使用Apache+Tomcat构建应用服务器集群

1.安装Apache HTTP server:http://httpd.apache.org/

2.安装2-3个(或更多)Tomcathttp://tomcat.apache.org/,安装zip版，因为安装多个Windows Service Installer版会出现错误（可以安装一个Installer版，其他两个用zip版）。

3.配置3个Tomcat，使得3个Tomcat在一台机器上可以同时运行：

修改三个Tomcat安装目录下的bin/startup.bat,将其中的CATALINA_HOME环境变量修改成互不相同的名字，比如CATALINA_HOME1，CATALINA_HOME2，CATALINA_HOME3。

4.配置集群

1) 修改Apache安装目录下的conf/httpd.conf文件，在文件末尾加入如下几行

ProxyRequests Off 
<proxy balancer://cluster> 
BalancerMember ajp://127.0.0.1:8009 loadfactor=1 route=jvm1
BalancerMember ajp://127.0.0.1:9009 loadfactor=1 route=jvm2
BalancerMember ajp://127.0.0.1:9099 loadfactor=1 route=jvm3
</proxy>

8009,9009,9099分别是三个Apache用来于Tomcat连接的端口oadfactor是指每一个tomcat的负载系数。

2) 修改Tomcat下的conf/server.xml

a.将所有3个Tomcat的server.xml中的

<Engine name="Catalina" defaultHost="localhost">

修改为<Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1">，3个tomcat的jvmRoute分别为jvm1,jvm2,jvm3

b.修改所有3个server.xml中的<Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />，将8009端口改为与上面Apache中配置的三个端口一致(这点很重要！)，与上面配置的jvm1，jvm2也要一致。也就是说，配置为jvm1的，这里端口改为8009，配置为jvm2的tomcat，这里端口给为9009，jvm3的为9099。

c.修改server.xml中的所有其他端口，使得3个tomcat没有重复的端口，包括：<Server port="8005"，<Connector port="8080"，redirectPort="8443" 这三个，三个tomcat的这三个端口都要不一样，其中每个tomcat中有两个redirectPort，同一个tomcat中的redirectPort一样，不同tomcat中的redirectPort不一样。

4.现在，集群就应该已经正确的构建完毕，访问Apache(localhost，端口为80)时，Apache就会将请求转发给这3个tomcat中的一个，可以自己写一个JSP或者servlet试试，注意，三个tomcat中的webapp下面都需要有一份JSP/servlet。

5.写一个实验程序(servlet)，发布到3个tomcat上，写一个客户端程序，多线程并发访问Apache，观察三个tomcat的负载均衡情况（可以调节一下loadfactor再观察），并绘制在线程越来越多的情况下，响应时间曲线。

由于规模较小的计算，响应时间非常快，可以忽略。所以选择一个计算量较大的运算： 判断一个数是否为素数，Sevlet代码如下：

package com.hw;
import java.io.IOException;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.MathContext;
import java.math.RoundingMode;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * Servlet implementation class JudgePrimeServlet
 */
public class JudgePrimeServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	private static final String TRUE_JSON = "{success:true}";
	private static final String FALSE_JSON = "{success:false}";
	
    public JudgePrimeServlet() {
    }
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String numStr =  request.getParameter("number");
		boolean ans;
		if(numStr.length() < 10)
			ans = isPrime(Long.parseLong(numStr));
		else
			ans = isPrime(new BigInteger(numStr));
		System.out.println(numStr + " : " + ans);
		response.getWriter().write(ans ? TRUE_JSON : FALSE_JSON);
		response.getWriter().flush();
		response.getWriter().close();
	}
	
