Re: Non existing monitor

[Joao Eduardo Luis <joao.luis@inktank.com>]

On 01/08/14 18:20, Pavan Rallabhandi wrote:
> Greg,
>
> The commands used were to start monitor for an instance id that is non existing, for which a leveldb store error is thrown:
>
> <snip>
>
> src/ceph-mon -i foo
> 2014-08-01 02:47:08.210208 7f7341c3c800 -1 failed to create new leveldb store
>
> <\snip>
>
> The idea is to fix this behavior by throwing a relevant error.

The infrastructure is there (ceph_mon.cc) but is not doing what I 
believe it should.  It was introduced in 
1eafe8dc45419a6b7d319345cac7fbc0d684d1b1.  I'm fixing it now.

   -Joao

>
> Thanks,
> -Pavan.
>
> -----Original Message-----
> From: Gregory Farnum [mailto:greg@inktank.com]
> Sent: Friday, August 01, 2014 6:16 PM
> To: Aanchal Agrawal
> Cc: ceph-devel@vger.kernel.org; Pavan Rallabhandi; Samuel Just; Joao Luis
> Subject: Re: Non existing monitor
>
> On Fri, Aug 1, 2014 at 6:03 AM, Aanchal Agrawal <Aanchal.Agrawal@sandisk.com> wrote:
>> Any help on this ...
>>
>> -----Original Message-----
>> From: Aanchal Agrawal
>> Sent: Wednesday, July 30, 2014 3:37 PM
>> To: 'ceph-devel@vger.kernel.org'
>> Cc: Pavan Rallabhandi
>> Subject: Non existing monitor
>>
>> Hi,
>>
>> We found a case(bug?) in ceph mon code, where in, an attempt to start a non-existing monitor is throwing up a levelDB error saying "failed to create new leveldb store", instead we thought an appropriate message say "No Monitor present with that id" would do, by checking for the monitor existence way ahead.
>>
>> It seems that 'mon_exists()' checks for the existence of the mon data directory(via 'mon_data_exists()') and also for the non-empty nature of that directory(via 'mon_data_empty()'). The fix seemed pretty simple, as to flag the appropriate message if 'mon_data_exists()' were to set 'exists' to 'false', in case mkfs is not set.
>>
>> The other behavior that we are seeking clarity, again in case of mkfs not being set is, if 'mon_data_exists()' sets 'exists' to 'true' and 'mon_data_empty()' sets 'exists' to 'false' (meaning the mon data directory is present, but it is empty), then the current code seems to be going ahead in an attempt to open the 'store.db', and when open fails, it tries to create a new 'store.db' (though mkfs is not set) and eventually gives up throwing "unable to read magic from mon data".
>>
>> The questions we had around this were:
>>
>> 1) Though in case of mkfs not being set, what is the reason for creating a new levelDB store in case an attempt to open the 'store.db' is a failure, as levelDB anyways seem to be throwing 'magic' error going forward. Are there any use cases for this scenario?
>> 2) And also, is it valid to flag "No Monitor present" in case the mon data directory is existing, but with no data('store.db') in it, in case mkfs is not set?
>
> This is a little unclear to me. Can you describe exactly what commands you're running and what the response from the monitor is?
> -Greg
> Software Engineer #42 @ http://inktank.com | http://ceph.com
>
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-- 
Joao Eduardo Luis
Software Engineer | http://inktank.com | http://ceph.com