Hadoop Bug Reproduction Part 2: Code [HDFS 14859: Performance Degradation Due to Safe Mode]

Hadoop Performance Degradation Due to unnecessary getNumLiveDataNodes check. When Hadoop starts up, it enters a "safe mode," where it doesn’t accept any request. Now, to exit safe mode, Hadoop requires two conditions to be met: 1) sufficient blocks being replicated, and 2) enough datanodes that came online. But we can skip the second check if the first condition is not met.
University of Chicago. CMSC 332000: Topics of Operating Systems.