propagator-jaeger extract header(traceFlag 0) returned result is incorrect, but traceFlag 1 is ok

[shmilyoo]

Please answer these questions before submitting a bug report.

What version of OpenTelemetry are you using?

@opentelemetry/propagator-jaeger: 1.0.1

What version of Node are you using?

node 14,16

What did you do?

extract jaeger header, uber-trace-id: '0000000000000000ffc0efb753f8cd38:ffc0efb753f8cd38:0000000000000000:0'
return spanContext
{
traceId: '0000000000000000ffc0efb753f8cd38',
spanId: 'ffc0efb753f8cd38',
isRemote: true,
traceFlags: 1
}

What did you expect to see?

traceFlags should be 0

What did you see instead?

traceFlags is 0

Additional context

if the traceFlag in header is 00, the extract result is right.

I check the code , in packages/opentelemetry-propagator-jaege/src/JaegerPropagator.ts , function deserializeSpanContext

const traceFlags = flags.match(/^[0-9a-f]{2}$/i) ? parseInt(flags) & 1 : 1;

should be

const traceFlags = flags.match(/^[0-9a-f]{1,2}$/i) ? parseInt(flags) & 1 : 1;

We can see the flags define in https://www.jaegertracing.io/docs/1.33/client-libraries/

One byte bitmap, as one or two hex digits (leading zero may be omitted)

And you have also taken into account the 1-digit and 2-digit compatibility, as I have seen in the unit tests

it 'should extract context of a sampled span from carrier with 1 bit flag'

But the test case passes with flag(1), but not with 0.

This causes an exception to the sampling judgment of baseParent. Maybe I can give a PR.