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}
	
	public static boolean isPrime(long n)
	{
		if(n % 2 == 0)
		{
			if(n == 2)
				return true;
			return false;
		}
		long up = (long)Math.sqrt((double)n);
		for(int i = 3; i <= up; i += 2)
			if(n % i == 0)
				return false;
		return true;
	}
	
	public static boolean isPrime(BigInteger n)
	{
		if(n.mod(BigInteger.valueOf(2)).equals(BigInteger.ZERO))
		{
			if(n.equals(BigInteger.valueOf(2)))
				return true;
			return false;
		}
		MathContext mc = new MathContext(n.toString().length(), RoundingMode.HALF_DOWN);
		BigInteger up = new BigDecimal(Math.sqrt(n.doubleValue()) ,mc).toBigInteger();
		for(BigInteger i = BigInteger.valueOf(3); i.compareTo(up) <= 0; i = i.add(BigInteger.valueOf(2)))
			if(n.mod(i).equals(BigInteger.ZERO))
				return false;
		return true;
	}	
}

，客户端的线程代码如下：

public class ClientTestThread extends Thread
{
	public static final long[] primeArr = new long[] { 2055437, 2057317, 5298991, 5300467, 5352869, 5377679, 6220229,
			7155887, 8491247, 8885837, 9999929, 9999931, 9999943, 9999971, 9999973, 9999991, 11547391, 12531809,
			13192643, 15766453, 16854379, 26459779, 26456789, 26453803, 29999791, 1000003871, 1015490783, 1800000011,
			1800000019, 1800000047, 1800000049, 1800000053, 1800000061, 1800000109, 1800000113, 1800001523, 1978012607,
			1978012609, 1978012633, 1978012669, 1978012703, 1978012709, 1978012739, 1978012741, 1978012759, 1978012763,
			2008693679, 2008693681, 2008693727, 2008693741, 2008693759, 2095462079, 2095462099, 2095462151, 2095462163,
			2095462207, 2099999999 };
	
	private static Long timer = 0L;
	@Override
	public void run()
	{
		URL url;
		HttpURLConnection conn;
		long millisec = GregorianCalendar.getInstance().getTimeInMillis();
		try
		{
			url = new URL("http://localhost/ClusterExp/JudgePrimeServlet?number=" + 2099999999);
			conn = (HttpURLConnection) url.openConnection();
			Scanner scan = new Scanner(conn.getInputStream());
			if(scan.hasNext())
				scan.nextLine();
			scan.close();
			ClientTestThread.addToTimer((GregorianCalendar.getInstance().getTimeInMillis() - millisec));
		}
		catch (MalformedURLException e)
		{
			e.printStackTrace();
		}
		catch (IOException e)
		{
			e.printStackTrace();
		}
	}
	public static void addToTimer(long time)
	{
		synchronized (timer)
		{
			timer += time;
		}
	}
	public static void clearTimer()
	{
		synchronized (timer)
		{
			timer = 0L;
		}
	}
	public static Long getTimer()
	{
		return timer;
	}
}

