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Website configured in Plesk sometimes inaccessible via HTTPS: SSL handshake failed

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Vladimir Chernikov
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Plesk for Linux kb: technical ABT: Group A

Applicable to:

  • Plesk for Linux

Symptoms

  • Under some load website configured in Plesk cannot be accessed;

  • Domains > example.com > Hosting Settings > Permanent SEO-safe 301 redirect from HTTP to HTTPS is enabled:
    Screenshot-2018-5-14_Hosting_Settings_for_example_com_-_Plesk_Onyx_17_8_11.png

  • Running stress-tests shows that server closes connection before completing the answer:

    # ab -c 400 -n 8000 -H "Host: example.com" -f TLS1.2 https://example.com:443/
    <...>
    SSL handshake failed (5).
    SSL handshake failed (5).
    SSL handshake failed (5).
    <...>
    Complete requests: 8000
    Failed requests: 4968

  • Failed requests are not written to any log file in /var/www/vhosts/system/example.com/logs/ directory

Cause

nginx cannot handle all connections and abruptly finishes some of them in the middle of TLS handshake

  • There is only one nginx worker:

    # grep worker_processes /etc/nginx/nginx.conf
    worker_processes 1;

Resolution

  1. Connect to the server via SSH;

  2. Open /etc/nginx/nginx.conf in any text editor and set worker_processes value as below:

    # grep worker_processes /etc/nginx/nginx.conf
    worker_processes auto;

    Note: When the value is set to auto, then nginx will automatically increase and decrease worker quantity according to server load.

  3. Test that configuration in correct:

    # nginx -t
    nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
    nginx: configuration file /etc/nginx/nginx.conf test is successful

  4. Reload the configuration:

    # service nginx reload

    Note: For further TLS optimization refer to the official nginx documentation.

Comments

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    Anthony (Edited )

    I tried the following command solved the problem partially but got a "ssl_stapling" error:

    sudo nginx -t

    nginx: [warn] "ssl_stapling" ignored, issuer certificate not found for certificate "/opt/psa/var/certificates/scfJGs3N7"

    nginx: the configuration file /etc/nginx/nginx.conf syntax is ok

    nginx: configuration file /etc/nginx/nginx.conf test is successful 

     

     

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