Re: Non existing monitor

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

On 07/30/2014 12:07 PM, Aanchal Agrawal wrote:
> 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?

Separate from Ceph it seems like bad behavior of a daemon to start 
creating directories when --mkfs is not supplied.

It should spit our errors about not being able to access it's data 
store, but not start creating them without explicitly being told to do so.

> 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?
>
> Thanks,
> Aanchal
>
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-- 
Wido den Hollander
42on B.V.
Ceph trainer and consultant

Phone: +31 (0)20 700 9902
Skype: contact42on