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Diffstat (limited to 'vendor/tracing-subscriber/src/registry/sharded.rs')
| -rw-r--r-- | vendor/tracing-subscriber/src/registry/sharded.rs | 908 |
1 files changed, 908 insertions, 0 deletions
diff --git a/vendor/tracing-subscriber/src/registry/sharded.rs b/vendor/tracing-subscriber/src/registry/sharded.rs new file mode 100644 index 000000000..797899767 --- /dev/null +++ b/vendor/tracing-subscriber/src/registry/sharded.rs @@ -0,0 +1,908 @@ +use sharded_slab::{pool::Ref, Clear, Pool}; +use thread_local::ThreadLocal; + +use super::stack::SpanStack; +use crate::{ + filter::{FilterId, FilterMap, FilterState}, + registry::{ + extensions::{Extensions, ExtensionsInner, ExtensionsMut}, + LookupSpan, SpanData, + }, + sync::RwLock, +}; +use std::{ + cell::{self, Cell, RefCell}, + sync::atomic::{fence, AtomicUsize, Ordering}, +}; +use tracing_core::{ + dispatcher::{self, Dispatch}, + span::{self, Current, Id}, + Event, Interest, Metadata, Subscriber, +}; + +/// A shared, reusable store for spans. +/// +/// A `Registry` is a [`Subscriber`] around which multiple [`Layer`]s +/// implementing various behaviors may be [added]. Unlike other types +/// implementing `Subscriber`, `Registry` does not actually record traces itself: +/// instead, it collects and stores span data that is exposed to any [`Layer`]s +/// wrapping it through implementations of the [`LookupSpan`] trait. +/// The `Registry` is responsible for storing span metadata, recording +/// relationships between spans, and tracking which spans are active and which +/// are closed. In addition, it provides a mechanism for [`Layer`]s to store +/// user-defined per-span data, called [extensions], in the registry. This +/// allows [`Layer`]-specific data to benefit from the `Registry`'s +/// high-performance concurrent storage. +/// +/// This registry is implemented using a [lock-free sharded slab][slab], and is +/// highly optimized for concurrent access. +/// +/// # Span ID Generation +/// +/// Span IDs are not globally unique, but the registry ensures that +/// no two currently active spans have the same ID within a process. +/// +/// One of the primary responsibilities of the registry is to generate [span +/// IDs]. Therefore, it's important for other code that interacts with the +/// registry, such as [`Layer`]s, to understand the guarantees of the +/// span IDs that are generated. +/// +/// The registry's span IDs are guaranteed to be unique **at a given point +/// in time**. This means that an active span will never be assigned the +/// same ID as another **currently active** span. However, the registry +/// **will** eventually reuse the IDs of [closed] spans, although an ID +/// will never be reassigned immediately after a span has closed. +/// +/// Spans are not [considered closed] by the `Registry` until *every* +/// [`Span`] reference with that ID has been dropped. +/// +/// Thus: span IDs generated by the registry should be considered unique +/// only at a given point in time, and only relative to other spans +/// generated by the same process. Two spans with the same ID will not exist +/// in the same process concurrently. However, if historical span data is +/// being stored, the same ID may occur for multiple spans times in that +/// data. If spans must be uniquely identified in historical data, the user +/// code storing this data must assign its own unique identifiers to those +/// spans. A counter is generally sufficient for this. +/// +/// Similarly, span IDs generated by the registry are not unique outside of +/// a given process. Distributed tracing systems may require identifiers +/// that are unique across multiple processes on multiple machines (for +/// example, [OpenTelemetry's `SpanId`s and `TraceId`s][ot]). `tracing` span +/// IDs generated by the registry should **not** be used for this purpose. +/// Instead, code which integrates with a distributed tracing system should +/// generate and propagate its own IDs