Logging

[bbengfort]

Create a logging system that has the following log levels:

• DEBUG
• INFO
• WARNING
• ERROR
• FATAL

And add logging system to FluidFS.

Note the logging must be configurable from the YAML file.

[bbengfort]

I do really like Dave Chaney's "Let's talk about logging" post which advocates only two levels: debug and info.

However, as this is a research project, I think having multiple levels of logging is necessary, as well as the ability to specify a log file for processes that run in the background (rather than relying on redirection of stdout).

To get going, here is the mechanism I've implemented:

• Logger struct that wraps a log.Logger
• Log levels and methods on the Logger that allow easy writing to the log.
• Log level of the logger will determine what gets written.
• On init - the Logger will create a new log.Logger with the file writer or stdout.

I played with the idea of passing a "debug" mode that would create another writer to stdout for debugging messages (io.Discard otherwise), but decided against it.

My hope is that wrapping this functionality will also ensure the ability to perform concurrent writes (but I am worried about that).