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High amount of sw-engine processes in process list hung on config.lock file

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Marc López
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Applicable to:

  • Plesk Onyx for Linux

Symptoms

  • Scheduled backups are not created.

  • Plesk utilities, e.g.:

    # plesk login

    hang.

  • There are lot of sw-engine processes:

    # ps -e fwww | grep sw-engine
    6846 ? S 2:37 _ sw-engine-fpm: pool plesk
    6890 ? S 2:37 _ sw-engine-fpm: pool plesk
    6903 ? S 2:36 _ sw-engine-fpm: pool plesk
    6904 ? S 2:36 _ sw-engine-fpm: pool plesk
    6918 ? S 2:36 _ sw-engine-fpm: pool plesk
    6920 ? S 2:36 _ sw-engine-fpm: pool plesk
    6921 ? S 2:37 _ sw-engine-fpm: pool plesk
    6924 ? S 2:36 _ sw-engine-fpm: pool plesk
    6936 ? S 2:37 _ sw-engine-fpm: pool plesk
    6939 ? S 2:36 _ sw-engine-fpm: pool plesk

    OR

    # ps -e fwww | grep sw-engine

    24695 ? Zs 0:00 | _ [sw-engine] <defunct>
    24875 ? Zs 0:00 | _ [sw-engine] <defunct>
    29217 ? Zs 0:00 | _ [sw-engine] <defunct>
    31327 ? Zs 0:00 | _ [sw-engine] <defunct>
    15254 ? Zs 0:00 | _ [sw-engine] <defunct>
    16243 ? Zs 0:00 | _ [sw-engine] <defunct>
    19463 ? Zs 0:00 | _ [sw-engine] <defunct>
    20472 ? Zs 0:00 | _ [sw-engine] <defunct>
    13502 ? Zs 0:00 | _ [sw-engine] <defunct>
    15067 ? Zs 0:00 | _ [sw-engine] <defunct>

  • The strace output of such processes contains the following:

    # strace -p6846

    <...>

    restart_syscall(<... resuming interrupted futex ...>) = -1 ETIMEDOUT (Connection timed out)
    fcntl(9, F_SETLKW, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0
    fcntl(7, F_SETLKW, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0
    fcntl(7, F_SETLK, {l_type=F_UNLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0
    fcntl(7, F_SETLKW, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0
    fcntl(7, F_SETLK, {l_type=F_UNLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0
    umask(02) = 022
    stat("/run/lock/lmlib/container_locks/plesk.0/node.1/service", {st_mode=S_IFDIR|S_ISGID|0775, st_size=60, ...}) = 0
    umask(022) = 02
    umask(0111) = 022
    creat("/run/lock/lmlib/container_locks/plesk.0/node.1/service/config.lock", 0777) = 10
    close(10) = 0
    umask(022) = 0111

  • In case of Multi-Server installation, Service Nodes are going offline periodically during the Daily Maintenance Task execution.

Cause

Product issue:

  • #PPPM-8929 "Installation of extensions no longer causes sw-engine scripts and CLI utilities to hang."
    Fixed in:

Resolution

Please consider updating your server:

Workaround

Upgrade to Plesk Onyx 17.8 or install latest Plesk updates in case already running Plesk Onyx 17.8.

Note: In case it is not possible, see Additional Information section at the bottom.

Workaround for older Plesk versions

  1. Connect to the server via SSH.

  2. Kill all sw-engine processes:

    # pkill sw-engine

  3. Restart sw-cp-server and sw-engine services:

    # service sw-engine restart
    # service sw-cp-server restart

  4. Uninstall New Relic extension:

    # plesk bin extension --uninstall new-relic

Additional information

In case upgrade is not an option, try using the ApiCli.zip from the attachment.

Note that the fix was not fully tested yet was working fine on some installations.

# wget https://support.plesk.com/hc/en-us/article_attachments/360010352974/ApiCli.zip
# unzip ApiCli.zip
# mv /usr/local/psa/admin/plib/pm/ApiCli.php{,.bkp}
# cp -a ApiCli.php /usr/local/psa/admin/plib/pm/

Comments

2 comments

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  • Avatar
    Csteamleads

    You will not be able to log into Plesk if you kill all sw-engine processes. You'll likely need to start/restart it as well:

    pkill sw-engine; systemctl restart sw-engine

    or

    pkill sw-engine; service sw-engine restart

    0
    Comment actions Permalink
  • Avatar
    Ivan Postnikov

    Hello @Csteamleads,

    thank you for noticing. The article will be reviewed and updated soon.

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