Hot-Reloading Refactor

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

src/core/log.rs

@@ -0,0 +1,79 @@
+use std::sync::Arc;
+
+use tracing_subscriber::{reload, EnvFilter};
+
+/// We need to store a reload::Handle value, but can't name it's type explicitly
+/// because the S type parameter depends on the subscriber's previous layers. In
+/// our case, this includes unnameable 'impl Trait' types.
+///
+/// This is fixed[1] in the unreleased tracing-subscriber from the master
+/// branch, which removes the S parameter. Unfortunately can't use it without
+/// pulling in a version of tracing that's incompatible with the rest of our
+/// deps.
+///
+/// To work around this, we define an trait without the S paramter that forwards
+/// to the reload::Handle::reload method, and then store the handle as a trait
+/// object.
+///
+/// [1]: <https://github.com/tokio-rs/tracing/pull/1035/commits/8a87ea52425098d3ef8f56d92358c2f6c144a28f>
+pub trait ReloadHandle<L> {
+	fn reload(&self, new_value: L) -> Result<(), reload::Error>;
+}
+
+impl<L, S> ReloadHandle<L> for reload::Handle<L, S> {
+	fn reload(&self, new_value: L) -> Result<(), reload::Error> { reload::Handle::reload(self, new_value) }
+}
+
+struct LogLevelReloadHandlesInner {
+	handles: Vec<Box<dyn ReloadHandle<EnvFilter> + Send + Sync>>,
+}
+
+/// Wrapper to allow reloading the filter on several several
+/// [`tracing_subscriber::reload::Handle`]s at once, with the same value.
+#[derive(Clone)]
+pub struct LogLevelReloadHandles {
+	inner: Arc<LogLevelReloadHandlesInner>,
+}
+
+impl LogLevelReloadHandles {
+	#[must_use]
+	pub fn new(handles: Vec<Box<dyn ReloadHandle<EnvFilter> + Send + Sync>>) -> LogLevelReloadHandles {
+		LogLevelReloadHandles {
+			inner: Arc::new(LogLevelReloadHandlesInner {
+				handles,
+			}),
+		}
+	}
+
+	pub fn reload(&self, new_value: &EnvFilter) -> Result<(), reload::Error> {
+		for handle in &self.inner.handles {
+			handle.reload(new_value.clone())?;
+		}
+		Ok(())
+	}
+}
+
+#[macro_export]
+macro_rules! error {
+    ( $($x:tt)+ ) => { tracing::error!( $($x)+ ); }
+}
+
+#[macro_export]
+macro_rules! warn {
+    ( $($x:tt)+ ) => { tracing::warn!( $($x)+ ); }
+}
+
+#[macro_export]
+macro_rules! info {
+    ( $($x:tt)+ ) => { tracing::info!( $($x)+ ); }
+}
+
+#[macro_export]
+macro_rules! debug {
+    ( $($x:tt)+ ) => { tracing::debug!( $($x)+ ); }
+}
+
+#[macro_export]
+macro_rules! trace {
+    ( $($x:tt)+ ) => { tracing::trace!( $($x)+ ); }
+}