[IMPALA-7157] Avoid unnecessarily pretty printing profiles per fragment instance

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: Impala 3.1.0
• Component/s: Distributed Exec
• Labels: logs
• Epic Color: ghx-label-9
• Assignee: Sailesh Mukil
• Reporter: Sailesh Mukil
• Created: 08/Jun/18 23:39
• Updated: 18/Jun/18 17:49
• Resolved: 18/Jun/18 17:49

Description

In SendReport(), if VLOG_FILE_IS_ON is 'true' (which is not the most verbose logging level, but is higher than default), we pretty print the profile for every fragment instance, which is a very expensive operation, as serializing the profile is non-trivial (look at RuntimeProfile::PrettyPrint()), and printing large amounts of information to the logs isn't cheap as well. Lastly, it is very noisy.

This seems unnecessary since this will not benefit us, as all the profiles are merged at the coordinator side. We could argue that this might be necessary when an executor fails to send the profile to the coordinator, but that signifies a network issue which will not be reflected in the profile of any fragment instance.

This will help reduce noise in the logs when the log level is bumped up to find other real issues that VLOG_FILE can help with.