[SPARK-12554] Standalone mode may hang if max cores is not a multiple of executor cores

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Incomplete
• Affects Version/s: 1.5.2
• Component/s: Deploy, Scheduler, Spark Core
• Labels: bulk-closed
• Assignee: Unassigned
• Reporter: Lijie Xu
• Created: 29/Dec/15 10:10
• Updated: 17/May/20 17:47
• Resolved: 21/May/19 04:16

Description

In scheduleExecutorsOnWorker() in Master.scala,
val keepScheduling = coresToAssign >= minCoresPerExecutor should be changed to val keepScheduling = coresToAssign > 0

Case 1:
Suppose that an app's requested cores is 10 (i.e., spark.cores.max = 10) and app.coresPerExecutor is 4 (i.e., spark.executor.cores = 4).

After allocating two executors (each has 4 cores) to this app, the app.coresToAssign = 2 and minCoresPerExecutor = coresPerExecutor = 4, so keepScheduling = false and no extra executor will be allocated to this app. If spark.scheduler.minRegisteredResourcesRatio is set to a large number (e.g., > 0.8 in this case), the app will hang and never finish.

Case 2: if a small app's coresPerExecutor is larger than its requested cores (e.g., spark.cores.max = 10, spark.executor.cores = 16), val keepScheduling = coresToAssign >= minCoresPerExecutor is always FALSE. As a result, this app will never get an executor to run.

Issue Links

• relates to: SPARK-20483 Mesos Coarse mode may starve other Mesos frameworks if max cores is not a multiple of executor cores
• links to: [Github] Pull Request #10507 (JerryLead)