NGINX工作过程和连接

设置 worker_processes 为 auto（即 CPU 核心数）以充分利用多核性能；2. 根据系统文件描述符限制和预期流量设置 worker_connections（如 1024 或更高），确保 ulimit -n 足够大；3. 最大并发连接数 = worker_processes × worker_connections，合理配置可支持数千至数万连接，避免瓶颈，提升 Nginx 生产环境性能。

When setting up Nginx for production use, two key directives—worker_processes and worker_connections—directly impact performance, scalability, and how efficiently Nginx handles traffic. Here's what you need to know:

✅ What Are worker_processes and worker_connections?

• worker_processes:
  This tells Nginx how many worker processes to run. Each process is a separate instance that handles requests independently (leveraging multiple CPU cores).

• worker_connections:
  This sets the maximum number of simultaneous connections each worker process can handle.

  

Together, they define Nginx’s total connection capacity:

Max clients = worker_processes × worker_connections

? How to Set worker_processes

Best Practice:
Set this equal to the number of CPU cores on your server.

• Auto-detect (recommended):

  worker_processes auto;

  Nginx will automatically match the number of available CPU cores—simple and effective.

• Manual (if needed):

  worker_processes 4;  # for a 4-core CPU

? Why not more than CPU cores?
Extra processes won’t improve performance and may cause overhead due to context switching.

? How to Set worker_connections

This depends on your expected traffic and system limits.

• Example:

  events {
      worker_connections 1024;
  }

• Check system limits first: Run:

  ulimit -n

  If this is less than worker_connections × worker_processes, you’ll hit errors.
  To increase it temporarily:

  ulimit -n 4096

• Also update /etc/security/limits.conf for persistence:

  * soft nofile 65536
  * hard nofile 65536

⚠️ Each connection (client → Nginx) uses one file descriptor. If you proxy to upstream servers, each connection to the backend also counts—so plan for more than just client connections.

? Real-World Example

Say you have:

• 4 CPU cores
• Each worker handles 1024 connections

Then:

Max concurrent connections = 4 × 1024 = 4096

That’s enough for moderate traffic. For high-traffic sites, scale up:

worker_processes auto;
events {
    worker_connections 4096;
}

→ Supports ~8K–16K connections depending on CPU count.

✅ Quick Tips

• Always test with nginx -t before reloading.
• Monitor with htop or top to see if workers are under-utilized or maxed out.
• Use ab or wrk to simulate load and verify limits.
• Don’t forget to adjust keepalive_timeout and enable keepalive for upstreams to reduce connection churn.

Basically, set worker_processes auto, tune worker_connections based on your traffic and system limits, and monitor. It’s not complex—but getting it right avoids bottlenecks early.

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