NGINX Introduction

What is NGINX?

• NGINX was initially launched as open source high performant webserver.
• since then NGINX has been matured and now widely serve as load balancer, reverse proxy, http caching, etc.

Why NGINX?

• delivers high performance, handles massive concurrent connections, and consumes minimal memory compared to traditional web servers.
• NGINX is fast primarily because of its asynchronous, event-driven architecture.
• unlike traditional web servers that create a new process or thread for every single user connection, NGINX handles thousands of connections concurrently within a very small number of fixed worker processes.
• NGINX is very easy to configure which makes it popular in K8s space too.

Notes

• nginx has one master process and several worker processes -> pgrep -a nginx

  3656 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
  3657 nginx: worker process
  3658 nginx: worker process
  3659 nginx: worker process
  3660 nginx: worker process
  3661 nginx: worker process
  3663 nginx: worker process
• master process reads and evaluates the configuration and also manages worker processes
• workder process does the actual processing of requests
• the requests are distributed efficiently among workers using event-based model and OS dependent mechanisms
• the number of workers can be set fixed in config file OR can also be dynamic based on available CPU cores which is managed by worker_processes module

Basic Tasks

The general syntax for nginx is:

nginx -s <signal>

nginx -t can be used to validate syntax of configuration files.

About nginx -s reload

• changes made to configuration files won’t be applied unless NGINX is reloaded
• whenever you make changes, nginx -s reload should be used
• when reload signal is received by NGINX, it checks syntax and everything else and tries to apply the new configuration
• if it succeeds, master process starts new worker processes and asks the old processes to stop serving (not shutdown immediately)
• old worker processes are not shutdown immediately, they just stops getting new requests but keep serving current requests and exit once all pending requests are served which is similar to graceful shutdown
• when NGINX is unable to apply new configuration, it rolls back and keep serving with the same old configuration

Process Files and Killing NGINX

• master process pid file is nginx.pid which can be at /usr/local/nginx/local directory or /var/run directory depending on OS and configuration
• you can use this pid file to directly kill NGINX master process as:

kill -s QUIT $(cat /var/run/nginx.pid)

• you can also use pgrep nginx | head -1 to get master process’ pid
• ps -ax | grep [n]ginx can be also used to get master and worker processes’ pid however pgrep nginx is modern way of greping pids

About Config Files

• config file is generally named as nginx.conf and can be found inside -> /etc/nginx, /usr/local/nginx/conf, /usr/local/etc/nginx depending on implementation
• NGINX has several modules which are controlled by directives inside the config file
• directives can be simple or block directives
• simple directive anatomy -> simple_directive param1 param2 paramN;
• block directive anatomy:

  block_directive {
      simple_directive param1 param2 paramN;
      ...
      another_block_directive {
          ...
      }
      ...
  }
• for example: root, listen, etc. are simple directives whereas server, location, etc. are block directives
• directives inside block directives are known as contexts
• directives in config file outside of any contexts are main directives
• for example: events and http directives reside in main context whereas server resides inside http and location resides inside server forming nested contexts:

  http {
      ...
      server {
          ...
          location {
              ...
          }
          ...
      }
      ...
  }

HTTP Status Code Quick Reference Table

The most important ones to remember

For everyday web development and troubleshooting, these are the ones you’ll encounter most often:

A useful way to remember the categories:

1xx = “I’m working on it”
2xx = “It worked”
3xx = “Go somewhere else / use something else”
4xx = “Your request has a problem”
5xx = “The server has a problem”

References

NGINX Beginners Guide -> https://nginx.org/en/docs/beginners_guide.html