Struct Layer

pub struct Layer<O: Output> { /* private fields */ }

A Layer implementation that displays all spans that own an event when it occurs.

When an event is printed, all the spans are printed. By default, if a new event occurs inside the same span, just the event is printed. Otherwise, only the divergent part of the span hierarchy will be printed.

Spans are normally not printed unless an event occurs within them. This behavior can be changed so that they are always printed when entered by calling Builder::log_spans.

Fields of spans and events are printed inline, so that each line is a log entry. However, calling Builder::multiline prints each field in a separate line.

If the feature timestamp is enabled, by default the timestamp is printed for each entry. However, it might be useful to omit it if, e.g., using jornald. That can be achieved by calling Builder::omit_timestamp.

Examples

let layer = Layer::builder(Stdout).build();
let subscriber = tracing_subscriber::registry().with(layer);
tracing::subscriber::set_global_default(subscriber).unwrap();

Implementations

impl<O: Output> Layer<O>

pub fn builder(output: O) -> Builder<O, false, false, true>

Creates a new Builder using output as the Output.

Examples

let layer = Layer::builder(Stdout).build();
let subscriber = tracing_subscriber::registry().with(layer);
tracing::subscriber::set_global_default(subscriber).unwrap();

Trait Implementations

impl<O: Output> Layer<Registry> for Layer<O>

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

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

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

Notifies this layer that an event has occurred.

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

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_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_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.