Dynamic Configuration Refactoring

old/middlewares/tracing/carrier.go

@@ -0,0 +1,25 @@
+package tracing
+
+import "net/http"
+
+// HTTPHeadersCarrier custom implementation to fix duplicated headers
+// It has been fixed in https://github.com/opentracing/opentracing-go/pull/191
+type HTTPHeadersCarrier http.Header
+
+// Set conforms to the TextMapWriter interface.
+func (c HTTPHeadersCarrier) Set(key, val string) {
+	h := http.Header(c)
+	h.Set(key, val)
+}
+
+// ForeachKey conforms to the TextMapReader interface.
+func (c HTTPHeadersCarrier) ForeachKey(handler func(key, val string) error) error {
+	for k, vals := range c {
+		for _, v := range vals {
+			if err := handler(k, v); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}

old/middlewares/tracing/datadog/datadog.go

@@ -0,0 +1,45 @@
+package datadog
+
+import (
+	"io"
+	"strings"
+
+	"github.com/containous/traefik/old/log"
+	"github.com/opentracing/opentracing-go"
+	ddtracer "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/opentracer"
+	datadog "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
+)
+
+// Name sets the name of this tracer
+const Name = "datadog"
+
+// Config provides configuration settings for a datadog tracer
+type Config struct {
+	LocalAgentHostPort string `description:"Set datadog-agent's host:port that the reporter will used. Defaults to localhost:8126" export:"false"`
+	GlobalTag          string `description:"Key:Value tag to be set on all the spans." export:"true"`
+	Debug              bool   `description:"Enable DataDog debug." export:"true"`
+}
+
+// Setup sets up the tracer
+func (c *Config) Setup(serviceName string) (opentracing.Tracer, io.Closer, error) {
+	tag := strings.SplitN(c.GlobalTag, ":", 2)
+
+	value := ""
+	if len(tag) == 2 {
+		value = tag[1]
+	}
+
+	tracer := ddtracer.New(
+		datadog.WithAgentAddr(c.LocalAgentHostPort),
+		datadog.WithServiceName(serviceName),
+		datadog.WithGlobalTag(tag[0], value),
+		datadog.WithDebugMode(c.Debug),
+	)
+
+	// Without this, child spans are getting the NOOP tracer
+	opentracing.SetGlobalTracer(tracer)
+
+	log.Debug("DataDog tracer configured")
+
+	return tracer, nil, nil
+}

old/middlewares/tracing/entrypoint.go

@@ -0,0 +1,57 @@
+package tracing
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/containous/traefik/old/log"
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/urfave/negroni"
+)
+
+type entryPointMiddleware struct {
+	entryPoint string
+	*Tracing
+}
+
+// NewEntryPoint creates a new middleware that the incoming request
+func (t *Tracing) NewEntryPoint(name string) negroni.Handler {
+	log.Debug("Added entrypoint tracing middleware")
+	return &entryPointMiddleware{Tracing: t, entryPoint: name}
+}
+
+func (e *entryPointMiddleware) ServeHTTP(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+	opNameFunc := generateEntryPointSpanName
+
+	ctx, _ := e.Extract(opentracing.HTTPHeaders, HTTPHeadersCarrier(r.Header))
+	span := e.StartSpan(opNameFunc(r, e.entryPoint, e.SpanNameLimit), ext.RPCServerOption(ctx))
+	ext.Component.Set(span, e.ServiceName)
+	LogRequest(span, r)
+	ext.SpanKindRPCServer.Set(span)
+
+	r = r.WithContext(opentracing.ContextWithSpan(r.Context(), span))
+
+	recorder := newStatusCodeRecoder(w, 200)
+	next(recorder, r)
+
+	LogResponseCode(span, recorder.Status())
+	span.Finish()
+}
+
+// generateEntryPointSpanName will return a Span name of an appropriate lenth based on the 'spanLimit' argument.  If needed, it will be truncated, but will not be less than 24 characters.
+func generateEntryPointSpanName(r *http.Request, entryPoint string, spanLimit int) string {
+	name := fmt.Sprintf("Entrypoint %s %s", entryPoint, r.Host)
+
+	if spanLimit > 0 && len(name) > spanLimit {
+		if spanLimit < EntryPointMaxLengthNumber {
+			log.Warnf("SpanNameLimit is set to be less than required static number of characters, defaulting to %d + 3", EntryPointMaxLengthNumber)
+			spanLimit = EntryPointMaxLengthNumber + 3
+		}
+		hash := computeHash(name)
+		limit := (spanLimit - EntryPointMaxLengthNumber) / 2
+		name = fmt.Sprintf("Entrypoint %s %s %s", truncateString(entryPoint, limit), truncateString(r.Host, limit), hash)
+	}
+
+	return name
+}

