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High CPU usage by Nginx is shown in Health Monitor

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Ivan Kamnev
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Plesk Onyx for Linux kb: technical ABT: Group B

Applicable to:

  • Plesk Onyx for Linux

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

Comments

6 comments

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  • Avatar
    Pitt Hitt

    nothing changed for me

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  • Avatar
    Ivan Kamnev

    Hello Pitt Hitt,

    In case the issue persists after applying the steps above, could you please submit a request to Plesk support that we can check this case

     

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  • Avatar
    Ananda

    I have the same problem, and nothing changed after increasing it... is there any other solution for this problem?

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  • Avatar
    Andrey Fedorov (Edited )

    Try this:

    sudo nano /lib/systemd/system/nginx.service

    #ExecStop=-/sbin/start-stop-daemon --quiet --stop --retry QUIT/5 --pidfile /run/nginx.pid 
    ExecStop=-/sbin/start-stop-daemon --quiet --stop --retry QUIT/5/TERM/5/KILL/5 --pidfile /run/nginx.pid

    sudo systemctl daemon-reload

    sudo service nginx restart

     

    Also add to nginx.conf:

    worker_shutdown_timeout 5

    (or 10/15...)

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  • Avatar
    Christopher Mulholland

    Nothing changes after updating worker process in nginx.conf file

    The updated nginx.conf file shows 

    events {

        worker_connections  6144;

    }

    If i run 

    ulimit -n

    Output still shows 1024

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  • Avatar
    Ivan Kamnev

    Hello @Christopher Mulholland,

    The "ulimit -n" command shows the configured limit for open files, it is not related to the worker_connections Nginx directive. 

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