1 files changed, 237 insertions, 0 deletions
diff --git a/vendor/tracing-subscriber-0.3.3/src/reload.rs b/vendor/tracing-subscriber-0.3.3/src/reload.rs
new file mode 100644
index 000000000..b8ec67dfa
--- /dev/null
+++ b/vendor/tracing-subscriber-0.3.3/src/reload.rs
@@ -0,0 +1,237 @@
+//! Wrapper for a `Layer` to allow it to be dynamically reloaded.
+//!
+//! This module provides a [`Layer` type] which wraps another type implementing
+//! the [`Layer` trait], allowing the wrapped type to be replaced with another
+//! instance of that type at runtime.
+//!
+//! This can be used in cases where a subset of `Subscriber` functionality
+//! should be dynamically reconfigured, such as when filtering directives may
+//! change at runtime. Note that this layer introduces a (relatively small)
+//! amount of overhead, and should thus only be used as needed.
+//!
+//! [`Layer` type]: struct.Layer.html
+//! [`Layer` trait]: ../layer/trait.Layer.html
+use crate::layer;
+use crate::sync::RwLock;
+
+use std::{
+    error, fmt,
+    marker::PhantomData,
+    sync::{Arc, Weak},
+};
+use tracing_core::{
+    callsite, span,
+    subscriber::{Interest, Subscriber},
+    Event, Metadata,
+};
+
+/// Wraps a `Layer`, allowing it to be reloaded dynamically at runtime.
+#[derive(Debug)]
+pub struct Layer<L, S> {
+    // TODO(eliza): this once used a `crossbeam_util::ShardedRwLock`. We may
+    // eventually wish to replace it with a sharded lock implementation on top
+    // of our internal `RwLock` wrapper type. If possible, we should profile
+    // this first to determine if it's necessary.
+    inner: Arc<RwLock<L>>,
+    _s: PhantomData<fn(S)>,
+}
+
+/// Allows reloading the state of an associated `Layer`.
+#[derive(Debug)]
+pub struct Handle<L, S> {
+    inner: Weak<RwLock<L>>,
+    _s: PhantomData<fn(S)>,
+}
+
+/// Indicates that an error occurred when reloading a layer.
+#[derive(Debug)]
+pub struct Error {
+    kind: ErrorKind,
+}
+
+#[derive(Debug)]
+enum ErrorKind {
+    SubscriberGone,
+    Poisoned,
+}
+
+// ===== impl Layer =====
+
+impl<L, S> crate::Layer<S> for Layer<L, S>
+where
+    L: crate::Layer<S> + 'static,
+    S: Subscriber,
+{
+    fn on_layer(&mut self, subscriber: &mut S) {
+        try_lock!(self.inner.write(), else return).on_layer(subscriber);
+    }
+
+    #[inline]
+    fn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest {
+        try_lock!(self.inner.read(), else return Interest::sometimes()).register_callsite(metadata)
+    }
+
+    #[inline]
+    fn enabled(&self, metadata: &Metadata<'_>, ctx: layer::Context<'_, S>) -> bool {
+        try_lock!(self.inner.read(), else return false).enabled(metadata, ctx)
+    }
+
+    #[inline]
+    fn on_new_span(&self, attrs: &span::Attributes<'_>, id: &span::Id, ctx: layer::Context<'_, S>) {
+        try_lock!(self.inner.read()).on_new_span(attrs, id, ctx)
+    }
+
+    #[inline]
+    fn on_record(&self, span: &span::Id, values: &span::Record<'_>, ctx: layer::Context<'_, S>) {
+        try_lock!(self.inner.read()).on_record(span, values, ctx)
+    }
+
+    #[inline]
+    fn on_follows_from(&self, span: &span::Id, follows: &span::Id, ctx: layer::Context<'_, S>) {
+        try_lock!(self.inner.read()).on_follows_from(span, follows, ctx)
+    }
+
+    #[inline]
+    fn on_event(&self, event: &Event<'_>, ctx: layer::Context<'_, S>) {
+        try_lock!(self.inner.read()).on_event(event, ctx)
+    }
+
+    #[inline]
+    fn on_enter(&self, id: &span::Id, ctx: layer::Context<'_, S>) {
+        try_lock!(self.inner.read()).on_enter(id, ctx)
+    }
+
+    #[inline]
+    fn on_exit(&self, id: &span::Id, ctx: layer::Context<'_, S>) {
+        try_lock!(self.inner.read()).on_exit(id, ctx)
+    }
+
+    #[inline]
+    fn on_close(&self, id: span::Id, ctx: layer::Context<'_, S>) {
+        try_lock!(self.inner.read()).on_close(id, ctx)
+    }
+
+    #[inline]
+    fn on_id_change(&self, old: &span::Id, new: &span::Id, ctx: layer::Context<'_, S>) {
+        try_lock!(self.inner.read()).on_id_change(old, new, ctx)
+    }
+}
+
+impl<L, S> Layer<L, S>
+where
+    L: crate::Layer<S> + 'static,
+    S: Subscriber,
+{
+    /// Wraps the given `Layer`, returning a `Layer` and a `Handle` that allows
+    /// the inner type to be modified at runtime.
