第4次实践作业

(1)使用Docker-compose实现Tomcat+Nginx负载均衡

项目结构

.
├── docker-compose.yml
├── nginx
│ └── default.conf
├── tomcat00
│ └── index.html
├── tomcat01
│ └── index.html
└── tomcat02
└── index.html

nginx配置文件

default.conf

upstream tomcats {
    server tomcat00:8080; 
    server tomcat01:8080; 
    server tomcat02:8080;
}

server {
    listen 2420;
    server_name localhost;

    location / {
        proxy_pass http://tomcats;
    }
}

docker-compose.yml

version: "3"
services:
    nginx:
        image: nginx
        container_name: nginx0
        ports:
            - 80:2420
        volumes:
            - ./nginx/default.conf:/etc/nginx/conf.d/default.conf # 挂载配置文件
        depends_on:
            - tomcat00
            - tomcat01
            - tomcat02

    tomcat00:
        image: tomcat
        container_name: tomcat00
        volumes:
            - ./tomcat00:/usr/local/tomcat/webapps/ROOT # 挂载web目录

    tomcat01:
        image: tomcat
        container_name: tomcat01
        volumes:
            - ./tomcat01:/usr/local/tomcat/webapps/ROOT

    tomcat02:
        image: tomcat
        container_name: tomcat02
        volumes:
            - ./tomcat02:/usr/local/tomcat/webapps/ROOT

localhost出错（暂时无法解决）

负载均衡测试

轮询策略（默认）

加权轮询，修改default.conf

2.使用Docker-compose部署javaweb运行环境

javaweb运行环境基于第一个tomcat+nginx负载均衡实验，由于web应用需要用到 JDBC，所以在volumes中还额外的添加了 JDBC相关的JAR包的依赖。数据库使用的是MySQL，使用dockerfile对其镜像进行定制，主要是数据库用户、密码、数据库和基本表的初始化。Dockerfile文件内容如下：

FROM mysql
ENV MYSQL_ROOT_PASSWORD=123456 \ 
        MYSQL_ALLOW_EMPTY_PASSWORD=no \
        MYSQL_DATABASE=logintimes
COPY tableinit.sql /docker-entrypoint-initdb.d

执行的sql语句如下：

use logintimes;
create table times(
        id int primary key,
        times int not null
)DEFAULT CHARSET=latin1;

完整的docker-compose文件内容如下：

version: "3"
services:
  proxy:
    image: nginx
    container_name: webproxy
    ports:
      - "80:80"
    volumes:
      - /usr/local/loadbalance/nginx.conf:/etc/nginx/nginx.conf
  cat01:
    image: tomcat:8.5.55-jdk8
    container_name: cat01
    volumes:
      - /var/lib/tomcat/apps1:/usr/local/tomcat/webapps
      - /var/lib/tomcat/lib/mysql-connector-java-8.0.20.jar:/usr/local/tomcat/lib/mysql-connector-java-8.0.20.jar
  cat02:
    image: tomcat:8.5.55-jdk8
    container_name: cat02
    volumes:
      - /var/lib/tomcat/apps2:/usr/local/tomcat/webapps
      - /var/lib/tomcat/lib/mysql-connector-java-8.0.20.jar:/usr/local/tomcat/lib/mysql-connector-java-8.0.20.jar
  cat03:
    image: tomcat:8.5.55-jdk8
    container_name: cat03
    volumes:
      - /var/lib/tomcat/apps3:/usr/local/tomcat/webapps
      - /var/lib/tomcat/lib/mysql-connector-java-8.0.20.jar:/usr/local/tomcat/lib/mysql-connector-java-8.0.20.jar
  database: 
    container_name: mydb
    build: ./mysql
    ports:
      - "3306:3306"
    volumes:
      - /var/lib/javaweb/mysql:/var/lib/mysql

从博客园中找到同学写的javaweb应用

简单的记录网站被访问次数并显示给用户，主要操作是从数据库中读取已被访问的次数，然后对次数加1再写入数据库，所以涉及的数据库操作为查询与更新。数据库使用的是MySQL8，与MySQL5有些差异。由于功能简单，在一个函数里就能够实现：

	// databaseRelated.class
	static final String JDBC_DRIVER = "com.mysql.cj.jdbc.Driver";// 与MySQL5有差异
    static final String DB_URL = "jdbc:mysql://mydb:3306/logintimes?useSSL=true&serverTimezone=GMT";// 与MySQL5有差异
    static final String USER = "root";
    static final String PASSWD = "123456";

    public static synchronized int updateTimes() {
        Connection connection = null;
        Statement statement = null;
        int times = 0;
        try {
            Class.forName(JDBC_DRIVER);
            System.out.println("Database Connecting...");
            connection = DriverManager.getConnection(DB_URL, USER, PASSWD);
            statement = connection.createStatement();
            String sqlCommand;
            sqlCommand = "select times from times where id = 1";
            System.out.println(sqlCommand);
            ResultSet resultSet = statement.executeQuery(sqlCommand);
            if (resultSet.next())
                times = resultSet.getInt("times") + 1;
            sqlCommand = "update times set times = " + times + " where id = 1";
            System.out.println(sqlCommand);
            statement.executeUpdate(sqlCommand);
            statement.close();
            connection.close();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return times;
    }

处理get与post请求的函数也极其简单：

    // updateTimes.class
	@Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        int times = databaseRelated.updateTimes();
        resp.getWriter().write("This website has been visited " + times + " times,this message comes from tomcat x.");// x取决于tomcat服务器，如x=1对应于tomcat01.
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }

将该web应用的servlet映射设置成如下形式：

	...
	<servlet>
        <servlet-name>counter</servlet-name>
        <servlet-class>updateTimes</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>counter</servlet-name>
        <url-pattern></url-pattern>
    </servlet-mapping>
	...

将整个web应用打成war包后，放入到tomcat服务器的持久化存储目录中。然后使用docker-compose up命令生成镜像并启动。使用浏览器通过url访问该web应用，可以看到如下内容：