--debug-level flag not working

[paulhauner]

Description

I suspect that the lighthosue --debug-level flag is not working.

The flag is defined here:

lighthouse/lighthouse/src/main.rs

Lines 45 to 53 in 97aa8b7

	.arg(
	Arg::with_name("debug-level")
	.long("debug-level")
	.value_name("LEVEL")
	.help("The title of the spec constants for chain config.")
	.takes_value(true)
	.possible_values(&["info", "debug", "trace", "warn", "error", "crit"])
	.default_value("trace"),
	)

The code that applies the level is here:

lighthouse/lighthouse/environment/src/lib.rs

Lines 95 to 134 in 97aa8b7

	/// Specifies that the `slog` asynchronous logger should be used. Ideal for production.
	///
	/// The logger is "async" because it has a dedicated thread that accepts logs and then
	/// asynchronously flushes them to stdout/files/etc. This means the thread that raised the log
	/// does not have to wait for the logs to be flushed.
	pub fn async_logger(mut self, debug_level: &str) -> Result<Self, String> {
	// Build the initial logger.
	let decorator = slog_term::TermDecorator::new().build();
	let decorator = logging::AlignedTermDecorator::new(decorator, logging::MAX_MESSAGE_WIDTH);
	let drain = slog_term::FullFormat::new(decorator).build().fuse();
	let drain = slog_async::Async::new(drain).build();
	let drain = match debug_level {
	"info" => drain.filter_level(Level::Info),
	"debug" => drain.filter_level(Level::Debug),
	"trace" => drain.filter_level(Level::Trace),
	"warn" => drain.filter_level(Level::Warning),
	"error" => drain.filter_level(Level::Error),
	"crit" => drain.filter_level(Level::Critical),
	unknown => return Err(format!("Unknown debug-level: {}", unknown)),
	};
	self.log = Some(Logger::root(drain.fuse(), o!()));
	Ok(self)
	}
	/// Consumes the builder, returning an `Environment`.
	pub fn build(self) -> Result<Environment<E>, String> {
	Ok(Environment {
	runtime: self
	.runtime
	.ok_or_else(|| "Cannot build environment without runtime".to_string())?,
	log: self
	.log
	.ok_or_else(|| "Cannot build environment without log".to_string())?,
	eth_spec_instance: self.eth_spec_instance,
	eth2_config: self.eth2_config,
	})
	}
	}

Steps to fix

1. Confirm my suspicion.
2. Fix it.
3. Prove to yourself that the level is effective.

[paulhauner]

So it turns out the flag is working when outputting to the CLI but not when outputting to file (using --log-file).