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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, set up a scheduled task which frequently restores SELinux context on MariaDB mysql.sock file /var/lib/mysql/mysql.sock​:

  1. Log into Plesk

  2. Navigate to Tools & Settings > Scheduled Tasks (Cron jobs) and click Add Task

  3. Set up the new scheduled the task with the following values:

    • Run a command
    • Command: /usr/sbin/restorecon -v /var/lib/mysql/mysql.sock
    • Run: Cron-style: * * * * *​
    • System user: root
    • Description: Restore MariaDB socket SELinux MDEV-24941:
    • Notify: Do not notify

  4. Click OK

    The scheduled task will execute restorecon command to temporarily resolve the issue. It will run automatically once in a minute.

  5. Resend the stuck e-mails

The following alternative workarounds are also available:

Comments

3 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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    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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