Ribbon 和 wowza 的集成开发

        前言
        Ribbon 是提供 REST 服务的区域感知负载均衡器，它在 wowza 的前端，应该部署在专业的 REST 容器下，而不是流媒体服务器 wowza 下。

本文介绍了 Ribbon 和 wowza 的集成，Ribbon 作为 wowza 的一个插件部署在了 wowza 容器下，仅供 Ribbon 开发、部署的技术參考，现实中绝不可能出现这样的情况。由于 Wowza 毕竟不是专业提供 REST 服务的容器。关于 Ribbon 和 Wowza 真实场景的架构部署，请关注作者兴许博客。
        本文是在《让你的 wowza 服务器提供 RESTful web 服务》样例的基础上进一步进行研发。
        1. 新建 maven 项目
        參考《让你的 wowza 服务器提供 RESTful web 服务》步骤。新建的 maven 项目 defonds-server-module 例如以下：

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        2. 编辑 Ribbon 配置文件
        依据你自己的集群。配置 Ribbon。比方作者 demo 用的配置文件例如以下：

# Max number of retries on the same server (excluding the first try)
sample-client.ribbon.MaxAutoRetries=1

# Max number of next servers to retry (excluding the first server)
sample-client.ribbon.MaxAutoRetriesNextServer=1

# Whether all operations can be retried for this client
sample-client.ribbon.OkToRetryOnAllOperations=true

# Interval to refresh the server list from the source
sample-client.ribbon.ServerListRefreshInterval=2000

# Connect timeout used by Apache HttpClient
sample-client.ribbon.ConnectTimeout=3000

# Read timeout used by Apache HttpClient
sample-client.ribbon.ReadTimeout=3000

# Initial list of servers, can be changed via Archaius dynamic property at runtime
sample-client.ribbon.listOfServers=www.baidu.com:80,www.163.com:80,www.csdn.net:80

然后把这个文件放在你的 classpath 下。
        3. 编写 LB 调用类

package com.defonds.wms.module.server;

import java.io.IOException;
import java.io.OutputStream;
import java.net.URI;
import java.net.URISyntaxException;

import com.netflix.client.ClientException;
import com.netflix.client.ClientFactory;
import com.netflix.client.http.HttpRequest;
import com.netflix.client.http.HttpResponse;
import com.netflix.config.ConfigurationManager;
import com.netflix.niws.client.http.RestClient;
import com.wowza.wms.http.HTTProvider2Base;
import com.wowza.wms.http.IHTTPRequest;
import com.wowza.wms.http.IHTTPResponse;
import com.wowza.wms.logging.WMSLogger;
import com.wowza.wms.logging.WMSLoggerFactory;
import com.wowza.wms.vhost.IVHost;

public class RibbonLBRestService extends HTTProvider2Base {
	private static final WMSLogger logger = WMSLoggerFactory.getInstance().getLoggerObj(RibbonLBRestService.class.getName());
	public static RestClient restClient = null;

	static {
		try {
			// Load the properties file using Archaius ConfigurationManager
			ConfigurationManager.loadPropertiesFromResources("sample-client.properties");
			// Use ClientFactory to create client and the load balancer
			RibbonLBRestService.restClient = (RestClient) ClientFactory.getNamedClient("sample-client");
		} catch (IOException e) {
			logger.error(e.getMessage(), e);
		}  

	}

	@Override
	public void onHTTPRequest(IVHost arg0, IHTTPRequest request, IHTTPResponse response) {
		String jsonObject = null;
		response.setHeader("Content-Type", "application/json");
		try {
			String serverURI = RibbonLBRestService.getURI();
			response.setResponseCode(200);
			jsonObject = "{\"server_uri\":\"" + serverURI + "\"}";
		} catch (ClientException e2) {
			response.setResponseCode(400);
			jsonObject = "{\"error_code\":\"40039\"}";
			logger.error(e2.getMessage(), e2);

		} catch (URISyntaxException e3) {
			response.setResponseCode(400);
			jsonObject = "{\"error_code\":\"40023\"}";
			logger.error(e3.getMessage(), e3);
		} finally {
			// Get the printwriter object from response to write the required json object to the output stream
			OutputStream out = response.getOutputStream();
			try {
				out.write(jsonObject.getBytes());
				out.flush();
			} catch (IOException e) {
				logger.error(e.getMessage(), e);
			}
		}

	}

	public synchronized static String getURI() throws ClientException, URISyntaxException {
		// Build the http request using the builder
		// Note that we only supply the path part (“/”) of the URI
		// The complete URI will be computed by the client once the server is chosen by the load balancer
		HttpRequest ribbonRequest = HttpRequest.newBuilder().uri(new URI("/")).build();
        HttpResponse ribbonResponse;
        // Call client.executeWithLoadBalancer() API, not the execute() API
		ribbonResponse = RibbonLBRestService.restClient.executeWithLoadBalancer(ribbonRequest);
		return ribbonResponse.getRequestedURI().toString();
	}

	public synchronized static void changeServersPoolDynamically(String serverList) throws ClientException {
        // Dynamically change the server pool from the configuration
        ConfigurationManager.getConfigInstance().setProperty(
        		"sample-client.ribbon.listOfServers", serverList);
        logger.debug("changing servers ...");
        try {
        	// Wait until server list is refreshed (2 seconds refresh interval defined in properties file)
			Thread.sleep(3000);
		} catch (InterruptedException e) {
			logger.error(e.getMessage(), e);
		}
	}

