Nginx基础-4:负载均衡

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负载均衡是为减轻单个服务器负担，将请求按照某种策略分发给多个服务器。

官方文档参考：http://nginx.org/en/docs/http/ngx_http_upstream_module.html#upstream

以2台Tomcat集群为例

Tomcat配置

Tomcat下载地址：https://tomcat.apache.org/download-80.cgi

1568258710917

解压后修改\tomcat\conf\目录下的server.xml

修改所有的端口号，避免冲突

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<Connector port="8080" protocol="HTTP/1.1"
           connectionTimeout="20000"
           redirectPort="8443" 
/>

本例中，Tomcat A部署在http://localhost:8080，Tomcat B部署在http://localhost:8082

分别在两个Tomcat下部署tomcat\webapps\demo\load-balance.html

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<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>

<body>
  <h1 style="color: pink">8080</h1>
</body>

</html>

用颜色和文字区分两个Tomcat

Nginx配置

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upstream tomcat {
    server localhost:8080;
    server localhost:8082;
}

server {
    listen       8088;
    server_name  localhost;

    charset utf-8;

    location / {
        proxy_pass   http://tomcat;
        proxy_redirect default;

        include proxy_params;
    }

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

进入浏览器，用http://localhost:8088/demo/load-balance.html进行访问

F5刷新页面，会依次地访问到8080和8082上的Tomcat

分发策略

1.轮询（默认）

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upstream tomcat {
    server localhost:8080;
    server localhost:8082;
}

按时间顺序，依次分发

2.加权轮询

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upstream tomcat {
    server localhost:8080 weight=1;
    server localhost:8082 weight=10;
}

weight值与访问几率成正比

3.ip_hash

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upstream tomcat {
	ip_hash;
    server localhost:8080;
    server localhost:8082;
}

考虑缓存的情况，保持会话

来自同一ip的请求会固定到一个server

4.最小连接

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upstream tomcat {
	least_conn；
    server localhost:8080;
    server localhost:8082;
}

根据连接数来分发，起到均分的作用

5.url_hash

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upstream tomcat {
	hash $request_url;
    server localhost:8080;
    server localhost:8082;
}

来自同一url的请求会固定到一个server

状态参数

1.down

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upstream tomcat {
    server localhost:8080 down;
    server localhost:8082;
}

当前server不参与负载均衡

2.backup

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upstream tomcat {
    server localhost:8080 down;
    server localhost:8082;
}

预留的server，当有其他的server挂掉或者忙的时候，才会参与负载

3.max_fails和fail_timeout

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upstream tomcat {
    server localhost:8080;
    server localhost:8082 max_fails=3 fail_timeout=30s;
}

最大连接错误次数3次，每次失败后，间隔30s再重新发起连接

4.max_conns

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upstream tomcat {
    server localhost:8080;
    server localhost:8082 max_conns=500;
}

超过最大连接数后，就不参与负载