title: Load balancer on Nginx give 502 Bad Gateway
body: <p>I'm trying to configure Nginx server as a load balancer. I set up VM with CentOS 7. I disable Firewall (for the sake of the test), install Nginx using yum (custom .repo). I'm running my 3 SpringBoot restApi Apps on ports 8081, 8082 and 8083 and start Nginx but when I try to connect with load balancer I get 502 Bad Gateway (on VM host machine and on VM machine also).I can get a response from each of App but not from load balancer. </p>
  
  <p><strong>My conf file :</strong></p>
  
  <pre><code>user  nginx;
  worker_processes  auto;
  
  error_log  /var/log/nginx/error.log warn;
  pid        /var/run/nginx.pid;
  
  events {
      worker_connections  1024;
  }
  
  
  http {
  
  upstream test1 {
      server 127.0.0.1:8081;
      server 127.0.0.1:8082;
      server 127.0.0.1:8083;
  }
  
  server {
  
      listen 8090;
      access_log /var/log/nginx/http_redirect.log;
      location / {
  
               proxy_pass http://test1;
                  }
  }
  
      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;
  }
  </code></pre>
  
  <p><strong>http_redirect.log:</strong></p>
  
  <pre><code>192.168.70.1 - - [01/Apr/2018:08:10:02 -0400] "GET /favicon.ico HTTP/1.1" 502 575 "http://192.168.70.4:8090/api/prime/100" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36"
  192.168.70.1 - - [01/Apr/2018:08:10:03 -0400] "GET /api/prime/100 HTTP/1.1" 502 575 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36"
  192.168.70.1 - - [01/Apr/2018:08:10:04 -0400] "GET /api/prime/100 HTTP/1.1" 502 575 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36"
  192.168.70.1 - - [01/Apr/2018:08:10:04 -0400] "GET /favicon.ico HTTP/1.1" 502 575 "http://192.168.70.4:8090/api/prime/100" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36"
  </code></pre>
  
  <p><strong>error.log</strong></p>
  
  <pre><code>2018/04/01 06:37:16 [crit] 2549#2549: *10 connect() to 127.0.0.1:8083 failed (13: Permission denied) while connecting to upstream, client: 192.168.70.1, server: localhost, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8083/", host: "192.168.70.4"
  2018/04/01 06:37:16 [warn] 2549#2549: *10 upstream server temporarily disabled while connecting to upstream, client: 192.168.70.1, server: localhost, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8083/", host: "192.168.70.4"
  2018/04/01 06:37:16 [crit] 2549#2549: *10 connect() to 127.0.0.1:8081 failed (13: Permission denied) while connecting to upstream, client: 192.168.70.1, server: localhost, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8081/", host: "192.168.70.4"
  2018/04/01 06:37:16 [warn] 2549#2549: *10 upstream server temporarily disabled while connecting to upstream, client: 192.168.70.1, server: localhost, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8081/", host: "192.168.70.4"
  2018/04/01 06:37:16 [crit] 2549#2549: *10 connect() to 127.0.0.1:8082 failed (13: Permission denied) while connecting to upstream, client: 192.168.70.1, server: localhost, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8082/", host: "192.168.70.4"
  2018/04/01 06:37:16 [warn] 2549#2549: *10 upstream server temporarily disabled while connecting to upstream, client: 192.168.70.1, server: localhost, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8082/", host: "192.168.70.4"
  </code></pre>