according to the rules specified by +/// the distributed tracing system. These IDs can be associated with +/// `tracing` spans using [fields] and/or [stored span data]. +/// +/// [span IDs]: tracing_core::span::Id +/// [slab]: sharded_slab +/// [`Layer`]: crate::Layer +/// [added]: crate::layer::Layer#composing-layers +/// [extensions]: super::Extensions +/// [closed]: https://docs.rs/tracing/latest/tracing/span/index.html#closing-spans +/// [considered closed]: tracing_core::subscriber::Subscriber::try_close() +/// [`Span`]: https://docs.rs/tracing/latest/tracing/span/struct.Span.html +/// [ot]: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/api.md#spancontext +/// [fields]: tracing_core::field +/// [stored span data]: crate::registry::SpanData::extensions_mut +#[cfg(feature = "registry")] +#[cfg_attr(docsrs, doc(cfg(all(feature = "registry", feature = "std"))))] +#[derive(Debug)] +pub struct Registry { + spans: Pool<DataInner>, + current_spans: ThreadLocal<RefCell<SpanStack>>, + next_filter_id: u8, +} + +/// Span data stored in a [`Registry`]. +/// +/// The registry stores well-known data defined by tracing: span relationships, +/// metadata and reference counts. Additional user-defined data provided by +/// [`Layer`s], such as formatted fields, metrics, or distributed traces should +/// be stored in the [extensions] typemap. +/// +/// [`Layer`s]: crate::layer::Layer +/// [extensions]: Extensions +#[cfg(feature = "registry")] +#[cfg_attr(docsrs, doc(cfg(all(feature = "registry", feature = "std"))))] +#[derive(Debug)] +pub struct Data<'a> { + /// Immutable reference to the pooled `DataInner` entry. + inner: Ref<'a, DataInner>, +} + +/// Stored data associated with a span. +/// +/// This type is pooled using [`sharded_slab::Pool`]; when a span is +/// dropped, the `DataInner` entry at that span's slab index is cleared +/// in place and reused by a future span. Thus, the `Default` and +/// [`sharded_slab::Clear`] implementations for this type are +/// load-bearing. +#[derive(Debug)] +struct DataInner { + filter_map: FilterMap, + metadata: &'static Metadata<'static>, + parent: Option<Id>, + ref_count: AtomicUsize, + // The span's `Extensions` typemap. Allocations for the `HashMap` backing + // this are pooled and reused in place. + pub(crate) extensions: RwLock<ExtensionsInner>, +} + +// === impl Registry === + +impl Default for Registry { + fn default() -> Self { + Self { + spans: Pool::new(), + current_spans: ThreadLocal::new(), + next_filter_id: 0, + } + } +} + +#[inline] +fn idx_to_id(idx: usize) -> Id { + Id::from_u64(idx as u64 + 1) +} + +#[inline] +fn id_to_idx(id: &Id) -> usize { + id.into_u64() as usize - 1 +} + +/// A guard that tracks how many [`Registry`]-backed `Layer`s have +/// processed an `on_close` event. +/// +/// This is needed to enable a [`Registry`]-backed Layer to access span +/// data after the `Layer` has recieved the `on_close` callback. +/// +/// Once all `Layer`s have processed this event, the [`Registry`] knows +/// that is able to safely remove the span tracked by `id`. `CloseGuard` +/// accomplishes this through a two-step process: +/// 1. Whenever a [`Registry`]-backed `Layer::on_close` method is +/// called, `Registry::start_close` is closed. +/// `Registry::start_close` increments a thread-local `CLOSE_COUNT` +/// by 1 and returns a `CloseGuard`. +/// 2. The `CloseGuard` is dropped at the end of `Layer::on_close`. On +/// drop, `CloseGuard` checks thread-local `CLOSE_COUNT`. If +/// `CLOSE_COUNT` is 0, the `CloseGuard` removes the span with the +/// `id` from the registry, as all `Layers` that might have seen the +/// `on_close` notification have processed it. If `CLOSE_COUNT` is +/// greater than 0, `CloseGuard` decrements the counter by one and +/// _does not_ remove the span from the [`Registry`]. +/// +pub(crate) struct CloseGuard<'a> { + id: Id, + registry: &'a Registry, + is_closing: bool, +} + +impl Registry { + fn get(&self, id: &Id) -> Option<Ref<'_, DataInner>> { + self.spans.get(id_to_idx(id)) + } + + /// Returns