Structured Streaming together with Cassandra Queries

[Martin Engen]

Hello,

I have a case where I am continuously getting a bunch sensor-data which is 
being stored into a Cassandra table (through Kafka). Every week or so, I want 
to manually enter additional data into the system - and I want this to trigger 
some calculations merging the manual entered data, and the weeks worth of 
streaming sensor-data.

Is there a way to make dynamic Cassandra queries based on data coming into 
Spark?

example: Pressure sensors are being continuously stored into Cassandra, and I 
enter a weeks worth of temperatures into the system at the end of the week (1 
day/row at a time).
I want each of these rows to trigger queries to Cassandra to get the pressures 
for every specific day, and do some calculations on this.

I have been looking at using Structured Streaming with the 
Cassandra-spark-connector, but I cant find  a way to take data from a row in 
structured streaming into account on the query being made. And I seem to have 
to query for 'everything', and then filter in Spark.

Any ideas or tips for how to solve this?

Re: Structured Streaming, Reading and Updating a variable

[Martin Engen]

Executor.scala:338)
at 
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at 
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:748)


Any ideas about how to handle this error?


Thanks,
Martin Engen

From: Lalwani, Jayesh <jayesh.lalw...@capitalone.com>
Sent: Tuesday, May 15, 2018 9:59 PM
To: Martin Engen; user@spark.apache.org
Subject: Re: Structured Streaming, Reading and Updating a variable


Do you have a code sample, and detailed error message/exception to show?



From: Martin Engen <martin.en...@outlook.com>
Date: Tuesday, May 15, 2018 at 9:24 AM
To: "user@spark.apache.org" <user@spark.apache.org>
Subject: Structured Streaming, Reading and Updating a variable



Hello,



I'm working with Structured Streaming, and I need a method of keeping a running 
average based on last 24hours of data.

To help with this, I can use Exponential Smoothing, which means I really only 
need to store 1 value from a previous calculation into the new, and update this 
variable as calculations carry on.



Implementing this is a much bigger challenge then I ever imagined.





I've tried using Accumulators and to Query/Store data to Cassandra after every 
calculation. Both methods worked somewhat locally , but I don't seem to be able 
to use these in the Spark Worker Nodes,  as I get the error

"java.lang.NoClassDefFoundError: Could not initialize class error" both for the 
accumulator and the cassandra connection libary



How can you read/update a variable while doing calculations using Structured 
Streaming?



Thank you







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Structured Streaming, Reading and Updating a variable

[Martin Engen]

Hello,

I'm working with Structured Streaming, and I need a method of keeping a running 
average based on last 24hours of data.
To help with this, I can use Exponential Smoothing, which means I really only 
need to store 1 value from a previous calculation into the new, and update this 
variable as calculations carry on.

Implementing this is a much bigger challenge then I ever imagined.


I've tried using Accumulators and to Query/Store data to Cassandra after every 
calculation. Both methods worked somewhat locally , but I don't seem to be able 
to use these in the Spark Worker Nodes,  as I get the error
"java.lang.NoClassDefFoundError: Could not initialize class error" both for the 
accumulator and the cassandra connection libary

How can you read/update a variable while doing calculations using Structured 
Streaming?

Thank you