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Mail stuck in the queue in the server with Plesk: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (13)

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Benjamin Weßel
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Plesk for Linux kb: technical ext: pes ABT: Group A

Applicable to:

  • Plesk for Linux

Symptoms

  • E-Mails are stuck in the queue with below messages in /var/log/maillog:

    amavis[26892]: (26892-01) (!)connect_to_sql: unable to connect to DSN 'DBI:mysql:database=emailsecurity;host=localhost;port=3306': Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (13)
    amavis[26892]: (26892-01) (!!)TROUBLE in process_request: connect_to_sql: unable to connect to any dataset at (eval 132) line 253.
    amavis[26892]: (26892-01) (!)Requesting process rundown after fatal error

  • MariaDB upgrade has been performed recently on the server with SELinux enabled

Cause

MariaDB bug #MDEV-24941: SElinux incorrect label for server socket.

The SELinux context for the MariaDB socket file /var/lib/mysql/mysql.sock has been lost because of the above because of upgrade to MariaDB version affected by the bug.

Resolution

To workaround the problem until the bug is resolved apply the following steps:

  1. Connect to the server via SSH

Warning: On applying the following step the database server MariaDB will be restarted, which leads to a short inaccessibility of other Plesk related services and websites accessing the database

  1. Run the following command:

    # printf '%s\n' '[Service]' 'ExecStartPost=/sbin/restorecon /var/lib/mysql/mysql.sock' > /etc/systemd/system/mariadb.service.d/restorecon_socket.conf && systemctl daemon-reload && systemctl restart mariadb

  2. Resend the stuck e-mails

The following alternative workarounds are also available:

Comments

5 comments

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  • Avatar
    Jon Ireland

    I get the following error with this work around any ideas?

    Task "/usr/sbin/restorecon -v /var/lib/mysql/mysql.sock​" completed with error in 0 seconds, output:
    /usr/sbin/restorecon: lstat(/var/lib/mysql/mysql.sock​) failed: No such file or directory
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  • Avatar
    Md Rasel Khan

    Number 5 step should I run one time right? No need to set cron job for this, right?

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  • Avatar
    Mikhail Krivoshein

    The issue is still open. Just faced on AlmaLinux host.

    First of all, to verify if you suffer from this problem, run:

    ls -Zl /var/lib/mysql/*sock

    If you see anything other than the line below, you probably experience this issue exactly.

    srwxrwxrwx. 1 mysql mysql system_u:object_r:mysqld_var_run_t:s0 0 May 29 16:30 /var/lib/mysql/mysql.sock

    On systems that run systemd it is possible to configure a command to run after service has started. Modify /etc/systemd/system/mariadb.service.d/override.conf and add lines below:

    # Workaround so socket gets correct linux context
    [Service]
    ExecStartPost=chcon -t mysqld_var_run_t /var/lib/mysql/mysql.sock

    then do configuration reload and mariadb restart:

     systemctl daemon-reload
     systemctl restart mariadb

    Verify if it helped with ls command. If it did help, verify it still works after host reboot. 

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  • Avatar
    maartenv

    There is no need to do a chcon as the default system policy is correct.

    Create a file /etc/systemd/system/mariadb.service.d/restorecon_socket.conf with the following contents:

    # Workaround so socket gets correct linux context

    [Service]
    ExecStartPost=/sbin/restorecon /var/lib/mysql/mysql.sock

    Next, run:
    # systemctl daemon-reload &&  systemctl restart mariadb

    Source: https://jira.mariadb.org/browse/MDEV-24941?focusedCommentId=233795&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-233795

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  • Avatar
    Benjamin Weßel

    Hello,
    Thank you for the recommendations. We updated the article with another workaround accordingly.

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