Add config options to coarsely disable log/tracing without initialization.

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/config/mod.rs

@@ -912,6 +912,26 @@ pub struct Config {
 	#[serde(default)]
 	pub log_to_stderr: bool,
 
+	/// Setting to false disables the logging/tracing system at a lower level.
+	/// In contrast to configuring an empty `log` string where the system is
+	/// still operating but muted, when this option is false the system was not
+	/// initialized and is not operating. Changing this option has no effect
+	/// after startup. This option is intended for developers and expert use
+	/// only: configuring an empty log string is preferred over using this.
+	///
+	/// default: true
+	#[serde(default = "true_fn")]
+	pub log_enable: bool,
+
+	/// Setting to false disables the logging/tracing system at a lower level
+	/// similar to `log_enable`. In this case the system is configured normally,
+	/// but not registered as the global handler in the final steps. This option
+	/// is for developers and expert use only.
+	///
+	/// default: true
+	#[serde(default = "true_fn")]
+	pub log_global_default: bool,
+
 	/// OpenID token expiration/TTL in seconds.
 	///
 	/// These are the OpenID tokens that are primarily used for Matrix account

src/core/log/mod.rs

@@ -8,23 +8,31 @@ pub mod fmt_span;
 mod reload;
 mod suppress;
 
-pub use capture::Capture;
-pub use console::{ConsoleFormat, ConsoleWriter, is_systemd_mode};
-pub use reload::{LogLevelReloadHandles, ReloadHandle};
-pub use suppress::Suppress;
-pub use tracing::Level;
+use std::sync::Arc;
+
+pub use tracing::{Level, subscriber::Subscriber};
 pub use tracing_core::{Event, Metadata};
 pub use tracing_subscriber::EnvFilter;
 
+pub use self::{
+	capture::Capture,
+	console::{ConsoleFormat, ConsoleWriter, is_systemd_mode},
+	reload::{LogLevelReloadHandles, ReloadHandle},
+	suppress::Suppress,
+};
+
 /// Logging subsystem. This is a singleton member of super::Server which holds
 /// all logging and tracing related state rather than shoving it all in
 /// super::Server directly.
-pub struct Log {
+pub struct Logging {
+	/// Subscriber assigned to globals and defaults; may also be NoSubscriber.
+	pub subscriber: Arc<dyn Subscriber + Send + Sync>,
+
 	/// General log level reload handles.
 	pub reload: LogLevelReloadHandles,
 
 	/// Tracing capture state for ephemeral/oneshot uses.
-	pub capture: std::sync::Arc<capture::State>,
+	pub capture: Arc<capture::State>,
 }
 
 // Wraps for logging macros. Use these macros rather than extern tracing:: or

src/core/server.rs

@@ -9,7 +9,7 @@ use std::{
 use ruma::OwnedServerName;
 use tokio::{runtime, sync::broadcast};
 
-use crate::{Err, Result, config, config::Config, log::Log, metrics::Metrics};
+use crate::{Err, Result, config, config::Config, log::Logging, metrics::Metrics};
 
 /// Server runtime state; public portion
 pub struct Server {
@@ -41,7 +41,7 @@ pub struct Server {
 	pub signal: broadcast::Sender<&'static str>,
 
 	/// Logging subsystem state
-	pub log: Log,
+	pub log: Logging,
 
 	/// Metrics subsystem state
 	pub metrics: Metrics,
@@ -49,7 +49,7 @@ pub struct Server {
 
 impl Server {
 	#[must_use]
-	pub fn new(config: Config, runtime: Option<runtime::Handle>, log: Log) -> Self {
+	pub fn new(config: Config, runtime: Option<runtime::Handle>, log: Logging) -> Self {
 		Self {
 			name: config.server_name.clone(),
 			config: config::Manager::new(config),

src/main/logging.rs

@@ -1,11 +1,12 @@
 use std::sync::Arc;
 
+use tracing::subscriber::NoSubscriber;
 use tracing_subscriber::{EnvFilter, Layer, Registry, fmt, layer::SubscriberExt, reload};
 use tuwunel_core::{
 	Result,
 	config::Config,
 	debug_warn, err,
-	log::{ConsoleFormat, ConsoleWriter, LogLevelReloadHandles, capture, fmt_span},
+	log::{ConsoleFormat, ConsoleWriter, LogLevelReloadHandles, Logging, capture, fmt_span},
 	result::UnwrapOrErr,
 };
 
@@ -14,13 +15,20 @@ pub(crate) type TracingFlameGuard =
 	Option<tracing_flame::FlushGuard<std::io::BufWriter<std::fs::File>>>;
 
 #[cfg(not(feature = "perf_measurements"))]
-pub(crate) type TracingFlameGuard = ();
+pub(crate) type TracingFlameGuard = Option<()>;
 
