What does sampled=1 mean in the context of AWS X-Ray

Question

I am trying to familiarize myself with AWS X-Ray. I see there are two levels of tracing: Active and PassThrough. The definition isn't quite helpful even after looking at this post. What does it mean if sampled=1? I can't find any documentation on this.

Answer 1

"Active" sampling means the service has some form of sampling algorithm, wherein if a request comes in with no trace header, or trace header comes in with no sampling set, a sampling decision is made.

"Passthrough" means no sampling decision will be made, but if there is a trace header attached to the request, the header will be "passed through" the service to any other downstream services on the critical path.

"sampled=1" means that trace is sampled and should report data to the AWS X-Ray backend.

Blog: https://medium.com/financial-engines-techblog/enabling-aws-x-ray-on-aws-lambda-40fdbd6740b1

X-Ray Trace header: https://docs.aws.amazon.com/xray/latest/devguide/xray-concepts.html#xray-concepts-tracingheader