old/middlewares/tracing/entrypoint_test.go

@@ -0,0 +1,70 @@
+package tracing
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestEntryPointMiddlewareServeHTTP(t *testing.T) {
+	expectedTags := map[string]interface{}{
+		"span.kind":   ext.SpanKindRPCServerEnum,
+		"http.method": "GET",
+		"component":   "",
+		"http.url":    "http://www.test.com",
+		"http.host":   "www.test.com",
+	}
+
+	testCases := []struct {
+		desc         string
+		entryPoint   string
+		tracing      *Tracing
+		expectedTags map[string]interface{}
+		expectedName string
+	}{
+		{
+			desc:       "no truncation test",
+			entryPoint: "test",
+			tracing: &Tracing{
+				SpanNameLimit: 0,
+				tracer:        &MockTracer{Span: &MockSpan{Tags: make(map[string]interface{})}},
+			},
+			expectedTags: expectedTags,
+			expectedName: "Entrypoint test www.test.com",
+		}, {
+			desc:       "basic test",
+			entryPoint: "test",
+			tracing: &Tracing{
+				SpanNameLimit: 25,
+				tracer:        &MockTracer{Span: &MockSpan{Tags: make(map[string]interface{})}},
+			},
+			expectedTags: expectedTags,
+			expectedName: "Entrypoint te... ww... 39b97e58",
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			e := &entryPointMiddleware{
+				entryPoint: test.entryPoint,
+				Tracing:    test.tracing,
+			}
+
+			next := func(http.ResponseWriter, *http.Request) {
+				span := test.tracing.tracer.(*MockTracer).Span
+
+				actual := span.Tags
+				assert.Equal(t, test.expectedTags, actual)
+				assert.Equal(t, test.expectedName, span.OpName)
+			}
+
+			e.ServeHTTP(httptest.NewRecorder(), httptest.NewRequest(http.MethodGet, "http://www.test.com", nil), next)
+		})
+	}
+}

old/middlewares/tracing/forwarder.go

@@ -0,0 +1,63 @@
+package tracing
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/containous/traefik/old/log"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/urfave/negroni"
+)
+
+type forwarderMiddleware struct {
+	frontend string
+	backend  string
+	opName   string
+	*Tracing
+}
+
+// NewForwarderMiddleware creates a new forwarder middleware that traces the outgoing request
+func (t *Tracing) NewForwarderMiddleware(frontend, backend string) negroni.Handler {
+	log.Debugf("Added outgoing tracing middleware %s", frontend)
+	return &forwarderMiddleware{
+		Tracing:  t,
+		frontend: frontend,
+		backend:  backend,
+		opName:   generateForwardSpanName(frontend, backend, t.SpanNameLimit),
+	}
+}
+
+func (f *forwarderMiddleware) ServeHTTP(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+	span, r, finish := StartSpan(r, f.opName, true)
+	defer finish()
+	span.SetTag("frontend.name", f.frontend)
+	span.SetTag("backend.name", f.backend)
+	ext.HTTPMethod.Set(span, r.Method)
+	ext.HTTPUrl.Set(span, fmt.Sprintf("%s%s", r.URL.String(), r.RequestURI))
+	span.SetTag("http.host", r.Host)
+
+	InjectRequestHeaders(r)
+
+	recorder := newStatusCodeRecoder(w, 200)
+
+	next(recorder, r)
+
+	LogResponseCode(span, recorder.Status())
+}
+
+// generateForwardSpanName will return a Span name of an appropriate lenth based on the 'spanLimit' argument.  If needed, it will be truncated, but will not be less than 21 characters
+func generateForwardSpanName(frontend, backend string, spanLimit int) string {
+	name := fmt.Sprintf("forward %s/%s", frontend, backend)
+
+	if spanLimit > 0 && len(name) > spanLimit {
+		if spanLimit < ForwardMaxLengthNumber {
+			log.Warnf("SpanNameLimit is set to be less than required static number of characters, defaulting to %d + 3", ForwardMaxLengthNumber)
+			spanLimit = ForwardMaxLengthNumber + 3
+		}
+		hash := computeHash(name)
+		limit := (spanLimit - ForwardMaxLengthNumber) / 2
+		name = fmt.Sprintf("forward %s/%s/%s", truncateString(frontend, limit), truncateString(backend, limit), hash)
+	}
+
+	return name
+}

