设置为isDead=true的状态
3.新开一个线程定时检查是否有空闲连接，如果空闲时间太长，主动断开，以节省开销。
4.get()方法从数组中捞一个可用的连接出来,取的时候要考虑到唤醒"沉睡"连接的情况，即如果当前池中只有2个活动连接，这时又来了请求，没有活动连接了，要从池中把断开的连接叫醒一个。
5.要控制并发控制，多个线程同时调用get()想从池中取可用连接时，可用Semaphore+Lock的机制来加以控制，可参考上一篇内容。
测试：
package yjmyzz;
import org.apache.thrift.transport.TSocket;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
public class PoolTest {
public static void main(String[] args) throws Exception {
//初始化一个连接池（poolsize=15,minsize=1,maxIdleSecond=5,checkInvervalSecond=10）
final ThriftTransportPool pool = new ThriftTransportPool(15, 1, 5, 10, getServers());
//模拟客户端调用
createClients(pool);
//等候清理空闲连接
Thread.sleep(30000);
//再模拟一批客户端，验证连接是否会重新增加
createClients(pool);
System.out.println("输入任意键退出...");
System.in.read();
//销毁连接池
pool.destory();
}
private static void createClients(final ThriftTransportPool pool) throws Exception {
//模拟5个client端
int clientCount = 5;
Thread thread[] = new Thread[clientCount];
FutureTask<String> task[] = new FutureTask[clientCount];
for (int i = 0; i < clientCount; i++) {
task[i] = new FutureTask<String>(new Callable<String>() {
public String call() throws Exception {
TSocket scoket = (TSocket) pool.get();//从池中取一个可用连接
//模拟调用RPC会持续一段时间
System.out.println(Thread.currentThread().getName() + " => " + pool.getWrapperInfo(scoket));
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
pool.release(scoket);//记得每次用完，要将连接释放（恢复可用状态）
return Thread.currentThread().getName() + " done.";
}
});
thread[i] = new Thread(task[i], "Thread" + i);
}
//启用所有client线程
for (int i = 0; i < clientCount; i++) {
thread[i].start();
Thread.sleep(10);
}
System.out.println("--------------");
//等待所有client调用完成
for (int i = 0; i < clientCount; i++) {
System.out.println(task[i].get());
System.out.println(pool);
System.out.println("--------------");
thread[i] = null;
}
}
private static List<ServerInfo> getServers() {
List<ServerInfo> servers = new ArrayList<ServerInfo>();
servers.add(new ServerInfo("localhost", 9000));
servers.add(new ServerInfo("localhost", 9001));
servers.add(new ServerInfo("localhost", 1002));//这一个故意写错的，模拟服务器挂了，连接不上的情景
return servers;
}
}
输出：
****************************
开始检测空闲连接...
当前活动连接数：1
Thread1 => hashCode:919192718,localhost:9001,isBusy:true,isDead:false,isOpen:true,isAvailable:false,lastUseTime:2015-09-27 16:09:59
Thread0 => hashCode:1510835162,localhost:9000,isBusy:true,isDead:false,isOpen:true,isAvailable:false,lastUseTime:2015-09-27 16:09:59
localhost:1002 java.net.ConnectException: Connection refused
Thread2 => hashCode:1466719669,localhost:9000,isBusy:true,isDead:false,isOpen:true,isAvailable:false,lastUseTime:2015-09-27 16:10:00
Thread3 => hashCode:2080503518,localhost:9001,isBusy:true,isDead:false,isOpen:true,isAvailable:false,lastUseTime:2015-09-27 16:10:00
localhost:1002 java.net.ConnectException: Connection refused
Thread4 => hashCode:411724643,localhost:9000,isBusy:true,isDead:false,isOpen:true,isAvailable:false,lastUseTime:2015-09-27 16:10:00
--------------
Thread0 done.
poolsize:15,minSize:1,maxIdleSecond:5,checkInvervalSecond:10,active:5,busy:3,dead:2
--------------
Thread1 done.
poolsize:15,minSize:1,maxIdleSecond:5,checkInvervalSecond:10,active:5,busy:3,dead:2
--------------
Thread2 done.
poolsize:15,minSize:1,maxIdleSecond:5,checkInvervalSecond:10,active:5,busy:2,dead:2
--------------
Thread3 done.
poolsize:15,minSize:1,maxIdleSecond:5,checkInvervalSecond:10,active:5,busy:1,dead:2
--------------
Thread4 done.
poolsize:15,minSize:1,maxIdleSecond:5,checkInvervalSecond:10,active:5,busy:0,dead:2
--------------
开始检测空闲连接...
1510835162,localhost:9000 超过空闲时间阀值被断开！
919192718,localhost:9001 超过空闲时间阀值被断开！
1466719669,localhost:9000 超过空闲时间阀值被断开！
2080503518,localhost:9001 超过空闲时间阀值被断开！
当前活动连接数：1
开始检测空闲连接...
当前活动连接数：1
开始检测空闲连接...
当前活动连接数：1
Thread0 => hashCode:411724643,localhost:9000,isBusy:true,isDead:false,isOpen:true,isAvailable:false,lastUseTime:2015-09-27 16:10:31
Thread1 => hashCode:1510835162,localhost:9000,isBusy:true,isDead:false,isOpen:true,isAvailable:false,lastUseTime:2015-09-27 16:10:31
Thread2 => hashCode:919192718,localhost:9001,isBusy:true,isDead:false,isOpen:true,isAvailable:false,lastUseTime:2015-09-27 16:10:31
Thread3 => hashCode:1466719669,localhost:9000,isBusy:true,isDead:false,isOpen:true,isAvailable:false,lastUseTime:2015-09-27 16:10:31
Thread4 => hashCode:2080503518,localhost:9001,isBusy:true,isDead:false,isOpen:true,isAvailable:false,lastUseTime:2015-09-27 16:10:31
--------------
Thread0 done.
poolsize:15,minSize:1,maxIdleSecond:5,checkInvervalSecond:10,active:5,busy:4,dead:2
--------------
Thread1 done.
poolsize:15,minSize:1,maxIdleSecond:5,checkInvervalSecond:10,active:5,busy:3,dead:2
--------------
Thread2 done.
poolsize:15,minSize:1,maxIdleSecond:5,checkInvervalSecond:10,active:5,busy:2,dead:2
--------------
Thread3 done.
poolsize:15,minSize:1,maxIdleSecond:5,checkInvervalSecond:10,active:5,busy:1,dead:2
--------------
Thread4 done.
poolsize:15,minSize:1,maxIdleSecond:5,checkInvervalSecond:10,active:5,busy:0,dead:2
--------------
输入任意键退出...
q
连接池被销毁！
***********************
注意上面高亮颜色的部分，2080503518 连接创建后，后来被check方法主动检测到空闲断开，然后第二轮调用时，又重新激活。411724643 则幸免于难，一直战斗到最后。另外由于故意写错了一个server地址，池中始终有二个dead的实例。
值得改进的地方：
主要是公平性的问题，在初始化的时候，如果服务器有3台，而指定的连接池大小为4，目前的做法是，用4对3取模，所以第1、4个连接实例都是连接到服务器1，get取可用连接的时候也有类似情况，是按pool数组从前向后遍历的，捞到第1个可用的连接就完事了，这样永远是排在List前面的服务器压力会大一些，这样有点不太符合负载"均衡"的本意。
不过，这个问题也很好解决，有一个很简单有效的技巧，实际应用中，服务器列表是从zk上取回来的，取回来后，先对数组做随机排序，这样整体看来下，多个连接池总体的连接分布情况就比较平均了。
