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From "zrc@zjdex.com" <...@zjdex.com>
Subject Re: Re: About the question of Spark Structured Streaming window output
Date Mon, 27 Aug 2018 03:36:04 GMT
Hi Jungtaek Lim & Gerard Mass:
Thanks very much.
When I put three batch data like following :

batch 0:
2018-08-27 09:53:00,1
2018-08-27 09:53:01,1

batch 1:
2018-08-27 11:04:00,1
2018-08-27 11:04:01,1

batch 2:
2018-08-27 11:17:00,1
2018-08-27 11:17:01,1

the agg result of time "2018-08-27 09:53:00" is output like following:
Batch: 2
-------------------------------------------
+-------------------+-------------------+--------+
|              start|                end|sumvalue|
+-------------------+-------------------+--------+
|2018-08-27 09:50:00|2018-08-27 09:55:00|       2|
+-------------------+-------------------+--------+

For the result, I wonder to know:
1、why the start time is "2018-08-27 09:50:00" not "2018-08-27 09:53:00"? When I define the
window, the starttime is not set.
2、why the agg result of time "2018-08-27 09:53:00 " is not output when the batch1 data is
comming?

Thanks a lot!





zrc@zjdex.com
 
From: Jungtaek Lim
Date: 2018-08-27 11:01
To: zrc@zjdex.com
CC: Gerard Maas; user; 王程浩
Subject: Re: Re: About the question of Spark Structured Streaming window output
You may want to add streaming listener to your query and see when/how watermark is updated.
In short, watermark is calculated from previous batch and calculated value is applied to current
batch. So you may think that the result is provided later than expected, maybe a batch.

2018년 8월 27일 (월) 오전 11:56, zrc@zjdex.com <zrc@zjdex.com>님이 작성:
Hi Gerard Mass:
Thanks a lot for your reply. 
When i use "append" model,  I send the following data:
2018-08-27 09:53:00,1
2018-08-27 09:53:01,1
The result (which has only schema, like the following) has received after the batch is end.
But when the time of window + watermark is up, there is no result to output. Is there something
I misss? Thanks in advance.





zrc@zjdex.com
 
From: Gerard Maas
Date: 2018-08-27 05:00
To: zrc
CC: spark users; wch
Subject: Re: About the question of Spark Structured Streaming window output
Hi,

When you use a window in Append mode, you need to wait for the end of the window + watermark
to see the final record from the "append" mode.
This is your query over time. Note the timestamp at the right side of the cell and the data
present in it.

val windowedCounts = dataSrc
      .withWatermark("timestamp", "1 minutes")
      .groupBy(window($"timestamp", "5 minutes"))
      .agg(sum("value") as "sumvalue")
      .select("window.start", "window.end","sumvalue")




Going back to your questions:
1、when I set the append output model,  I send inputdata, but there is no result to output.
How to use append model in window aggreate case ?
Wait for the window + watermark to expire and you'll see the append record output

2、when I set the update output model, I send inputdata, the result is output every batch
.But I want output the result only once when window is end. How can I do?
Use `append` mode.

kr, Gerard.

On Thu, Aug 23, 2018 at 4:31 AM zrc@zjdex.com <zrc@zjdex.com> wrote:
Hi :
   I have some questions about spark structured streaming window output  in spark 2.3.1. 
I write the application code as following:

case class DataType(time:Timestamp, value:Long) {}

val spark = SparkSession
      .builder
      .appName("StructuredNetworkWordCount")
      .master("local[1]")
      .getOrCreate()
 
import spark.implicits._
// Create DataFrame representing the stream of input lines from connection to localhost:9999
val lines = spark.readStream
  .format("socket")
  .option("host", "localhost")
  .option("port", 9999)
  .load()

val words = lines.as[String].map(l => {
  var tmp = l.split(",")
  DataType(Timestamp.valueOf(tmp(0)), tmp(1).toLong)
}).as[DataType]

val windowedCounts = words
      .withWatermark("time", "1 minutes")
      .groupBy(window($"time", "5 minutes"))
      .agg(sum("value") as "sumvalue")
      .select("window.start", "window.end","sumvalue")

val query = windowedCounts.writeStream
  .outputMode("update")
  .format("console")
  .trigger(Trigger.ProcessingTime("10 seconds"))
  .start()

query.awaitTermination()

the input data format is :
2018-08-20 12:01:00,1
2018-08-20 12:02:01,1

My questions are:
1、when I set the append output model,  I send inputdata, but there is no result to output.
How to use append model in window aggreate case ?
2、when I set the update output model, I send inputdata, the result is output every batch
.But I want output the result only once when window is end. How can I do?

Thanks in advance!




zrc@zjdex.com
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