nrpe relation does not support systemd

[Alvaro Uria]

Partially related to lp#1578922

ceph-osd charm does not support nrpe checks on systemd env (ie. Xenial).

See workarounds, http://pastebin.ubuntu.com/23085378/

[Doug Parrish (dparrish)]

In testing part of the workaround, listed in bug description above, with ceph-osd-241, i.e. making edits to ceph_hooks.py but not nrpe.py as it appears the latter has some systemd updates, it appears a check_nrpe limit was reached when checking a system with many OSDs. The output of the check_ceph-osd exceeded 1024 bytes.

$ /usr/lib/nagios/plugins/check_nrpe -H 127.0.0.1 -c check_ceph-osd
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: [e-mail] is running
OK: ceph-osd@30

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/18.05
Review: https://review.openstack.org/590251

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/590251
Committed: https://git.openstack.org/cgit/openstack/charm-ceph-osd/commit/?id=0356c22f282ad3ebadc97cd1b64bb198b0ad93a4
Submitter: Zuul
Branch: stable/18.05

commit 0356c22f282ad3ebadc97cd1b64bb198b0ad93a4
Author: Alvaro Uria <email address hidden>
Date: Thu Aug 9 13:22:49 2018 +0200

    Support systemd nrpe check for ceph-osd@N units

    ceph-osd<->nrpe relation adds a single check that parses the service
    status of all the ceph-osd processes. The check supported sysv and
    upstart environments, but not systemd, which has been added.

    add_init_service_checks does support systemd but it would create a
    nrpe check per OSD (vs a single check for all OSDs)

    Change-Id: I19689740b4d95107c46435f56d808139c071b826
    Closes-Bug: 1616525
    Signed-off-by: Alvaro Uria <email address hidden>