We're not using a Window but a more basic ProcessFunction to handle sessions. We made this choice because we have to handle (millions of) sessions that can last from 10 seconds to 24 hours so we wanted to handle things manually using the State class. We're using the watermark as an event-time "clock" to: * compute "lateness" of a message relatively to the watermark (most recent message from the stream) * fire timer events
We're using event-time instead of processing time because our stream will be late and data arrive by hourly bursts. Maybe we're misusing the watermark ? B.R. -----Original Message----- From: Nico Kruber [mailto:n...@data-artisans.com] Sent: jeudi 3 août 2017 16:30 To: user@flink.apache.org Cc: Gwenhael Pasquiers <gwenhael.pasqui...@ericsson.com> Subject: Re: Event-time and first watermark Hi Gwenhael, "A Watermark(t) declares that event time has reached time t in that stream, meaning that there should be no more elements from the stream with a timestamp t’ <= t (i.e. events with timestamps older or equal to the watermark)." [1] Therefore, they should be behind the actual event with timestamp t. What is it that you want to achieve in the end? What do you want to use the watermark for? They are basically a means to defining when an event time window ends. Nico [1] https://ci.apache.org/projects/flink/flink-docs-release-1.2/dev/ event_time.html#event-time-and-watermarks On Thursday, 3 August 2017 10:24:35 CEST Gwenhael Pasquiers wrote: > Hi, > > From my tests it seems that the initial watermark value is > Long.MIN_VALUE even though my first data passed through the timestamp > extractor before arriving into my ProcessFunction. It looks like the > watermark "lags" behind the data by one message. > > Is there a way to have a watermark more "up to date" ? Or is the only > way to compute it myself into my ProcessFunction ? > > Thanks.
