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Diffstat (limited to 'vendor/tracing-subscriber/src/layer/layered.rs')
| -rw-r--r-- | vendor/tracing-subscriber/src/layer/layered.rs | 554 |
1 files changed, 554 insertions, 0 deletions
diff --git a/vendor/tracing-subscriber/src/layer/layered.rs b/vendor/tracing-subscriber/src/layer/layered.rs new file mode 100644 index 000000000..f09c58c97 --- /dev/null +++ b/vendor/tracing-subscriber/src/layer/layered.rs @@ -0,0 +1,554 @@ +use tracing_core::{metadata::Metadata, span, Dispatch, Event, Interest, LevelFilter, Subscriber}; + +use crate::{ + filter, + layer::{Context, Layer}, + registry::LookupSpan, +}; +#[cfg(all(feature = "registry", feature = "std"))] +use crate::{filter::FilterId, registry::Registry}; +use core::{ + any::{Any, TypeId}, + cmp, fmt, + marker::PhantomData, +}; + +/// A [`Subscriber`] composed of a `Subscriber` wrapped by one or more +/// [`Layer`]s. +/// +/// [`Layer`]: crate::Layer +/// [`Subscriber`]: tracing_core::Subscriber +#[derive(Clone)] +pub struct Layered<L, I, S = I> { + /// The layer. + layer: L, + + /// The inner value that `self.layer` was layered onto. + /// + /// If this is also a `Layer`, then this `Layered` will implement `Layer`. + /// If this is a `Subscriber`, then this `Layered` will implement + /// `Subscriber` instead. + inner: I, + + // These booleans are used to determine how to combine `Interest`s and max + // level hints when per-layer filters are in use. + /// Is `self.inner` a `Registry`? + /// + /// If so, when combining `Interest`s, we want to "bubble up" its + /// `Interest`. + inner_is_registry: bool, + + /// Does `self.layer` have per-layer filters? + /// + /// This will be true if: + /// - `self.inner` is a `Filtered`. + /// - `self.inner` is a tree of `Layered`s where _all_ arms of those + /// `Layered`s have per-layer filters. + /// + /// Otherwise, if it's a `Layered` with one per-layer filter in one branch, + /// but a non-per-layer-filtered layer in the other branch, this will be + /// _false_, because the `Layered` is already handling the combining of + /// per-layer filter `Interest`s and max level hints with its non-filtered + /// `Layer`. + has_layer_filter: bool, + + /// Does `self.inner` have per-layer filters? + /// + /// This is determined according to the same rules as + /// `has_layer_filter` above. + inner_has_layer_filter: bool, + _s: PhantomData<fn(S)>, +} + +// === impl Layered === + +impl<L, S> Layered<L, S> +where + L: Layer<S>, + S: Subscriber, +{ + /// Returns `true` if this [`Subscriber`] is the same type as `T`. + pub fn is<T: Any>(&self) -> bool { + self.downcast_ref::<T>().is_some() + } + + /// Returns some reference to this [`Subscriber`] value if it is of type `T`, + /// or `None` if it isn't. + pub fn downcast_ref<T: Any>(&self) -> Option<&T> { + unsafe { + let raw = self.downcast_raw(TypeId::of::<T>())?; + if raw.is_null() { + None + } else { + Some(&*(raw as *const T)) + } + } + } +} + +impl<L, S> Subscriber for Layered<L, S> +where + L: Layer<S>, + S: Subscriber, +{ + fn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest { + self.pick_interest(self.layer.register_callsite(metadata), || { + self.inner.register_callsite(metadata) + }) + } + + fn enabled(&self, metadata: &Metadata<'_>) -> bool { + if self.layer.enabled(metadata, self.ctx()) { + // if the outer layer enables the callsite metadata, ask the subscriber. + self.inner.enabled(metadata) + } else { + // otherwise, the callsite is disabled by the layer + + // If per-layer filters are in use, and we are short-circuiting + // (rather than calling into the inner type), clear the current + // per-layer filter `enabled` state. + #[cfg(feature = "registry")] + filter::FilterState::clear_enabled(); + + false + } + } + + fn max_level_hint(&self) -> Option<LevelFilter> { + self.pick_level_hint( + self.layer.max_level_hint(), + self.inner.max_level_hint(), + super::subscriber_is_none(&self.inner), + ) + } + + fn new_span(&self, span: &span::Attributes<'_>) -> span::Id { + let id = self.inner.new_span(span); + self.layer.on_new_span(span, &id, self.ctx()); + id + } + + fn record(&self, span: &span::Id, values: &span::Record<'_>) { + self.inner.record(span, values); + self.layer.on_record(span, values, self.ctx()); + } + + fn