Struct ParentBasedSampler 

pub struct ParentBasedSampler { /* private fields */ }

A ShouldSample sampler that lets each of the 5 branches defined by the ParentBased sampler spec be configured independently: the root sampler (no parent or an invalid parent), and a sampler for each combination of remote/local parent and sampled/not-sampled. Any branch left unset falls back to the spec default (Sampler::AlwaysOn for the two *_sampled branches, Sampler::AlwaysOff for the two *_not_sampled branches).

Unlike Sampler::ParentBased, which keeps only the delegate’s SamplingDecision and always returns the parent’s trace state with no attributes, this returns the selected delegate’s SamplingResult unchanged, preserving any attributes it adds and any trace state it modifies. Worth keeping in mind when moving an existing custom root sampler over to this API.

Build one with ParentBasedSampler::new or Sampler::parent_based.

Implementations

impl ParentBasedSampler

pub fn new(root: impl Into<Box<dyn ShouldSample>>) -> Self

Create a new ParentBasedSampler with root as the sampler used for spans with no parent or an invalid parent.

The other 4 branches default to the [ParentBased sampler spec] values:

• remote_parent_sampled: Sampler::AlwaysOn
• remote_parent_not_sampled: Sampler::AlwaysOff
• local_parent_sampled: Sampler::AlwaysOn
• local_parent_not_sampled: Sampler::AlwaysOff

Each of these branches can be configured using their respective with_* methods.

pub fn with_remote_parent_sampled( self, sampler: impl Into<Box<dyn ShouldSample>>, ) -> Self

Sampler used when the parent’s SpanContext is remote and sampled. Defaults to Sampler::AlwaysOn.

pub fn with_remote_parent_not_sampled( self, sampler: impl Into<Box<dyn ShouldSample>>, ) -> Self

Sampler used when the parent’s SpanContext is remote and not sampled. Defaults to Sampler::AlwaysOff.

pub fn with_local_parent_sampled( self, sampler: impl Into<Box<dyn ShouldSample>>, ) -> Self

Sampler used when the parent’s SpanContext is local and sampled. Defaults to Sampler::AlwaysOn.

pub fn with_local_parent_not_sampled( self, sampler: impl Into<Box<dyn ShouldSample>>, ) -> Self

Sampler used when the parent’s SpanContext is local and not sampled. Defaults to Sampler::AlwaysOff.

Trait Implementations

impl Clone for ParentBasedSampler

fn clone(&self) -> ParentBasedSampler

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ParentBasedSampler

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

Formats the value using the given formatter.

impl ShouldSample for ParentBasedSampler

fn should_sample( &self, parent_context: Option<&Context>, trace_id: TraceId, name: &str, span_kind: &SpanKind, attributes: &[KeyValue], links: &[Link], ) -> SamplingResult

Returns the SamplingDecision for a Span to be created.