學習Express之nginx配置負載均衡
來自： http://my.oschina.net/songzhu/blog/610376
關于 express-demo
雖然 PM2 已有負載均衡的功能，但是他只對多進程之間進行處理，如果是多個服務器之間，就無法辦到了，這里我們選用nginx。
服務器準備
s0：CentOS，172.16.70.175，nginx 服務器
s1：CentOS，172.16.70.174，web 服務器
s2：CentOS，172.16.70.173，web 服務器
1、配置 s1，s2
由于之前已有說明，這不再細說。參考：http://my.oschina.net/songzhu/blog/610337
修改 s1 服務器的 config.js 內容為：
var config = {
server:"172.16.70.174"
};
module.exports = config; 重啟 web
pm2 restart pm2-start.json
修改 s2 服務器的 config.js 內容為：
var config = {
server:"172.16.70.173"
};
module.exports = config; 重啟 web
pm2 restart pm2-start.json
2、配置 s0
安裝 nginx
$ rpm -ivh http://nginx.org/packages/centos/7/x86_64/RPMS/nginx-1.8.0-1.el7.ngx.x86_64.rpm
啟動 nginx
$ service nginx start
驗證
$ curl http://localhost/
配置負載均衡，編輯 /etc/nginx/nginx.conf，在 http 節點里面增加以下內容：
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 $proxy_add_x_forwarded_for;
}
} 完整的 /etc/nginx/nginx.conf 內容如下：
user nginx;
worker_processes 1;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;
events {
worker_connections 1024;
}
http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
log_format main '$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;
}
}
} 編輯完成之后，重啟 nginx
$ service nginx restart
修改本地hosts文件，增加：172.16.70.175 my.server.com
在本地執行：
$ 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>
結果和預期一樣，nginx 成功將請求平均分配到兩臺服務器上了。
3、遇到的問題
502 bag getway.
通過查看錯誤日志：
$ cat /var/log/nginx/error.log
發現具體的錯誤是：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"
解決辦法是，執行以下命令
$ sudo setsebool -P httpd_can_network_connect 1 $ service nginx restart
解決錯誤參考網址：http://blog.frag-gustav.de/2013/07/21/nginx-selinux-me-mad/
項目代碼：https://git.oschina.net/cavintang/express-demo.git