[HDFS-7492] If multiple threads call FsVolumeList#checkDirs at the same time, we should only do checkDirs once and give the results to all waiting threads

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Duplicate
• Component/s: datanode
• Assignee: Elliott Neil Clark
• Reporter: Colin McCabe
• Created: 08/Dec/14 22:16
• Updated: 17/Sep/15 18:52
• Resolved: 16/Sep/15 00:24

Description

checkDirs is called when we encounter certain I/O errors. It's rare to get just a single I/O error... normally you start getting many errors when a disk is going bad. For this reason, we shouldn't start a new checkDirs scan for each error. Instead, if multiple threads call FsVolumeList#checkDirs at around the same time, we should only do checkDirs once and give the results to all the waiting threads.

Issue Links

• is superceded by: HDFS-7531 Improve the concurrent access on FsVolumeList
• relates to: HDFS-7489 Incorrect locking in FsVolumeList#checkDirs can hang datanodes