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