Re: /var/lib/ceph/*/*/config

[Wido den Hollander <wido@42on.com>]

On 27-01-16 16:45, Sage Weil wrote:
> On Wed, 27 Jan 2016, Wido den Hollander wrote:
>> On 27-01-16 15:59, Sage Weil wrote:
>>> Loic pointed out that adding a new config file that is overrides/combines 
>>> with the global config makes our already-complicated config infrastructure 
>>> even more so.  And it turned out to be more complicated to implement than 
>>> I'd hoped.  On the other hand, I think there are valid use-cases for a 
>>> global config, e.g.:
>>>
>>>  - most config on the osd disk itself
>>>  - /etc/ceph/ceph.conf containing crush_location and mon_host
>>>
>>> ...and with a single config I'm not sure how we'd get the datacenter 
>>> location set properly.
>>>
>>
>> Yes, you probably want the mon_host variable in a global config. We
>> might and I say *might* want to look at a DNS lookup at some time?
>>
>> A lookup for 'ceph-monitor' in the current DNS search domain. But that
>> might be offtopic here.
> 
> Yeah, I think if we make standard practice setting up DNS with an A or 
> AAAA record for each monitor then we can avoid a global mon_host.  But 
> there's still the crush location piece...
>  

Yes. I created a issue for that: http://tracker.ceph.com/issues/14527

>>> Anyway, I have two versions implemented.  The first just adds 
>>> $data_dir/config to the search pathh:
>>>
>>> 	https://github.com/ceph/ceph/pull/7377
>>>
>>
>> I like the first patch, but it doesn't seem to merge the config files,
>> right?
>>
>> If a global /etc/ceph/ceph.conf is found it doesn't search any further.
>>
>>> The second adds the extra_config infrastructure.  It's just the last patch 
>>> that is different:
>>>
>>> 	https://github.com/ceph/ceph/pull/7378
>>>
>>
>> The --extra-config seems weird to me. Isn't there a way where you supply
>> --config multiple times with multiple files?
> 
> Right now config is a search path, and when it finds a match, it stops and 
> uses that config file exclusively.  extra_config is a way to merge two of 
> them.  I agree it's not ideal...
> 
> An alternative approach would be to support 'include <file>' so that the 
> $data_dir/config, if present, would include something from /etc/ceph.
> 

I think that a include would be much nicer. I filed a issue for that
some time ago: http://tracker.ceph.com/issues/4771

The default config we created for a daemon could be just a one-liner:


/var/lib/ceph/osd/ceph-0/ceph.conf:

include "/etc/ceph/ceph.conf"

Wido

> sage
>