dotcloud/docker

package otelutil

import (
    "os"
)

const (
    traceParentKey = "traceparent"
    traceStateKey  = "tracestate"

    // See https://github.com/open-telemetry/opentelemetry-specification/issues/740
    // and https://github.com/open-telemetry/oteps/pull/258.
    traceParentEnvVar = "TRACEPARENT"
    traceStateEnvVar  = "TRACESTATE"
)

type EnvironCarrier struct {
    TraceParent, TraceState string
}

// Get returns the value associated with the passed key.
func (c *EnvironCarrier) Get(key string) string {
    switch key {
    case traceParentKey:
        return c.TraceParent
    case traceStateKey:
        return c.TraceState
    }
    return ""
}

// Set stores the key-value pair.
func (c *EnvironCarrier) Set(key, value string) {
    switch key {
    case traceParentKey:
        c.TraceParent = value
    case traceStateKey:
        c.TraceState = value
    }
    // Other keys are not supported at this time.
}

// Keys lists the keys stored in this carrier.
func (c *EnvironCarrier) Keys() []string {
    var k []string
    if c.TraceParent != "" {
        k = append(k, traceParentKey)
    }
    if c.TraceState != "" {
        k = append(k, traceStateKey)
    }
    return k
}

func (c *EnvironCarrier) Environ() []string {
    var env []string
    if c.TraceParent != "" {
        env = append(env, traceParentEnvVar+"="+c.TraceParent)
    }
    if c.TraceState != "" {
        env = append(env, traceStateEnvVar+"="+c.TraceState)
    }
    return env
}

func PropagateFromEnvironment() *EnvironCarrier {
    return &EnvironCarrier{
        TraceParent: os.Getenv(traceParentEnvVar),
        TraceState:  os.Getenv(traceStateEnvVar),
    }
}