Module otel 

OpenTelemetry-compatible distributed tracing.

OtelLayer is a Middleware that:

1. Reads the W3C traceparent header from incoming requests and continues an existing trace, or starts a fresh one.
2. Creates an HTTP server span with standard semantic attributes.
3. Stores the active span context in thread-local storage so downstream middleware (e.g. crate::proxy::ReverseProxy) can propagate it.
4. Records the completed span to a configurable exporter.

Quick start

use rust_web_server::app::App;
use rust_web_server::core::New;
use rust_web_server::otel::{OtelLayer, TracingConfig, ExporterConfig};

// Dev: print spans to stdout.
rust_web_server::otel::setup(TracingConfig {
    service_name: "my-service".to_string(),
    service_version: env!("CARGO_PKG_VERSION").to_string(),
    exporter: ExporterConfig::Stdout,
    sample_rate: 1.0,
    batch_size: 128,
});

let app = App::new().wrap(OtelLayer);

Production: OTLP HTTP export

use rust_web_server::otel::{ExporterConfig, TracingConfig};

rust_web_server::otel::setup(TracingConfig {
    service_name: "my-service".to_string(),
    service_version: "1.0.0".to_string(),
    exporter: ExporterConfig::Otlp {
        endpoint: "http://localhost:4318".to_string(),
    },
    sample_rate: 0.1,
    batch_size: 512,
});

Alternatively, set environment variables before calling setup_from_env:

OTEL_SERVICE_NAME=my-service
OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318
OTEL_TRACES_SAMPLER_ARG=0.1    # sample rate 0.0–1.0 (default 1.0)

Structs

CapturingExporter

Captures spans in memory instead of exporting them. Use in unit tests.

OtelLayer

Middleware that creates an HTTP server span for each request.

OtlpHttpExporter

Send spans to an OTLP-compatible collector over HTTP (JSON encoding).

SpanData

A completed span ready for export.

StdoutExporter

Print one JSON line per span to stdout. Useful for development and for piping into jq or a log aggregator.

TraceContext

Parsed W3C traceparent header value.

TracingConfig

Configuration for the tracing subsystem.

Enums

ExporterConfig

Which backend to export spans to.

Traits

Exporter

Destination for completed spans.

Functions

current_traceparent

Return the W3C traceparent value for the span currently being processed on this thread. Returns None when no OtelLayer span is active.

flush

Flush buffered spans without shutting down. Useful in tests.

new_span_id

Generate a new 64-bit span ID.

new_trace_id

Generate a new 128-bit trace ID. Not cryptographically random but unique enough for tracing purposes across service restarts.

setup

Initialize tracing with an explicit config. Call once at startup before the server starts accepting requests.

setup_from_env

Initialize tracing from standard OpenTelemetry environment variables:

shutdown

Flush all buffered spans to the exporter. Call before the process exits to ensure no spans are lost.