[ClusterLabs] Antw: [EXT] Trying to understand dampening (ping)

[Ulrich Windl]

Hi!

IMHO "dampening" was a very bad term, and it had confused me right from the
start.
Maybe "change_ignore_time" would have been better.
But actually a true moving average (over a fixed window) would be much
preferrable.
Maybe exponential averaging, too.

And the description in pingd is very poor, also:
dampen (integer, [1s]): Dampening interval
    The time to wait (dampening) further changes occur

Regards,
Ulrich

>>> martin doc <db1280 at hotmail.com> schrieb am 13.10.2021 um 17:01 in
Nachricht
<PS2P216MB0546168E8F60EE9D89131EFCC2B79 at PS2P216MB0546.KORP216.PROD.OUTLOOK.COM>:

> In the ping resource script, there's support for "dampen" in the use of 
> attrd_updater.
> 
> My expectation is that it will cause "ping", "no‑ping", "ping" to result in

> the service being continually presented as up rather than to flap about.
> 
> In testing I can't demonstrate this, even using attrd_updater directly.
> 
> To test out how attrd_updater works, I wrote a small script to do this:
> 
> attrd_updater ‑n my_ping ‑D
> attrd_updater ‑n my_ping ‑p ‑B 1000 ‑d 3s
> sleep 1
> for i in 0 1 2 3 4 5 6 7 8 9; do
> attrd_updater ‑n my_ping ‑Q
> sleep 1
> attrd_updater ‑n my_ping ‑p ‑U 0 ‑d 3s
> done
> 
> The output always has the first line as 1000 and every other line with a 
> valud of "0" ‑ as if there was no dampening actually happening.
> 
> Even if I modify the above to do ‑U 1000, ‑U 0, ‑U 1000, doing ‑Q at any
point 
> always shows the last value supplied, with no evidence of any smoothng as a

> result of dampening.
> 
> Is the problem here that the ‑Q doesn't retrieve the value for my_ping using

> the same method as is used for resource scripts?
> 
> Am I totally misunderstanding how dampening works?
> 
> Thanks.