TraceContextExtractor

opentelemetry_lambda_tower

Trait TraceContextExtractor 

Source 
pub trait TraceContextExtractor<T>:
    Clone
    + Send
    + Sync
    + 'static {
    // Required methods
    fn extract_context(&self, payload: &T) -> Context;
    fn trigger_type(&self) -> &'static str;
    fn span_name(&self, payload: &T, lambda_ctx: &LambdaContext) -> String;
    fn record_attributes(&self, payload: &T, span: &Span);

    // Provided method
    fn extract_links(&self, _payload: &T) -> Vec<Link> { ... }
}
Expand description

Extracts trace context from Lambda event payloads.

Different event sources carry trace context in different locations:

  • HTTP: traceparent header using W3C Trace Context
  • SQS: AWSTraceHeader in message system attributes
  • SNS: Similar to SQS

Implementations of this trait provide event-specific extraction logic and semantic attributes following OpenTelemetry conventions.

§Type Parameters

  • T - The Lambda event payload type (e.g., ApiGatewayV2httpRequest, SqsEvent)

§Example

ⓘ
use opentelemetry_lambda_tower::TraceContextExtractor;

struct MyExtractor;

impl TraceContextExtractor<MyEvent> for MyExtractor {
    fn extract_context(&self, _payload: &MyEvent) -> opentelemetry::Context {
        opentelemetry::Context::current()
    }

    fn trigger_type(&self) -> &'static str {
        "other"
    }

    fn span_name(&self, _payload: &MyEvent, ctx: &LambdaContext) -> String {
        ctx.env_config.function_name.clone()
    }

    fn record_attributes(&self, _payload: &MyEvent, _span: &tracing::Span) {}
}

Required Methods§

Source

fn extract_context(&self, payload: &T) -> Context

Extracts parent context for creating child spans.

For HTTP events, this extracts the W3C traceparent header. For message-based events, this typically returns the current context since span links are used instead of parent-child relationships.

Returns Context::current() if no valid parent context is found.

Source

fn trigger_type(&self) -> &'static str

Returns the FaaS trigger type for semantic conventions.

Valid values per OpenTelemetry spec:

  • "http" - HTTP/API Gateway triggers
  • "pubsub" - Message queue triggers (SQS, SNS)
  • "datasource" - Database triggers (DynamoDB Streams)
  • "timer" - Scheduled triggers (EventBridge, CloudWatch Events)
  • "other" - Other trigger types
Source

fn span_name(&self, payload: &T, lambda_ctx: &LambdaContext) -> String

Generates span name based on event and Lambda context.

For HTTP events, this should return "{method} {route}" format. For SQS events, this should return "{queue_name} process" format. Falls back to the function name from Lambda context.

Source

fn record_attributes(&self, payload: &T, span: &Span)

Records event-specific attributes on the span.

This method is called after span creation to add semantic attributes specific to the event type. Implementations should use span.record() to add attributes.

Common attributes by trigger type:

HTTP:

  • http.request.method
  • url.path
  • http.route

SQS/SNS:

  • messaging.system
  • messaging.operation.type
  • messaging.destination.name

Provided Methods§

Extracts span links for async message correlation.

Used for SQS/SNS where messages may come from different traces. Each message’s trace context becomes a link rather than a parent, preserving the async boundary semantics.

Default implementation returns an empty vector (no links).

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors§