[openstack-dev] [olso] [cinder] upgrade issues in lock_path in cinder after oslo utils sync

Sean Dague sean at dague.net
Mon Dec 9 16:55:24 UTC 2013

On 12/09/2013 11:38 AM, Clint Byrum wrote:
> Excerpts from Sean Dague's message of 2013-12-09 08:17:45 -0800:
>> On 12/06/2013 05:40 PM, Ben Nemec wrote:
>>> On 2013-12-06 16:30, Clint Byrum wrote:
>>>> Excerpts from Ben Nemec's message of 2013-12-06 13:38:16 -0800:
>>>>> On 2013-12-06 15:14, Yuriy Taraday wrote:
>>>>>> Hello, Sean.
>>>>>> I get the issue with upgrade path. User doesn't want to update
>>>>> config unless one is forced to do so.
>>>>>> But introducing code that weakens security and let it stay is an
>>>>> unconditionally bad idea.
>>>>>> It looks like we have to weigh two evils: having troubles upgrading
>>>>> and lessening security. That's obvious.
>>>>>> Here are my thoughts on what we can do with it:
>>>>>> 1. I think we should definitely force user to do appropriate
>>>>> configuration to let us use secure ways to do locking.
>>>>>> 2. We can wait one release to do so, e.g. issue a deprecation
>>>>> warning now and force user to do it the right way later.
>>>>>> 3. If we are going to do 2. we should do it in the service that is
>>>>> affected not in the library because library shouldn't track releases
>>>>> of an application that uses it. It should do its thing and do it
>>>>> right (secure).
>>>>>> So I would suggest to deal with it in Cinder by importing
>>>>> 'lock_path' option after parsing configs and issuing a deprecation
>>>>> warning and setting it to tempfile.gettempdir() if it is still None.
>>>>> This is what Sean's change is doing, but setting lock_path to
>>>>> tempfile.gettempdir() is the security concern.
>>>> Yuriy's suggestion is that we should let Cinder override the config
>>>> variable's default with something insecure. Basically only deprecate
>>>> it in Cinder's world, not oslo's. That makes more sense from a library
>>>> standpoint as it keeps the library's expected interface stable.
>>> Ah, I see the distinction now.  If we get this split off into
>>> oslo.lockutils (which I believe is the plan), that's probably what we'd
>>> have to do.
>>>>> Since there seems to be plenty of resistance to using /tmp by default,
>>>>> here is my proposal:
>>>>> 1) We make Sean's change to open files in append mode. I think we can
>>>>> all agree this is a good thing regardless of any config changes.
>>>>> 2) Leave lockutils broken in Icehouse if lock_path is not set, as I
>>>>> believe Mark suggested earlier. Log an error if we find that
>>>>> configuration. Users will be no worse off than they are today, and if
>>>>> they're paying attention they can get the fixed lockutils behavior
>>>>> immediately.
>>>> Broken how? Broken in that it raises an exception, or broken in that it
>>>> carries a security risk?
>>> Broken as in external locks don't actually lock.  If we fall back to
>>> using a local semaphore it might actually be a little better because
>>> then at least the locks work within a single process, whereas before
>>> there was no locking whatsoever.
>> Right, so broken as in "doesn't actually locks, potentially completely
>> scrambles the user's data, breaking them forever."
> Things I'd like to see OpenStack do in the short term, ranked in ascending
> order of importance:
> 4) Upgrade smoothly.
> 3) Scale.
> 2) Help users manage external risks.
> 1) Not do what Sean described above.
> I mean, how can we even suggest silently destroying integrity?
> I suggest merging Sean's patch and putting a warning in the release
> notes that running without setting this will be deprecated in the next
> release. If that is what this is preventing this debate should not have
> happened, and I sincerely apologize for having delayed it. I believe my
> mistake was assuming this was something far more trivial than "without
> this patch we destroy users' data".
> I thought we were just talking about making upgrades work. :-P

Honestly, I haven't looked exactly how bad the corruption would be. But
we are locking to handle something around simultaneous db access in
cinder, so I'm going to assume the worst here.


Sean Dague

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