[YARN-9808] Zero length files in container log output haven't got a header

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.2.0
• Fix Version/s: 3.3.0
• Component/s: log-aggregation, yarn
• Target Version/s: 3.3.0
• Hadoop Flags: Reviewed
• Assignee: Adam Antal
• Reporter: Adam Antal
• Created: 02/Sep/19 14:42
• Updated: 25/Sep/19 09:45
• Resolved: 25/Sep/19 08:29

Description

Using the Yarn logs CLI for containers that have zero length files produces output similar to this:

End of LogType:stderr
***********************************************************************


End of LogType:prelaunch.err
******************************************************************************

Container: container_e25_1567431105510_0001_01_000002 on host-1
LogAggregationType: AGGREGATED
=======================================================================================================
LogType:container.log
LogLastModifiedTime:Mon Sep 02 06:34:48 -0700 2019
LogLength:5442
LogContents:
...
...

Note that stderr and prelaunch.err are both zero length files. Though the output is not misleading, the header is missing.

I suggest to add the header for zero length files as well, primarily for the following reasons:

• for applications having multiple files with the same name you may want to distinguish them by host - if many of those are of zero length, you can not extract this information from here. Note that this is a common case for stderr and prelaunch.err.
• you may want to see the modification time (which corresponds to the creation time of the zero length file)
• would explicitly display the "LogLength:0" line, which would avoid any confusion from end user side.

Issue Links

• is related to: YARN-9856 Remove log-aggregation related duplicate function