[YARN-7135] Clean up lock-try order in common scheduler code

• Type: Improvement
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.0.0-alpha4
• Component/s: scheduler
• Labels: newbie
• Assignee: weiyuan
• Reporter: Daniel Templeton
• Created: 30/Aug/17 22:05
• Updated: 02/Oct/19 17:14

Description

There are many places that follow the pattern:

try {
  lock.lock();
  ...
} finally {
  lock.unlock();
}

There are a couple of reasons that's a bad idea. The correct pattern is:

lock.lock();
try {
  ...
} finally {
  lock.unlock();
}