[jira] [Created] (SPARK-28850) Binary Files RDD allocates false number of threads

["Marco Lotz (Jira)" <ji...@apache.org>]

Marco Lotz created SPARK-28850:
----------------------------------

             Summary: Binary Files RDD allocates false number of threads
                 Key: SPARK-28850
                 URL: https://issues.apache.org/jira/browse/SPARK-28850
             Project: Spark
          Issue Type: Bug
          Components: Input/Output
    Affects Versions: 2.4.3
            Reporter: Marco Lotz


When making a call to:

```scala

sc.binaryFiles(somePath)

```

It creates a BinaryFileRDD. Some sections of that code are run inside the driver container. The current source code for BinaryFileRDD is available here:
[https://github.com/apache/spark/blob/2d085c13b7f715dbff23dd1f81af45ff903d1a79/core/src/main/scala/org/apache/spark/rdd/BinaryFileRDD.scala

]The problematic line is:

```scala

conf.setIfUnset(FileInputFormat.LIST_STATUS_NUM_THREADS, Runtime.getRuntime.availableProcessors().toString)

```

This line sets the number of Threads to be used (in the case of multi-threading reading) to the number of cores (including Hyper Threading ones) available one the driver host machine.


This number is false, since what really matters is the number of cores allocated to the driver container by YARN and not the number of cores available in the host machine. This can easily impact the Spark-UI and the driver application performance, since the number of threads is far bigger than the true amount of allocated cores - which increases the number of unrequired preemptions and context switches

The solution is to retrieve the number of cores allocated to the Application Master by YARN instead.

Once confirmed the problem, I can work on retrieving that information and making a PR.



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