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From Michael Armbrust <mich...@databricks.com>
Subject Re: select count * doesnt seem to respect update mode in Kafka Structured Streaming?
Date Wed, 21 Mar 2018 00:00:39 GMT
Those options will not affect structured streaming.  You are looking for

.option("maxOffsetsPerTrigger", "1000")

We are working on improving this by building a generic mechanism into the
Streaming DataSource V2 so that the engine can do admission control on the
amount of data returned in a source independent way.

On Tue, Mar 20, 2018 at 2:58 PM, kant kodali <kanth909@gmail.com> wrote:

> I am using spark 2.3.0 and Kafka 0.10.2.0 so I assume structured streaming
> using Direct API's although I am not sure? If it is direct API's the only
> parameters that are relevant are below according to this
> <https://www.linkedin.com/pulse/enable-back-pressure-make-your-spark-streaming-production-lan-jiang>
> article
>
>    - spark.conf("spark.streaming.backpressure.enabled", "true")
>    - spark.conf("spark.streaming.kafka.maxRatePerPartition", "10000")
>
> I set both of these and I run select count * on my 10M records I still
> don't see any output until it finishes the initial batch of 10M and this
> takes a while. so I am wondering if I miss something here?
>
> On Tue, Mar 20, 2018 at 6:09 AM, Geoff Von Allmen <geoff@ibleducation.com>
> wrote:
>
>> The following
>> <http://spark.apache.org/docs/latest/configuration.html#spark-streaming> settings
>> may be what you’re looking for:
>>
>>    - spark.streaming.backpressure.enabled
>>    - spark.streaming.backpressure.initialRate
>>    - spark.streaming.receiver.maxRate
>>    - spark.streaming.kafka.maxRatePerPartition
>>
>> ​
>>
>> On Mon, Mar 19, 2018 at 5:27 PM, kant kodali <kanth909@gmail.com> wrote:
>>
>>> Yes it indeed makes sense! Is there a way to get incremental counts when
>>> I start from 0 and go through 10M records? perhaps count for every micro
>>> batch or something?
>>>
>>> On Mon, Mar 19, 2018 at 1:57 PM, Geoff Von Allmen <
>>> geoff@ibleducation.com> wrote:
>>>
>>>> Trigger does not mean report the current solution every 'trigger
>>>> seconds'. It means it will attempt to fetch new data and process it no
>>>> faster than trigger seconds intervals.
>>>>
>>>> If you're reading from the beginning and you've got 10M entries in
>>>> kafka, it's likely pulling everything down then processing it completely
>>>> and giving you an initial output. From here on out, it will check kafka
>>>> every 1 second for new data and process it, showing you only the updated
>>>> rows. So the initial read will give you the entire output since there is
>>>> nothing to be 'updating' from. If you add data to kafka now that the
>>>> streaming job has completed it's first batch (and leave it running), it
>>>> will then show you the new/updated rows since the last batch every 1 second
>>>> (assuming it can fetch + process in that time span).
>>>>
>>>> If the combined fetch + processing time is > the trigger time, you will
>>>> notice warnings that it is 'falling behind' (I forget the exact verbiage,
>>>> but something to the effect of the calculation took XX time and is falling
>>>> behind). In that case, it will immediately check kafka for new messages and
>>>> begin processing the next batch (if new messages exist).
>>>>
>>>> Hope that makes sense -
>>>>
>>>>
>>>> On Mon, Mar 19, 2018 at 13:36 kant kodali <kanth909@gmail.com> wrote:
>>>>
>>>>> Hi All,
>>>>>
>>>>> I have 10 million records in my Kafka and I am just trying to
>>>>> spark.sql(select count(*) from kafka_view). I am reading from kafka and
>>>>> writing to kafka.
>>>>>
>>>>> My writeStream is set to "update" mode and trigger interval of one
>>>>> second (Trigger.ProcessingTime(1000)). I expect the counts to be
>>>>> printed every second but looks like it would print after going through
all
>>>>> 10M. why?
>>>>>
>>>>> Also, it seems to take forever whereas Linux wc of 10M rows would take
>>>>> 30 seconds.
>>>>>
>>>>> Thanks!
>>>>>
>>>>
>>>
>>
>

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