[Bug 1591411] Re: systemd-logind must be restarted every ~1000 SSH logins to prevent a ~25 second delay

[Łukasz Zemczak]

I think I will just go forward and start preparing the release of dbus
with this fix in zesty and then backporting it to yakkety and xenial.
Upstream didn't seem to officially review the fix or provide any
feedback on our test results, but the fix is enough high-priority to
consider including it anyway. I will of course get someone to review all
this, but I suppose we'll be pushing upstream about it separately.

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Title:
  systemd-logind must be restarted every ~1000 SSH logins to prevent a
  ~25 second delay

Status in D-Bus:
  Unknown
Status in systemd:
  Unknown
Status in dbus package in Ubuntu:
  Confirmed
Status in systemd package in Ubuntu:
  Fix Released
Status in dbus source package in Xenial:
  Confirmed
Status in systemd source package in Xenial:
  Invalid
Status in dbus source package in Yakkety:
  Confirmed
Status in systemd source package in Yakkety:
  Invalid

Bug description:
  I noticed on a system that accepts large numbers of SSH connections
  that after awhile, SSH sessions were taking ~25 seconds to complete.

  Looking in /var/log/auth.log, systemd-logind starts failing with the
  following:

  Jun 10 23:55:28 test sshd[3666]: pam_unix(sshd:session): session opened for user ubuntu by (uid=0)
  Jun 10 23:55:28 test systemd-logind[105]: New session c1052 of user ubuntu.
  Jun 10 23:55:28 test systemd-logind[105]: Failed to abandon session scope: Transport endpoint is not connected
  Jun 10 23:55:28 test sshd[3666]: pam_systemd(sshd:session): Failed to create session: Message recipient disconnected from message bus without replying

  I reproduced this in an LXD container by doing something like:

  lxc launch ubuntu:x test
  lxc exec test -- login -f ubuntu
  ssh-import-id <whatever>

  Then ran a script as follows (passing in ubuntu@<container-ip>):

  while [ 1 ]; do
      (time ssh $1 "echo OK > /dev/null") 2>&1 | grep ^real >> log
  done

  In my case, after 1052 logins, the 1053rd and thereafter were taking
  25+ seconds to complete. Here are some snippets from the log file:

  $ cat log | grep 0m0 | wc -l
  1052

  $ cat log | grep 0m25 | wc -l
  4

  $ tail -5 log
  real	0m0.222s
  real	0m25.232s
  real	0m25.235s
  real	0m25.236s
  real	0m25.239s

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: systemd 229-4ubuntu5
  ProcVersionSignature: Ubuntu 4.4.0-22.40-generic 4.4.8
  Uname: Linux 4.4.0-22-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2
  Architecture: amd64
  Date: Sat Jun 11 00:09:34 2016
  MachineType: Notebook W230SS
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-22-generic root=/dev/mapper/ubuntu--vg-root ro quiet splash
  SourcePackage: systemd
  SystemdDelta:
   [EXTENDED]   /lib/systemd/system/rc-local.service → /lib/systemd/system/rc-local.service.d/debian.conf
   [EXTENDED]   /lib/systemd/system/systemd-timesyncd.service → /lib/systemd/system/systemd-timesyncd.service.d/disable-with-time-daemon.conf

   2 overridden configuration files found.
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 04/15/2014
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: 4.6.5
  dmi.board.asset.tag: Tag 12345
  dmi.board.name: W230SS
  dmi.board.vendor: Notebook
  dmi.board.version: Not Applicable
  dmi.chassis.asset.tag: No Asset Tag
  dmi.chassis.type: 9
  dmi.chassis.vendor: Notebook
  dmi.chassis.version: N/A
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr4.6.5:bd04/15/2014:svnNotebook:pnW230SS:pvrNotApplicable:rvnNotebook:rnW230SS:rvrNotApplicable:cvnNotebook:ct9:cvrN/A:
  dmi.product.name: W230SS
  dmi.product.version: Not Applicable
  dmi.sys.vendor: Notebook

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