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Subject: Re: Delay in Flink timers
From: Aljoscha Krettek <aljoscha@apache.org>
In-Reply-To: <f7ea8e12-0085-682c-65f7-662176992403@web.de>
Date: Thu, 14 Sep 2017 12:34:42 +0200
Cc: user@flink.apache.org
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Message-Id: <46FDF5D7-F7FD-436A-851F-3BB5D063060D@apache.org>
References: <87bmmj2emv.fsf@vicarie>
 <f7ea8e12-0085-682c-65f7-662176992403@web.de>
To: Chesnay Schepler <c.schepler@web.de>
archived-at: Thu, 14 Sep 2017 10:34:48 -0000

Hi,

Yes, execution of these methods is protected by a synchronized block. =
This is not a fair lock so incoming data might starve timer callbacks. =
What is the number of timers we are talking about here?

Best,
Aljoscha

> On 11. Sep 2017, at 19:38, Chesnay Schepler <c.schepler@web.de> wrote:
>=20
> It is true that onTimer and processElement are never called at the =
same time.
>=20
> I'm not entirely sure whether there is any prioritization/fairness =
between these methods
> (if not if could be that onTimer is starved) , looping in Aljoscha who =
hopefully knows more
> about this.
>=20
> On 10.09.2017 09:31, Narendra Joshi wrote:
>> Hi,
>>=20
>> We are using Flink as a timer scheduler and delay in timer execution =
is
>> a huge problem for us. What we have experienced is that as the number =
of
>> Timers we register increases the timers start getting delayed (for =
more
>> than 5 seconds). Can anyone point us in the right direction to figure
>> out what might be happening?
>>=20
>> I have been told that `onTimer` and `processElement` are called with =
a
>> mutually exclusive lock. Could this locking be the reason this is
>> happening? In both the functions there is no IO happening and it =
should
>> not take 5 seconds.
>>=20
>> Is it possible that calls to `processElement` starve `onTimer` calls?
>>=20
>>=20
>> --
>> Narendra Joshi
>>=20
>=20