I can see the issue. But it raised other questions. Pardon my ignorance. Even
though partitions are processed independently, windows can be aggregating state
from records read from many partitions. Let us say there is a groupByKey
followed by aggregate. In this case how is the state reconciled across all the
application instances ? Is there a designated instance for a particular key ?
In my case, there was only one instance processing records from all partitions
and it is kind of odd that windows did not expire even though I understand why
now.
Thanks
Mohan
On 6/21/19, 2:25 PM, "John Roesler" <j...@confluent.io> wrote:
No problem. It's definitely a subtlety. It occurs because each
partition is processed completely independently of the others, so
"stream time" is tracked per partition, and there's no way to look
across at the other partitions to find out what stream time they have.
In general, it's not a problem because you'd expect all partitions to
receive updates over time, but if you're specifically trying to send
events that cause stuff to get flushed from the buffers, it can mess
with you. It's especially notable in tests. So, for most tests, I just
configure the topics to have one partition.
-John
On Fri, Jun 21, 2019 at 3:56 PM Parthasarathy, Mohan <mpart...@hpe.com>
wrote:
>
> That change "In the same partition" must explain what we are seeing.
Unless you see one message per partition, all windows will not expire. That is
an interesting twist. Thanks for the correction ( I will go back and confirm
this.
>
> -mohan
>
>
> On 6/21/19, 12:40 PM, "John Roesler" <j...@confluent.io> wrote:
>
> Sure, the record cache attempts to save downstream operators from
> unnecessary updates by also buffering for a short amount of time
> before forwarding. It forwards results whenever the cache fills up or
> whenever there is a commit. If you're happy to wait at least "commit
> interval" amount of time for updates, then you don't need to do
> anything, but if you're on the edge of your seat, waiting for these
> results, you can set cache.max.bytes.buffering to 0 to disable the
> record cache entirely. Note that this would hurt throughput in
> general, though.
>
> Just a slight modification:
> * a new record with new timestamp > (all the previous timestamps +
> grace period) will cause all the old windows *in the same partition*
> to close
> * yes, expiry of the window depends only on the event time
>
> Hope this helps!
> -John
>
> On Thu, Jun 20, 2019 at 11:42 AM Parthasarathy, Mohan
<mpart...@hpe.com> wrote:
> >
> > Could you tell me a little more about the delays about the record
caches and how I can disable it ?
> >
> > If I could summarize my problem:
> >
> > -A new record with a new timestamp > all records sent before, I
expect *all* of the old windows to close
> > -Expiry of the windows depends only on the event time and not on
the key
> >
> > Are these two statements correct ?
> >
> > Thanks
> > Mohan
> >
> > On 6/20/19, 9:17 AM, "John Roesler" <j...@confluent.io> wrote:
> >
> > Hi!
> >
> > In addition to setting the grace period to zero (or some small
> > number), you should also consider the delays introduced by
record
> > caches upstream of the suppression. If you're closely watching
the
> > timing of records going into and coming out of the topology,
this
> > might also spoil your expectations. You could always disable the
> > record cache to make the system more predictable (although this
would
> > hurt throughput in production).
> >
> > Thanks,
> > -John
> >
> > On Wed, Jun 19, 2019 at 3:01 PM Parthasarathy, Mohan
<mpart...@hpe.com> wrote:
> > >
> > > We do explicitly set the grace period to zero. I am going to
try the new version
> > >
> > > -mohan
> > >
> > >
> > > On 6/19/19, 12:50 PM, "Parthasarathy, Mohan"
<mpart...@hpe.com> wrote:
> > >
> > > Thanks. We will give it a shot.
> > >
> > > On 6/19/19, 12:42 PM, "Bruno Cadonna"
<br...@confluent.io> wrote:
> > >
> > > Hi Mohan,
> > >
> > > I realized that my previous statement was not clear.
With a grace
> > > period of 12 hour, suppress would wait for late
events until stream
> > > time has advanced 12 hours before a result would be
emitted.
> > >
> > > Best,
> > > Bruno
> > >
> > > On Wed, Jun 19, 2019 at 9:21 PM Bruno Cadonna
<br...@confluent.io> wrote:
> > > >
> > > > Hi Mohan,
> > > >
> > > > if you do not set a grace period, the grace period
defaults to 12
> > > > hours. Hence, suppress would wait for an event that
occurs 12 hour
> > > > later before it outputs a result. Try to explicitly
set the grace
> > > > period to 0 and let us know if it worked.
> > > >
> > > > If it still does not work, upgrade to version 2.2.1
if it is possible
> > > > for you. We had a couple of bugs in suppress
recently that are fixed
> > > > in that version.
> > > >
> > > > Best,
> > > > Bruno
> > > >
> > > > On Wed, Jun 19, 2019 at 8:37 PM Parthasarathy,
Mohan <mpart...@hpe.com> wrote:
> > > > >
> > > > > No, I have not set any grace period. Is that
mandatory ? Have you seen problems with suppress and windows expiring ?
> > > > >
> > > > > Thanks
> > > > > Mohan
> > > > >
> > > > > On 6/19/19, 12:41 AM, "Bruno Cadonna"
<br...@confluent.io> wrote:
> > > > >
> > > > > Hi Mohan,
> > > > >
> > > > > Did you set a grace period on the window?
> > > > >
> > > > > Best,
> > > > > Bruno
> > > > >
> > > > > On Tue, Jun 18, 2019 at 2:04 AM
Parthasarathy, Mohan <mpart...@hpe.com> wrote:
> > > > > >
> > > > > > On further debugging, what we are seeing is
that windows are expiring rather randomly as new messages are being processed.
. We tested with new key for every new message. We waited for the window time
before replaying new messages. Sometimes a new message would come in and create
state. It takes several messages to make some of the old windows to be closed
(go past suppress to the next stage). We have also seen where one of them never
closed even but several other older ones expired. Then we explicitly sent a
message with the same old key and then it showed up. Also, for every new
message, only one of the previous window expires even though there are several
pending.
> > > > > >
> > > > > > If we don't use suppress, then there is
never an issue. With suppress, the behavior we are seeing is weird. We are
using 2.1.0 version in DSL mode. Any clues on what we could be missing ? Why
isn't there an order in the way windows are closed ? As event time progresses
by the new messages arriving, the older ones should expire. Is that right
understanding or not ?
> > > > > >
> > > > > > Thanks
> > > > > > Mohan
> > > > > >
> > > > > > On 6/17/19, 3:43 PM, "Parthasarathy, Mohan"
<mpart...@hpe.com> wrote:
> > > > > >
> > > > > > Hi,
> > > > > >
> > > > > > We are using suppress in the
application. We see some state being created at some point in time. Now there
is no new data for a day or two. We send new data but the old window of data
(where we see the state being created) is not closing i.e not seeing it go
through suppress and on to the next stage. It is as though the state created
earlier was purged. Is this possible ?
> > > > > >
> > > > > > Thanks
> > > > > > Mohan
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > >
> > >
> > >
> > >
> >
> >
>
>
