[ClusterLabs] systemd's TasksMax and pacemaker

Jan Pokorný jpokorny at redhat.com
Wed Nov 15 05:16:05 EST 2017

On 14/11/17 15:07 -0600, Ken Gaillot wrote:
> It is conceivable in a large cluster that Pacemaker could exceed
> this limit

[of 512 or 4915 tasks allowed per service process tree, possibly
overridden with systemd-system.conf(5) configuration],

> so we are now recommending that users set TasksMax=infinity in the
> Pacemaker unit file if building from scratch, or in a local override
> if already deployed, to disable the limit.

Thanks for broadcasting this ;)

> We are not setting TasksMax=infinity in the shipped unit file in the
> soon-to-be-released version 1.1.18 because older versions of systemd
> will log a warning about an "Unknown lvalue". However, we will set it
> in the 2.0.0 release, when we'll be making a number of behavioral
> changes.
> Particular OS distributions may have backported the TasksMax feature to
> an older version of systemd, and/or changed its default value. For
> example, in RHEL, TasksMax was backported as of RHEL 7.3, but the
> default was changed to infinity.

Note also Ansible playbooks and other means of automation and
provisioning may have a final say on the system-wide default limit.
These unattended changes shall also be put into decision whether you
need a local customization of pristine pacemaker service file, at
least for versions prior to 2.0.0, to avoid any unpleasant surprises
with process proliferation limiting ("anti-fork-bomb") systemd.

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