81 lines
1.8 KiB
Go
81 lines
1.8 KiB
Go
// Package trace implements OpenTracing-based tracing
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package trace
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import (
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"fmt"
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"sync"
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"sync/atomic"
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"github.com/miekg/coredns/middleware"
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"github.com/miekg/dns"
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ot "github.com/opentracing/opentracing-go"
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zipkin "github.com/openzipkin/zipkin-go-opentracing"
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"golang.org/x/net/context"
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)
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// Trace holds the tracer and endpoint info
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type Trace struct {
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Next middleware.Handler
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ServiceEndpoint string
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Endpoint string
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EndpointType string
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Tracer ot.Tracer
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serviceName string
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clientServer bool
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every uint64
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count uint64
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Once sync.Once
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}
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// OnStartup sets up the tracer
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func (t *Trace) OnStartup() error {
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var err error
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t.Once.Do(func() {
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switch t.EndpointType {
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case "zipkin":
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err = t.setupZipkin()
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default:
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err = fmt.Errorf("Unknown endpoint type: %s", t.EndpointType)
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}
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})
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return err
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}
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func (t *Trace) setupZipkin() error {
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collector, err := zipkin.NewHTTPCollector(t.Endpoint)
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if err != nil {
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return err
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}
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recorder := zipkin.NewRecorder(collector, false, t.ServiceEndpoint, t.serviceName)
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t.Tracer, err = zipkin.NewTracer(recorder, zipkin.ClientServerSameSpan(t.clientServer))
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if err != nil {
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return err
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}
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return nil
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}
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// Name implements the Handler interface.
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func (t *Trace) Name() string {
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return "trace"
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}
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// ServeDNS implements the middleware.Handle interface.
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func (t *Trace) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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trace := false
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if t.every > 0 {
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queryNr := atomic.AddUint64(&t.count, 1)
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if queryNr%t.every == 0 {
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trace = true
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}
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}
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if span := ot.SpanFromContext(ctx); span == nil && trace {
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span := t.Tracer.StartSpan("servedns")
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defer span.Finish()
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ctx = ot.ContextWithSpan(ctx, span)
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}
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return middleware.NextOrFailure(t.Name(), t.Next, ctx, w, r)
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}
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