old/middlewares/tracing/forwarder_test.go

@@ -0,0 +1,93 @@
+package tracing
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTracingNewForwarderMiddleware(t *testing.T) {
+	testCases := []struct {
+		desc     string
+		tracer   *Tracing
+		frontend string
+		backend  string
+		expected *forwarderMiddleware
+	}{
+		{
+			desc: "Simple Forward Tracer without truncation and hashing",
+			tracer: &Tracing{
+				SpanNameLimit: 101,
+			},
+			frontend: "some-service.domain.tld",
+			backend:  "some-service.domain.tld",
+			expected: &forwarderMiddleware{
+				Tracing: &Tracing{
+					SpanNameLimit: 101,
+				},
+				frontend: "some-service.domain.tld",
+				backend:  "some-service.domain.tld",
+				opName:   "forward some-service.domain.tld/some-service.domain.tld",
+			},
+		}, {
+			desc: "Simple Forward Tracer with truncation and hashing",
+			tracer: &Tracing{
+				SpanNameLimit: 101,
+			},
+			frontend: "some-service-100.slug.namespace.environment.domain.tld",
+			backend:  "some-service-100.slug.namespace.environment.domain.tld",
+			expected: &forwarderMiddleware{
+				Tracing: &Tracing{
+					SpanNameLimit: 101,
+				},
+				frontend: "some-service-100.slug.namespace.environment.domain.tld",
+				backend:  "some-service-100.slug.namespace.environment.domain.tld",
+				opName:   "forward some-service-100.slug.namespace.enviro.../some-service-100.slug.namespace.enviro.../bc4a0d48",
+			},
+		},
+		{
+			desc: "Exactly 101 chars",
+			tracer: &Tracing{
+				SpanNameLimit: 101,
+			},
+			frontend: "some-service1.namespace.environment.domain.tld",
+			backend:  "some-service1.namespace.environment.domain.tld",
+			expected: &forwarderMiddleware{
+				Tracing: &Tracing{
+					SpanNameLimit: 101,
+				},
+				frontend: "some-service1.namespace.environment.domain.tld",
+				backend:  "some-service1.namespace.environment.domain.tld",
+				opName:   "forward some-service1.namespace.environment.domain.tld/some-service1.namespace.environment.domain.tld",
+			},
+		},
+		{
+			desc: "More than 101 chars",
+			tracer: &Tracing{
+				SpanNameLimit: 101,
+			},
+			frontend: "some-service1.frontend.namespace.environment.domain.tld",
+			backend:  "some-service1.backend.namespace.environment.domain.tld",
+			expected: &forwarderMiddleware{
+				Tracing: &Tracing{
+					SpanNameLimit: 101,
+				},
+				frontend: "some-service1.frontend.namespace.environment.domain.tld",
+				backend:  "some-service1.backend.namespace.environment.domain.tld",
+				opName:   "forward some-service1.frontend.namespace.envir.../some-service1.backend.namespace.enviro.../fa49dd23",
+			},
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			actual := test.tracer.NewForwarderMiddleware(test.frontend, test.backend)
+
+			assert.Equal(t, test.expected, actual)
+			assert.True(t, len(test.expected.opName) <= test.tracer.SpanNameLimit)
+		})
+	}
+}

