tracing-datadog

A tracing exporter layer for Datadog, without dependencies on opentelemetry.

• Exporter for tracing traces to Datadog APM
• (Optional) Datadog-compatible log formatting and APM ↔ log correlation
• (Optional) Distributed tracing support for HTTP requests via W3C Trace Context headers or Datadog's proprietary headers
• (Optional) Container-ID tracking for infrastructure metrics in APM

Crate features

• ahash - Use AHashMaps instead of std HashMaps for performance
• http - HTTP Trace Context header support (W3C Trace Context and Datadog)

Usage

To enable both trace data and log collection, use the DatadogTraceLayer layer in your tracing subscriber:

use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
use tracing_datadog::DatadogTraceLayer;

tracing_subscriber::registry()
   .with(
       DatadogTraceLayer::builder()
           .service("my-service")
           .env("production")
           .version("git sha")
           .agent_address("localhost:8126")
           .enable_logs(true)
           .build()
           .expect("failed to build DatadogTraceLayer"),
   )
   .init();

Logs will be emitted to stdout in the Datadog JSON format.

Span tag semantics

Certain span tags have special meaning in Datadog:

• service - can be used to override the service on a per-span basis
• operation - maps to Datadog APM operations
• resource - maps to Datadog APM resources
• span.kind - defaults to internal, but can be set to client, server, producer, or consumer. Internal spans do not generate trace metrics.
• span.type - defaults to custom, but can be set to web for request handlers, http for HTTP client requests, or any of sql, cassandra, memcached, mongodb, elasticsearch, opensearch, redis, or db for data store queries. custom can be used for any other type of span.

There are few other semantic conventions, like the ones for errors. This page lists a lot of them.

Distributed tracing over HTTP

To enable distributed tracing over HTTP, enable the http feature and use DatadogContext to extract and inject trace context from/into HTTP headers. See the API documentation for examples.

Prior Art

Some code has been adopted for the following projects:

• tracing-opentelemetry
• DatadogFormattingLayer
• fastrace-datadog

See also komoju-datadog for opinionated usage of this library.