+    pub fn new(inner: L) -> (Self, Handle<L, S>) {
+        let this = Self {
+            inner: Arc::new(RwLock::new(inner)),
+            _s: PhantomData,
+        };
+        let handle = this.handle();
+        (this, handle)
+    }
+
+    /// Returns a `Handle` that can be used to reload the wrapped `Layer`.
+    pub fn handle(&self) -> Handle<L, S> {
+        Handle {
+            inner: Arc::downgrade(&self.inner),
+            _s: PhantomData,
+        }
+    }
+}
+
+// ===== impl Handle =====
+
+impl<L, S> Handle<L, S>
+where
+    L: crate::Layer<S> + 'static,
+    S: Subscriber,
+{
+    /// Replace the current layer with the provided `new_layer`.
+    pub fn reload(&self, new_layer: impl Into<L>) -> Result<(), Error> {
+        self.modify(|layer| {
+            *layer = new_layer.into();
+        })
+    }
+
+    /// Invokes a closure with a mutable reference to the current layer,
+    /// allowing it to be modified in place.
+    pub fn modify(&self, f: impl FnOnce(&mut L)) -> Result<(), Error> {
+        let inner = self.inner.upgrade().ok_or(Error {
+            kind: ErrorKind::SubscriberGone,
+        })?;
+
+        let mut lock = try_lock!(inner.write(), else return Err(Error::poisoned()));
+        f(&mut *lock);
+        // Release the lock before rebuilding the interest cache, as that
+        // function will lock the new layer.
+        drop(lock);
+
+        callsite::rebuild_interest_cache();
+        Ok(())
+    }
+
+    /// Returns a clone of the layer's current value if it still exists.
+    /// Otherwise, if the subscriber has been dropped, returns `None`.
+    pub fn clone_current(&self) -> Option<L>
+    where
+        L: Clone,
+    {
+        self.with_current(L::clone).ok()
+    }
+
+    /// Invokes a closure with a borrowed reference to the current layer,
+    /// returning the result (or an error if the subscriber no longer exists).
+    pub fn with_current<T>(&self, f: impl FnOnce(&L) -> T) -> Result<T, Error> {
+        let inner = self.inner.upgrade().ok_or(Error {
+            kind: ErrorKind::SubscriberGone,
+        })?;
+        let inner = try_lock!(inner.read(), else return Err(Error::poisoned()));
+        Ok(f(&*inner))
+    }
+}
+
+impl<L, S> Clone for Handle<L, S> {
+    fn clone(&self) -> Self {
+        Handle {
+            inner: self.inner.clone(),
+            _s: PhantomData,
+        }
+    }
+}
+
+// ===== impl Error =====
+
+impl Error {
+    fn poisoned() -> Self {
+        Self {
+            kind: ErrorKind::Poisoned,
+        }
+    }
+
+    /// Returns `true` if this error occurred because the layer was poisoned by
+    /// a panic on another thread.
+    pub fn is_poisoned(&self) -> bool {
+        matches!(self.kind, ErrorKind::Poisoned)
+    }
+
+    /// Returns `true` if this error occurred because the `Subscriber`
+    /// containing the reloadable layer was dropped.
+    pub fn is_dropped(&self) -> bool {
+        matches!(self.kind, ErrorKind::SubscriberGone)
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let msg = match self.kind {
+            ErrorKind::SubscriberGone => "subscriber no longer exists",
+            ErrorKind::Poisoned => "lock poisoned",
+        };
+        f.pad(msg)
+    }
+}
+
+impl error::Error for Error {}