Struct tracing_subscriber::registry::SpanRef

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

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

impl<'a, R> SpanRef<'a, R>where
    R: LookupSpan<'a>,

pub fn id(&self) -> Id

Returns this span’s ID.

pub fn metadata(&self) -> &'static Metadata<'static>

Returns a static reference to the span’s metadata.

pub fn name(&self) -> &'static str

Returns the span’s name,

pub fn fields(&self) -> &FieldSet

Returns a list of fields defined by the span.

pub fn parent_id(&self) -> Option<&Id>

👎Deprecated since 0.2.21: this method cannot properly support per-layer filtering, and may return the Id of a disabled span if per-layer filtering is in use. use .parent().map(SpanRef::id) instead.

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

pub fn parent(&self) -> Option<Self>

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

pub fn scope(&self) -> Scope<'a, R>

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"]
});

pub fn parents(&self) -> Parents<'a, R>

👎Deprecated: equivalent to self.parent().into_iter().flat_map(SpanRef::scope), but consider whether excluding self is actually intended

Returns an iterator over all parents of this span, starting with the immediate parent.

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

pub fn from_root(&self) -> FromRoot<'a, R>

👎Deprecated since 0.2.19: equivalent to self.parent().into_iter().flat_map(|span| span.scope().from_root()), but consider whether excluding self is actually intended

Returns an iterator over all parents of this span, starting with the root of the trace tree.

The iterator will return the root of the trace tree, followed by the next span, and then the next, until this span’s immediate parent is returned.

Note: this will allocate if there are many spans remaining, or if the “smallvec” feature flag is not enabled.

pub fn extensions(&self) -> Extensions<'_>

Returns a reference to this span’s Extensions.

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

pub fn extensions_mut(&self) -> ExtensionsMut<'_>

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

impl<'a, R: Debug + LookupSpan<'a>> Debug for SpanRef<'a, R>where
    R::Data: Debug,

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

Formats the value using the given formatter.