Re: Preferred location for utility execution

[John Spray <john.spray@redhat.com>]

On 29/06/2015 19:44, Handzik, Joe wrote:
> Thanks for the reply, John. I knew where you stood. :)
>
> I tend to agree with you for much of this, I should be able to pull a fair amount of drive metadata out of /sys, and now that I've added the device node to bootstrap off of, that sort of data collection should be easy to initiate alongside the rest of the metadata collection here: https://github.com/ceph/ceph/blob/master/src/osd/OSD.cc#L4566
>
> Something I'm not sure of is, say, Gregory's commit to Calamari. Does your opinion extend to functionality like that? Should SMART be collected within Ceph, rather than via a salt script initiated by Calamari?

Good question...  It depends on your position: if you're someone already 
using or developing Calamari, then it's a perfectly reasonable thing to 
add into Calamari.  If you're looking for a way to provide functionality 
for most ordinary ceph users, and enable involvement of most ceph 
developers, then Calamari brings quite a bit of baggage with it, and 
it's much more desirable to have it baked into Ceph.

The good news is that there's no rule against doing these things both 
places, so there's not really a wrong answer (at least in my opinion).  
We might find that while Calamari remains a minority thing, it's useful 
to have a whizz-bang version of a feature in Calamari, and something 
more basic baked into Ceph.  That's kind of already true for e.g. 
calamari's /server API vs. ceph's built in "node ls".

Finally, going a bit off topic: in an ideal world, the answer would be 
to get Calamari where it needs to be, and then add hardware monitoring 
functionality into Calamari while keeping the core of Ceph lightweight.  
This applies to other pieces of functionality, like the recent "node ls" 
functionality, continued existence of ceph-rest-api, some of the recent 
MDS health check stuff, all the kind of things that we would add in the 
python layer if we had one that was positioned to be present in all Ceph 
deployments, rather than only some.  Instead, we're writing these things 
into the C++ part because that's the only way to reach all the users.  
Calamari can only take up that role once it's:
  * Packaged (without any onerous dependencies)
  * Comprehensive (can do anything the CLI can do)
  * Lightweight (nothing to prevent us from enabling it by default)

John