feat: Add XRayExtractor to obtain Trace ID from environment (#494).

[johannesfloriangeiger]

Fixes #494

Changes

See title: Adds an XRayExtractor to obtain the Trace ID from an environment variable.

With the XRayPropagator looking for the x-amzn-trace-id field in the extractor, setting the context based on a Lambda invocation alone required extracting the Trace ID via the environment variable _X_AMZN_TRACE_ID when wanting to set the correct context. The XRayExtractor combines the extraction of the Trace ID from an HTTP header or, as a fallback, from the aforementioned environment variable.

Example use:

main.rs

async fn handler(_: LambdaEvent<Value>) -> Result<(), Error> {
    let x_amzn_trace_id = env::var("_X_AMZN_TRACE_ID").unwrap();
    println!("x_amzn_trace_id: {}", x_amzn_trace_id);

    println!(
        "Initial trace_id: {}",
        Context::current().span().span_context().trace_id()
    );

    let context = global::get_text_map_propagator(|propagator| {
        propagator.extract_with_context(&Context::current(), &XRayExtractor::new())
    });

    println!(
        "trace_id pre attach: {}",
        Context::current().span().span_context().trace_id()
    );

    let _guard = context.attach();

    println!(
        "trace_id post attach: {}",
        Context::current().span().span_context().trace_id()
    );

    Ok(())
}

#[tokio::main]
async fn main() -> Result<(), Error> {
    global::set_text_map_propagator(XrayPropagator::new());
    let tracer_provider = opentelemetry_sdk::trace::SdkTracerProvider::builder().build();
    let tracer = tracer_provider.tracer(env::var("OTEL_SERVICE_NAME").unwrap());
    tracing_subscriber::registry()
        .with(tracing_opentelemetry::OpenTelemetryLayer::new(tracer))
        .init();

    Runtime::new(service_fn(handler))
        .layer(OTELLayer::new(|| {}))
        .run()
        .await
}

Start with OTEL_SERVICE_NAME=HTTPRustLambda cargo lambda watch, invoke with cargo lambda invoke --data-ascii '{}', see how the initial Trace ID differs from the environment variable and how after attaching the context the Trace ID is correct then.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: cijothomas / name: Cijo Thomas (523934e, 6da3b84, dabc1cf, e4e3a89)
• ✅ login: johannesfloriangeiger / name: Johannes Geiger (03589bc, 0a7a83d, 3ab2a18, 3b141c7, 6cee9e6, 6d282a8, 88c35e3, 15dc585, 2b061a9, 38ab54e, 49e54ef, 5fb11c6, 6e01d5b, 893a8aa, 8ca4c71, 8d17afd, 8dce62a, 8ea08f3, 9691d2e, 98eb6d2, a6c2d06, a70b79e, acb0634, ada7030, adf2e7a, b3bd35b, c20ff3f, c5c69b9, e48ffb3, fcd8bdf)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.0%. Comparing base (c3e3914) to head (b1829f3).

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #510     +/-   ##
=======================================
+ Coverage   76.4%   77.0%   +0.5%     
=======================================
  Files        127     130      +3     
  Lines      24255   24795    +540     
=======================================
+ Hits       18539   19093    +554     
+ Misses      5716    5702     -14     

Flag	Coverage Δ
etw-integration	51.1% <ø> (?)
user-events-integration	82.6% <ø> (ø)

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[cijothomas]

@jj22ee Could you review?

[cijothomas]

@jj22ee Could you review?

@jj22ee Gentle reminder!

[cijothomas]

Not an AWS expert to formally review. There isn't anyone from AWS reviewing either.

[johannesfloriangeiger]

LGTM once the comments are addressed and the CHANGELOG is updated.

All comments addressed and CHANGELOG updated!

[johannesfloriangeiger]

After some more work with X-Ray Trace ID (based off SQS messages, to come) I decided to restructure the logic around Trace ID - instead of using the environment variable as basis and overwriting it with the header value, the map with values will now contain both values and it's the responsibility of the propagator to select which value is used (preferable the header and using the environment variable as fallback). This will pave the way for the next step which will add the Trace ID based off SQS message attributes as a third source of Trace ID.

[chinmaychahar]

Please update the branch to resolve merge conflicts

[cijothomas]

@johannesfloriangeiger Can you rebase and resolve conflicts please? This is good to merge then.

[johannesfloriangeiger]

Apologies @chinmaychahar and @cijothomas, as this has been sitting around for some time I forgot to check in!

[cijothomas]

Apologies @chinmaychahar and @cijothomas, as this has been sitting around for some time I forgot to check in!

No worries. We are still sorting out this repo's processes and @chinmaychahar has stepped up to own AWS components recently!