[Bug 1811554] Re: bind9 slow response after netplan apply

[Christian Ehrhardt ]

I added a netplan.io bug task so that cyphermox sees this ug as well.
He will know best all the substeps that happen one "netplan apply" and if one of them could be related. Furthermore he might have seen such reports but against netplan.io instead of bind.

** Also affects: netplan.io (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1811554

Title:
  bind9 slow response after netplan apply

Status in bind9 package in Ubuntu:
  Incomplete
Status in netplan.io package in Ubuntu:
  New

Bug description:
  System:
  VM running on ESXI 6.0
  Description: Ubuntu 18.04.1 LTS
  Release: 18.04

  Package:
  bind9:
    Installed: 1:9.11.3+dfsg-1ubuntu1.3
    Candidate: 1:9.11.3+dfsg-1ubuntu1.3
    Version table:
   *** 1:9.11.3+dfsg-1ubuntu1.3 500
          500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
          100 /var/lib/dpkg/status
       1:9.11.3+dfsg-1ubuntu1.2 500
          500 http://archive.ubuntu.com/ubuntu bionic-security/main amd64 Packages
       1:9.11.3+dfsg-1ubuntu1 500
          500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages

  3. Expected to happen: After issuing the command "sudo netplan apply"
  with no network changes bind to continue to run as it had.

  This happened once to reapply config, and once during a "Daily apt
  upgrade and clean activities"

  4. After the netplan apply completed within 2 minutes we started
  seeing timeouts and long response times from the server. We have 2
  identical builds currently running as caching servers for a large
  network, the servers were built on the same day and have both
  experienced the issue. These servers are under heavy load and are
  replying to 100's of queries a second or more. When investigating the
  logs for bind and the syslog there are no indications of maximum
  number of connections, maximum open files, or any other limits
  reached. Though there are noticed dropped packets and external
  monitoring on the bind service begins to flap, and manual testing
  shows some queries timing out.

  Issuing a "sudo systemctl restart bind9" instantly resolves the issue.

  If there is any other information you need please let me know, but I
  am unsure of where to look as the named log, kernel log, and syslog
  are all clear of errors during the timeout issue.

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