record_follows_from(&self, span: &span::Id, follows: &span::Id) { + self.inner.record_follows_from(span, follows); + self.layer.on_follows_from(span, follows, self.ctx()); + } + + fn event_enabled(&self, event: &Event<'_>) -> bool { + if self.layer.event_enabled(event, self.ctx()) { + // if the outer layer enables the event, ask the inner subscriber. + self.inner.event_enabled(event) + } else { + // otherwise, the event is disabled by this layer + false + } + } + + fn event(&self, event: &Event<'_>) { + self.inner.event(event); + self.layer.on_event(event, self.ctx()); + } + + fn enter(&self, span: &span::Id) { + self.inner.enter(span); + self.layer.on_enter(span, self.ctx()); + } + + fn exit(&self, span: &span::Id) { + self.inner.exit(span); + self.layer.on_exit(span, self.ctx()); + } + + fn clone_span(&self, old: &span::Id) -> span::Id { + let new = self.inner.clone_span(old); + if &new != old { + self.layer.on_id_change(old, &new, self.ctx()) + }; + new + } + + #[inline] + fn drop_span(&self, id: span::Id) { + self.try_close(id); + } + + fn try_close(&self, id: span::Id) -> bool { + #[cfg(all(feature = "registry", feature = "std"))] + let subscriber = &self.inner as &dyn Subscriber; + #[cfg(all(feature = "registry", feature = "std"))] + let mut guard = subscriber + .downcast_ref::<Registry>() + .map(|registry| registry.start_close(id.clone())); + if self.inner.try_close(id.clone()) { + // If we have a registry's close guard, indicate that the span is + // closing. + #[cfg(all(feature = "registry", feature = "std"))] + { + if let Some(g) = guard.as_mut() { + g.set_closing() + }; + } + + self.layer.on_close(id, self.ctx()); + true + } else { + false + } + } + + #[inline] + fn current_span(&self) -> span::Current { + self.inner.current_span() + } + + #[doc(hidden)] + unsafe fn downcast_raw(&self, id: TypeId) -> Option<*const ()> { + // Unlike the implementation of `Layer` for `Layered`, we don't have to + // handle the "magic PLF downcast marker" here. If a `Layered` + // implements `Subscriber`, we already know that the `inner` branch is + // going to contain something that doesn't have per-layer filters (the + // actual root `Subscriber`). Thus, a `Layered` that implements + // `Subscriber` will always be propagating the root subscriber's + // `Interest`/level hint, even if it includes a `Layer` that has + // per-layer filters, because it will only ever contain layers where + // _one_ child has per-layer filters. + // + // The complex per-layer filter detection logic is only relevant to + // *trees* of layers, which involve the `Layer` implementation for + // `Layered`, not *lists* of layers, where every `Layered` implements + // `Subscriber`. Of course, a linked list can be thought of as a + // degenerate tree...but luckily, we are able to make a type-level + // distinction between individual `Layered`s that are definitely + // list-shaped (their inner child implements `Subscriber`), and + // `Layered`s that might be tree-shaped (the inner child is also a + // `Layer`). + + // If downcasting to `Self`, return a pointer to `self`. + if id == TypeId::of::<Self>() { + return Some(self as *const _ as *const ()); + } + + self.layer + .downcast_raw(id) + .or_else(|| self.inner.downcast_raw(id)) + } +} + +impl<S, A, B> Layer<S> for Layered<A, B, S> +where + A: Layer<S>, + B: Layer<S>, + S: Subscriber, +{ + fn on_register_dispatch(&self, subscriber: &Dispatch) { + self.layer.on_register_dispatch(subscriber); + self.inner.on_register_dispatch(subscriber); + } + + fn on_layer(&mut self, subscriber: &mut S) { + self.layer.on_layer(subscriber); + self.inner.on_layer(subscriber); + } + + fn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest { + self.pick_interest(self.layer.register_callsite(metadata), || { + self.inner.register_callsite(metadata) + }) + } + + fn enabled(&self, metadata: &Metadata<'_>, ctx: Context<'_, S>) -> bool { + if self.layer.enabled(metadata, ctx.clone()) { + // if the outer subscriber enables the callsite metadata, ask the inner layer. + self.inner.enabled(metadata, ctx) + } else { + // otherwise, the callsite is disabled by this layer + false + } + } + + fn max_level_hint(&self) -> Option<LevelFilter> { + self.pick_level_hint( + self.layer.max_level_hint(), + self.inner.max_level_hint(), + super::layer_is_none(&self.inner), + ) + } + + #[inline] + fn