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pub struct SpanRef<'a, R: LookupSpan<'a>> { /* private fields */ }
Expand description

A reference to span data and the associated registry.

This type implements all the same methods as SpanData, and provides additional methods for querying the registry based on values from the span.

Implementations

Returns this span’s ID.

Returns a static reference to the span’s metadata.

Returns the span’s name,

Returns a list of fields defined by the span.

Returns a SpanRef describing this span’s parent, or None if this span is the root of its trace tree.

Returns an iterator over all parents of this span, starting with this span, ordered from leaf to root.

The iterator will first return the span, then the span’s immediate parent, followed by that span’s parent, and so on, until it reaches a root span.

use tracing::{span, Subscriber};
use tracing_subscriber::{
    layer::{Context, Layer},
    prelude::*,
    registry::LookupSpan,
};

struct PrintingLayer;
impl<S> Layer<S> for PrintingLayer
where
    S: Subscriber + for<'lookup> LookupSpan<'lookup>,
{
    fn on_enter(&self, id: &span::Id, ctx: Context<S>) {
        let span = ctx.span(id).unwrap();
        let scope = span.scope().map(|span| span.name()).collect::<Vec<_>>();
        println!("Entering span: {:?}", scope);
    }
}

tracing::subscriber::with_default(tracing_subscriber::registry().with(PrintingLayer), || {
    let _root = tracing::info_span!("root").entered();
    // Prints: Entering span: ["root"]
    let _child = tracing::info_span!("child").entered();
    // Prints: Entering span: ["child", "root"]
    let _leaf = tracing::info_span!("leaf").entered();
    // Prints: Entering span: ["leaf", "child", "root"]
});

If the opposite order (from the root to this span) is desired, calling Scope::from_root on the returned iterator reverses the order.

impl<S> Layer<S> for PrintingLayer
where
    S: Subscriber + for<'lookup> LookupSpan<'lookup>,
{
    fn on_enter(&self, id: &span::Id, ctx: Context<S>) {
        let span = ctx.span(id).unwrap();
        let scope = span.scope().from_root().map(|span| span.name()).collect::<Vec<_>>();
        println!("Entering span: {:?}", scope);
    }
}

tracing::subscriber::with_default(tracing_subscriber::registry().with(PrintingLayer), || {
    let _root = tracing::info_span!("root").entered();
    // Prints: Entering span: ["root"]
    let _child = tracing::info_span!("child").entered();
    // Prints: Entering span: ["root", "child"]
    let _leaf = tracing::info_span!("leaf").entered();
    // Prints: Entering span: ["root", "child", "leaf"]
});

Returns a reference to this span’s Extensions.

The extensions may be used by Layers to store additional data describing the span.

Returns a mutable reference to this span’s Extensions.

The extensions may be used by Layers to store additional data describing the span.

Trait Implementations

Formats the value using the given formatter. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

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

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.