学习Express之nginx配置负载均衡
来自： http://my.oschina.net/songzhu/blog/610376
关于 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
启动 nginx
$ service nginx start
验证
$ curl http://localhost/
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