a guard which tracks how many `Layer`s have + /// processed an `on_close` notification via the `CLOSE_COUNT` thread-local. + /// For additional details, see [`CloseGuard`]. + /// + pub(crate) fn start_close(&self, id: Id) -> CloseGuard<'_> { + CLOSE_COUNT.with(|count| { + let c = count.get(); + count.set(c + 1); + }); + CloseGuard { + id, + registry: self, + is_closing: false, + } + } + + pub(crate) fn has_per_layer_filters(&self) -> bool { + self.next_filter_id > 0 + } + + pub(crate) fn span_stack(&self) -> cell::Ref<'_, SpanStack> { + self.current_spans.get_or_default().borrow() + } +} + +thread_local! { + /// `CLOSE_COUNT` is the thread-local counter used by `CloseGuard` to + /// track how many layers have processed the close. + /// For additional details, see [`CloseGuard`]. + /// + static CLOSE_COUNT: Cell<usize> = Cell::new(0); +} + +impl Subscriber for Registry { + fn register_callsite(&self, _: &'static Metadata<'static>) -> Interest { + if self.has_per_layer_filters() { + return FilterState::take_interest().unwrap_or_else(Interest::always); + } + + Interest::always() + } + + fn enabled(&self, _: &Metadata<'_>) -> bool { + if self.has_per_layer_filters() { + return FilterState::event_enabled(); + } + true + } + + #[inline] + fn new_span(&self, attrs: &span::Attributes<'_>) -> span::Id { + let parent = if attrs.is_root() { + None + } else if attrs.is_contextual() { + self.current_span().id().map(|id| self.clone_span(id)) + } else { + attrs.parent().map(|id| self.clone_span(id)) + }; + + let id = self + .spans + // Check out a `DataInner` entry from the pool for the new span. If + // there are free entries already allocated in the pool, this will + // preferentially reuse one; otherwise, a new `DataInner` is + // allocated and added to the pool. + .create_with(|data| { + data.metadata = attrs.metadata(); + data.parent = parent; + data.filter_map = crate::filter::FILTERING.with(|filtering| filtering.filter_map()); + #[cfg(debug_assertions)] + { + if data.filter_map != FilterMap::default() { + debug_assert!(self.has_per_layer_filters()); + } + } + + let refs = data.ref_count.get_mut(); + debug_assert_eq!(*refs, 0); + *refs = 1; + }) + .expect("Unable to allocate another span"); + idx_to_id(id) + } + + /// This is intentionally not implemented, as recording fields + /// on a span is the responsibility of layers atop of this registry. + #[inline] + fn record(&self, _: &span::Id, _: &span::Record<'_>) {} + + fn record_follows_from(&self, _span: &span::Id, _follows: &span::Id) {} + + fn event_enabled(&self, _event: &Event<'_>) -> bool { + if self.has_per_layer_filters() { + return FilterState::event_enabled(); + } + true + } + + /// This is intentionally not implemented, as recording events + /// is the responsibility of layers atop of this registry. + fn event(&self, _: &Event<'_>) {} + + fn enter(&self, id: &span::Id) { + if self + .current_spans + .get_or_default() + .borrow_mut() + .push(id.clone()) + { + self.clone_span(id); + } + } + + fn exit(&self, id: &span::Id) { + if let Some(spans) = self.current_spans.get() { + if spans.borrow_mut().pop(id) { + dispatcher::get_default(|dispatch| dispatch.try_close(id.clone())); + } + } + } + + fn clone_span(&self, id: &span::Id) -> span::Id { + let span = self + .get(id) + .unwrap_or_else(|| panic!( + "tried to clone {:?}, but no span exists with that ID\n\ + This may be caused by consuming a parent span (`parent: span`) rather than borrowing it (`parent: &span`).", + id, + )); + // Like `std::sync::Arc`, adds to the ref count (on clone) don't require + // a strong ordering; if we call` clone_span`, the reference count must + // always at least 1. The only synchronization necessary is between + // calls to `try_close`: we have to ensure that all threads have + // dropped their refs to the span before the span is closed. + let refs = span.ref_count.fetch_add(1, Ordering::Relaxed); + assert_ne!( + refs, 0, + "tried to clone a span ({:?