Feat: standardize logging

[ctlong]

Description

Standardize logging across agents.

Checklist:

• This PR is being made against the main branch, or relevant version branch
• I have made corresponding changes to the documentation
• I have added testing for my changes

If you have any questions, or want to get attention for a PR or issue please reach out on the #logging-and-metrics channel in the cloudfoundry slack

[chombium]

Hi @ctlong,

I really like the idea of standardizing the logging, I have three questions though:

1. Why not using some logging library? Do you think that we need our custom solution, because we have some special logging needs?
2. What's the meaning of a session? Can you give some examples how it should be used?
3. I was expecting to see a log level: ERROR, INFO, DEBUG etc. as well and based on the level, the appropriate messages to be written to the log. Do you plan to add log level as well?

This looks like a wip to me, so I want to know what are the ideas how it should work ;)

[ctlong]

@chombium this is definitely a WIP 😅. I left it in draft format for that reason, but also didn't expect anyone to look at it so quickly.

As to your questions:

1. I'm happy to use a logging library instead. I started this way partly because I was curious to see if this was easy without a logging library, and partly because it was hard to choose a logging library out of everything available.
2. In my head starting a session represents entering some area of the code, and adding a new prefix to the existing prefixes to represent that. (i.e. after logr := logr.Session("egress"), logr.Infof("my log line") will output <timestamp> INFO egress: my log line)
3. This code already includes log levels, check out the individual methods. (i.e. Infof, Errorf)

[chombium]

Thanks for the clarification @ctlong. Thb I'm also not sure if we need some logging library...

When I've written about log levels, I meant that the user sets a log level and it doesn't get the log messages which are with lower priority than this level. A parameter with which the "log chattiness" of the app can be controlled.
For example:

• ERROR: prints only errors
• WARNING: prints errors and warnings
• INFO: prints errors, warnings and info messages
• DEBUG: prints everything

[ctlong]

When I've written about log levels, I meant that the user sets a log level and it doesn't get the log messages which are with lower priority than this level. A parameter with which the "log chattiness" of the app can be controlled.
For example:

ERROR: prints only errors
WARNING: prints errors and warnings
INFO: prints errors, warnings and info messages
DEBUG: prints everything

Thanks for clarifying! Yeah, I agree that makes sense compared to using conditionals throughout code to check whether to run an log.Infof or whatever 😄.

[ctlong]

Just amended the commit to include log levels.

[ctlong]

Now planning to wait until structured logging comes to the Go standard library (expected in Go 1.21).