Ribbon 和 wowza 的集成開發

        前言
        Ribbon 是提供 REST 服務的區域感知負載均衡器，它在 wowza 的前端，應該部署在專業的 REST 容器下，而不是流媒體服務器 wowza 下。

本文介紹了 Ribbon 和 wowza 的集成，Ribbon 做爲 wowza 的一個插件部署在了 wowza 容器下，僅供 Ribbon 開發、部署的技術參考，現實中毫不可能出現這樣的狀況。因爲 Wowza 畢竟不是專業提供 REST 服務的容器。關於 Ribbon 和 Wowza 真實場景的架構部署，請關注做者興許博客。
        本文是在《讓你的 wowza 服務器提供 RESTful web 服務》樣例的基礎上進一步進行研發。
        1. 新建 maven 項目
        參考《讓你的 wowza 服務器提供 RESTful web 服務》步驟。新建的 maven 項目 defonds-server-module 例如如下：

        2. 編輯 Ribbon 配置文件
        依據你本身的集羣。配置 Ribbon。比方做者 demo 用的配置文件例如如下：

# 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

        而後把這個文件放在你的 classpath 下。
        3. 編寫 LB 調用類

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);
		} 
	}


}

        這個類將會給 ribbonLB 的 REST 請求返回一臺服務器地址。假設請求失敗，返回對應的錯誤碼。

這個類還提供了一個公開方法，用於動態調整負載均衡節點。
        4. 編寫動態改動負載均衡節點接口

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);
			}
		}
		
	} 


}

        這個類提供了一個用於動態改動負載均衡節點池的接口。假設改動成功返回錯誤碼爲 0，不然爲其它值。

        5. 編輯 maven 依賴

        編輯項目 pom.xml。將上邊依賴到的包導入：

		<!-- 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. 編輯 VHost.xml
        編輯 %wowza%/conf/VHost.xml，把上邊寫的兩個 HTTPProvider 加入進去：

					<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. 項目又一次打包部署
        命令行切換到你的 defonds-server-module 項目文件夾下，運行
mvn package
        8. 訪問接口
        debug 啓動 defonds-server-module，而後在瀏覽器訪問 http://localhost:1935/ribbonLB，以向 Ribbon 要一個服務器地址，返回結果例如如下：
{"server_uri":"http://www.csdn.net:80/"}
        返回的是服務器 URL 是 http://www.csdn.net:80/。而後在瀏覽器訪問 http://localhost:1935/ribbonChange?server_list=www.qq.com:80,www.126.com:80。以動態調整負載均衡節點。返回結果例如如下：
{"error_code":"0"}
        這個返回碼說明已經調整成功。咱們可以繼續訪問 http://localhost:1935/ribbonLB 驗證一下，返回結果是：
{"server_uri":"http://www.qq.com:80/"}
        沒錯，確實成功了。

        注意
        以上 Ribbon 動態調整的負載均衡節點是內存裏的配置。服務器下的 sample-client.properties 配置的節點依然是：

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

        這樣 REST 服務從新啓動後。讀取的負載均衡節點依然是改動前的。假設你想在 REST 服務器斷電從新啓動後讀取改動後的。最好把 Ribbon 屬性在分佈式緩存服務器中進行存放和讀取，比方 Redis。

另：本文演示樣例代碼已上傳 CSDN 資源。下載地址：http://download.csdn.net/detail/defonds/7526359。