一、前言

nginx 作為目前最流行的開源反向代理HTTP Server，用於實現資源快取、web
server負載均衡等功能，由於其輕量級、高效能、高可靠等特點在網際網路專案中有著非常普遍的應用，相關概念網上有豐富的介紹。分散式web
server叢集部署後需要實現session共享，針對 tomcat 伺服器的實現方案多種多樣，比如 tomcat cluster
session 廣播、nginx IP hash策略、nginx sticky module等方案，本文主要介紹了使用 redis
伺服器進行 session 統一儲存管理的共享方案。

相關應用結構參照下圖：

二、環境配置

系統：Centos7
tomcat：apache-tomcat-7.0.78
redis：redis-2.8.9

三、構建 tomcat-redis-session-manager-master

1、由於原始碼構建基於 gradle，請先配置 gradle 環境。
2、從 github 獲取 tomcat-redis-session-manager-master 原始碼，地址如下：

https://github.com/jcoleman/tomcat-redis-session-manager

3、找到原始碼中的 build.gradle 檔案，由於作者使用了第三方倉庫（sonatype），需要註冊帳號，太麻煩，註釋後直接使用maven中央倉庫，同時註釋簽名相關指令碼並增加依賴包的輸出指令碼 copyJars（dist目錄），修改後的 build.gradle 檔案如下：

apply plugin: 'java'
apply plugin: 'maven'
apply plugin: 'signing'

group = 'com.orangefunction'
version = '2.0.0'

repositories {
  mavenCentral()
}

compileJava {
  sourceCompatibility = 1.7
  targetCompatibility = 1.7
}

dependencies {
  compile group: 'org.apache.tomcat', name: 'tomcat-catalina'
 
, version: '7.0.27'
  compile group: 'redis.clients', name: 'jedis', version: '2.5.2'
  compile group: 'org.apache.commons', name: 'commons-pool2', version: '2.2'
  //compile group: 'commons-codec', name: 'commons-codec', version: '1.9'

  testCompile group: 'junit', name: 'junit', version: '4.+'
  testCompile 'org.hamcrest:hamcrest-core:1.3'
  testCompile 'org.hamcrest:hamcrest-library:1.3'
  testCompile 'org.mockito:mockito-all:1.9.5'
  testCompile group: 'org.apache.tomcat', name: 'tomcat-coyote', version: '7.0.27'
}

task javadocJar(type: Jar, dependsOn: javadoc) {
  classifier = 'javadoc'
  from 'build/docs/javadoc'
}

task sourcesJar(type: Jar) {
  from sourceSets.main.allSource
  classifier = 'sources'
}

artifacts {
  archives jar

  archives javadocJar
  archives sourcesJar
}

//signing {
//  sign configurations.archives
//}

task copyJars(type: Copy) {
  from configurations.runtime
  into 'dist'  
}

uploadArchives {
  repositories {
    mavenDeployer {
      beforeDeployment { MavenDeployment deployment -> signing.signPom(deployment) }

      //repository(url: "https://oss.sonatype.org/service/local/staging/deploy/maven2/") {
      //  authentication(userName: sonatypeUsername, password: sonatypePassword)
      //}
      //repository(url: "https://oss.sonatype.org/content/repositories/snapshots") {
      //  authentication(userName: sonatypeUsername, password: sonatypePassword)
      //}

      pom.project {
        name 'tomcat-redis-session-manager'
        packaging 'jar'
        description 'Tomcat Redis Session Manager is a Tomcat extension to store sessions in Redis'
        url 'https://github.com/jcoleman/tomcat-redis-session-manager'

        issueManagement {
          url 'https://github.com:jcoleman/tomcat-redis-session-manager/issues'
          system 'GitHub Issues'
        }

        scm {
          url 'https://github.com:jcoleman/tomcat-redis-session-manager'
          connection 'scm:git:git://github.com/jcoleman/tomcat-redis-session-manager.git'
          developerConnection 'scm:git:[email protected]:jcoleman/tomcat-redis-session-manager.git'
        }

        licenses {
          license {
            name 'MIT'
            url 'http://opensource.org/licenses/MIT'
            distribution 'repo'
          }
        }

        developers {
          developer {
            id 'jcoleman'
            name 'James Coleman'
            email '[email protected]'
            url 'https://github.com/jcoleman'
          }
        }
      }
    }
  }
}

4、執行gradle命令構建原始碼，編譯輸出tomcat-redis-session-manager-master 及依賴jar包

gradle build -x test  copyJars

檔案列表如下：

四、tomcat 配置

兩臺tomcat伺服器分別在不同的虛擬機器上，地址：

http://192.168.31.84:8080
http://192.168.31.82:8080

五、編寫測試頁面

在tomcat安裝目錄下webapps/ROOT/新增test.jsp檔案，內容為：

<%@ page contentType="text/html;charset=UTF-8" isELIgnored="false"%>
 SessionID:<%=session.getId()%><BR>
 SessionIP:<%=request.getServerName()%> <BR>
 SessionPort:<%=request.getServerPort()%>
 <%     out.println("This is Tomcat Server 82（根據情況修改，以便區別） ！");     %>

六、tomcat session manager 配置

1.新增commons-pool2-2.2、jedis-2.5.2、tomcat-redis-session-manager-master-2.0.0jar包到tomcat 安裝目錄的 lib 資料夾；
2.修改兩臺tomcat的context.xml檔案，使 tomcat-redis-session-manager-master 作為session管理器，同時指定redis地址和埠。

context.xml配置：

<Context>
    <WatchedResource>WEB-INF/web.xml</WatchedResource>

   <Valve className="com.orangefunction.tomcat.redissessions.RedisSessionHandlerValve" />
   <Manager className="com.orangefunction.tomcat.redissessions.RedisSessionManager"
           host="192.168.31.84"
           port="6379"
           database="0"
           maxInactiveInterval="60" />
</Context>

3.重啟兩臺tomcat

七、nginx 配置

1.修改nginx.conf檔案，內容如下：

#user  nobody;
worker_processes  1;

events {
    worker_connections  1024;
}

http {
    include       mime.types;
    default_type  application/octet-stream;

    sendfile        on;
    keepalive_timeout  65;

    upstream tomcat_nginx {
        server localhost:8080;
        server 192.168.31.82:8080;
    }

    server {
        listen       80;
        server_name  localhost;
        location / {
            proxy_pass http://tomcat_nginx;
            root   html;
            index  index.html index.htm;
        }

        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}

2.重啟nginx：

nginx -s reload

八、測試

nginx預設採用輪詢的方式進行負載均衡，重新整理頁面：