Looks like all that's necessary is a single delayed conflict write attempt, and
all subsequent delayed commits won't be commit, the header never gets written.
1.0 loses data. This is ridiculously bad.
We need a test to reproduce this and fix.
-Damien
On Aug 7, 2010, at 4:35 PM, Adam Kocoloski wrote:
> Good sleuthing guys, and my apologies for letting this through. Randall,
> your patch in COUCHDB-794 was actually fine, it was my reworking of it that
> caused this serious bug.
>
> With respect to that gist 513282, I think it would be better to return
> Db#db{waiting_delayed_commit=nil} when the headers match instead of moving
> the cancel_timer() command as you did. After all, we did perform the check
> here -- it was just that nothing needed to be committed.
>
> Adam
>
> On Aug 7, 2010, at 6:55 PM, Damien Katz wrote:
>
>> Yes, I think it requires 2 conflicting writes in row, because it needs to
>> trigger the delayed_commit timer without actually having anything to commit,
>> so the header never changes.
>>
>> Try to reproduce this and add a test case.
>>
>> -Damien
>>
>>
>> On Aug 7, 2010, at 3:47 PM, Randall Leeds wrote:
>>
>>> I think you may be right, Damien.
>>> If ever a write happens that only contains conflicts while waiting for
>>> a delayed commit message we might still be cancelling the timer. Is
>>> this what you're thinking? This would be the fix:
>>> http://gist.github.com/513282
>>>
>>> On Sat, Aug 7, 2010 at 15:42, Damien Katz <[email protected]> wrote:
>>>> I think the problem might be that 2 conflicting write attempts in row can
>>>> leave the #db.waiting_delayed_commit set but the timer has been cancelled.
>>>> One that happens, the header may never be written, as it always thinks a
>>>> delayed commit will fire soon.
>>>>
>>>> -Damien
>>>>
>>>>
>>>> On Aug 7, 2010, at 12:08 PM, Randall Leeds wrote:
>>>>
>>>>> On Sat, Aug 7, 2010 at 11:56, Randall Leeds <[email protected]>
>>>>> wrote:
>>>>>> I agree completely! I immediately thought of this because I wrote that
>>>>>> change. I spent a while staring at it last night but still can't
>>>>>> imagine how it's a problem.
>>>>>>
>>>>>> On Sat, Aug 7, 2010 at 11:12, Damien Katz <[email protected]> wrote:
>>>>>>> SVN commit r954043 looks suspicious. Digging further.
>>>>>>>
>>>>>>> -Damien
>>>>>>
>>>>>
>>>>> I still want to stare at r954043, but it looks to me like there's at
>>>>> least one situation where we do not commit data correctly during
>>>>> compaction. This has to do with the way we now use the path to sync
>>>>> outside the couch_file:process. Check this diff:
>>>>> http://gist.github.com/513081
>>>>
>>>>
>>
>
