[HDFS-16209] Add description for dfs.namenode.caching.enabled

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.1.0
• Fix Version/s: 3.4.0
• Component/s: documentation
• Labels: pull-request-available
• Target Version/s: 3.4.0
• Hadoop Flags: Reviewed
• Assignee: Tao Li
• Reporter: Tao Li
• Created: 03/Sep/21 04:20
• Updated: 11/Feb/24 09:30
• Resolved: 08/Sep/21 04:39

Description

Namenode config:
dfs.namenode.write-lock-reporting-threshold-ms=50ms
dfs.namenode.caching.enabled=true (default)

 

In fact, the caching feature is not used in our cluster, but this switch is turned on by default(dfs.namenode.caching.enabled=true), incurring some additional write lock overhead. We count the number of write lock warnings in a log file, and find that the number of rescan cache warnings reaches about 32%, which greatly affects the performance of Namenode.

 

We should set 'dfs.namenode.caching.enabled' to false by default and turn it on when we wants to use it.

Issue Links

• links to: GitHub Pull Request #3378