on_new_span(&self, attrs: &span::Attributes<'_>, id: &span::Id, ctx: Context<'_, S>) { + self.inner.on_new_span(attrs, id, ctx.clone()); + self.layer.on_new_span(attrs, id, ctx); + } + + #[inline] + fn on_record(&self, span: &span::Id, values: &span::Record<'_>, ctx: Context<'_, S>) { + self.inner.on_record(span, values, ctx.clone()); + self.layer.on_record(span, values, ctx); + } + + #[inline] + fn on_follows_from(&self, span: &span::Id, follows: &span::Id, ctx: Context<'_, S>) { + self.inner.on_follows_from(span, follows, ctx.clone()); + self.layer.on_follows_from(span, follows, ctx); + } + + #[inline] + fn event_enabled(&self, event: &Event<'_>, ctx: Context<'_, S>) -> bool { + if self.layer.event_enabled(event, ctx.clone()) { + // if the outer layer enables the event, ask the inner subscriber. + self.inner.event_enabled(event, ctx) + } else { + // otherwise, the event is disabled by this layer + false + } + } + + #[inline] + fn on_event(&self, event: &Event<'_>, ctx: Context<'_, S>) { + self.inner.on_event(event, ctx.clone()); + self.layer.on_event(event, ctx); + } + + #[inline] + fn on_enter(&self, id: &span::Id, ctx: Context<'_, S>) { + self.inner.on_enter(id, ctx.clone()); + self.layer.on_enter(id, ctx); + } + + #[inline] + fn on_exit(&self, id: &span::Id, ctx: Context<'_, S>) { + self.inner.on_exit(id, ctx.clone()); + self.layer.on_exit(id, ctx); + } + + #[inline] + fn on_close(&self, id: span::Id, ctx: Context<'_, S>) { + self.inner.on_close(id.clone(), ctx.clone()); + self.layer.on_close(id, ctx); + } + + #[inline] + fn on_id_change(&self, old: &span::Id, new: &span::Id, ctx: Context<'_, S>) { + self.inner.on_id_change(old, new, ctx.clone()); + self.layer.on_id_change(old, new, ctx); + } + + #[doc(hidden)] + unsafe fn downcast_raw(&self, id: TypeId) -> Option<*const ()> { + match id { + // If downcasting to `Self`, return a pointer to `self`. + id if id == TypeId::of::<Self>() => Some(self as *const _ as *const ()), + + // Oh, we're looking for per-layer filters! + // + // This should only happen if we are inside of another `Layered`, + // and it's trying to determine how it should combine `Interest`s + // and max level hints. + // + // In that case, this `Layered` should be considered to be + // "per-layer filtered" if *both* the outer layer and the inner + // layer/subscriber have per-layer filters. Otherwise, this `Layered + // should *not* be considered per-layer filtered (even if one or the + // other has per layer filters). If only one `Layer` is per-layer + // filtered, *this* `Layered` will handle aggregating the `Interest` + // and level hints on behalf of its children, returning the + // aggregate (which is the value from the &non-per-layer-filtered* + // child). + // + // Yes, this rule *is* slightly counter-intuitive, but it's + // necessary due to a weird edge case that can occur when two + // `Layered`s where one side is per-layer filtered and the other + // isn't are `Layered` together to form a tree. If we didn't have + // this rule, we would actually end up *ignoring* `Interest`s from + // the non-per-layer-filtered layers, since both branches would + // claim to have PLF. + // + // If you don't understand this...that's fine, just don't mess with + // it. :) + id if filter::is_plf_downcast_marker(id) => { + self.layer.downcast_raw(id).and(self.inner.downcast_raw(id)) + } + + // Otherwise, try to downcast both branches normally... + _ => self + .layer + .downcast_raw(id) + .or_else(|| self.inner.downcast_raw(id)), + } + } +} + +impl<'a, L, S> LookupSpan<'a> for Layered<L, S> +where + S: Subscriber + LookupSpan<'a>, +{ + type Data = S::Data; + + fn span_data(&'a self, id: &span::Id) -> Option<Self::Data> { + self.inner.span_data(id) + } + + #[cfg(all(feature = "registry", feature = "std"))] + fn register_filter(&mut self) -> FilterId { + self.inner.register_filter() + } +} + +impl<L, S> Layered<L, S> +where + S: Subscriber, +{ + fn ctx(&self) -> Context<'_, S> { + Context::new(&self.inner) + } +} + +impl<A, B, S> Layered<A, B, S> +where + A: Layer<S>, + S: Subscriber, +{ + pub(super) fn new(layer: A, inner: B, inner_has_layer_filter: bool) -> Self { + #[cfg(all(feature = "registry", feature = "std"))] + let inner_is_registry = TypeId::of::<S>() == TypeId::of::<crate::registry::Registry>(); + + #[cfg(not(all(feature = "registry", feature = "std")))] + let inner_is_registry = false; + + let inner_has_layer_filter = inner_has_layer_filter || inner_is_registry; + let has_layer_filter = filter::layer_has_plf(&layer); + Self { + layer, + inner, + has_layer_filter, + inner_has_layer_filter, + inner_is_registry, + _s: PhantomData, + } + } + + fn pick_interest(&self, outer: Interest, inner: impl FnOnce() -> Interest) -> Interest { + if self.has_layer_filter { + return inner(); + } + + // If the outer layer has disabled the callsite, return now so that + // the inner layer/subscriber doesn't get its hopes up. + if outer.is_never() { + // If per-layer filters are in use, and we are short-circuiting + // (rather than calling into the inner type), clear the current + // per-layer filter interest state. + #[cfg(feature = "registry")] + filter::FilterState::take_interest(); + + return outer; + } + + // The `inner` closure will call `inner.register_callsite()`. We do this + // before the `if` statement to ensure that the inner subscriber is + // informed that the callsite exists regardless of the outer layer's + // filtering decision. + let inner = inner(); + if outer.is_sometimes() { + // if this interest is "sometimes", return "sometimes" to ensure that + // filters are reevaluated. + return outer; + } + + // If there is a per-layer filter in the `inner` stack, and it returns + // `never`, change the interest to `sometimes`, because the `outer` + // layer didn't return `never`. This means that _some_ layer still wants + // to see that callsite, even though the inner stack's per-layer filter + // didn't want it. Therefore, returning `sometimes` will ensure + // `enabled` is called so that the per-layer filter can skip that + // span/event, while the `outer` layer still gets to see it. + if inner.is_never() && self.inner_has_layer_filter { + return Interest::sometimes(); + } + + // otherwise, allow the inner subscriber or collector to weigh in. + inner + } + + fn pick_level_hint( + &self, + outer_hint: Option<LevelFilter>, + inner_hint: Option<LevelFilter>, + inner_is_none: bool, + ) -> Option<LevelFilter> { + if self.inner_is_registry { + return outer_hint; + } + + if self.has_layer_filter && self.inner_has_layer_filter { + return Some(cmp::max(outer_hint?, inner_hint?)); + } + + if self.has_layer_filter && inner_hint.is_none() { + return None; + } + + if self.inner_has_layer_filter && outer_hint.is_none() { + return None; + } + + // If the layer is `Option::None`, then we + // want to short-circuit the layer underneath, if it + // returns `None`, to override the `None` layer returning + // `Some(OFF)`, which should ONLY apply when there are + // no other layers that return `None`. Note this + // `None` does not == `Some(TRACE)`, it means + // something more like: "whatever all the other + // layers agree on, default to `TRACE` if none + // have an opinion". We also choose do this AFTER + // we check for per-layer filters, which + // have their own logic. + // + // Also note that this does come at some perf cost, but + // this function is only called on initialization and + // subscriber reloading. + if super::layer_is_none(&self.layer) { + return cmp::max(outer_hint, Some(inner_hint?)); + } + + // Similarly, if the layer on the inside is `None` and it returned an + // `Off` hint, we want to override that with the outer hint. + if inner_is_none && inner_hint == Some(LevelFilter::OFF) { + return outer_hint; + } + + cmp::max(outer_hint, inner_hint) + } +} + +impl<A, B, S> fmt::Debug for Layered<A, B, S> +where + A: fmt::Debug, + B: fmt::Debug, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + #[cfg(all(feature = "registry", feature = "std"))] + let alt = f.alternate(); + let mut s = f.debug_struct("Layered"); + // These additional fields are more verbose and usually only necessary + // for internal debugging purposes, so only print them if alternate mode + // is enabled. + + #[cfg(all(feature = "registry", feature = "std"))] + { + if alt { + s.field("inner_is_registry", &self.inner_is_registry) + .field("has_layer_filter", &self.has_layer_filter) + .field("inner_has_layer_filter", &self.inner_has_layer_filter); + } + } + + s.field("layer", &self.layer) + .field("inner", &self.inner) + .finish() + } +} |