traefik/vendor/github.com/openzipkin-contrib/zipkin-go-opentracing/flag/flags.go

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2018-01-10 16:48:04 +00:00
package flag
// Flags provides the ability to create and communicate feature flags.
type Flags uint64
// Flags is a bitset
const (
Debug Flags = 1 << 0
// All flags below deal with binaryPropagators. They will be discarded in the
// textMapPropagator (not read and not set)
// SamplingSet and Sampled handle Sampled tribool logic for interop with
// instrumenting libraries / propagation channels not using a separate Sampled
// header and potentially encoding this in flags.
//
// When we receive a flag we do this:
// 1. Sampled bit is set => true
// 2. Sampled bit is not set => inspect SamplingSet bit.
// 2a. SamplingSet bit is set => false
// 2b. SamplingSet bit is not set => null
// Note on 2b.: depending on the propagator having a separate Sampled header
// we either assume Sampling is false or unknown. In the latter case we will
// run our sampler even though we are not the root of the trace.
//
// When propagating to a downstream service we will always be explicit and
// will provide a set SamplingSet bit in case of our binary propagator either
SamplingSet Flags = 1 << 1
Sampled Flags = 1 << 2
// When set, we can ignore the value of the parentId. This is used for binary
// fixed width transports or transports like proto3 that return a default
// value if a value has not been set (thus not enabling you to distinguish
// between the value being set to the default or not set at all).
//
// While many zipkin systems re-use a trace id as the root span id, we know
// that some don't. With this flag, we can tell for sure if the span is root
// as opposed to the convention trace id == span id == parent id.
IsRoot Flags = 1 << 3
)