Nginx Basics

Links: 112 Nginx Index

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NGINX Basics

Location of nginx configuration files in docker: /etc/nginx

Configuration file: nginx.conf

• The key value pairs in nginx are known as directives.
  • Directives must end with semicolon.
  • 

• The blocks of code in the curly braces is known as context.

  • Within the context we can have directives particular to that context.

• When we change nginx configuration we need to RELOAD it.

  • nginx -s reload
• Validating NGINX configuration files.
  • nginx -t

Variables

events {
}

http {
    server {
        listen 80;
        server_name nginx-handbook.test;
        return 200 "Host - $host\nURI - $uri\nArgs - $args\n";
    }
}

# output
# curl http://nginx-handbook.test/user?name=Farhan

# Host - nginx-handbook.test
# URI - /user
# Args - name=Farhan

Logging

• By default, NGINX's log files are located inside /var/log/nginx
• Any request to the server is logged by the acces.log file.
• We can have different access file names for different contexts.
• Example:

  events {}
  http {
      server {
          listen 80;
          server_name nginx-handbook.test;
  
          location / {
              return 200 "this will be logged to the default file.\n";
          }
  
          location = /admin {
              access_log /var/logs/nginx/admin.log;
              return 200 "this will be logged in a separate file.\n";
          }
  
          location = /no_logging {
              access_log off;
              return 200 "this will not be logged.\n";
          }
      }
  }
  

curl http://nginx-handbook.test/no_logging
# this will not be logged

sudo cat /var/log/nginx/access.log
# empty

curl http://nginx-handbook.test/admin
# this will be logged in a separate file.

sudo cat /var/log/nginx/access.log
# empty

sudo cat /var/log/nginx/admin.log 
# 192.168.20.20 - - [25/Apr/2021:11:13:53 +0000] "GET /admin HTTP/1.1" 200 40 "-" "curl/7.68.0"

curl  http://nginx-handbook.test/
# this will be logged to the default file.

sudo cat /var/log/nginx/access.log 
# 192.168.20.20 - - [25/Apr/2021:11:15:14 +0000] "GET / HTTP/1.1" 200 41 "-" "curl/7.68.0"

• The error.log file holds the failure logs.
  • To make an entry to the error.log, you'll have to make NGINX crash.

For some reason if you are not seeing logs use nginx -s reopen

Custom logging format

• Custom logging format can be defined only in the http directive

  events {
    worker_connections 768;
    # multi_accept on; 
  }
  
  http {
  
      log_format json_combined escape=json
        '{' 
          '"time_local":"$time_local",'
          '"remote_addr":"$remote_addr",'
          '"remote_user":"$remote_user",'
          '"request":"$request",'
          '"status": "$status",'
          '"body_bytes_sent":"$body_bytes_sent",'
          '"http_referrer":"$http_referer",'
          '"http_user_agent":"$http_user_agent",'
          '"request_time":"$request_time",'
          '"host": "$host", '
          '"request_method": "$request_method", '
          '"http_x_forwarded_for": "$http_x_forwarded_for", '
          '"http_cf_ray": "$http_cf_ray", '
          '"server_name": "$server_name", '
          '"upstream_address": "$upstream_addr", '
          '"upstream_status": "$upstream_status", '
          '"upstream_response_time": "$upstream_response_time", '
          '"request_uri": "$request_uri"'
        '}';
  
    server {
      listen 80; 
  
      location / { 
        access_log /test.log json_combined;
        proxy_pass http://localhost:3000/;
      }   
    }
  }
  

• NGINX Access & Error Logs Configuration: Logging Explained - Sematext

Nginx Performance

• A rule of thumb in determining the optimal number of worker processes is number of worker process = number of CPU cores.

  • Getting the number of CPU cores in linux nproc

• NGINX provides a better way to deal with this issue.

  • You can simply set the number of worker processes to auto and NGINX will set the number of processes based on the number of CPUs automatically. -worker_processes auto;

• Worker connection indicates the highest number of connections a single worker process can handle.

  • This can be found using ulimit -n

    events {
        worker_connections 1024;
    }
    

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Last updated: 2022-11-06