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[SPARK-23186][SQL] Initialize DriverManager first before loading JDBC Drivers #20359

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[SPARK-23186][SQL] Initialize DriverManager first before loading JDBC Drivers #20359

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[SPARK-23186][SQL] Initialize DriverManager first before loading Drivers
dongjoon-hyun Jan 23, 2018
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dongjoon-hyun Feb 3, 2018
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3 changes: 3 additions & 0 deletions sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/DriverRegistry.scala
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Expand Up @@ -32,6 +32,9 @@ import org.apache.spark.util.Utils
*/
object DriverRegistry extends Logging {

// Initialize DriverManager first to prevent potential deadlocks between DriverManager and Driver
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We need to say more about why this can avoid deadlock.

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we can copy something from the storm PR: https://github.com/apache/storm/pull/2134/files

DriverManager.getDrivers
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Hi, @rxin .
Could you give me some comments on this?

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More context about this change? Based on your PR description, this is to resolve the deadlocks among executors? How does it work after applying this change?

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@dongjoon-hyun dongjoon-hyun Jan 24, 2018 •
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It's the same situation like STORM in the PR description and this occurs in Spark, too.
In the Spark executor, the stacks shows the deadlock between DriverManager and Driver.

  • Pheonix library call DriverManager.loadInitialDrivers()
  • Spark DriverRegistry call PhoenixDriver constructor before DriverManager created.

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Unfortunately, so far, I only have this log only. It's difficult to reproduce this deadlock.

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How did you test it?

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We need a test; otherwise, it is not the right thing to merge such a PR.

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Do you mean a unit test case?

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I'm wondering if you can merge this PR if I can test this patch in somewhere of our customer cluster. :)

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@cloud-fan cloud-fan Jan 25, 2018 •
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if it's too hard to write a UT, I think a manual test is also fine.

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Thank you for review, @cloud-fan .
So far, this deadlock situation is reported intermittently without any logs.


private val wrapperMap: mutable.Map[String, DriverWrapper] = mutable.Map.empty

def register(className: String): Unit = {
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