Re: Print on screen DataStream content

Posted by Timo Walther on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/Print-on-screen-DataStream-content-tp39728p39741.html

Hi Simone,

if you are just executing DataStream pipelines locally in your IDE while
prototyping. You should be able to use `DataStream#print()` which just
prints to standard out [1] (It might be hidden between the log messages).

For debugging locally, you can also just set breakpoints in your
functions like in `StatefulSessionCalculator` and use the debugging mode
of your IDE.

Regards,
Timo

[1]
https://github.com/apache/flink/blob/master/flink-examples/flink-examples-streaming/src/main/java/org/apache/flink/streaming/examples/wordcount/WordCount.java


On 24.11.20 11:09, Simone Cavallarin wrote:

> I tried to `DataStream#print()` but I don't quite understand how to
> implement it. Could you please give me an example? I'm using Intellij so
> what I would need is just to see the data on my screen.
>
> Thanks
>
> ------------------------------------------------------------------------
> *From:* David Anderson <[hidden email]>
> *Sent:* 24 November 2020 10:01
> *To:* Pankaj Chand <[hidden email]>
> *Cc:* Austin Cawley-Edwards <[hidden email]>; Simone Cavallarin
> <[hidden email]>; [hidden email] <[hidden email]>
> *Subject:* Re: Print on screen DataStream content
> When Flink is running on a cluster, `DataStream#print()` prints to files
> in the log directory.
>
> Regards,
> David
>
> On Tue, Nov 24, 2020 at 6:03 AM Pankaj Chand <[hidden email]
> <mailto:[hidden email]>> wrote:
>
>     Please correct me if I am wrong. `DataStream#print()` only prints to
>     the screen when running from the IDE, but does not work (print to
>     the screen) when running on a cluster (even a local cluster).
>
>     Thanks,
>
>     Pankaj
>
>     On Mon, Nov 23, 2020 at 5:31 PM Austin Cawley-Edwards
>     <[hidden email] <mailto:[hidden email]>> wrote:
>
>         Hey Simone,
>
>         I'd suggest trying out the `DataStream#print()` function to
>         start, but there are a few other easy-to-integrate sinks for
>         testing that you can check out in the docs here[1]
>
>         Best,
>         Austin
>
>         [1]:
>         https://ci.apache.org/projects/flink/flink-docs-release-1.11/dev/datastream_api.html#data-sinks
>         <https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fci.apache.org%2Fprojects%2Fflink%2Fflink-docs-release-1.11%2Fdev%2Fdatastream_api.html%23data-sinks&data=04%7C01%7C%7C27267479d99245bad55408d8905fea55%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637418088905500774%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=9YFLY5slrok3wXJ5n1F3s0BNYuzNs%2F70RLWLsWJCkzE%3D&reserved=0>
>
>         On Mon, Nov 23, 2020 at 3:56 PM Simone Cavallarin
>         <[hidden email] <mailto:[hidden email]>> wrote:
>
>             Hi All,
>
>             On my code I have a DataStream that I would like to access.
>             I need to understand what I'm getting for each
>             transformation to check if the data that I'm working on make
>             sense. How can I print into the console or get a file (csv,
>             txt) for the variables: "stream", "enriched" and "result"?
>
>             I have tried different way but no way to get the data.
>
>             Thanks!
>             /
>             /
>             /
>             /
>             /        FlinkKafkaConsumer<Event> kafkaData =/
>             /                new FlinkKafkaConsumer("CorID_1", new
>             EventDeserializationSchema(), p);/
>             /        WatermarkStrategy<Event> wmStrategy =/
>             /                WatermarkStrategy/
>             /                        .<Event>forMonotonousTimestamps()/
>             /                        .withIdleness(Duration.ofMinutes(1))/
>             /                        .withTimestampAssigner((event,
>             timestamp) -> {/
>             /                            return event.get_Time();/
>             /                        });/
>             /        DataStream<Event> *stream *= env.addSource(/
>             /              
>             kafkaData.assignTimestampsAndWatermarks(wmStrategy));/
>             /
>             /
>             /        DataStream<Tuple2<Event, Long>> *enriched* = stream/
>             /                .keyBy((Event KafkaMSG) -> KafkaMSG.CorrID)/
>             /                .map(new StatefulSessionCalculator());/
>             /
>             /
>             /        WindowedStream<Tuple2<Event, Long>, String,
>             TimeWindow> *result* = enriched/
>             /                .keyBy(new MyKeySelector())/
>             /              
>             .window(EventTimeSessionWindows.withDynamicGap(new
>             DynamicSessionWindows()));/
>