110 nginx timeout_error ai_generated true

upstream timed out (110: Connection timed out) while connecting to upstream, client: 10.0.0.1, server: example.com, upstream: "http://127.0.0.1:8080"

ID: nginx/upstream-timed-out-110-connection-timed-out-while-connecting-to-upstream

Also available as: JSON · Markdown · 中文

85%Fix Rate

85%Confidence

1Evidence

2023-10-05First Seen

Version Compatibility

Version	Status	Introduced	Deprecated	Notes
nginx 1.24.0	active	—	—	—
nginx 1.22.1	active	—	—	—
nginx 1.20.2	active	—	—	—
nginx 1.18.0	active	—	—	—

Root Cause

Nginx cannot establish a TCP connection to the upstream server because the server is unreachable, firewalled, or overloaded, causing the connection attempt to exceed the proxy_connect_timeout.

generic

中文

Nginx 无法与上游服务器建立 TCP 连接，因为服务器不可达、被防火墙阻止或过载，导致连接尝试超过 proxy_connect_timeout。

Official Documentation

https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_connect_timeout

Workarounds

80% success Increase proxy_connect_timeout to allow more time for connection: proxy_connect_timeout 30s; Also verify upstream reachability: telnet 127.0.0.1 8080 Check firewall rules: iptables -L -n | grep 8080
```
Increase proxy_connect_timeout to allow more time for connection:
proxy_connect_timeout 30s;
Also verify upstream reachability: telnet 127.0.0.1 8080
Check firewall rules: iptables -L -n | grep 8080
```
75% success Add upstream server health checks and remove unhealthy servers: upstream backend { server 127.0.0.1:8080 max_fails=3 fail_timeout=30s; server 10.0.0.2:8080 backup; } This allows nginx to skip unresponsive servers.
```
Add upstream server health checks and remove unhealthy servers:
upstream backend {
    server 127.0.0.1:8080 max_fails=3 fail_timeout=30s;
    server 10.0.0.2:8080 backup;
}
This allows nginx to skip unresponsive servers.
```
90% success Check if the upstream server is running and listening: systemctl status myapp netstat -tlnp | grep 8080 Restart the upstream service if needed.
```
Check if the upstream server is running and listening:
systemctl status myapp
netstat -tlnp | grep 8080
Restart the upstream service if needed.
```

中文步骤

增加 proxy_connect_timeout 以允许更多连接时间：
proxy_connect_timeout 30s;
同时验证上游可达性：telnet 127.0.0.1 8080
检查防火墙规则：iptables -L -n | grep 8080

添加上游服务器健康检查并移除不健康的服务器：
upstream backend {
    server 127.0.0.1:8080 max_fails=3 fail_timeout=30s;
    server 10.0.0.2:8080 backup;
}
这允许 nginx 跳过无响应的服务器。

检查上游服务器是否正在运行并监听：
systemctl status myapp
netstat -tlnp | grep 8080
如有必要，重新启动上游服务。

Dead Ends

Common approaches that don't work:

60% fail
The timeout occurs during the TCP handshake, not during data transfer; these settings do not affect connect timeout.
40% fail
The error is at the transport layer; protocol version is irrelevant.
30% fail
Keepalive only helps after a connection is established; it does not prevent connection timeouts.