Nginx作为Grafana反向代理时出现Bad Gateway错误求助（附配置及错误日志）

Alright, let's tackle that frustrating 502 error you're seeing. The connect() failed (111 connection refused) log entry tells us exactly what's going wrong: Nginx can't establish a connection to your Grafana instance running on port 8080. Let's walk through the most likely fixes step by step.

1. Verify Grafana's Protocol & Listener First #

The biggest red flag here is your Nginx config using https://localhost:8080 as the upstream, but default Grafana installs use HTTP, not HTTPS, by default.

• Test if you can reach Grafana directly from the server:

  # Try HTTP first (default)
  curl -I http://localhost:8080
  # Then try HTTPS if the above fails
  curl -I https://localhost:8080 --insecure
  

  If the HTTP request works but HTTPS doesn't, that's your issue. Update your Nginx proxy_pass lines to use http://localhost:8080 instead of https://.

• Double-check Grafana's config file (usually /etc/grafana/grafana.ini) in the [server] section:

  • Ensure http_port = 8080 matches what you're targeting
  • Check protocol = http (if you haven't explicitly enabled Grafana's SSL, this will be the default)

2. Check Firewall/SELinux Restrictions #

Even if Grafana is running, your server's security tools might be blocking Nginx from accessing port 8080:

• Firewall: Verify port 8080 allows local connections. For firewalld:

  firewall-cmd --add-port=8080/tcp --permanent
  firewall-cmd --reload
  

  For iptables, ensure there's no rule dropping traffic to 127.0.0.1:8080.

• SELinux: By default, SELinux prevents Nginx from making outgoing network connections. Fix this with:

  setsebool -P httpd_can_network_connect 1
  

3. Confirm Grafana's Listening Address #

Sometimes Grafana is configured to only listen on a specific IP, not localhost or all interfaces:

• In grafana.ini, check the http_addr setting. If it's set to something other than 127.0.0.1 or 0.0.0.0, update it to 127.0.0.1 (for local access only) or 0.0.0.0 (to allow all interfaces). Then restart Grafana:

  systemctl restart grafana-server
  

4. Fix Nginx Config Syntax & Path Issues #

Your config has two small but important issues that could cause problems even after fixing the connection:

• Wrong quotes: The line proxy_set_header Connection “Upgrade”; uses Chinese double quotes instead of English ones. Replace them with standard quotes:

  proxy_set_header Connection "Upgrade";
  

• Incorrect proxy_pass path for /api/live: Right now, your /api/live location proxies to https://localhost:8080/, which strips the /api/live path. Update it to preserve the path:

  location /api/live {
      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection "Upgrade";
      proxy_set_header Host $http_host;
      proxy_pass https://localhost:8080; # Remove the trailing slash to keep the path
  }
  

After making these changes, restart Nginx to apply them:

systemctl restart nginx

内容的提问来源于stack exchange，提问作者Mohamed Emad