Introduction to Nginx

Sidharth KhattriSr. Software ConsultantKnoldus Software

What is Nginx

Why use Nginx

Installing/running Nginx

Nginx process model

High availability

Understanding configurations

Agenda

What is Nginx

Pronounced as Engine X

Open source web and reverse proxy server

High performance HTTP, HTTPS, SMTP, IMAP,
POP3 server

Load balancing and HTTP caching

Asynchronous event-driven architecture

Web server

Created by Ignor Sysoev in 2002 to address C10K problem

Who uses Nginx

Why use Nginx

Lightweight with small memory footprint

Uses predictable memory under load

Provides high level of concurrency

Serves static content quickly

Handles connections asynchronously

Uses single thread

Draw comparisons between request/thread

Take a scenario in which a server on a URL transmits 100KB of information almost immediately. On client side the connection is relatively slow, let's say 10 KB/s. now it'd take approx 10 seconds for a client to get this 100KB of data and during this time the connection is still alive. Now image if each connection uses 1 MB of memory on the web server, for 1000 clients it'd be using 1000 MB (almost 1 GB) of memory which is a lot !! So a web server software should be able to scale non-linearly with growing number of simultaneous connections.

Installing Nginx

Add stable Nginx repository
sudo add-apt-repository ppa:nginx/stable

Update repositories
sudo apt-get update

Installing NGINX
sudo apt-get install nginx

Ppa personal package archives

Starting/restarting Nginx

Check that Nginx is running
sudo service nginx status

Starting, stopping and restarting Nginx
sudo service nginx start
sudo service nginx stop
sudo service nginx restart

Nginx Process Model

Master process

Reads & validates configurations

Creates and binds sockets

Creates child processes

Cache loader loads cache in memory

Cache manager prunes cache periodically

Worker processes handles connections, IO and
communicate to upstream server

Master process initializes worker process with nginx configurations

ps -ef --forest | grep nginxps (PROCESS STATUS)-e displays all processes-f adds full details--forest displays hierarchy

Child process

Child process

Worker is single threaded

One worker process per CPU core
# directive worker_processes auto;

Communicate with each other using shared memory

Handles multiple connections asynchronously

Polls for events on listen & connection sockets

New incoming connections trigger events

Each new connection creates a new file descriptor and uses small amount of memory

State machine is a set of instructions that tell NGINX how to process a request

Connections are processed in a highly efficient run-loop in a limited number of single-threaded processes called workers. Within each worker nginx can handle many thousands of concurrent connections and requests per second.

Child process

Events on listen sockets start a new connection

Events on connection socket handles subsequent
requests

Connections are submitted to state machine
HTTP Stream Mail (SMTP, IMAP and POP3)

High availability

High availability

As simple as doing nginx -s reload
-s sends signal to master process

A small CPU spike

Nginx conf

main context

events context

http context

server context
(nested context)

Areas within {} are called contexts

Directive can only be used in the contexts which they are designed for

Events context contains directives that define how work processes should handle connections. Connection processing method is automatically selected based on the most efficient one available for the platform. Linux - epoll

worker_connections sets the maximum number of simultaneous connections what can be opened by a worker process. Note that this should not exceed the maximum number of open files limit

sendfile copies data directly from one file descriptor to another removing the need to copy data from file descriptor to buffer, helps in serving static files

tcp_nodelay disables nagles algorithm. Nginx uses tcp_nodelay on keepalive connections

tcp_nopush which activates tcp_cork on linux blocks until packet reaches a minimum size before sending

Server configurations

Areas within {} are called contexts

Directive can only be used in the contexts which they are designed for

Events context contains directives that define how work processes should handle connections. Connection processing method is automatically selected based on the most efficient one available for the platform. Linux - epoll

worker_connections sets the maximum number of simultaneous connections what can be opened by a worker process. Note that this should not exceed the maximum number of open files limit

sendfile copies data directly from one file descriptor to another removing the need to copy data from file descriptor to buffer, helps in serving static files

tcp_nodelay disables nagles algorithm. Nginx uses tcp_nodelay on keepalive connections

tcp_nopush which activates tcp_cork on linux blocks until packet reaches a minimum size before sending

References

https://www.nginx.com/blog/inside-nginx-how-we-designed-for-performance-scale/

https://t37.net/nginx-optimization-understanding-sendfile-tcp_nodelay-and-tcp_nopush.html

Thank You