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The sampled value should be a boolean, not a string. Currently the result is that the trace is always sampled. #1
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…sult is that the trace is always sampled.
| if (!(ctxSampled in ['0', '1'])) { | ||
| ctxSampled = '0'; | ||
| } | ||
| let ctxSampledAsString = grpcMetadataFromIncomingCtx.get('x-b3-sampled')[0]; |
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cool. while unlikely, the header could be not present (that's why the Option type is used)
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The grpcMetadataFromIncomingCtx is a grpc.Metadata type.
If the header is not present it returns an empty array []; Taking the zeroth value will then be an undefined.
An undefined is not equal to either '1' or 'true' and thus result to false.
So, this should be fine, right?
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No we need to use Opion.None as false is not the same. reason is this:
undefined is "lack of a sampling decision" whereas false is "upstream
sampled and said no" make sense?
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When using a sample rate of 1%, I still saw traces from the nodejs application. After digging through it , it turns out that the sampled value is propagated as a string with either '0' or '1'. Further on in the trace of zipkin.js when the recordAnnotation is done it is checked with: if (!sampled) return; A string is always truthy, so it will always sample.
This pull request transforms the incoming string into a boolean.