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https://issues.apache.org/jira/browse/SPARK-36328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17395218#comment-17395218
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Apache Spark commented on SPARK-36328:
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User 'Shockang' has created a pull request for this issue:
https://github.com/apache/spark/pull/33674
> HadoopRDD#getPartitions fetches FileSystem Delegation Token for every
> partition
> -------------------------------------------------------------------------------
>
> Key: SPARK-36328
> URL: https://issues.apache.org/jira/browse/SPARK-36328
> Project: Spark
> Issue Type: Improvement
> Components: Spark Core
> Affects Versions: 3.1.2
> Reporter: Prabhu Joseph
> Priority: Major
>
> Spark Job creates a separate JobConf for every RDD (every hive table
> partition) in HadoopRDD#getPartitions.
> {code}
> override def getPartitions: Array[Partition] = {
> val jobConf = getJobConf()
> // add the credentials here as this can be called before SparkContext
> initialized
> SparkHadoopUtil.get.addCredentials(jobConf)
> {code}
> Hadoop FileSystem fetches FileSystem Delegation Token and sets into the
> Credentials which is part of JobConf. On further requests, will reuse the
> token from the Credentials if already exists.
> {code}
> if (serviceName != null) { // fs has token, grab it
> final Text service = new Text(serviceName);
> Token<?> token = credentials.getToken(service);
> if (token == null) {
> token = getDelegationToken(renewer);
> if (token != null) {
> tokens.add(token);
> credentials.addToken(service, token);
> }
> }
> }
> {code}
> But since Spark Job creates a new JobConf (which will have a new
> Credentials) for every hive table partition, the token is not reused and gets
> fetched for every partition. This is slowing down the query as each
> delegation token has to go through KDC and SSL handshake on Secure Clusters.
> *Improvement:*
> Spark can add the credentials from previous JobConf into the new JobConf to
> reuse the FileSystem Delegation Token similar to how the User Credentials are
> added into JobConf after construction.
> {code}
> val jobConf = getJobConf()
> // add the credentials here as this can be called before SparkContext
> initialized
> SparkHadoopUtil.get.addCredentials(jobConf)
> {code}
> *Repro*
> {code}
> beeline>
> create table parttable (key char(1), value int) partitioned by (p int);
> insert into table parttable partition(p=100) values ('d', 1), ('e', 2), ('f',
> 3);
> insert into table parttable partition(p=200) values ('d', 1), ('e', 2), ('f',
> 3);
> insert into table parttable partition(p=300) values ('d', 1), ('e', 2), ('f',
> 3);
> spark-sql>
> select value, count(*) from parttable group by value
> {code}
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