old/middlewares/tracing/jaeger/jaeger.go

@@ -0,0 +1,73 @@
+package jaeger
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/containous/traefik/old/log"
+	"github.com/opentracing/opentracing-go"
+	jaegercfg "github.com/uber/jaeger-client-go/config"
+	"github.com/uber/jaeger-client-go/zipkin"
+	jaegermet "github.com/uber/jaeger-lib/metrics"
+)
+
+// Name sets the name of this tracer
+const Name = "jaeger"
+
+// Config provides configuration settings for a jaeger tracer
+type Config struct {
+	SamplingServerURL  string  `description:"set the sampling server url." export:"false"`
+	SamplingType       string  `description:"set the sampling type." export:"true"`
+	SamplingParam      float64 `description:"set the sampling parameter." export:"true"`
+	LocalAgentHostPort string  `description:"set jaeger-agent's host:port that the reporter will used." export:"false"`
+	Gen128Bit          bool    `description:"generate 128 bit span IDs." export:"true"`
+	Propagation        string  `description:"which propgation format to use (jaeger/b3)." export:"true"`
+}
+
+// Setup sets up the tracer
+func (c *Config) Setup(componentName string) (opentracing.Tracer, io.Closer, error) {
+	jcfg := jaegercfg.Configuration{
+		Sampler: &jaegercfg.SamplerConfig{
+			SamplingServerURL: c.SamplingServerURL,
+			Type:              c.SamplingType,
+			Param:             c.SamplingParam,
+		},
+		Reporter: &jaegercfg.ReporterConfig{
+			LogSpans:           true,
+			LocalAgentHostPort: c.LocalAgentHostPort,
+		},
+	}
+
+	jMetricsFactory := jaegermet.NullFactory
+
+	opts := []jaegercfg.Option{
+		jaegercfg.Logger(&jaegerLogger{}),
+		jaegercfg.Metrics(jMetricsFactory),
+		jaegercfg.Gen128Bit(c.Gen128Bit),
+	}
+
+	switch c.Propagation {
+	case "b3":
+		p := zipkin.NewZipkinB3HTTPHeaderPropagator()
+		opts = append(opts,
+			jaegercfg.Injector(opentracing.HTTPHeaders, p),
+			jaegercfg.Extractor(opentracing.HTTPHeaders, p),
+		)
+	case "jaeger", "":
+	default:
+		return nil, nil, fmt.Errorf("unknown propagation format: %s", c.Propagation)
+	}
+
+	// Initialize tracer with a logger and a metrics factory
+	closer, err := jcfg.InitGlobalTracer(
+		componentName,
+		opts...,
+	)
+	if err != nil {
+		log.Warnf("Could not initialize jaeger tracer: %s", err.Error())
+		return nil, nil, err
+	}
+	log.Debug("Jaeger tracer configured")
+
+	return opentracing.GlobalTracer(), closer, nil
+}

old/middlewares/tracing/jaeger/logger.go

@@ -0,0 +1,15 @@
+package jaeger
+
+import "github.com/containous/traefik/old/log"
+
+// jaegerLogger is an implementation of the Logger interface that delegates to traefik log
+type jaegerLogger struct{}
+
+func (l *jaegerLogger) Error(msg string) {
+	log.Errorf("Tracing jaeger error: %s", msg)
+}
+
+// Infof logs a message at debug priority
+func (l *jaegerLogger) Infof(msg string, args ...interface{}) {
+	log.Debugf(msg, args...)
+}

