當Nginx出現“Too many open files”錯誤時，通常是因為系統(tǒng)或進程達到了文件描述符限制。解決方法包括：1. 提高Linux系統(tǒng)的軟硬限制，在/etc/security/limits.conf中設置nginx或運行用戶的相關參數；2. 調整Nginx的worker_connections值以適應預期流量，並確保重載配置；3. 增加系統(tǒng)級文件描述符上限fs.file-max，編輯/etc/sysctl.conf並應用更改；4. 優(yōu)化日誌和資源使用，減少不必要的文件句柄佔用，例如使用open_log_file_cache、合併日誌、避免冗餘代理連接等。完成調整後，可通過lsof命令監(jiān)控實際打開的文件數。

When Nginx throws a “Too many open files” error, it usually means the system or process has hit its file descriptor limit. This can lead to failed connections, stalled services, or even crashes if not addressed.

Here's what typically causes this issue and how to handle it.

1. File Descriptor Limits in Linux

Linux systems impose limits on the number of file descriptors (FDs) that a process can open. These limits come in two flavors: soft and hard.

• Soft limit – What the process is currently allowed to use.
• Hard limit – The maximum value the soft limit can be raised to.

If Nginx reaches the soft limit, you'll see the “Too many open files” message in the logs. You can check current limits using:

 ulimit -n

To increase the limit, edit /etc/security/limits.conf and add:

 nginx soft nofile 65536
nginx hard nofile 65536

Or for the user running Nginx:

 www-data soft nofile 65536
www-data hard nofile 65536

Also make sure pam_limits.so is enabled in your PAM config so these settings are applied at login.

2. Nginx Worker Connections Setting

In nginx.conf , there's a directive called worker_connections . It defines how many simultaneous connections each worker process can handle.

This line might look like:

 events {
    worker_connections 1024;
}

Each connection uses at least one file descriptor — sometimes more if SSL or upstream connections are involved.

So if you're handling thousands of concurrent users, the default 1024 may be too low.

You should:

• Estimate your expected traffic.
• Multiply by the average FDs per connection (often 2–4).
• Set worker_connections higher than that.

Don't forget to reload Nginx after changing this:

 nginx -s reload

Also keep an eye on the total number of worker processes multiplied by worker_connections , because that gives you the total max connections across all workers.

3. System-wide File Descriptor Cap

Even if you configure Nginx and user limits correctly, the entire system also has a global FD cap controlled by fs.file-max .

Check current value with:

 cat /proc/sys/fs/file-max

If it's low, raise it by editing /etc/sysctl.conf :

 fs.file-max = 2097152

Then apply changes:

 sysctl -p

This step is often overlooked but essential under high load. Think of it as the ceiling for all processes combined — including Nginx, PHP, MySQL, etc.

4. Open Log Files and Unused Resources

Every access log, error log, or upstream connection Nginx opens consumes a file descriptor.

If you have dozens of virtual hosts, each writing to separate logs, those add up fast.

Some things to consider:

• Use open_log_file_cache to reduce overhead.
• Consolidate logs where possible.
• Avoid unnecessary upstream blocks or proxy connections.

Also, some modules or misconfigured third-party integrations might leak FDs over time — especially if they don't close upstream connections properly.

Basically, the "Too many open files" error comes down to limits being too low for the workload. Check ulimits, tweak worker_connections , raise system-wide caps, and minimize unnecessary file handles. Once configured, monitor with tools like lsof -p $(pidof nginx) to see what's actually open.

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