}) that already closed", + id + ); + id.clone() + } + + fn current_span(&self) -> Current { + self.current_spans + .get() + .and_then(|spans| { + let spans = spans.borrow(); + let id = spans.current()?; + let span = self.get(id)?; + Some(Current::new(id.clone(), span.metadata)) + }) + .unwrap_or_else(Current::none) + } + + /// Decrements the reference count of the span with the given `id`, and + /// removes the span if it is zero. + /// + /// The allocated span slot will be reused when a new span is created. + fn try_close(&self, id: span::Id) -> bool { + let span = match self.get(&id) { + Some(span) => span, + None if std::thread::panicking() => return false, + None => panic!("tried to drop a ref to {:?}, but no such span exists!", id), + }; + + let refs = span.ref_count.fetch_sub(1, Ordering::Release); + if !std::thread::panicking() { + assert!(refs < std::usize::MAX, "reference count overflow!"); + } + if refs > 1 { + return false; + } + + // Synchronize if we are actually removing the span (stolen + // from std::Arc); this ensures that all other `try_close` calls on + // other threads happen-before we actually remove the span. + fence(Ordering::Acquire); + true + } +} + +impl<'a> LookupSpan<'a> for Registry { + type Data = Data<'a>; + + fn span_data(&'a self, id: &Id) -> Option<Self::Data> { + let inner = self.get(id)?; + Some(Data { inner }) + } + + fn register_filter(&mut self) -> FilterId { + let id = FilterId::new(self.next_filter_id); + self.next_filter_id += 1; + id + } +} + +// === impl CloseGuard === + +impl<'a> CloseGuard<'a> { + pub(crate) fn set_closing(&mut self) { + self.is_closing = true; + } +} + +impl<'a> Drop for CloseGuard<'a> { + fn drop(&mut self) { + // If this returns with an error, we are already panicking. At + // this point, there's nothing we can really do to recover + // except by avoiding a double-panic. + let _ = CLOSE_COUNT.try_with(|count| { + let c = count.get(); + // Decrement the count to indicate that _this_ guard's + // `on_close` callback has completed. + // + // Note that we *must* do this before we actually remove the span + // from the registry, since dropping the `DataInner` may trigger a + // new close, if this span is the last reference to a parent span. + count.set(c - 1); + + // If the current close count is 1, this stack frame is the last + // `on_close` call. If the span is closing, it's okay to remove the + // span. + if c == 1 && self.is_closing { + self.registry.spans.clear(id_to_idx(&self.id)); + } + }); + } +} + +// === impl Data === + +impl<'a> SpanData<'a> for Data<'a> { + fn id(&self) -> Id { + idx_to_id(self.inner.key()) + } + + fn metadata(&self) -> &'static Metadata<'static> { + (*self).inner.metadata + } + + fn parent(&self) -> Option<&Id> { + self.inner.parent.as_ref() + } + + fn extensions(&self) -> Extensions<'_> { + Extensions::new(self.inner.extensions.read().expect("Mutex poisoned")) + } + + fn extensions_mut(&self) -> ExtensionsMut<'_> { + ExtensionsMut::new(self.inner.extensions.write().expect("Mutex poisoned")) + } + + #[inline] + fn is_enabled_for(&self, filter: FilterId) -> bool { + self.inner.filter_map.is_enabled(filter) + } +} + +// === impl DataInner === + +impl Default for DataInner { + fn default() -> Self { + // Since `DataInner` owns a `&'static Callsite` pointer, we need + // something to use as the initial default value for that callsite. + // Since we can't access a `DataInner` until it has had actual span data + // inserted into it, the null metadata will never actually be accessed. + struct NullCallsite; + impl tracing_core::callsite::Callsite for NullCallsite { + fn set_interest(&self, _: Interest) { + unreachable!( + "/!\\ Tried to register the null callsite /!\\\n \ + This should never have happened and is definitely a bug. \ + A `tracing` bug report would be appreciated." + ) + } + + fn metadata(&self) -> &Metadata<'_> { + unreachable!( + "/!\\ Tried to access the null callsite's metadata /!