Sample spans always in Nodejs sample app

[serkan-ozal]

Because

• by default trace context is propagated through AWS XRay in Lambda handlers as long as it is not explicitly disabled (https://github.com/open-telemetry/opentelemetry-js-contrib/blob/de7a6cb77e643ed0de82e514510089fba5ae0405/plugins/node/opentelemetry-instrumentation-aws-lambda/src/instrumentation.ts#L395)
• and when AWS XRay tracing mode is PassThrough, sampled flag is set to false (0) (for ex. Root=1-66ca4895-3f6cef844dab67fb6f6461a4;Parent=27c4bbf84acc163c;Sampled=0;Lineage=d4d48d4d:0)
• and since default sampling strategy is parentbased_always_on, child spans are sampled only if their parent span is sampled
• hence, since propagated parent span context by AWS XRay is not sampled (because AWS XRay tracing mode is configured as PassThrough in the example, sampled flag is set to false as mentioned above), spans starting from handler span are not sampled and not recorded as well (that is why we see Recording is off, propagating context in a non-recording span logs).

So, to fix this issue in the sample Node.js sample app, I have set sampling policy to always_on and they will be sampled always even though parent span context by AWS XRay is not sampled.

The alternative solutions might be

• set AWS XRay tracing mode to Active here
• or disable AWS context propagation for lambda by setting OTEL_LAMBDA_DISABLE_AWS_CONTEXT_PROPAGATION env var to true in the example (https://github.com/open-telemetry/opentelemetry-js-contrib/blob/de7a6cb77e643ed0de82e514510089fba5ae0405/plugins/node/opentelemetry-instrumentation-aws-lambda/src/instrumentation.ts#L86)

[pragmaticivan]

LGTM https://cloud-native.slack.com/archives/C04HVBETC9Z/p1724567488232599