old/middlewares/tracing/status_code.go

@@ -0,0 +1,57 @@
+package tracing
+
+import (
+	"bufio"
+	"net"
+	"net/http"
+)
+
+type statusCodeRecoder interface {
+	http.ResponseWriter
+	Status() int
+}
+
+type statusCodeWithoutCloseNotify struct {
+	http.ResponseWriter
+	status int
+}
+
+// WriteHeader captures the status code for later retrieval.
+func (s *statusCodeWithoutCloseNotify) WriteHeader(status int) {
+	s.status = status
+	s.ResponseWriter.WriteHeader(status)
+}
+
+// Status get response status
+func (s *statusCodeWithoutCloseNotify) Status() int {
+	return s.status
+}
+
+// Hijack hijacks the connection
+func (s *statusCodeWithoutCloseNotify) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	return s.ResponseWriter.(http.Hijacker).Hijack()
+}
+
+// Flush sends any buffered data to the client.
+func (s *statusCodeWithoutCloseNotify) Flush() {
+	if flusher, ok := s.ResponseWriter.(http.Flusher); ok {
+		flusher.Flush()
+	}
+}
+
+type statusCodeWithCloseNotify struct {
+	*statusCodeWithoutCloseNotify
+}
+
+func (s *statusCodeWithCloseNotify) CloseNotify() <-chan bool {
+	return s.ResponseWriter.(http.CloseNotifier).CloseNotify()
+}
+
+// newStatusCodeRecoder returns an initialized statusCodeRecoder.
+func newStatusCodeRecoder(rw http.ResponseWriter, status int) statusCodeRecoder {
+	recorder := &statusCodeWithoutCloseNotify{rw, status}
+	if _, ok := rw.(http.CloseNotifier); ok {
+		return &statusCodeWithCloseNotify{recorder}
+	}
+	return recorder
+}

