exporter/jaeger: Links are missing LinkType

odeke-em commented 5 years ago

We need the ability to translate a span's LinkType to a jaeger RefType.

It currently is https://github.com/census-instrumentation/opencensus-go/blob/94fd1d08391b28f9c9f721b2a67fcf57bfd0a70e/exporter/jaeger/jaeger.go#L214-L220

But needs to translate *SpanData.Links[].Type i.e.

for _, link := range data.Links { 
    refs = append(refs, &gen.SpanRef{ 
        TraceIdHigh: bytesToInt64(link.TraceID[0:8]), 
        TraceIdLow:  bytesToInt64(link.TraceID[8:16]), 
        SpanId:      bytesToInt64(link.SpanID[:]), 
                 RefType: asJaegerLinkType(link.Type),
    }) 
 } 

func asJaegerLinkType(t LinkTypeChild) SpanRefType {
        if t == LinkTypeChild {
           return gen.SpanRefType_CHILD_OF
        }
        // Other OpenCensus LinkTypes don't map to Jaeger's LinkTypes
        // TODO: file an issue with Jaeger and ask about the various LinkTypes
        return gen.SpanRefType_FOLLOWS_FROM
}