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// Package trace implements OpenTracing-based tracing
package trace
import (
"context"
"fmt"
"sync"
"sync/atomic"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/metadata"
"github.com/coredns/coredns/plugin/pkg/dnstest"
"github.com/coredns/coredns/plugin/pkg/log"
"github.com/coredns/coredns/plugin/pkg/rcode"
_ "github.com/coredns/coredns/plugin/pkg/trace" // Plugin the trace package.
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
ot "github.com/opentracing/opentracing-go"
otext "github.com/opentracing/opentracing-go/ext"
otlog "github.com/opentracing/opentracing-go/log"
zipkinot "github.com/openzipkin-contrib/zipkin-go-opentracing"
"github.com/openzipkin/zipkin-go"
zipkinhttp "github.com/openzipkin/zipkin-go/reporter/http"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/opentracer"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
)
const (
defaultTopLevelSpanName = "servedns"
metaTraceIdKey = "trace/traceid"
)
type traceTags struct {
Name string
Type string
Rcode string
Proto string
Remote string
}
var tagByProvider = map[string]traceTags{
"default": {
Name: "coredns.io/name",
Type: "coredns.io/type",
Rcode: "coredns.io/rcode",
Proto: "coredns.io/proto",
Remote: "coredns.io/remote",
},
"datadog": {
Name: "coredns.io@name",
Type: "coredns.io@type",
Rcode: "coredns.io@rcode",
Proto: "coredns.io@proto",
Remote: "coredns.io@remote",
},
}
type trace struct {
count uint64 // as per Go spec, needs to be first element in a struct
Next plugin.Handler
Endpoint string
EndpointType string
tracer ot.Tracer
serviceEndpoint string
serviceName string
clientServer bool
every uint64
datadogAnalyticsRate float64
Once sync.Once
tagSet traceTags
}
func (t *trace) Tracer() ot.Tracer {
return t.tracer
}
// OnStartup sets up the tracer
func (t *trace) OnStartup() error {
var err error
t.Once.Do(func() {
switch t.EndpointType {
case "zipkin":
err = t.setupZipkin()
case "datadog":
tracer := opentracer.New(
tracer.WithAgentAddr(t.Endpoint),
tracer.WithDebugMode(log.D.Value()),
tracer.WithGlobalTag(ext.SpanTypeDNS, true),
tracer.WithServiceName(t.serviceName),
tracer.WithAnalyticsRate(t.datadogAnalyticsRate),
)
t.tracer = tracer
t.tagSet = tagByProvider["datadog"]
default:
err = fmt.Errorf("unknown endpoint type: %s", t.EndpointType)
}
})
return err
}
func (t *trace) setupZipkin() error {
reporter := zipkinhttp.NewReporter(t.Endpoint)
recorder, err := zipkin.NewEndpoint(t.serviceName, t.serviceEndpoint)
if err != nil {
log.Warningf("build Zipkin endpoint found err: %v", err)
}
tracer, err := zipkin.NewTracer(
reporter,
zipkin.WithLocalEndpoint(recorder),
zipkin.WithSharedSpans(t.clientServer),
)
if err != nil {
return err
}
t.tracer = zipkinot.Wrap(tracer)
t.tagSet = tagByProvider["default"]
return err
}
// Name implements the Handler interface.
func (t *trace) Name() string { return "trace" }
// ServeDNS implements the plugin.Handle interface.
func (t *trace) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
trace := false
if t.every > 0 {
queryNr := atomic.AddUint64(&t.count, 1)
if queryNr%t.every == 0 {
trace = true
}
}
span := ot.SpanFromContext(ctx)
if !trace || span != nil {
return plugin.NextOrFailure(t.Name(), t.Next, ctx, w, r)
}
req := request.Request{W: w, Req: r}
span = t.Tracer().StartSpan(defaultTopLevelSpanName)
defer span.Finish()
switch spanCtx := span.Context().(type) {
case zipkinot.SpanContext:
metadata.SetValueFunc(ctx, metaTraceIdKey, func() string { return spanCtx.TraceID.String() })
case ddtrace.SpanContext:
metadata.SetValueFunc(ctx, metaTraceIdKey, func() string { return fmt.Sprint(spanCtx.TraceID()) })
}
rw := dnstest.NewRecorder(w)
ctx = ot.ContextWithSpan(ctx, span)
status, err := plugin.NextOrFailure(t.Name(), t.Next, ctx, rw, r)
span.SetTag(t.tagSet.Name, req.Name())
span.SetTag(t.tagSet.Type, req.Type())
span.SetTag(t.tagSet.Proto, req.Proto())
span.SetTag(t.tagSet.Remote, req.IP())
rc := rw.Rcode
if !plugin.ClientWrite(status) {
// when no response was written, fallback to status returned from next plugin as this status
// is actually used as rcode of DNS response
// see https://github.com/coredns/coredns/blob/master/core/dnsserver/server.go#L318
rc = status
}
span.SetTag(t.tagSet.Rcode, rcode.ToString(rc))
if err != nil {
otext.Error.Set(span, true)
span.LogFields(otlog.Event("error"), otlog.Error(err))
}
return status, err
}
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