old/middlewares/tracing/tracing.go

@@ -0,0 +1,197 @@
+package tracing
+
+import (
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/containous/traefik/old/log"
+	"github.com/containous/traefik/old/middlewares/tracing/datadog"
+	"github.com/containous/traefik/old/middlewares/tracing/jaeger"
+	"github.com/containous/traefik/old/middlewares/tracing/zipkin"
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+)
+
+// ForwardMaxLengthNumber defines the number of static characters in the Forwarding Span Trace name : 8 chars for 'forward ' + 8 chars for hash + 2 chars for '_'.
+const ForwardMaxLengthNumber = 18
+
+// EntryPointMaxLengthNumber defines the number of static characters in the Entrypoint Span Trace name : 11 chars for 'Entrypoint ' + 8 chars for hash + 2 chars for '_'.
+const EntryPointMaxLengthNumber = 21
+
+// TraceNameHashLength defines the number of characters to use from the head of the generated hash.
+const TraceNameHashLength = 8
+
+// Tracing middleware
+type Tracing struct {
+	Backend       string          `description:"Selects the tracking backend ('jaeger','zipkin', 'datadog')." export:"true"`
+	ServiceName   string          `description:"Set the name for this service" export:"true"`
+	SpanNameLimit int             `description:"Set the maximum character limit for Span names (default 0 = no limit)" export:"true"`
+	Jaeger        *jaeger.Config  `description:"Settings for jaeger"`
+	Zipkin        *zipkin.Config  `description:"Settings for zipkin"`
+	DataDog       *datadog.Config `description:"Settings for DataDog"`
+
+	tracer opentracing.Tracer
+	closer io.Closer
+}
+
+// StartSpan delegates to opentracing.Tracer
+func (t *Tracing) StartSpan(operationName string, opts ...opentracing.StartSpanOption) opentracing.Span {
+	return t.tracer.StartSpan(operationName, opts...)
+}
+
+// Inject delegates to opentracing.Tracer
+func (t *Tracing) Inject(sm opentracing.SpanContext, format interface{}, carrier interface{}) error {
+	return t.tracer.Inject(sm, format, carrier)
+}
+
+// Extract delegates to opentracing.Tracer
+func (t *Tracing) Extract(format interface{}, carrier interface{}) (opentracing.SpanContext, error) {
+	return t.tracer.Extract(format, carrier)
+}
+
+// Backend describes things we can use to setup tracing
+type Backend interface {
+	Setup(serviceName string) (opentracing.Tracer, io.Closer, error)
+}
+
+// Setup Tracing middleware
+func (t *Tracing) Setup() {
+	var err error
+
+	switch t.Backend {
+	case jaeger.Name:
+		t.tracer, t.closer, err = t.Jaeger.Setup(t.ServiceName)
+	case zipkin.Name:
+		t.tracer, t.closer, err = t.Zipkin.Setup(t.ServiceName)
+	case datadog.Name:
+		t.tracer, t.closer, err = t.DataDog.Setup(t.ServiceName)
+	default:
+		log.Warnf("Unknown tracer %q", t.Backend)
+		return
+	}
+
+	if err != nil {
+		log.Warnf("Could not initialize %s tracing: %v", t.Backend, err)
+	}
+}
+
+// IsEnabled determines if tracing was successfully activated
+func (t *Tracing) IsEnabled() bool {
+	if t == nil || t.tracer == nil {
+		return false
+	}
+	return true
+}
+
+// Close tracer
+func (t *Tracing) Close() {
+	if t.closer != nil {
+		err := t.closer.Close()
+		if err != nil {
+			log.Warn(err)
+		}
+	}
+}
+
+// LogRequest used to create span tags from the request
+func LogRequest(span opentracing.Span, r *http.Request) {
+	if span != nil && r != nil {
+		ext.HTTPMethod.Set(span, r.Method)
+		ext.HTTPUrl.Set(span, r.URL.String())
+		span.SetTag("http.host", r.Host)
+	}
+}
+
+// LogResponseCode used to log response code in span
+func LogResponseCode(span opentracing.Span, code int) {
+	if span != nil {
+		ext.HTTPStatusCode.Set(span, uint16(code))
+		if code >= 400 {
+			ext.Error.Set(span, true)
+		}
+	}
+}
+
+// GetSpan used to retrieve span from request context
+func GetSpan(r *http.Request) opentracing.Span {
+	return opentracing.SpanFromContext(r.Context())
+}
+
+// InjectRequestHeaders used to inject OpenTracing headers into the request
+func InjectRequestHeaders(r *http.Request) {
+	if span := GetSpan(r); span != nil {
+		err := opentracing.GlobalTracer().Inject(
+			span.Context(),
+			opentracing.HTTPHeaders,
+			HTTPHeadersCarrier(r.Header))
+		if err != nil {
+			log.Error(err)
+		}
+	}
+}
+
+// LogEventf logs an event to the span in the request context.
+func LogEventf(r *http.Request, format string, args ...interface{}) {
+	if span := GetSpan(r); span != nil {
+		span.LogKV("event", fmt.Sprintf(format, args...))
+	}
+}
+
+// StartSpan starts a new span from the one in the request context
+func StartSpan(r *http.Request, operationName string, spanKinClient bool, opts ...opentracing.StartSpanOption) (opentracing.Span, *http.Request, func()) {
+	span, ctx := opentracing.StartSpanFromContext(r.Context(), operationName, opts...)
+	if spanKinClient {
+		ext.SpanKindRPCClient.Set(span)
+	}
+	r = r.WithContext(ctx)
+	return span, r, func() {
+		span.Finish()
+	}
+}
+
+// SetError flags the span associated with this request as in error
+func SetError(r *http.Request) {
+	if span := GetSpan(r); span != nil {
+		ext.Error.Set(span, true)
+	}
+}
+
+// SetErrorAndDebugLog flags the span associated with this request as in error and create a debug log.
+func SetErrorAndDebugLog(r *http.Request, format string, args ...interface{}) {
+	SetError(r)
+	log.Debugf(format, args...)
+	LogEventf(r, format, args...)
+}
+
+// SetErrorAndWarnLog flags the span associated with this request as in error and create a debug log.
+func SetErrorAndWarnLog(r *http.Request, format string, args ...interface{}) {
+	SetError(r)
+	log.Warnf(format, args...)
+	LogEventf(r, format, args...)
+}
+
+// truncateString reduces the length of the 'str' argument to 'num' - 3 and adds a '...' suffix to the tail.
+func truncateString(str string, num int) string {
+	text := str
+	if len(str) > num {
+		if num > 3 {
+			num -= 3
+		}
+		text = str[0:num] + "..."
+	}
+	return text
+}
+
+// computeHash returns the first TraceNameHashLength character of the sha256 hash for 'name' argument.
+func computeHash(name string) string {
+	data := []byte(name)
+	hash := sha256.New()
+	if _, err := hash.Write(data); err != nil {
+		// Impossible case
+		log.Errorf("Fail to create Span name hash for %s: %v", name, err)
+	}
+
+	return fmt.Sprintf("%x", hash.Sum(nil))[:TraceNameHashLength]
+}

