High CPU usage by Nginx is shown in Health Monitor

Symptoms

• The high CPU usage by Nginx can be found in Plesk > Health Monitoring.
• Many Nginx processes as below can be found on the server:
  

  # top -c
  19296 nginx 20 0 318720 223848 2212 S 0.3 2.1 0:00.23 nginx: worker process

  ---

  # top -c 
  19289 nginx 20 0 318720 223848 2212 S 0.3 2.1 0:00.23 nginx: worker process is shutting down

Cause

Incorrect value of worker_connections directive.

Resolution

1. Log into the server via SSH.

2. Create a backup for Nginx configuration file:

   # cp /etc/nginx/nginx.conf{,.orig}

3. Get the number of CPU cores (in the example below this value is equal to 4):
   

   # cat /proc/cpuinfo | grep processor | wc -l
   4

4. Using the vi text editor open the/etc/nginx/nginx.conf file and change the value for theworker_connections equals to 1024 * number of CPU cores:

   CONFIG_TEXT: worker_connections 4096;

5. Restart the Nginx service to apply changes:

   # service nginx restart