Comment 14 for bug 1928353

Reviewed: https://review.opendev.org/c/starlingx/config/+/791285
Committed: https://opendev.org/starlingx/config/commit/bf547186d19a218c03e73f31c5d7cafd1a5d4bd3
Submitter: "Zuul (22348)"
Branch: master

commit bf547186d19a218c03e73f31c5d7cafd1a5d4bd3
Author: Dan Voiculeasa <email address hidden>
Date: Wed May 12 15:16:32 2021 +0300

    Add service parameter to control pod pids limit

    Create a config section for kubernetes service.
    Create a parameter named pod_max_pids to have similar name as
    the kubernetes parameter pod-max-pids.
    Store the value in the config section.

    This will create a system-wide entry in hieradata when unlocking:
    plattform::kubernetes::params::k8s_pod_max_pids

    This affects hosts with kubelet running, meaning controller and
    worker personalities. A config out of date will be raised for all hosts
    of both personalities, even for parameters that target only a specific
    personality.

    After modifying the parameter a host-lock then host-unlock is required.

    Platform pods use under 20 processes in steady state.
    Some openstack pods reach ~450 processes in steady state.
    Since StarlingX provides some optional apps we provide a default value
    that takes into account the most hungry app, that being openstack.
    The database entry will be populated considering openstack will be
    applied.(I707ddc4ca67595fbf809c6ffc15ecd4fb21f4661), but we shouldn't
    restrict the minimum based on optional apps, as this allows the user
    to set a lower minimum if there is no plan to use openstack.

    Tested on Standard+dedicated storage:
    - out of sync raised for controllers and workers when using
    service-parameter modify
    - alarm cleared after host-lock, host-unlock
    - new value correctly generated and used
    - add with system service-parameter-add
    - modify with system service-parameter-modify

    Tested on top of: I10c1684fe3145e0a46b011f8e87f7a23557ddd4a
    Partial-Bug: 1928353
    Signed-off-by: Dan Voiculeasa <email address hidden>
    Change-Id: I74fcf2bd405c2a3811a4f27a55b28c0d001430e1