old/middlewares/tracing/tracing_test.go

@@ -0,0 +1,133 @@
+package tracing
+
+import (
+	"testing"
+
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/log"
+	"github.com/stretchr/testify/assert"
+)
+
+type MockTracer struct {
+	Span *MockSpan
+}
+
+type MockSpan struct {
+	OpName string
+	Tags   map[string]interface{}
+}
+
+type MockSpanContext struct {
+}
+
+// MockSpanContext:
+func (n MockSpanContext) ForeachBaggageItem(handler func(k, v string) bool) {}
+
+// MockSpan:
+func (n MockSpan) Context() opentracing.SpanContext { return MockSpanContext{} }
+func (n MockSpan) SetBaggageItem(key, val string) opentracing.Span {
+	return MockSpan{Tags: make(map[string]interface{})}
+}
+func (n MockSpan) BaggageItem(key string) string { return "" }
+func (n MockSpan) SetTag(key string, value interface{}) opentracing.Span {
+	n.Tags[key] = value
+	return n
+}
+func (n MockSpan) LogFields(fields ...log.Field)                          {}
+func (n MockSpan) LogKV(keyVals ...interface{})                           {}
+func (n MockSpan) Finish()                                                {}
+func (n MockSpan) FinishWithOptions(opts opentracing.FinishOptions)       {}
+func (n MockSpan) SetOperationName(operationName string) opentracing.Span { return n }
+func (n MockSpan) Tracer() opentracing.Tracer                             { return MockTracer{} }
+func (n MockSpan) LogEvent(event string)                                  {}
+func (n MockSpan) LogEventWithPayload(event string, payload interface{})  {}
+func (n MockSpan) Log(data opentracing.LogData)                           {}
+func (n MockSpan) Reset() {
+	n.Tags = make(map[string]interface{})
+}
+
+// StartSpan belongs to the Tracer interface.
+func (n MockTracer) StartSpan(operationName string, opts ...opentracing.StartSpanOption) opentracing.Span {
+	n.Span.OpName = operationName
+	return n.Span
+}
+
+// Inject belongs to the Tracer interface.
+func (n MockTracer) Inject(sp opentracing.SpanContext, format interface{}, carrier interface{}) error {
+	return nil
+}
+
+// Extract belongs to the Tracer interface.
+func (n MockTracer) Extract(format interface{}, carrier interface{}) (opentracing.SpanContext, error) {
+	return nil, opentracing.ErrSpanContextNotFound
+}
+
+func TestTruncateString(t *testing.T) {
+	testCases := []struct {
+		desc     string
+		text     string
+		limit    int
+		expected string
+	}{
+		{
+			desc:     "short text less than limit 10",
+			text:     "short",
+			limit:    10,
+			expected: "short",
+		},
+		{
+			desc:     "basic truncate with limit 10",
+			text:     "some very long pice of text",
+			limit:    10,
+			expected: "some ve...",
+		},
+		{
+			desc:     "truncate long FQDN to 39 chars",
+			text:     "some-service-100.slug.namespace.environment.domain.tld",
+			limit:    39,
+			expected: "some-service-100.slug.namespace.envi...",
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			actual := truncateString(test.text, test.limit)
+
+			assert.Equal(t, test.expected, actual)
+			assert.True(t, len(actual) <= test.limit)
+		})
+	}
+}
+
+func TestComputeHash(t *testing.T) {
+	testCases := []struct {
+		desc     string
+		text     string
+		expected string
+	}{
+		{
+			desc:     "hashing",
+			text:     "some very long pice of text",
+			expected: "0258ea1c",
+		},
+		{
+			desc:     "short text less than limit 10",
+			text:     "short",
+			expected: "f9b0078b",
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			actual := computeHash(test.text)
+
+			assert.Equal(t, test.expected, actual)
+		})
+	}
+}

