[HDFS-11577] Combine the old and the new chooseRandom for better performance

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.9.0, 3.0.0-alpha4
• Component/s: namenode
• Hadoop Flags: Reviewed
• Assignee: Chen Liang
• Reporter: Chen Liang
• Created: 24/Mar/17 20:11
• Updated: 24/Aug/17 18:19
• Resolved: 28/Mar/17 15:08

Description

As discussed in HDFS-11535, this JIRA adds a new function combining both the new and the old chooseRandom methods for better performance.

More specifically, when choosing a random node with storage type requirement, the combined method first tries the old method of blindly picking a random node. If this node satisfies, it is returned. Otherwise, the new chooseRandom is called, which guarantees to find a eligible node in one call (if there is one at all).