 #[allow(clippy::redundant_clone)]
-pub(crate) fn init(
-	config: &Config,
-) -> Result<(LogLevelReloadHandles, TracingFlameGuard, Arc<capture::State>)> {
+pub(crate) fn init(config: &Config) -> Result<(TracingFlameGuard, Logging)> {
 	let reload_handles = LogLevelReloadHandles::default();
+	let cap_state = Arc::new(capture::State::new());
+
+	if !config.log_enable {
+		return Ok((None, Logging {
+			reload: reload_handles,
+			capture: cap_state,
+			subscriber: Arc::new(NoSubscriber::new()),
+		}));
+	}
 
 	let console_span_events = fmt_span::from_str(&config.log_span_events).unwrap_or_err();
 
@@ -37,14 +45,11 @@ pub(crate) fn init(
 		.event_format(ConsoleFormat::new(config))
 		.with_writer(ConsoleWriter::new(config));
 
-	let (console_reload_filter, console_reload_handle) =
-		reload::Layer::new(console_filter.clone());
+	let (console_reload_filter, console_reload_handle) = reload::Layer::new(console_filter);
 
 	reload_handles.add("console", Box::new(console_reload_handle));
 
-	let cap_state = Arc::new(capture::State::new());
 	let cap_layer = capture::Layer::new(&cap_state);
-
 	let subscriber = Registry::default()
 		.with(console_layer.with_filter(console_reload_filter))
 		.with(cap_layer);
@@ -117,33 +122,43 @@ pub(crate) fn init(
 		not(feature = "perf_measurements"),
 		allow(clippy::let_unit_value)
 	)]
-	let flame_guard = ();
+	let flame_guard = None;
 
-	let ret = (reload_handles, flame_guard, cap_state);
+	let subscriber = Arc::new(subscriber);
 
 	// Enable the tokio console. This is slightly kludgy because we're judggling
 	// compile-time and runtime conditions to elide it, each of those changing the
 	// subscriber's type.
 	let (console_enabled, console_disabled_reason) = tokio_console_enabled(config);
 	#[cfg(all(feature = "tokio_console", tokio_unstable, tuwunel_disable))]
-	if console_enabled {
+	if console_enabled && config.log_global_default {
 		let console_layer = console_subscriber::ConsoleLayer::builder()
 			.with_default_env()
 			.spawn();
 
-		set_global_default(subscriber.with(console_layer));
-		return Ok(ret);
+		set_global_default(subscriber.clone().with(console_layer));
+		return Ok((flame_guard, Log {
+			reload: reload_handles,
+			capture: cap_state,
+			subscriber,
+		}));
 	}
 
-	set_global_default(subscriber);
+	if config.log_global_default {
+		set_global_default(subscriber.clone());
+	}
 
 	// If there's a reason the tokio console was disabled when it might be desired
 	// we output that here after initializing logging
-	if !console_enabled && !console_disabled_reason.is_empty() {
+	if !console_enabled && !console_disabled_reason.is_empty() && config.log_global_default {
 		debug_warn!("{console_disabled_reason}");
 	}
 
-	Ok(ret)
+	Ok((flame_guard, Logging {
+		reload: reload_handles,
+		capture: cap_state,
+		subscriber,
+	}))
 }
 
 fn tokio_console_enabled(config: &Config) -> (bool, &'static str) {

src/main/server.rs

@@ -5,7 +5,6 @@ use tuwunel_core::{
 	Error, Result,
 	config::Config,
 	implement, info,
-	log::Log,
 	utils::{stream, sys},
 };
 
@@ -45,7 +44,7 @@ pub fn new(args: Option<&Args>, runtime: Option<&runtime::Handle>) -> Result<Arc
 		.and_then(|raw| args::update(raw, args))
 		.and_then(|raw| Config::new(&raw))?;
 
-	let (tracing_reload_handle, tracing_flame_guard, capture) = crate::logging::init(&config)?;
+	let (tracing_flame_guard, logger) = crate::logging::init(&config)?;
 
 	config.check()?;
 
@@ -67,8 +66,6 @@ pub fn new(args: Option<&Args>, runtime: Option<&runtime::Handle>) -> Result<Arc
 		tuwunel_core::version(),
 	);
 
-	let logger = Log { reload: tracing_reload_handle, capture };
-
 	Ok(Arc::new(Self {
 		server: Arc::new(tuwunel_core::Server::new(config, runtime.cloned(), logger)),
 

tuwunel-example.toml

@@ -751,6 +751,22 @@
 #
 #log_to_stderr = false
 
+# Setting to false disables the logging/tracing system at a lower level.
+# In contrast to configuring an empty `log` string where the system is
+# still operating but muted, when this option is false the system was not
+# initialized and is not operating. Changing this option has no effect
+# after startup. This option is intended for developers and expert use
+# only: configuring an empty log string is preferred over using this.
+#
+#log_enable = true
+
+# Setting to false disables the logging/tracing system at a lower level
+# similar to `log_enable`. In this case the system is configured normally,
+# but not registered as the global handler in the final steps. This option
+# is for developers and expert use only.
+#
+#log_global_default = true
+
 # OpenID token expiration/TTL in seconds.
 #
 # These are the OpenID tokens that are primarily used for Matrix account