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package tracing
import (
"context"
"os"
"strings"
opentracing "github.com/opentracing/opentracing-go"
"github.com/opentracing/opentracing-go/ext"
"gitlab.com/gitlab-org/labkit/correlation"
)
// ExtractFromEnv will extract a span from the environment after it has been passed in
// from the parent process. Returns a new context, and a defer'able function, which
// should be called on process termination
func ExtractFromEnv(ctx context.Context, opts ...ExtractFromEnvOption) (context.Context, func()) {
/* config not yet used */ applyExtractFromEnvOptions(opts)
tracer := opentracing.GlobalTracer()
// Extract the Correlation-ID
envMap := environAsMap(os.Environ())
correlationID := envMap[envCorrelationIDKey]
if correlationID != "" {
ctx = correlation.ContextWithCorrelation(ctx, correlationID)
}
// Attempt to deserialize tracing identifiers
wireContext, err := tracer.Extract(
opentracing.TextMap,
opentracing.TextMapCarrier(envMap))
if err != nil {
/* Clients could send bad data, in which case we simply ignore it */
return ctx, func() {}
}
// Create the span referring to the RPC client if available.
// If wireContext == nil, a root span will be created.
additionalStartSpanOpts := []opentracing.StartSpanOption{
ext.RPCServerOption(wireContext),
}
if correlationID != "" {
additionalStartSpanOpts = append(additionalStartSpanOpts, opentracing.Tag{Key: "correlation_id", Value: correlationID})
}
serverSpan := opentracing.StartSpan(
"execute",
additionalStartSpanOpts...,
)
ctx = opentracing.ContextWithSpan(ctx, serverSpan)
return ctx, func() { serverSpan.Finish() }
}
func environAsMap(env []string) map[string]string {
envMap := make(map[string]string, len(env))
for _, v := range env {
s := strings.SplitN(v, "=", 2)
envMap[s[0]] = s[1]
}
return envMap
}
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