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# Nginx

NGINX is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server. NGINX is known for its high performance, stability, rich feature set, simple configuration, and low resource consumption

the nginx configuration file can be found in: /etc/nginx/nginx.conf

This file consists of:

-   directive: the option that consists of name and parameters; it should end with a semicolon
```nginx
gzip on;
```
-   context: the section where you can declare directives (similar to scope in programming languages)
```nginx
worker_processes 2; # directive in global context
http {              # http context
    gzip on;        # directive in http context
    server {          # server context
      listen 80;      # directive in server context
  }
}
```

## Processing requests

Inside nginx, you can specify multiple virtual servers, each described by a `server { }` context.

```nginx
server {
  listen      *:80 default_server;
  server_name netguru.co;
  return 200 "Hello from netguru.co";
}

server {
  listen      *:80;
  server_name foo.co;
  return 200 "Hello from foo.co";
}

server {
  listen      *:81;
  server_name bar.co;
  return 200 "Hello from bar.co";
}
```
Nginx will first check the `listen` directive to test which virtual server is listening on the given IP:port combination. 
Then, the value from `server_name` directive is tested against the `Host` header, which stores the domain name of the server.

Nginx will choose the virtual server in the following order:

1.  Server listing on IP:port, with a matching  `server_name`  directive;
2.  Server listing on IP:port, with the `default_server`  flag;
3.  Server listing on IP:port, first one defined;
4.  If there are no matches, refuse the connection.

#### server_name directive
```
server_name netguru.co www.netguru.co; # exact match
server_name *.netguru.co;              # wildcard matching
server_name netguru.*;                 # wildcard matching
server_name  ~^[0-9]*\.netguru\.co$;   # regexp matching
```

#### Gzip

Enabling  `gzip`  should significantly reduce the weight of your response, thus it will appear faster on the client side.


#### SSL and TLS

SSL (standing for Socket Secure Layer) is a protocol providing a secure connection over HTTP.
Technically SSL and TLS are different (as each is describing the different version of a protocol) - but many use those names interchangeably.

##### Base SSL/TLS setup
```nginx
server {
  listen 443 ssl default_server;
  listen [::]:443 ssl default_server;

  ssl_certificate /etc/nginx/ssl/netguru.crt;
  ssl_certificate_key /etc/nginx/ssl/netguru.key;
}
```
![enter image description here](http://bartoz.no-ip.org/wp-content/uploads/2014/10/TLS-client-server1.jpg)

### Reverse proxy
A reverse proxy is an intermediary proxy service which takes a client request, passes it on to one or more servers, and subsequently delivers the server’s response to the client.
Benefits:
- Load Balancing
- Increases security
- Easy loggin and auditing

https://medium.com/@mohsin061/forward-proxy-and-reverse-proxy-500b9bd4bf8e

### PHP

PHP-FPM

```nginx
  location ~* \.php$ {
        fastcgi_pass unix:/run/php/php7.0-fpm.sock;      
  }
```
    #fastcgi_pass   127.0.0.1:9000; #tcp connection
    #fastcgi_pass   unix:/tmp/php5-fpm.sock; #unix socket
    
Using a socket (e.g. listen = '/tmp/php-fpm.sock') makes sense when both the front-end (e.g. Nginx) and php-fpm are in the same box and


C10K problem is referred for the network socket unable to handle a large number of client (10,000) at the same time.

![enter image description here](https://i.stack.imgur.com/bvJHw.png)
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