[IMPALA-9541] Document for dynamic log level changes

• Type: Documentation
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Impala 4.0.0
• Component/s: Docs
• Epic Color: ghx-label-10
• Assignee: shajini thayasingh
• Reporter: Quanlong Huang
• Created: 21/Mar/20 08:39
• Updated: 03/Jun/20 01:34
• Resolved: 03/Jun/20 01:34

Description

There is a /log_level tab in the debug page of all Impala servers. We can use it to dynamically adjust log levels without restarting the server. Although it's a feature implemented years ago (IMPALA-4822), there are no documents about it. I think we should add a section in https://impala.apache.org/docs/build/html/topics/impala_logging.html about it. Also it's good to explain the pattern of each line in logs.

For FE debugging, I usually set log level of org.apache.impala to TRACE.
For log pattern, it's
${level}${month}${day} HH:MM:SS.${us} ${thread-id} ${source-file}:${line}] ${query-id}] ${message}