\\\n \ + This should never have happened and is definitely a bug. \ + A `tracing` bug report would be appreciated." + ) + } + } + + static NULL_CALLSITE: NullCallsite = NullCallsite; + static NULL_METADATA: Metadata<'static> = tracing_core::metadata! { + name: "", + target: "", + level: tracing_core::Level::TRACE, + fields: &[], + callsite: &NULL_CALLSITE, + kind: tracing_core::metadata::Kind::SPAN, + }; + + Self { + filter_map: FilterMap::default(), + metadata: &NULL_METADATA, + parent: None, + ref_count: AtomicUsize::new(0), + extensions: RwLock::new(ExtensionsInner::new()), + } + } +} + +impl Clear for DataInner { + /// Clears the span's data in place, dropping the parent's reference count. + fn clear(&mut self) { + // A span is not considered closed until all of its children have closed. + // Therefore, each span's `DataInner` holds a "reference" to the parent + // span, keeping the parent span open until all its children have closed. + // When we close a span, we must then decrement the parent's ref count + // (potentially, allowing it to close, if this child is the last reference + // to that span). + // We have to actually unpack the option inside the `get_default` + // closure, since it is a `FnMut`, but testing that there _is_ a value + // here lets us avoid the thread-local access if we don't need the + // dispatcher at all. + if self.parent.is_some() { + // Note that --- because `Layered::try_close` works by calling + // `try_close` on the inner subscriber and using the return value to + // determine whether to call the `Layer`'s `on_close` callback --- + // we must call `try_close` on the entire subscriber stack, rather + // than just on the registry. If the registry called `try_close` on + // itself directly, the layers wouldn't see the close notification. + let subscriber = dispatcher::get_default(Dispatch::clone); + if let Some(parent) = self.parent.take() { + let _ = subscriber.try_close(parent); + } + } + + // Clear (but do not deallocate!) the pooled `HashMap` for the span's extensions. + self.extensions + .get_mut() + .unwrap_or_else(|l| { + // This function can be called in a `Drop` impl, such as while + // panicking, so ignore lock poisoning. + l.into_inner() + }) + .clear(); + + self.filter_map = FilterMap::default(); + } +} + +#[cfg(test)] +mod tests { + use super::*; + use crate::{layer::Context, registry::LookupSpan, Layer}; + use std::{ + collections::HashMap, + sync::{Arc, Mutex, Weak}, + }; + use tracing::{self, subscriber::with_default}; + use tracing_core::{ + dispatcher, + span::{Attributes, Id}, + Subscriber, + }; + + #[derive(Debug)] + struct DoesNothing; + impl<S: Subscriber> Layer<S> for DoesNothing {} + + struct AssertionLayer; + impl<S> Layer<S> for AssertionLayer + where + S: Subscriber + for<'a> LookupSpan<'a>, + { + fn on_close(&self, id: Id, ctx: Context<'_, S>) { + dbg!(format_args!("closing {:?}", id)); + assert!(&ctx.span(&id).is_some()); + } + } + + #[test] + fn single_layer_can_access_closed_span() { + let subscriber = AssertionLayer.with_subscriber(Registry::default()); + + with_default(subscriber, || { + let span = tracing::debug_span!("span"); + drop(span); + }); + } + + #[test] + fn multiple_layers_can_access_closed_span() { + let subscriber = AssertionLayer + .and_then(AssertionLayer) + .with_subscriber(Registry::default()); + + with_default(subscriber, || { + let span = tracing::debug_span!("span"); + drop(span); + }); + } + + struct CloseLayer { + inner: Arc<Mutex<CloseState>>, + } + + struct CloseHandle { + state: Arc<Mutex<CloseState>>, + } + + #[derive(Default)] + struct CloseState { + open: HashMap<&'static str, Weak<()>>, + closed: Vec<(&'static str, Weak<()>)>, + } + + struct SetRemoved(Arc<()>); + + impl<S> Layer<S> for CloseLayer + where + S: Subscriber + for<'a> LookupSpan<'a>, + { + fn on_new_span(&self, _: &Attributes<'_>, id: &Id, ctx: Context<'_, S>) { + let span = ctx.span(id).expect("Missing span; this is a bug"); + let mut lock = self.inner.lock().unwrap(); + let is_removed = Arc::new(()); + assert!