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

[Stan Hu]

That's correct: only the dbus patch is absolutely necessary, but since
the patch wasn't merged yet to dbus I am still not 100% sure if it is
considered ready for prime time. It seems to work for us.

As Łukasz observed, the systemd patch is a lot more extensive. Even
though it was merged to master, we were only going to attempt to
backport the fix if it were absolutely necessary. It doesn't look like
it was in this case, so we did not attempt to do it.

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

Status in dbus package in Ubuntu:
  New
Status in systemd package in Ubuntu:
  Fix Released
Status in dbus source package in Xenial:
  New
Status in systemd source package in Xenial:
  Confirmed

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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