[SENTRY-966] SqoopAuthBindingSingleton uses bad double check locking idiom

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.7.0
• Component/s: Sqoop plugin
• Flags: Patch
• Assignee: Colm O hEigeartaigh
• Reporter: Colm O hEigeartaigh
• Created: 19/Nov/15 12:40
• Updated: 27/Nov/15 01:58
• Resolved: 27/Nov/15 01:58

Description

The SqoopAuthBindingSingleton uses the bad double check locking idiom:

http://www.javaworld.com/article/2074979/java-concurrency/double-checked-locking--clever--but-broken.html

An easy solution is just to make the variable volatile, but a much better approach is to use the Lazy init holder class idiom, which avoid synchronization altogether.