Alright, I updated the configs in our production cluster and restarted
the OSDs (after removing the manual mapping from their unit.run
files), everything good.
@Zac: Would you agree that it makes sense to add this to the docs [1]
for cephadm clusters? They only cover the legacy world.
Thanks!
Eugen
Zitat von Wyll Ingersoll <wyllys.ingersoll@xxxxxxxxxxxxxx>:
Yeah, now that you mention it, I recall figuring that out also at
some point. I think I did it originally when I was debugging the
problem without the container.
________________________________
From: Eugen Block <eblock@xxxxxx>
Sent: Friday, May 3, 2024 8:37 AM
To: Wyll Ingersoll <wyllys.ingersoll@xxxxxxxxxxxxxx>
Cc: ceph-users@xxxxxxx <ceph-users@xxxxxxx>
Subject: Re: cephadm custom crush location hooks
Hm, I wonder why the symlink is required, the OSDs map / to /rootfs
anyway (excerpt of unit.run file):
-v /:/rootfs
So I removed the symlink and just added /rootfs to the crush location hook:
ceph config set osd.0 crush_location_hook
/rootfs/usr/local/bin/custom_crush_location
After OSD restart the OSD finds its correct location. So I actually
only need to update the location path, nothing else, it seems.
Zitat von Eugen Block <eblock@xxxxxx>:
I found your (open) tracker issue:
https://tracker.ceph.com/issues/53562
Your workaround works great, I tried it in a test cluster
successfully. I will adopt it to our production cluster as well.
Thanks!
Eugen
Zitat von Eugen Block <eblock@xxxxxx>:
Thank you very much for the quick response! I will take a look
first thing tomorrow and try that in a test cluster. But I agree,
it would be helpful to have a way with cephadm to apply these hooks
without these workarounds. I'll check if there's a tracker issue
for that, and create one if necessary.
Thanks!
Eugen
Zitat von Wyll Ingersoll <wyllys.ingersoll@xxxxxxxxxxxxxx>:
I've found the crush location hook script code to be problematic
in the containerized/cephadm world.
Our workaround is to place the script in a common place on each
OSD node, such as /etc/crush/crushhook.sh, and then make a link
from /rootfs -> /, and set the configuration value so that the
path to the hook script starts with /rootfs. The container that
the OSDs run in has access to /rootfs and this hack allows them to
all view the crush script without having to manually modify unit
files.
For example:
1.
put crushhook script on the host OS in /etc/crush/crushhook.sh
2.
make a link on the host os: $ cd /; sudo ln -s / /rootfs
3.
ceph config set osd crush_location_hook /rootfs/etc/crush/crushhook.sh
The containers see "/rootfs" and will then be able to access your
script. Be aware though that if your script requires any sort of
elevated access, it may fail because the hook runs as ceph:ceph in
a minimal container so not all functions are available. I had to
add lots of debug output and logging in mine (it's rather
complicated) to figure out what was going on when it was running.
I would love to see the "crush_location_hook" script be something
that can be stored in the config entirely instead of as a link,
similar to how the ssl certificates for RGW or the dashboard are
stored (ceph config-key set ...). The current situation is not
ideal.
________________________________
From: Eugen Block <eblock@xxxxxx>
Sent: Thursday, May 2, 2024 10:23 AM
To: ceph-users@xxxxxxx <ceph-users@xxxxxxx>
Subject: cephadm custom crush location hooks
Hi,
we've been using custom crush location hooks for some OSDs [1] for
years. Since we moved to cephadm, we always have to manually edit the
unit.run file of those OSDs because the path to the script is not
mapped into the containers. I don't want to define custom location
hooks for all OSDs globally in the OSD spec, even if those are limited
to two hosts only in our case. But I'm not aware of a method to target
only specific OSDs to have some files mapped into the container [2].
Is my assumption correct that we'll have to live with the manual
intervention until we reorganize our osd tree? Or did I miss something?
Thanks!
Eugen
[1]
https://docs.ceph.com/en/latest/rados/operations/crush-map/#custom-location-hooks
[2]
https://docs.ceph.com/en/latest/cephadm/services/#mounting-files-with-extra-container-arguments
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