Re: Antw: Re: Q: dampening explained?

Andrew Beekhof <[email protected]>
Newsgroups gmane.linux.highavailability.user
Message-ID <[email protected]>
On 9 Sep 2014, at 4:11 pm, Ulrich Windl <[email protected]> wrote:

>>>> Andrew Beekhof <[email protected]> schrieb am 09.09.2014 um 00:25 in Nachricht
> <[email protected]>:
> 
>> On 8 Sep 2014, at 5:19 pm, Ulrich Windl <[email protected]> 
>> wrote:
>> 
>>> Hi!
>>> 
>>> I remember having asked this before, but I'l still missing a good 
>> explanation:
>>> 
>>> What are the precise semantics of "dampening" (attrd_updater -d)?
>>> 
>>> The manual page just says:
>>>      -d, --delay=value
>>>             The time to wait (dampening) in seconds further changes occur
>>> 
>>> Who is waiting?
>> 
>> attrd before it updates the cib
> 
> So the RA sees an extra delay of -d seconds?

No. attrd does the waiting, not attrd_updater

> 
>> 
>>> What changes?
>> 
>> other processes or nodes calling attrd_updater
> 
> So it means that if you call "attr_updater -d X" and then "attr_updater -d Y" the second update will be delayed until at least X seconds since the first update passed?

No.  It means wait X seconds for another update (locally or on another node) before writing the value to the CIB.
If another update does arrive, reset the clock and wait another X seconds.  Repeat.

Usually only the -d from the first call to attrd_updater has any affect.
Subsequent calls re-use the -d value from the first.

> If a third "attr_updater -d Z" is called, will the system ensure that at least X + Y seconds passed since the first update before appying the third update?

No.

> 
> If the delay is not over, does the next update wait (as I guessed), or is the next update simply ignored?
> 
>> 
>>> Please explain!
> 
> As you see, there are too many questions that are still unanswered.
> 
>>> (pacemaker-1.1.10-0.15.25 of SLES11 SP3)
>>> 
>>> Regards,
>>> Ulrich
> 
> 
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