Struct TracingLayer 

pub struct TracingLayer { /* private fields */ }

Available on crate feature tracing and (crate features log or tracing) only.

A tracing layer that writes events through a Logger.

• Event levels map one to one; the event’s target, file and line are preserved.
• The message field becomes the record message; every other event field becomes a record field. Integers, floats and booleans keep their type; strings, Debug values and errors are rendered to text.
• Fields of the spans enclosing the event (root first) are attached as context. A field on an inner span shadows the same field on an outer span, and event fields shadow span fields.
• The logger’s filter is applied per event. The layer does not implement Layer::enabled, because returning false there would disable the event for every other layer too; combine it with tracing-subscriber’s own filters if you need callsite-level filtering.

Event fields are collected into a reused thread-local buffer, so an event does not allocate in steady state; each span’s fields are stored once, when the span is created or recorded.

The layer needs a subscriber that stores spans, such as tracing_subscriber::Registry (enable tracing-subscriber’s registry feature in your own Cargo.toml).

Examples

use log_io::compat::TracingLayer;
use log_io::{Level, Logger};
use tracing_subscriber::layer::SubscriberExt;

let logger = Logger::builder().level(Level::Info).stdout_json().build();
let subscriber = tracing_subscriber::registry().with(TracingLayer::new(logger));

tracing::subscriber::with_default(subscriber, || {
    let span = tracing::info_span!("request", id = 7);
    let _entered = span.enter();
    tracing::info!(status = 200, "handled");
});

Implementations

impl TracingLayer

pub const fn new(logger: Logger) -> Self

Wrap logger.

pub const fn logger(&self) -> &Logger

The wrapped logger.

Trait Implementations

impl Clone for TracingLayer

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for TracingLayer

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

Formats the value using the given formatter.

impl<S> Layer<S> for TracingLayer

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

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: &SpanRecord<'_>, ctx: Context<'_, S>)

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

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

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

Available on crate features alloc or std only.

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