使用nginx设置负载均衡器

Question

我正在学习如何在AWS上使用nginx设置负载均衡器。

我在AWS上设置了一个基本的ubuntu 18.04服务器，然后执行了以下操作：

sudo apt-get update
sudo apt-get upgrade -y
sudo apt-get install nginx -y

然后，我将/etc/nginx/nginx.conf替换为：

upstream backend {
    server xxx.24.20.11;
    server xxx.24.20.12;
}

server {
    listen 80;
    location / {
        proxy_pass http://backend;
    }
}

然后，我尝试通过执行以下操作重新启动nginx服务器：

sudo service nginx stop
sudo service nginx start

但我收到了错误消息：

Job for nginx.service failed because the control process exited with error code.
See "systemctl status nginx.service" and "journalctl -xe" for details.

所以，我做了

systemctl status nginx.service

下面是我得到的信息：

nginx.service - A high performance web server and a reverse proxy server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Wed 2019-04-03 01:13:27 UTC; 23s ago
     Docs: man:nginx(8)
  Process: 1822 ExecStop=/sbin/start-stop-daemon --quiet --stop --retry QUIT/5 --pidfile /run/nginx.pid (code=exited, status=0/SUCCESS)
  Process: 1748 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
  Process: 1865 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=1/FAILURE)
  Main PID: 1752 (code=exited, status=0/SUCCESS)

Apr 03 01:13:27 load-balancer.xxxx.com systemd[1]: Starting A high performance web server and a reverse proxy server...
Apr 03 01:13:27 load-balancer.xxx.com nginx[1865]: nginx: [emerg] "upstream" directive is not allowed here in /etc/nginx/nginx.conf:2
Apr 03 01:13:27 load-balancer.xxx.com nginx[1865]: nginx: configuration file /etc/nginx/nginx.conf test failed
Apr 03 01:13:27 load-balancer.xxx.com systemd[1]: nginx.service: Control process exited, code=exited status=1
Apr 03 01:13:27 load-balancer.xxx.com systemd[1]: nginx.service: Failed with result 'exit-code'.
Apr 03 01:13:27 load-balancer.xxx.com systemd[1]: Failed to start A high performance web server and a reverse proxy server.

我看了两个不同的教程，它们都使用了"upstream“指令。有什么想法吗？

编辑：

我将nginx.conf恢复为其原始格式：

sudo cp /etc/nginx/nginx.original /etc/nginx/nginx.conf

然后，我做了以下工作：

sudo su
echo > /etc/nginx/sites-available/load-balancer.conf

然后，我将以下内容添加到/etc/nginx/sites available/load-balancer.conf中

http {
  upstream backend {
    server docker-one.xxxxxxx.com;
    server docker-two.xxxxxxx.com;
  }

  server {
    listen 80;
    server_name load-balancer.xxxxxxx.com;
    location / {
      proxy_pass http://backend;
    }
  }
}

load-balancer.xxxxxx.com是我用于测试的域名，docker-one和docker-2是运行实际web应用程序的两个域。

然后我做了一个符号链接：

ln -s /etc/nginx/sites-available/load-balancer.conf /etc/nginx/sites-enabled/

然后我重新启动了服务器。当它重新启动时，我执行了以下操作：

sudo service nginx stop
sudo service nginx start

我收到一条错误消息，告诉我nginx服务失败，所以我这样做了：

systemctl status nginx.service

这给了我以下错误：

● nginx.service - A high performance web server and a reverse proxy server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Wed 2019-04-03 19:42:34 UTC; 19s ago
     Docs: man:nginx(8)
  Process: 1549 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=1/FAILURE)

Apr 03 19:42:34 load-balancer.xxxxxxx.com systemd[1]: Starting A high performance web server and a reverse proxy server...
Apr 03 19:42:34 load-balancer.xxxxxxx.com nginx[1549]: nginx: configuration file /etc/nginx/nginx.conf test failed
Apr 03 19:42:34 load-balancer.xxxxxxx.com systemd[1]: nginx.service: Control process exited, code=exited status=1
Apr 03 19:42:34 load-balancer.xxxxxxx.com systemd[1]: nginx.service: Failed with result 'exit-code'.
Apr 03 19:42:34 load-balancer.xxxxxxx.com systemd[1]: Failed to start A high performance web server and a reverse proxy server.

Answer 1

正在覆盖您删除的整个nginx.conf上下文。根据https://nginx.org/en/docs/http/ngx_http_upstream_module.html#upstream，仅允许在http {}块内上行

Debian/ubuntu使用/etc/nginx/ site -available/*进行站点定义，您需要在其中创建自己的配置文件，如果需要，每个vhost一个配置文件。然后启用它，这样它就会变成符号链接到/etc/nginx/sites enabled/*。或者，为简单起见，使用/etc/nginx/sites available/default作为现有配置文件，在其中进行更改。保存原始文件，直到你让它正常工作。并在所述更改之后重新加载nginx。当然，还要还原原始的/etc/nginx/nginx.conf。