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Subject: Re: How to clear registered timers for a merged window?
From: Stefan Richter <s.richter@data-artisans.com>
In-Reply-To: <CAM+=HTYTMX2zjBAqbQ2g4kDOHTh7S0Ffoh2SV_trP=_UbqO1DQ@mail.gmail.com>
Date: Tue, 26 Sep 2017 11:17:07 +0200
Cc: user <user@flink.apache.org>,
 Aljoscha Krettek <aljoscha@data-artisans.com>
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Message-Id: <8F079AC7-4436-48F9-AF47-8F26126726FF@data-artisans.com>
References: <CAM+=HTYTMX2zjBAqbQ2g4kDOHTh7S0Ffoh2SV_trP=_UbqO1DQ@mail.gmail.com>
To: =?utf-8?B?IllhbiBaaG91IFtGRFMgU2NpZW5jZV0gwq0i?= <yzhou@coupang.com>
archived-at: Tue, 26 Sep 2017 09:17:14 -0000

Hi,

I think that it is currently not possible to delete timers that did not =
trigger, because currently some of the data structures used for timers =
do not support random deletes efficiently. For the second part of the =
question about keeping the state of merged windows, I added Aljoscha in =
CC who might provide more information about the topic.

Best,
Stefan

> Am 25.09.2017 um 22:59 schrieb Yan Zhou [FDS Science] =C2=AD =
<yzhou@coupang.com>:
>=20
> Hi,
>=20
> I am implementing a merge-able trigger, and having a problem in =
clearing the registered timers for a merged window (a window has been =
merged into the merging result). For my implementation, the trigger =
registers multiple timers for each element at Trigger#onElement(). State =
is used to keep track of the registered event time, so that timer can be =
removed at Trigger#clear() later.
>=20
> However, clearing the registered timers in this way doesn't work if =
the window has been merged. The state of origin window is removed during =
merging. Method AbstractHeapMergingState#mergeNamespaces() removes the =
state of merged window. I think the ContinuousEventTimeTrigger shipped =
with flink would have same issue.
>=20
> My question is is there a way to keep the state for a merged window? =
One way I can think of is to implement a custom heap state that add the =
state back in AbstractHeapMergingState#mergeState() method. Or is there =
a way to clear the timers without using state? Can I twist the internal =
timer's source code to expose a method to remove all timers for a =
specified window?
>=20
> Please advise and thank you for your help.
>=20
> Best
> Yan