old/middlewares/tracing/wrapper.go

@@ -0,0 +1,66 @@
+package tracing
+
+import (
+	"net/http"
+
+	"github.com/urfave/negroni"
+)
+
+// NewNegroniHandlerWrapper return a negroni.Handler struct
+func (t *Tracing) NewNegroniHandlerWrapper(name string, handler negroni.Handler, clientSpanKind bool) negroni.Handler {
+	if t.IsEnabled() && handler != nil {
+		return &NegroniHandlerWrapper{
+			name:           name,
+			next:           handler,
+			clientSpanKind: clientSpanKind,
+		}
+	}
+	return handler
+}
+
+// NewHTTPHandlerWrapper return a http.Handler struct
+func (t *Tracing) NewHTTPHandlerWrapper(name string, handler http.Handler, clientSpanKind bool) http.Handler {
+	if t.IsEnabled() && handler != nil {
+		return &HTTPHandlerWrapper{
+			name:           name,
+			handler:        handler,
+			clientSpanKind: clientSpanKind,
+		}
+	}
+	return handler
+}
+
+// NegroniHandlerWrapper is used to wrap negroni handler middleware
+type NegroniHandlerWrapper struct {
+	name           string
+	next           negroni.Handler
+	clientSpanKind bool
+}
+
+func (t *NegroniHandlerWrapper) ServeHTTP(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+	var finish func()
+	_, r, finish = StartSpan(r, t.name, t.clientSpanKind)
+	defer finish()
+
+	if t.next != nil {
+		t.next.ServeHTTP(rw, r, next)
+	}
+}
+
+// HTTPHandlerWrapper is used to wrap http handler middleware
+type HTTPHandlerWrapper struct {
+	name           string
+	handler        http.Handler
+	clientSpanKind bool
+}
+
+func (t *HTTPHandlerWrapper) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
+	var finish func()
+	_, r, finish = StartSpan(r, t.name, t.clientSpanKind)
+	defer finish()
+
+	if t.handler != nil {
+		t.handler.ServeHTTP(rw, r)
+	}
+
+}

old/middlewares/tracing/zipkin/zipkin.go

@@ -0,0 +1,49 @@
+package zipkin
+
+import (
+	"io"
+	"time"
+
+	"github.com/containous/traefik/old/log"
+	"github.com/opentracing/opentracing-go"
+	zipkin "github.com/openzipkin/zipkin-go-opentracing"
+)
+
+// Name sets the name of this tracer
+const Name = "zipkin"
+
+// Config provides configuration settings for a zipkin tracer
+type Config struct {
+	HTTPEndpoint string  `description:"HTTP Endpoint to report traces to." export:"false"`
+	SameSpan     bool    `description:"Use Zipkin SameSpan RPC style traces." export:"true"`
+	ID128Bit     bool    `description:"Use Zipkin 128 bit root span IDs." export:"true"`
+	Debug        bool    `description:"Enable Zipkin debug." export:"true"`
+	SampleRate   float64 `description:"The rate between 0.0 and 1.0 of requests to trace." export:"true"`
+}
+
+// Setup sets up the tracer
+func (c *Config) Setup(serviceName string) (opentracing.Tracer, io.Closer, error) {
+	collector, err := zipkin.NewHTTPCollector(c.HTTPEndpoint)
+	if err != nil {
+		return nil, nil, err
+	}
+	recorder := zipkin.NewRecorder(collector, c.Debug, "0.0.0.0:0", serviceName)
+	tracer, err := zipkin.NewTracer(
+		recorder,
+		zipkin.ClientServerSameSpan(c.SameSpan),
+		zipkin.TraceID128Bit(c.ID128Bit),
+		zipkin.DebugMode(c.Debug),
+		zipkin.WithSampler(zipkin.NewBoundarySampler(c.SampleRate, time.Now().Unix())),
+	)
+
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Without this, child spans are getting the NOOP tracer
+	opentracing.SetGlobalTracer(tracer)
+
+	log.Debug("Zipkin tracer configured")
+
+	return tracer, collector, nil
+}