Learn NGINX: Basics and Examples

What is NGINX?

it is high performance web server used to serve static files like http and it also act as Reverse proxy, load balancer, http caching etc

Why nginx, not httpd ?

nginx is event driven architecture and httpd is thread based architecture
nginx is simple and high performance
low memory usage - become a choice for cloud native application
Serves the static content very fast

Use official documentation to install nginx in your OS.

NGINX and webserver

webserver means is servers the static content that present in the file like html etc

  cd /etc/nginx #all nginx config files are present
  cd site-available/ #where we can add domain configuration files

in site-available we can add domain specific configuration and if you need all site’s to be served in single domain we can use default file in that folder
to create to domain specific file like example.com in the file update the configurations same as present in default file with different port number or root location and path to be servers etc
after that we need to create symlink file in system enabled to serve that configuration file
nginx.conf is the default config of nginx peferred to use the same if required we can modify as we required

NGINX as Reverse Proxy

After deploying the application and you provide the ip address of the application for accessing it, for that other then you client someone try to access it and may do some DDoS attack, can exceed rate limiting or may do vulnerability attack on your application so to avoiding that we need to handle all things in the application only (which is impossible due to some reasons) or they can use Reverse proxy where client send the requests to reverse proxy instead of directly accessing the application they access the reverse proxy(nginx) that will forward our requests to application
Reverse proxy like nginx have advance capability to avoid DDoS attack by adding rate limiting, nginx can also implement WAF (web accessibility firewall), security related features like TLS, SSL. These are the in-built features in nginx so that it enough to develop only application from the developers

Now let take simple node backend and add a nginx reverse proxy to it

Install the node and npm in the machine
and create a folder and create a server.js file init and add the below content inti

  const http = require('http');
  http.createServer((req, res) => {
    res.end('Hello from Node.js backend!');
  }).listen(3000);

  node server.js #it will run the server and you can access the backed in port 3000

Now we can setup the reverse proxy
So, now go to folder /etc/nginx/sites-available/
edit the default file using vim editor (any other) and add the below code in location section

  location / {
      proxy_pass http://localhost:3000; #forward the request for path / to the provide address
      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
  }

  sudo nginx -t #check the syntax error , id there is no error it will return OK
  sudo systemctl reload nginx #it will reload the nginx server

after all you can access the backed directly on IP no required of port
and make sure you are running the backed if not you will get “Bad Gateway” error

NGINX as Load Balancer

It is the process of distributing incoming traffic across the multiple servers
Nginx will deal with multiple type of load balancer like round robin, weight based balancing, particular request based routing (IP based/ customer based)
Steps to make nginx as load balancer as well as reverse proxy
- Edit the default file present in /etc/nginx/site-available/ folder. Add the below code just before the server block
```
  upstream backend_app { #this is the block where you can add many servers that the traffic need to be forwarded
      server 127.0.0.1:3001 ;
      server 127.0.0.1:3002 ;
  }
```
- And change the proxy_pass address to the name of the upstream
```
  location / {
      proxy_pass http://backend_app; #replace with upstream name
      proxy_set_header X-Real-IP $remote_addr;
  }
```
- Now check the syntax and reload the nginx server
- before testing run the application in both the port mentioned in upstream. you can run multiple servers by duplicating the same folder and change the port then run them with & symbol at last like below
```
  node server.js & #in 3001 port app folder
  node server.js & #in 3002 port app folder
```
- Now you can test the application

Different type of load balancer

If we didn’t specify it then it is Round Robin Load balancing

to change you can add extra line in upstream block as below

  upstream backend_app { #this is the block where you can add many servers that the traffic need to be forwarded
      least_conn; #load balancing type least connection
      server 127.0.0.1:3001 ;
      server 127.0.0.1:3002 ;
  }

  upstream backend_app { #this is the block where you can add many servers that the traffic need to be forwarded
      ip_hash; #load balancing type ip hash -> similar to sticky sesssion
      server 127.0.0.1:3001 ;
      server 127.0.0.1:3002 ;
  }

NGINX with SSL or TLS (using self signed certificate)

Self signed certificate only works on the machine where it is created or else you need to provide the certificate explicitly to open it in https
Let create a certificate using openssl use below command
```
  sudo openssl req -x509 -nodes -days 365 \
   -newkey rsa:2048 \
   -keyout /etc/ssl/private/nginx-selfsigned.key \
   -out /etc/ssl/certs/nginx-selfsigned.crt
```
the above command says that self signed certificate expires in 365 days & encryption type is RSA & location of the private key & location of the certificate
The above command will ask some random questions fill them as below
where ever it ask for the common name please provide answer as localhost , you can change other questions as your requirement

After that add the below code in default file present in /etc/nginx/site-available/ folder

  server {     
          #add the below config above the location block   
          listen 443 ssl ;
          server_name localhost;
          ssl_certificate /etc/ssl/certs/nginx-selfsigned.crt;
          ssl_certificate_key /etc/ssl/private/nginx-selfsigned.key;
  }

  # Optional: Redirect HTTP to HTTPS
  server {
      listen 80;
      server_name localhost;
      return 301 https://$host$request_uri;
  }

So, you can test it only on your machine using curl https://localhost -k provide -k option or else it will ask you to provide the key for verification

NGINX basics with examples