David, note that KafkaIO in Beam requires Kafka server version should be >= 0.9
On Thu, Jul 7, 2016 at 4:27 PM, David Desberg <[email protected]> wrote: > Dan, > > Yeah, it’s setting it to the ingestion time. I will look into KafkaIO, as > it looks to provide exactly the functionality I want. I was wondering how > to set the timestamp correctly, at the source. Thank you for your help! > > David > > On Jul 7, 2016, at 4:25 PM, Dan Halperin <[email protected]> wrote: > > Hi David, > > In Beam pipelines, the event time is initially set on the source. > Downstream code can make an event *later* just fine, but, making it > *earlier* might move it before the current watermark. This would effective > tur data that we believe is on-time into late data, and would in general be > very bad! Allowed lateness is a feature that lets you move data earlier by > a fixed amount, so if you have a tight bound on the time set by the source, > this can sometimes help. But it's generally discouraged in favor of proper > timestamps in the first place. > > My guess is that UnboundedFlinkSource is using the *processing time*, aka > current time when the element is received, rather than any event time > provided by the element. It might be possible using that source to provide > the element time. > > Alternately, I think you should be using KafkaIO and setting the event > time there using withTimestampFn: > https://github.com/apache/incubator-beam/blob/master/sdks/java/io/kafka/src/main/java/org/apache/beam/sdk/io/kafka/KafkaIO.java#L136 > > This way the elements will come into the system from Kafka with good > timestamps, and you don't need a downstream DoFn to transport them back in > time. > > Thanks, > Dan > > On Thu, Jul 7, 2016 at 4:15 PM, amir bahmanyari <[email protected]> > wrote: > >> Hi David, >> I am doing pretty much the same thing using Beam KafkaIO. >> For the simple thing I am doing, its working as expected. >> Can you provide the code how you are invoking/receiving from Kafka pls? >> Cheers >> >> >> ------------------------------ >> *From:* David Desberg <[email protected]> >> *To:* [email protected] >> *Sent:* Thursday, July 7, 2016 12:54 PM >> *Subject:* Event time processing with Flink runner and Kafka source >> >> Hi all, >> >> I’m struggling to get a basic Beam application setup, windowed based upon >> event time. I’m reading from an UnboundedFlinkSource of a >> FlinkKafkaConsumer to begin my pipeline. To set up event time processing, I >> applied a DoFn transformation (via ParDo) that calls >> ProcessContext.outputWithTimestamp using a timestamp extracted from each >> Kafka message. However, this results in an exception telling me to >> override getAllowedTimestampSkew, since evidently the messages are already >> timestamped and I am moving these timestamps back in time, but only >> shifting to the future is allowed. getAllowedTimestampSkew, however, is >> deprecated, and if I do override it and allow skew, the windowing I am >> applying later in the pipeline fails. I decided to backtrack and look at >> how the timestamps are even being assigned initially, since the Flink >> source has no concept of the structure of my messages and thus shouldn’t >> know how to assign any time at all. I found that it turns out that the >> pipeline runner marks each incoming message with ingestion time, in a >> manner that cannot be overridden/is not configurable (see >> https://github.com/apache/incubator-beam/blob/master/runners/flink/runner/src/main/java/org/apache/beam/runners/flink/translation/FlinkStreamingTransformTranslators.java#L273 >> ) >> >> Why is this the case? Since part of the point of Beam is to allow >> event-time processing, I’m sure I’m missing something here. How can I >> correctly ingest message from Kafka and stamp them with event time, rather >> than ingestion time? >> >> >> > >
