ceph OSD facts file

ceph OSD facts file

[Ken Dreyer]

Hi Loic,

In Red Hat we're interested in having a Ceph "facts" file that we can
integrate with RHEL's subscription-manager (upstream
http://www.candlepinproject.org/ fyi) in order to report on the
available raw disk capacity available per OSD.

We need a script to write a "/etc/rhsm/facts/ceph_disk.facts" file.
That file needs to contain JSON of the form:

{
  "band.storage.usage": <integer number of TB used on this node, such as 55>
}

for example:
{
  "band.storage.usage": 55
}

As long as that file exists (and it can be named anything that ends in
".facts") the contents will be read in and added to the system facts.
On RHEL this can be verified by running `subscription-manager facts`
to ensure that your value is showing up properly.

In terms of creating this .facts file, we will need a script to do
that. We could call it /usr/bin/ceph-update-fact-file, or make it a
ceph-disk sub-command, or whatever you want, really.

The facts file should be kept up-to-date every four hours, which makes
me think that we could implement this as a systemd service and timer.
Something like

  $ cat /etc/systemd/system/ceph-update-facts-file.service

  [Unit]
  Description=Update Ceph OSD fact file

  [Service]
  Type=oneshot
  ExecStart=/usr/bin/ceph-update-fact-file


...and:

  $ cat /etc/systemd/system/ceph-update-facts-file.timer
  [Unit]
  Description=Trigger an automatic rewrite every four hours

  [Timer]
  OnCalendar=4hours
  Persistent=true

  [Install]
  WantedBy=multi-user.target

(The above is untested, it's just an idea).  What do you think?

Re: ceph OSD facts file

[Loic Dachary]

Hi Ken,

I'll work on http://tracker.ceph.com/issues/14972 and create that script.

Thanks for a nice and precise description :-)

On 03/03/2016 05:50, Ken Dreyer wrote:
> Hi Loic,
> 
> In Red Hat we're interested in having a Ceph "facts" file that we can
> integrate with RHEL's subscription-manager (upstream
> http://www.candlepinproject.org/ fyi) in order to report on the
> available raw disk capacity available per OSD.
> 
> We need a script to write a "/etc/rhsm/facts/ceph_disk.facts" file.
> That file needs to contain JSON of the form:
> 
> {
>   "band.storage.usage": <integer number of TB used on this node, such as 55>
> }
> 
> for example:
> {
>   "band.storage.usage": 55
> }
> 
> As long as that file exists (and it can be named anything that ends in
> ".facts") the contents will be read in and added to the system facts.
> On RHEL this can be verified by running `subscription-manager facts`
> to ensure that your value is showing up properly.
> 
> In terms of creating this .facts file, we will need a script to do
> that. We could call it /usr/bin/ceph-update-fact-file, or make it a
> ceph-disk sub-command, or whatever you want, really.
> 
> The facts file should be kept up-to-date every four hours, which makes
> me think that we could implement this as a systemd service and timer.
> Something like
> 
>   $ cat /etc/systemd/system/ceph-update-facts-file.service
> 
>   [Unit]
>   Description=Update Ceph OSD fact file
> 
>   [Service]
>   Type=oneshot
>   ExecStart=/usr/bin/ceph-update-fact-file
> 
> 
> ...and:
> 
>   $ cat /etc/systemd/system/ceph-update-facts-file.timer
>   [Unit]
>   Description=Trigger an automatic rewrite every four hours
> 
>   [Timer]
>   OnCalendar=4hours
>   Persistent=true
> 
>   [Install]
>   WantedBy=multi-user.target
> 
> (The above is untested, it's just an idea).  What do you think?
> --
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-- 
Loïc Dachary, Artisan Logiciel Libre
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