Struct SpanCollector 

pub struct SpanCollector { /* private fields */ }

Thread-local span collector with zero-atomic submit path.

Completed spans are buffered in a thread-local Vec and periodically flushed to a shared outbox. The exporter calls drain_into to harvest all pending spans.

Created explicitly and held as Arc<SpanCollector>.

Implementations

impl SpanCollector

pub fn new(_num_shards: usize, _capacity_per_shard: usize) -> Self

Create a new collector.

The _num_shards and _capacity_per_shard parameters are accepted for API compatibility but are no longer used — each thread gets its own buffer automatically, and buffers are unbounded.

pub fn start_span( self: &Arc<Self>, name: impl Into<Cow<'static, str>>, kind: SpanKind, ) -> Span

Create a new root span with a fresh trace ID.

The span is associated with this collector and will be submitted here when it drops. Under high load, adaptive sampling may return a no-op span that skips all recording and submission.

pub fn start_span_from_traceparent( self: &Arc<Self>, traceparent: Option<&str>, name: impl Into<Cow<'static, str>>, kind: SpanKind, ) -> Span

Create a root span from an incoming W3C traceparent header.

If the header is valid, the span inherits the remote trace ID and sets parent_span_id to the remote span ID. If the header is None or invalid, behaves like start_span (new trace ID).

Adaptive sampling applies: under load, may return a no-op span.

pub fn flush_local(&self)

Flush the current thread’s local buffer to the shared outbox.

Call this before drain_into when running on the same thread that submitted spans (e.g., in tests or single-threaded exporters). In production, thread-local buffers are flushed automatically when they reach [FLUSH_THRESHOLD] or on thread exit.

pub fn drain_into(&self, buf: &mut Vec<CompletedSpan>)

Drain all pending spans into the provided buffer.

This is the primary method for exporters. It collects spans from all registered thread outboxes. Spans still in thread-local buffers below the flush threshold are NOT included unless flush_local is called first (or the thread exits).

The caller can reuse the buffer across export cycles to avoid repeated allocation.

pub fn dropped_count(&self) -> u64

Number of spans that were dropped.

Always returns 0. Retained for API compatibility; use sampled_out_count for adaptive sampling stats.

pub fn recorded_count(&self) -> u64

Total spans that passed adaptive sampling and were recorded.

pub fn sampled_out_count(&self) -> u64

Total spans that were dropped by adaptive sampling.

pub fn len(&self) -> usize

Current number of spans waiting across all outboxes.

Does not include spans still in thread-local buffers that haven’t been flushed yet.

pub fn is_empty(&self) -> bool

Returns true if all outboxes are empty.

Does not account for spans in thread-local buffers below the flush threshold.