( + lock.open + .insert(span.name(), Arc::downgrade(&is_removed)) + .is_none(), + "test layer saw multiple spans with the same name, the test is probably messed up" + ); + let mut extensions = span.extensions_mut(); + extensions.insert(SetRemoved(is_removed)); + } + + fn on_close(&self, id: Id, ctx: Context<'_, S>) { + let span = if let Some(span) = ctx.span(&id) { + span + } else { + println!( + "span {:?} did not exist in `on_close`, are we panicking?", + id + ); + return; + }; + let name = span.name(); + println!("close {} ({:?})", name, id); + if let Ok(mut lock) = self.inner.lock() { + if let Some(is_removed) = lock.open.remove(name) { + assert!(is_removed.upgrade().is_some()); + lock.closed.push((name, is_removed)); + } + } + } + } + + impl CloseLayer { + fn new() -> (Self, CloseHandle) { + let state = Arc::new(Mutex::new(CloseState::default())); + ( + Self { + inner: state.clone(), + }, + CloseHandle { state }, + ) + } + } + + impl CloseState { + fn is_open(&self, span: &str) -> bool { + self.open.contains_key(span) + } + + fn is_closed(&self, span: &str) -> bool { + self.closed.iter().any(|(name, _)| name == &span) + } + } + + impl CloseHandle { + fn assert_closed(&self, span: &str) { + let lock = self.state.lock().unwrap(); + assert!( + lock.is_closed(span), + "expected {} to be closed{}", + span, + if lock.is_open(span) { + " (it was still open)" + } else { + ", but it never existed (is there a problem with the test?)" + } + ) + } + + fn assert_open(&self, span: &str) { + let lock = self.state.lock().unwrap(); + assert!( + lock.is_open(span), + "expected {} to be open{}", + span, + if lock.is_closed(span) { + " (it was still open)" + } else { + ", but it never existed (is there a problem with the test?)" + } + ) + } + + fn assert_removed(&self, span: &str) { + let lock = self.state.lock().unwrap(); + let is_removed = match lock.closed.iter().find(|(name, _)| name == &span) { + Some((_, is_removed)) => is_removed, + None => panic!( + "expected {} to be removed from the registry, but it was not closed {}", + span, + if lock.is_closed(span) { + " (it was still open)" + } else { + ", but it never existed (is there a problem with the test?)" + } + ), + }; + assert!( + is_removed.upgrade().is_none(), + "expected {} to have been removed from the registry", + span + ) + } + + fn assert_not_removed(&self, span: &str) { + let lock = self.state.lock().unwrap(); + let is_removed = match lock.closed.iter().find(|(name, _)| name == &span) { + Some((_, is_removed)) => is_removed, + None if lock.is_open(span) => return, + None => unreachable!(), + }; + assert!( + is_removed.upgrade().is_some(), + "expected {} to have been removed from the registry", + span + ) + } + + #[allow(unused)] // may want this for future tests + fn assert_last_closed(&self, span: Option<&str>) { + let lock = self.state.lock().unwrap(); + let last = lock.closed.last().map(|(span, _)| span); + assert_eq!( + last, + span.as_ref(), + "expected {:?} to have closed last", + span + ); + } + + fn assert_closed_in_order(&self, order: impl AsRef<[&'static str]>) { + let lock = self.state.lock().unwrap(); + let order = order.as_ref(); + for (i, name) in order.iter().enumerate() { + assert_eq!( + lock.closed.get(i).map(|(span, _)| span), + Some(name), + "expected close order: {:?}, actual: {:?}", + order, + lock.closed.iter().map(|(name, _)| name).collect::<Vec<_>>() + ); + } + } + } + + #[test] + fn spans_are_removed_from_registry() { + let (close_layer, state) = CloseLayer::new(); + let subscriber = AssertionLayer + .and_then(close_layer) + .with_subscriber(Registry::default()); + + // Create a `Dispatch` (which is internally reference counted) so that + // the subscriber lives to the end of the test. Otherwise, if we just + // passed the subscriber itself to `with_default`, we could see the span + // be dropped when the subscriber itself is dropped, destroying the + // registry. + let dispatch = dispatcher::Dispatch::new(subscriber); + + dispatcher::with_default(&dispatch, || { + let span = tracing::debug_span!