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学习Express之nginx配置负载均衡

2016-01-27 14:42 661 查看

关于 express-demo

关于部署 express-demo

虽然 PM2 已有负载均衡的功能，但是他只对多进程之间进行处理，如果是多个服务器之间，就无法办到了，这里我们选用nginx。

服务器准备

s0：CentOS，172.16.70.175，nginx 服务器

s1：CentOS，172.16.70.174，web 服务器

s2：CentOS，172.16.70.173，web 服务器

1、配置 s1，s2

由于之前已有说明，这不再细说。参考：http://my.oschina.net/songzhu/blog/610337

修改 s1 服务器的 config.js 内容为：

var config = {
server:"172.16.70.174"
};

module.exports = config;

重启 web

pm2 restart pm2-start.json

修改 s2 服务器的 config.js 内容为：

var config = {
server:"172.16.70.173"
};

module.exports = config;

重启 web

pm2 restart pm2-start.json

2、配置 s0

安装 nginx

$ rpm -ivh http://nginx.org/packages/centos/7/x86_64/RPMS/nginx-1.8.0-1.el7.ngx.x86_64.rpm[/code] 启动 nginx

$ service nginx start

验证

$ curl http://localhost/[/code] 配置负载均衡，编辑 /etc/nginx/nginx.conf，在 http 节点里面增加以下内容：

upstream web-server {
server 172.16.70.173:3000;
server 172.16.70.174:3000;
}

server {
listen 80;
server_name my.server.com;
location / {
proxy_pass http://web-server; proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}

完整的 /etc/nginx/nginx.conf 内容如下：

user  nginx;
worker_processes  1;

error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;

events {
worker_connections  1024;
}

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

log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';

access_log  /var/log/nginx/access.log  main;

sendfile        on;
#tcp_nopush     on;

keepalive_timeout  65;

#gzip  on;

include /etc/nginx/conf.d/*.conf;

upstream web-server {
server 172.16.70.173:3000;
server 172.16.70.174:3000;
}

server {
listen 80;
server_name my.server.com;
location / {
proxy_pass http://web-server; proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}
}

编辑完成之后，重启 nginx

$ service nginx restart

修改本地hosts文件，增加：172.16.70.175 my.server.com

在本地执行：

$ curl http://my.server.com/ <!DOCTYPE html><html><head><title>Express</title><link rel="stylesheet" href="/stylesheets/style.css"></head><body><h1>Express</h1><p>Welcome to Express on 172.16.70.173</p></body></html>
$ curl http://my.server.com/ <!DOCTYPE html><html><head><title>Express</title><link rel="stylesheet" href="/stylesheets/style.css"></head><body><h1>Express</h1><p>Welcome to Express on 172.16.70.174</p></body></html>
$ curl http://my.server.com/ <!DOCTYPE html><html><head><title>Express</title><link rel="stylesheet" href="/stylesheets/style.css"></head><body><h1>Express</h1><p>Welcome to Express on 172.16.70.173</p></body></html>
$ curl http://my.server.com/ <!DOCTYPE html><html><head><title>Express</title><link rel="stylesheet" href="/stylesheets/style.css"></head><body><h1>Express</h1><p>Welcome to Express on 172.16.70.174</p></body></html>

结果和预期一样，nginx 成功将请求平均分配到两台服务器上了。

3、遇到的问题

502 bag getway.

通过查看错误日志：

$ cat /var/log/nginx/error.log

发现具体的错误是：connect() to 172.16.70.174:3000 failed (13: Permission denied) while connecting to upstream, client: 172.16.70.9, server: my.server.com, request: "GET / HTTP/1.1", upstream: "http://172.16.70.174:3000/", host: "my.server.com:80"

解决办法是，执行以下命令

$ sudo setsebool -P httpd_can_network_connect 1
$ service nginx restart

解决错误参考网址：http://blog.frag-gustav.de/2013/07/21/nginx-selinux-me-mad/

项目代码：https://git.oschina.net/cavintang/express-demo.git

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标签： nginx 负载均衡 502 bad getway Permission denied

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