Struct TraceContext 

pub struct TraceContext { /* private fields */ }

The W3C Trace Context a client sent in a request’s _meta.

Obtain one from RequestContext::trace_context, or parse a value directly with TraceContext::parse. See the module documentation for the parsing rules.

Implementations

impl TraceContext

pub fn parse(traceparent: &str, tracestate: Option<&str>) -> Option<Self>

Parse a traceparent value and an optional tracestate value.

Returns None when traceparent is malformed. An invalid tracestate is dropped and the traceparent is kept.

pub fn from_meta(meta: &Value) -> Option<Self>

Read the trace context from a request’s _meta object.

Returns None when meta is not an object or has no traceparent. A traceparent that is present but not a well-formed string discards both keys and emits a debug-level event. A tracestate that is not a string reads as absent.

pub fn version(&self) -> u8

The traceparent version, 00 for every value defined today.

pub fn trace_id(&self) -> &str

The trace id: 32 lowercase hex digits, never all zeros.

pub fn parent_id(&self) -> &str

The caller’s span id (parent-id): 16 lowercase hex digits, never all zeros. The server’s own span is a child of this one.

pub fn trace_flags(&self) -> u8

The raw trace-flags byte.

pub fn sampled(&self) -> bool

Whether the caller set the sampled flag (bit 0 of the flags).

pub fn tracestate(&self) -> Option<&str>

The raw tracestate string, if one was sent and it passed the length and member-count limits.

pub fn traceparent(&self) -> String

The traceparent value for this context, formatted as version-trace-id-parent-id-trace-flags.

A context parsed from a later traceparent version formats with that version and its first four fields only; trailing fields are not kept.

pub fn entries(&self) -> impl Iterator<Item = (&'static str, String)> + '_

The _meta entries that carry this context: traceparent, then tracestate when there is one.

These are the exact key names the server reads, and the same pairs are what an OpenTelemetry TextMapPropagator reads from or writes to a carrier, so they can be collected into a HashMap<String, String> for extract.

use tower_mcp::TraceContext;

let ctx = TraceContext::parse(
    "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01",
    Some("vendor=value"),
)
.unwrap();
let entries: Vec<_> = ctx.entries().collect();
assert_eq!(entries[0].0, "traceparent");
assert_eq!(entries[1], ("tracestate", "vendor=value".to_string()));

Trait Implementations

impl Clone for TraceContext

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 TraceContext

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

Formats the value using the given formatter.

impl Eq for TraceContext

impl PartialEq for TraceContext

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for TraceContext