[LU-3692] Versatile LLAPI logging

• Type: Technical task
• Resolution: Fixed
• Priority: Major
• Fix Version/s: Lustre 2.6.0, Lustre 2.5.1
• Affects Version/s: Lustre 2.5.0
• Labels: HSM liblustreapi patch
• Assignee: Jinshan Xiong (Inactive)
• Reporter: Henri Doreau (Inactive)

Description

LLAPI provides logging primitives but these only write on stdout or stderr.

Userland tools would benefit a lot from a logging API that, despite minimal, would allow them to register a logging callback function.

LLAPI could maybe provide a couple pre-implemented callbacks for stdout/stderr or syslog.

Third party products such as Robinhood policy engine could integrate LLAPI log messages as part of their own logs and Lustre tools (such as the HSM posix copytool) could easily log to syslog.