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From yeshwanth kumar <yeshwant...@gmail.com>
Subject RDD Partitions on HDFS file in Hive on Spark Query
Date Mon, 21 Nov 2016 22:17:56 GMT
Hi,

we are running Hive on Spark, we have an external table over snappy
compressed csv file of size 917.4 M
HDFS block size is set to 256 MB

as per my Understanding, if i run a query over that external table , it
should launch 4 tasks. one for each block.
but i am seeing one executor and one task processing all the file.

trying to understand the reason behind,

i went one step further to understand the block locality
when i get the block locations for that file, i found

[DatanodeInfoWithStorage[10.11.0.226:50010
,DS-bf39d33d-48e1-4a8f-be48-b0953fdaad37,DISK],
 DatanodeInfoWithStorage[10.11.0.227:50010
,DS-a760c1c8-ce0c-4eb8-8183-8d8ff5f24115,DISK],
 DatanodeInfoWithStorage[10.11.0.228:50010
,DS-0e5427e2-b030-43f8-91c9-d8517e68414a,DISK]]

DatanodeInfoWithStorage[10.11.0.226:50010
,DS-f50ddf2f-b827-4845-b043-8b91ae4017c0,DISK],
DatanodeInfoWithStorage[10.11.0.228:50010
,DS-e8c9785f-c352-489b-8209-4307f3296211,DISK],
DatanodeInfoWithStorage[10.11.0.225:50010
,DS-6f6a3ffd-334b-45fd-ae0f-cc6eb268b0d2,DISK]]

DatanodeInfoWithStorage[10.11.0.226:50010
,DS-f8bea6a8-a433-4601-8070-f6c5da840e09,DISK],
DatanodeInfoWithStorage[10.11.0.227:50010
,DS-8aa3f249-790e-494d-87ee-bcfff2182a96,DISK],
DatanodeInfoWithStorage[10.11.0.228:50010
,DS-d06714f4-2fbb-48d3-b858-a023b5c44e9c,DISK]

DatanodeInfoWithStorage[10.11.0.226:50010
,DS-b3a00781-c6bd-498c-a487-5ce6aaa66f48,DISK],
DatanodeInfoWithStorage[10.11.0.228:50010
,DS-fa5aa339-e266-4e20-a360-e7cdad5dacc3,DISK],
DatanodeInfoWithStorage[10.11.0.225:50010
,DS-9d597d3f-cd4f-4c8f-8a13-7be37ce769c9,DISK]]

and in the spark UI i see the Locality Level is  RACK_LOCAL. for that task

if it is RACK_LOCAL then it should run either in node 10.11.0.226 or
10.11.0.228, because these 2 nodes has all the four blocks needed for
computation
but the executor is running in 10.11.0.225

my theory is not applying anywhere.

please help me in understanding how spark/yarn calculates number of
executors/tasks.

Thanks,
-Yeshwanth

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