[YARN-8164] Fix a potential NPE in AbstractSchedulerPlanFollower

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.0-beta1
• Fix Version/s: 2.10.0, 3.2.0
• Hadoop Flags: Reviewed
• Assignee: lujie
• Reporter: lujie
• Created: 15/Apr/18 14:04
• Updated: 17/Apr/18 00:33
• Resolved: 17/Apr/18 00:33

Description

We have developed a static analysis tool NPEDetector to find some potential NPE. Our analysis shows that some callees may return null in corner case(e.g. node crash , IO exception), some of their callers have  !=null check but some do not have.

Callee FairScheduler#getAppsInQueue can return null

public List<ApplicationAttemptId> getAppsInQueue(String queueName) {
    FSQueue queue = queueMgr.getQueue(queueName);
   if (queue == null) {
      return null;//here
  }
}

it has 4 callers, three of them have null checker, one does not have. In this issue we post a patch which can add  !=null  based on existed !=null  check.