### What changes were proposed in this pull request?
Improved warning message in Barrier Execution Mode when required slots > maximum slots.
The new message contains information about required slots, maximum slots and how many times retry failed.
### Why are the changes needed?
Providing to users with the number of required slots, maximum slots and how many times retry failed might help users to decide what they should do.
For example, continuing to wait for retry succeeded or killing jobs.
### Does this PR introduce any user-facing change?
Yes.
If `spark.scheduler.barrier.maxConcurrentTaskCheck.maxFailures=3`, we get following warning message.
Before applying this change:
```
19/08/18 15:18:09 WARN DAGScheduler: The job 2 requires to run a barrier stage that requires more slots than the total number of slots in the cluster currently.
19/08/18 15:18:24 WARN DAGScheduler: The job 2 requires to run a barrier stage that requires more slots than the total number of slots in the cluster currently.
19/08/18 15:18:39 WARN DAGScheduler: The job 2 requires to run a barrier stage that requires more slots than the total number of slots in the cluster currently.
19/08/18 15:18:54 WARN DAGScheduler: The job 2 requires to run a barrier stage that requires more slots than the total number of slots in the cluster currently.
org.apache.spark.scheduler.BarrierJobSlotsNumberCheckFailed: [SPARK-24819]: Barrier execution mode does not allow run a barrier stage that requires more slots than the total number of slots in the cluster currently. Please init a new cluster with more CPU cores or repartition the input RDD(s) to reduce the number of slots required to run this barrier stage.
at org.apache.spark.scheduler.DAGScheduler.checkBarrierStageWithNumSlots(DAGScheduler.scala:439)
at org.apache.spark.scheduler.DAGScheduler.createResultStage(DAGScheduler.scala:453)
at org.apache.spark.scheduler.DAGScheduler.handleJobSubmitted(DAGScheduler.scala:983)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.doOnReceive(DAGScheduler.scala:2140)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:2132)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:2121)
at org.apache.spark.util.EventLoop$$anon$1.run(EventLoop.scala:49)
at org.apache.spark.scheduler.DAGScheduler.runJob(DAGScheduler.scala:749)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2080)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2101)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2120)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2145)
at org.apache.spark.rdd.RDD.$anonfun$collect$1(RDD.scala:961)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
at org.apache.spark.rdd.RDD.withScope(RDD.scala:366)
at org.apache.spark.rdd.RDD.collect(RDD.scala:960)
... 47 elided
```
After applying this change:
```
19/08/18 16:52:23 WARN DAGScheduler: The job 0 requires to run a barrier stage that requires 3 slots than the total number of slots(2) in the cluster currently.
19/08/18 16:52:38 WARN DAGScheduler: The job 0 requires to run a barrier stage that requires 3 slots than the total number of slots(2) in the cluster currently (Retry 1/3 failed).
19/08/18 16:52:53 WARN DAGScheduler: The job 0 requires to run a barrier stage that requires 3 slots than the total number of slots(2) in the cluster currently (Retry 2/3 failed).
19/08/18 16:53:08 WARN DAGScheduler: The job 0 requires to run a barrier stage that requires 3 slots than the total number of slots(2) in the cluster currently (Retry 3/3 failed).
org.apache.spark.scheduler.BarrierJobSlotsNumberCheckFailed: [SPARK-24819]: Barrier execution mode does not allow run a barrier stage that requires more slots than the total number of slots in the cluster currently. Please init a new cluster with more CPU cores or repartition the input RDD(s) to reduce the number of slots required to run this barrier stage.
at org.apache.spark.scheduler.DAGScheduler.checkBarrierStageWithNumSlots(DAGScheduler.scala:439)
at org.apache.spark.scheduler.DAGScheduler.createResultStage(DAGScheduler.scala:453)
at org.apache.spark.scheduler.DAGScheduler.handleJobSubmitted(DAGScheduler.scala:983)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.doOnReceive(DAGScheduler.scala:2140)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:2132)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:2121)
at org.apache.spark.util.EventLoop$$anon$1.run(EventLoop.scala:49)
at org.apache.spark.scheduler.DAGScheduler.runJob(DAGScheduler.scala:749)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2080)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2101)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2120)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2145)
at org.apache.spark.rdd.RDD.$anonfun$collect$1(RDD.scala:961)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
at org.apache.spark.rdd.RDD.withScope(RDD.scala:366)
at org.apache.spark.rdd.RDD.collect(RDD.scala:960)
... 47 elided
```
### How was this patch tested?
I tested manually using Spark Shell with following configuration and script. And then, checked log message.
```
$ bin/spark-shell --master local[2] --conf spark.scheduler.barrier.maxConcurrentTasksCheck.maxFailures=3
scala> sc.parallelize(1 to 100, sc.defaultParallelism+1).barrier.mapPartitions(identity(_)).collect
```
Closes#25487 from sarutak/barrier-exec-mode-warning-message.
Authored-by: Kousuke Saruta <sarutak@oss.nttdata.com>
Signed-off-by: Sean Owen <sean.owen@databricks.com>
33e45ec7b8