，客户端界面以及生成多线程、绘制响应时间曲线代码如下（使用SWT，如果要运行，需要使用eclipse.org的SWT包）：

package com.hw.client;
import org.eclipse.swt.SWT;
public class TestClient
{
	protected Shell shell;
	private Text lowField;
	private Text highField;
	private Group lineGroup;
	private static final int unit = 10;
	private static final int off = 10;
	private static final int width = 800;
	private static final int height = 600;
	/**
	 * Launch the application.
	 * 
	 * @param args
	 */
	public static void main(String[] args)
	{
		try
		{
			TestClient window = new TestClient();
			window.open();
		}
		catch (Exception e)
		{
			e.printStackTrace();
		}
	}
	/**
	 * Open the window.
	 */
	public void open()
	{
		Display display = Display.getDefault();
		createContents();
		shell.open();
		shell.layout();
		while (!shell.isDisposed())
		{
			if (!display.readAndDispatch())
			{
				display.sleep();
			}
		}
	}
	/**
	 * Create contents of the window.
	 */
	protected void createContents()
	{
		shell = new Shell();
		shell.setSize(1024, 768);
		shell.setText("/u8D1F/u8F7D/u5E73/u8861/u6D4B/u8BD5/u5BA2/u6237/u7AEF");
		shell.setLayout(null);
		Composite composite = new Composite(shell, SWT.NONE);
		composite.setBounds(10, 10, 655, 97);
		Group group = new Group(composite, SWT.NONE);
		group.setBounds(10, 23, 422, 64);
		group.setText("/u6D4B/u8BD5/u7684/u7EBF/u7A0B/u6570/u91CF/u533A/u95F4");
		group.setLayout(null);
		Label label = new Label(group, SWT.NONE);
		label.setBounds(10, 27, 60, 12);
		label.setText("/u4E0B/u9650");
		lowField = new Text(group, SWT.BORDER);
		lowField.setBounds(76, 24, 106, 18);
		Label label_1 = new Label(group, SWT.NONE);
		label_1.setBounds(198, 27, 60, 12);
		label_1.setText("/u4E0A/u9650");
		highField = new Text(group, SWT.BORDER);
		highField.setBounds(265, 24, 106, 18);
		Button button = new Button(composite, SWT.NONE);
		button.addSelectionListener(new SelectionAdapter() {
			@Override
			public void widgetSelected(SelectionEvent arg0) {
				GC gc = new GC(lineGroup);
				gc.setForeground(new Color(Display.getCurrent(), 255, 0, 0));
				gc.drawLine(off, height - off, width + off, height - off);
				gc.drawLine(off, height - off, off, off);
				for(int i = 1; i < width / unit; ++ i)
				{
					if( i % 5 == 0)
						gc.drawString(String.valueOf(i), i * unit + off - 2, height - off + 3);
				}
				gc.drawString("线程数", width + off, height - off - 10);
				gc.setBackground(new Color(Display.getCurrent(), 255, 0, 0));
				for(int i = 1; i < width / unit; ++ i)
				{
					gc.fillRectangle(i * unit + off, height - off - 3, 2, 3);
				}
				for(int i = 1; i < height / unit; ++ i)
				{
					gc.fillRectangle(off, height - off - i * unit, 3, 2);
				}
				
				int low = Integer.parseInt(lowField.getText());
				int high = Integer.parseInt(highField.getText());
				int lastX = off, lastY = height - off;
				int x, y;
				for (int i = low; i <= high; ++i)
				{
					Thread[] multiThread = new ClientTestThread[i];
					for (Thread t : multiThread)
					{
						t = new ClientTestThread();
						t.start();
					}
					boolean allFinished = false;
					while (!allFinished)
					{
						allFinished = true;
						for (Thread t : multiThread)
						{
							if (t != null && t.isAlive())
							{
								allFinished = false;
								Thread.yield();
								break;
							}
						}
					}
					x = i * unit + off;
					y = height - off - ClientTestThread.getTimer().intValue() / i / 3;
					if(y < 0)
						y = 0;
					gc.drawLine(lastX, lastY, x, y);
					System.out.println(x  + "," + y);
					lastX = x;
					lastY =y;
					//gc.fillOval(i, 600 - ClientTestThread.getTimer().intValue(), 3,3);
					// gc.drawPoint(i, ClientTestThread.getTimer().intValue());
					ClientTestThread.clearTimer();
				}
			}
		});
		button.addMouseListener(new MouseAdapter()
		{
			@Override
			public void mouseDown(MouseEvent arg0)
			{
			}
		});
		button.setBounds(476, 53, 72, 22);
		button.setText("/u6D4B/u8BD5");
		lineGroup = new Group(shell, SWT.NONE);
		lineGroup.setText("/u8D1F/u8F7D/u66F2/u7EBF");
		lineGroup.setBounds(10, 113, 996, 618);
	}
}

,运行后，三个tomcat的控制台都会输出结果，说明请求被分发给三个tomcat，运行1-75个线程的响应时间曲线如下：