Struct DcontextLayer 

pub struct DcontextLayer<S> { /* private fields */ }

A tracing_subscriber::Layer that automatically creates dcontext scopes when tracing spans are entered.

Levels of Integration

1. Auto-scoping (zero config): Every span enter creates a new dcontext scope that inherits the parent scope’s values. The scope is reverted on span exit.

2. Field extraction: Extract tracing span fields into dcontext values. Configure via TracingField metadata at registration time.

3. Span info: Optionally expose span metadata (name, target, level) as a SpanInfo context value.

Example

use tracing_subscriber::prelude::*;
use dcontext_tracing::TracingField;

// Configure extraction + enrichment at registration time:
builder.register_with::<String>("request_id", |opts| {
    opts.cached().with_metadata(
        TracingField::builder("rid")
            .extract_from_str(|s| Some(s.to_string()))
            .enrich_display::<String>()
            .build()
    )
});

// The layer auto-discovers metadata — no field configuration needed:
tracing_subscriber::registry()
    .with(dcontext_tracing::DcontextLayer::new())
    .init();

Implementations

impl<S> DcontextLayer<S>

pub fn new() -> Self

Create a new DcontextLayer with default settings (auto-scoping only).

Field extraction is auto-discovered from TracingField metadata in the registry. No explicit field configuration is needed.

pub fn builder() -> DcontextLayerBuilder<S>

Create a DcontextLayerBuilder for configuring the layer.

Trait Implementations

impl<S> Default for DcontextLayer<S>

fn default() -> Self

Returns the “default value” for a type.

impl<S> Layer<S> for DcontextLayer<S>

where S: Subscriber + for<'a> LookupSpan<'a>,

fn on_new_span(&self, attrs: &Attributes<'_>, id: &Id, ctx: Context<'_, S>)

Notifies this layer that a new span was constructed with the given Attributes and Id.

fn on_record(&self, id: &Id, values: &Record<'_>, ctx: Context<'_, S>)

Notifies this layer that a span with the given Id recorded the given values.

fn on_enter(&self, id: &Id, ctx: Context<'_, S>)

Notifies this layer that a span with the given ID was entered.

fn on_exit(&self, id: &Id, _ctx: Context<'_, S>)

Notifies this layer that the span with the given ID was exited.

fn on_close(&self, id: Id, ctx: Context<'_, S>)

Notifies this layer that the span with the given ID has been closed.

fn on_register_dispatch(&self, subscriber: &Dispatch)

Performs late initialization when installing this layer as a Subscriber.

fn on_layer(&mut self, subscriber: &mut S)

Performs late initialization when attaching a Layer to a Subscriber.

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

Registers a new callsite with this layer, returning whether or not the layer is interested in being notified about the callsite, similarly to Subscriber::register_callsite.

fn enabled(&self, metadata: &Metadata<'_>, ctx: Context<'_, S>) -> bool

Returns true if this layer is interested in a span or event with the given metadata in the current Context, similarly to Subscriber::enabled.

fn on_follows_from(&self, _span: &Id, _follows: &Id, _ctx: Context<'_, S>)

Notifies this layer that a span with the ID span recorded that it follows from the span with the ID follows.

fn event_enabled(&self, _event: &Event<'_>, _ctx: Context<'_, S>) -> bool

Called before on_event, to determine if on_event should be called.

fn on_event(&self, _event: &Event<'_>, _ctx: Context<'_, S>)

Notifies this layer that an event has occurred.

fn on_id_change(&self, _old: &Id, _new: &Id, _ctx: Context<'_, S>)

Notifies this layer that a span ID has been cloned, and that the subscriber returned a different ID.

fn and_then<L>(self, layer: L) -> Layered<L, Self, S>

where L: Layer<S>, Self: Sized,

Composes this layer around the given Layer, returning a Layered struct implementing Layer.

fn with_subscriber(self, inner: S) -> Layered<Self, S>

where Self: Sized,

Composes this Layer with the given Subscriber, returning a Layered struct that implements Subscriber.

fn with_filter<F>(self, filter: F) -> Filtered<Self, F, S>

where Self: Sized, F: Filter<S>,

Combines self with a Filter, returning a Filtered layer.

fn boxed(self) -> Box<dyn Layer<S> + Send + Sync>

where Self: Sized + Layer<S> + Send + Sync + 'static, S: Subscriber,

Erases the type of this Layer, returning a Boxed dyn Layer trait object.