[HADOOP-11209] Configuration#updatingResource/finalParameters are not thread-safe

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.6.0
• Fix Version/s: 2.7.0
• Component/s: conf
• Target Version/s: 2.7.0
• Hadoop Flags: Reviewed
• Assignee: Varun Saxena
• Reporter: Josh Rosen
• Created: 17/Oct/14 21:38
• Updated: 19/May/15 23:21
• Resolved: 22/Jan/15 05:18

Description

Configuration objects are not fully thread-safe, which causes problems in multi-threaded frameworks like Spark that use these configurations to interact with existing Hadoop APIs (such as InputFormats).

SPARK-2546 is an example of a problem caused by this lack of thread-safety. In that bug, multiple concurrent modifications of the same Configuration (in third-party code) caused an infinite loop because Configuration's internal java.util.HashMap is not thread-safe.

One workaround is for our code to clone Configuration objects; unfortunately, this also suffers from thread-safety issues on older Hadoop versions because Configuration's constructor wasn't thread-safe (HADOOP-10456).

Looking at a recent version of Configuration.java, it seems that the private updatingResource HashMap and finalParameters HashSet fields the only non-thread-safe collections in Configuration (Java's Properties class is thread-safe), so I don't think that it would be hard to make Configuration fully thread-safe.

Issue Links

• duplicates: HADOOP-11274 ConcurrentModificationException in Configuration Copy Constructor
• is related to: SPARK-2546 Configuration object thread safety issue
• is related to: HADOOP-11984 Enable parallel JUnit tests in pre-commit.