}

这个类将会给 ribbonLB 的 REST 请求返回一台服务器地址。假设请求失败，返回对应的错误码。

这个类还提供了一个公开方法，用于动态调整负载均衡节点。
        4. 编写动态改动负载均衡节点接口

package com.defonds.wms.module.server;

import java.io.IOException;
import java.io.OutputStream;

import com.netflix.client.ClientException;
import com.wowza.wms.http.HTTProvider2Base;
import com.wowza.wms.http.IHTTPRequest;
import com.wowza.wms.http.IHTTPResponse;
import com.wowza.wms.logging.WMSLogger;
import com.wowza.wms.logging.WMSLoggerFactory;
import com.wowza.wms.vhost.IVHost;

public class RibbonChangeInstanceService extends HTTProvider2Base {
	private static final WMSLogger logger = WMSLoggerFactory.getInstance().getLoggerObj(RibbonChangeInstanceService.class.getName());

	@Override
	public void onHTTPRequest(IVHost arg0, IHTTPRequest request, IHTTPResponse response) {
		String serverList = request.getParameter("server_list");

		// TODO Authorization

		// TODO serverList str check

		String jsonObject = null;
		response.setHeader("Content-Type", "application/json");
		try {
			RibbonLBRestService.changeServersPoolDynamically(serverList);
			response.setResponseCode(200);
			jsonObject = "{\"error_code\":\"0\"}"; // server list is changed successfully
		} catch (ClientException e2) {
			response.setResponseCode(400);
			jsonObject = "{\"error_code\":\"40039\"}";
			logger.error(e2.getMessage(), e2);
		} finally {
			// Get the printwriter object from response to write the required json object to the output stream
			OutputStream out = response.getOutputStream();
			try {
				out.write(jsonObject.getBytes());
				out.flush();
			} catch (IOException e) {
				logger.error(e.getMessage(), e);
			}
		}

	} 

}

这个类提供了一个用于动态改动负载均衡节点池的接口。假设改动成功返回错误码为 0，否则为其它值。

5. 编辑 maven 依赖

编辑项目 pom.xml。将上边依赖到的包导入：

		<!-- ribbon -->
		<dependency>
			<groupId>com.netflix.ribbon</groupId>
			<artifactId>ribbon-core</artifactId>
			<version>0.3.12</version>
		</dependency>
		<dependency>
			<groupId>com.netflix.ribbon</groupId>
			<artifactId>ribbon-httpclient</artifactId>
			<version>0.3.12</version>
		</dependency>

6. 编辑 VHost.xml
        编辑 %wowza%/conf/VHost.xml，把上边写的两个 HTTPProvider 加入进去：

					<HTTPProvider>
						<BaseClass>com.defonds.wms.module.server.RibbonLBRestService</BaseClass>
						<RequestFilters>ribbonLB*</RequestFilters>
						<AuthenticationMethod>none</AuthenticationMethod>
					</HTTPProvider>
					<HTTPProvider>
						<BaseClass>com.defonds.wms.module.server.RibbonChangeInstanceService</BaseClass>
						<RequestFilters>ribbonChange*</RequestFilters>
						<AuthenticationMethod>none</AuthenticationMethod>
					</HTTPProvider>

7. 项目又一次打包部署
        命令行切换到你的 defonds-server-module 项目文件夹下，运行
mvn package
        8. 訪问接口
        debug 启动 defonds-server-module，然后在浏览器訪问 http://localhost:1935/ribbonLB，以向 Ribbon 要一个服务器地址，返回结果例如以下：
{"server_uri":"http://www.csdn.net:80/"}
        返回的是服务器 URL 是 http://www.csdn.net:80/。然后在浏览器訪问 http://localhost:1935/ribbonChange?server_list=www.qq.com:80,www.126.com:80。以动态调整负载均衡节点。返回结果例如以下：
{"error_code":"0"}
        这个返回码说明已经调整成功。我们能够继续訪问 http://localhost:1935/ribbonLB 验证一下，返回结果是：
{"server_uri":"http://www.qq.com:80/"}
        没错，确实成功了。

注意
        以上 Ribbon 动态调整的负载均衡节点是内存里的配置。服务器下的 sample-client.properties 配置的节点依然是：

sample-client.ribbon.listOfServers=www.baidu.com:80,www.163.com:80,www.csdn.net:80

这样 REST 服务重新启动后。读取的负载均衡节点依然是改动前的。假设你想在 REST 服务器断电重新启动后读取改动后的。最好把 Ribbon 属性在分布式缓存服务器中进行存放和读取，比方 Redis。

另：本文演示样例代码已上传 CSDN 资源。下载地址：http://download.csdn.net/detail/defonds/7526359。