Struct BreadcrumbLayer 

pub struct BreadcrumbLayer { /* private fields */ }

A tracing layer that records every event it sees as a breadcrumb.

Cheap by construction: events below min_level are rejected before their fields are visited, and a recorded crumb costs one bounded-ring push. Recording is a no-op until crate::init runs, so installing the layer early is harmless.

Implementations

impl BreadcrumbLayer

pub fn new() -> Self

A layer recording every event at INFO or above, from any target.

pub fn min_level(self, level: TracingLevel) -> Self

Record events at level and above. Lowering this to DEBUG or TRACE buys a denser trail at the cost of evicting older crumbs sooner — the ring is bounded, so verbosity trades depth for reach.

pub fn only_targets<I, S>(self, targets: I) -> Self

where I: IntoIterator<Item = S>, S: Into<String>,

Record only events whose target starts with one of these prefixes, e.g. ["myapp", "myapp_storage"]. Empty (the default) accepts every target.

Worth setting in a binary with chatty dependencies: a bounded ring full of HTTP client logs has crowded out the storage operations that explain the corruption.

pub fn with_span(self, yes: bool) -> Self

Attach the enclosing span’s name to each crumb (default true).

Trait Implementations

impl Default for BreadcrumbLayer

fn default() -> Self

Returns the “default value” for a type.

impl<S> Layer<S> for BreadcrumbLayer

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

fn on_event(&self, event: &Event<'_>, ctx: Context<'_, S>)

Notifies this layer that an event has occurred.

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_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, _span: &Id, _values: &Record<'_>, _ctx: Context<'_, S>)

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

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_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_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> + Sync + Send>

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

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