("span1"); + drop(span); + let span = tracing::info_span!("span2"); + drop(span); + }); + + state.assert_removed("span1"); + state.assert_removed("span2"); + + // Ensure the registry itself outlives the span. + drop(dispatch); + } + + #[test] + fn spans_are_only_closed_when_the_last_ref_drops() { + let (close_layer, state) = CloseLayer::new(); + let subscriber = AssertionLayer + .and_then(close_layer) + .with_subscriber(Registry::default()); + + // Create a `Dispatch` (which is internally reference counted) so that + // the subscriber lives to the end of the test. Otherwise, if we just + // passed the subscriber itself to `with_default`, we could see the span + // be dropped when the subscriber itself is dropped, destroying the + // registry. + let dispatch = dispatcher::Dispatch::new(subscriber); + + let span2 = dispatcher::with_default(&dispatch, || { + let span = tracing::debug_span!("span1"); + drop(span); + let span2 = tracing::info_span!("span2"); + let span2_clone = span2.clone(); + drop(span2); + span2_clone + }); + + state.assert_removed("span1"); + state.assert_not_removed("span2"); + + drop(span2); + state.assert_removed("span1"); + + // Ensure the registry itself outlives the span. + drop(dispatch); + } + + #[test] + fn span_enter_guards_are_dropped_out_of_order() { + let (close_layer, state) = CloseLayer::new(); + let subscriber = AssertionLayer + .and_then(close_layer) + .with_subscriber(Registry::default()); + + // Create a `Dispatch` (which is internally reference counted) so that + // the subscriber lives to the end of the test. Otherwise, if we just + // passed the subscriber itself to `with_default`, we could see the span + // be dropped when the subscriber itself is dropped, destroying the + // registry. + let dispatch = dispatcher::Dispatch::new(subscriber); + + dispatcher::with_default(&dispatch, || { + let span1 = tracing::debug_span!("span1"); + let span2 = tracing::info_span!("span2"); + + let enter1 = span1.enter(); + let enter2 = span2.enter(); + + drop(enter1); + drop(span1); + + state.assert_removed("span1"); + state.assert_not_removed("span2"); + + drop(enter2); + state.assert_not_removed("span2"); + + drop(span2); + state.assert_removed("span1"); + state.assert_removed("span2"); + }); + } + + #[test] + fn child_closes_parent() { + // This test asserts that if a parent span's handle is dropped before + // a child span's handle, the parent will remain open until child + // closes, and will then be closed. + + let (close_layer, state) = CloseLayer::new(); + let subscriber = close_layer.with_subscriber(Registry::default()); + + let dispatch = dispatcher::Dispatch::new(subscriber); + + dispatcher::with_default(&dispatch, || { + let span1 = tracing::info_span!("parent"); + let span2 = tracing::info_span!(parent: &span1, "child"); + + state.assert_open("parent"); + state.assert_open("child"); + + drop(span1); + state.assert_open("parent"); + state.assert_open("child"); + + drop(span2); + state.assert_closed("parent"); + state.assert_closed("child"); + }); + } + + #[test] + fn child_closes_grandparent() { + // This test asserts that, when a span is kept open by a child which + // is *itself* kept open by a child, closing the grandchild will close + // both the parent *and* the grandparent. + let (close_layer, state) = CloseLayer::new(); + let subscriber = close_layer.with_subscriber(Registry::default()); + + let dispatch = dispatcher::Dispatch::new(subscriber); + + dispatcher::with_default(&dispatch, || { + let span1 = tracing::info_span!("grandparent"); + let span2 = tracing::info_span!(parent: &span1, "parent"); + let span3 = tracing::info_span!(parent: &span2, "child"); + + state.assert_open("grandparent"); + state.assert_open("parent"); + state.assert_open("child"); + + drop(span1); + drop(span2); + state.assert_open("grandparent"); + state.assert_open("parent"); + state.assert_open("child"); + + drop(span3); + + state.assert_closed_in_order(&["child", "parent", "grandparent"]); + }); + } +} |