🛈 Note: This is pre-release documentation for the upcoming tracing 0.2.0 ecosystem.

For the release documentation, please see docs.rs, instead.

Struct tracing_subscriber::registry::Registry

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pub struct Registry { /* private fields */ }
Available on crate features registry and std only.
Expand description

A shared, reusable store for spans.

A Registry is a Collect around which multiple subscribers implementing various behaviors may be added. Unlike other types implementing Collect, Registry does not actually record traces itself: instead, it collects and stores span data that is exposed to any subscribers 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 subscribers to store user-defined per-span data, called extensions, in the registry. This allows Subscriber-specific data to benefit from the Registry’s high-performance concurrent storage.

This registry is implemented using a lock-free sharded 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 subscribers, 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 SpanIds and TraceIds). 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.

Trait Implementations§

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impl Collect for Registry

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fn record(&self, _: &Id, _: &Record<'_>)

This is intentionally not implemented, as recording fields on a span is the responsibility of subscribers atop of this registry.

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fn event(&self, _: &Event<'_>)

This is intentionally not implemented, as recording events is the responsibility of subscribers atop of this registry.

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fn try_close(&self, id: Id) -> bool

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.

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fn register_callsite(&self, _: &'static Metadata<'static>) -> Interest

Registers a new callsite with this collector, returning whether or not the collector is interested in being notified about the callsite. Read more
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fn enabled(&self, _: &Metadata<'_>) -> bool

Returns true if a span or event with the specified metadata would be recorded. Read more
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fn new_span(&self, attrs: &Attributes<'_>) -> Id

Visit the construction of a new span, returning a new span ID for the span being constructed. Read more
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fn record_follows_from(&self, _span: &Id, _follows: &Id)

Adds an indication that span follows from the span with the id follows. Read more
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fn event_enabled(&self, _event: &Event<'_>) -> bool

Determine if an Event should be recorded. Read more
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fn enter(&self, id: &Id)

Records that a span has been entered. Read more
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fn exit(&self, id: &Id)

Records that a span has been exited. Read more
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fn clone_span(&self, id: &Id) -> Id

Notifies the collector that a span ID has been cloned. Read more
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fn current_span(&self) -> Current

Returns a type representing this collector’s view of the current span. Read more
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fn on_register_dispatch(&self, collector: &Dispatch)

Invoked when this collector becomes a Dispatch. Read more
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fn max_level_hint(&self) -> Option<LevelFilter>

Returns the highest verbosity level that this Collector will enable, or None, if the collector does not implement level-based filtering or chooses not to implement this method. Read more
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fn drop_span(&self, _id: Id)

👎Deprecated since 0.1.2: use Collector::try_close instead
This method is deprecated. Read more
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unsafe fn downcast_raw(&self, id: TypeId) -> Option<NonNull<()>>

If self is the same type as the provided TypeId, returns an untyped NonNull pointer to that type. Otherwise, returns None. Read more
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impl Debug for Registry

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl Default for Registry

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fn default() -> Self

Returns the “default value” for a type. Read more
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impl<'a> LookupSpan<'a> for Registry

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type Data = Data<'a>

The type of span data stored in this registry.
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fn span_data(&'a self, id: &Id) -> Option<Self::Data>

Returns the SpanData for a given Id, if it exists. Read more
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fn register_filter(&mut self) -> FilterId

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fn span(&'a self, id: &Id) -> Option<SpanRef<'_, Self>>
where Self: Sized,

Returns a SpanRef for the span with the given Id, if it exists. Read more

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<C> CollectExt for C
where C: Collect,

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fn with<S>(self, subscriber: S) -> Layered<S, Self>
where S: Subscribe<Self>, Self: Sized,

Wraps self with the provided subscriber.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> SubscriberInitExt for T
where T: Into<Dispatch>,

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fn set_default(self) -> DefaultGuard

Available on crate feature std only.
Sets self as the default subscriber in the current scope, returning a guard that will unset it when dropped. Read more
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fn try_init(self) -> Result<(), TryInitError>

Attempts to set self as the global default subscriber in the current scope, returning an error if one is already set. Read more
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fn init(self)

Attempts to set self as the global default subscriber in the current scope, panicking if this fails. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> WithCollector for T

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fn with_collector<C>(self, collector: C) -> WithDispatch<Self>
where C: Into<Dispatch>,

Attaches the provided collector to this type, returning a WithDispatch wrapper. Read more
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fn with_current_collector(self) -> WithDispatch<Self>

Attaches the current default collector to this type, returning a WithDispatch wrapper. Read more