Struct OtelFactorState 

pub struct OtelFactorState { /* private fields */ }

Manages access to the OtelFactor tracing state for the purpose of maintaining proper span parent/child relationships when WASI Otel spans are being created.

Implementations

impl OtelFactorState

pub fn from_prepare_context<T: RuntimeFactors, F: Factor>( prepare_context: &mut PrepareContext<'_, T, F>, ) -> Result<Self>

Creates an OtelFactorState from a [PrepareContext].

If [RuntimeFactors] does not contain an OtelFactor, then calling OtelFactorState::reparent_tracing_span will be a no-op.

pub fn reparent_tracing_span(&self)

Reparents the current tracing span to be a child of the last active guest span.

The otel factor enables guests to emit spans that should be part of the same trace as the host is producing for a request. Below is an example trace. A request is made to an app, a guest span is created and then the host is re-entered to fetch a key value.

| GET /... _________________________________|
   | execute_wasm_component foo ___________|
      | my_guest_span ___________________|
         | spin_key_value.get |

Setting the guest spans parent as the host is enabled through current_span_context. However, the more difficult task is having the host factor spans be children of the guest span. OtelFactorState::reparent_tracing_span handles this by reparenting the current span to be a child of the last active guest span (which is tracked internally in the otel factor).

Note that if the otel factor is not in your [RuntimeFactors] than this is effectively a no-op.

This MUST only be called from a factor host implementation function that is instrumented.

This MUST be called at the very start of the function before any awaits.

Trait Implementations

impl Default for OtelFactorState

fn default() -> OtelFactorState

Returns the “default value” for a type.