[MAPREDUCE-6059] Speed up history server startup time

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.0
• Fix Version/s: 2.7.0
• Hadoop Flags: Reviewed
• Assignee: Siqi Li
• Reporter: Siqi Li
• Created: 28/Jul/14 20:58
• Updated: 24/Apr/15 23:15
• Resolved: 05/Feb/15 01:36

Description

When history server starts up, It scans every history directories and put all history files into a cache, whereas this cache only stores 20K recent history files. Therefore, it is wasting a large portion of time loading old history files into the cache, and the startup time will keep increasing if we don't trim the number of history files. For example, when history server starts up with 2.5M history files in HDFS, it took ~5 minutes.