[Tracing]: Start root span on Proxy

changelog/unreleased/root-tracing.md

@@ -0,0 +1,5 @@
+Enhancement: Create a root span on proxy that propagates down to consumers
+
+In order to propagate and correctly associate a span with a request we need a root span that gets sent to other services.
+
+https://github.com/owncloud/ocis-proxy/pull/64

go.sum

@@ -175,6 +175,7 @@ github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
 github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
 github.com/cespare/xxhash/v2 v2.1.0 h1:yTUvW7Vhb89inJ+8irsUqiWjh8iT6sQPZiQzI6ReGkA=
 github.com/cespare/xxhash/v2 v2.1.0/go.mod h1:dgIUBU3pDso/gPgZ1osOZ0iQf77oPR28Tjxl5dIMyVM=
+github.com/cespare/xxhash/v2 v2.1.1 h1:6MnRN8NT7+YBpUIWxHtefFZOKTAPgGjpQSxqLNn0+qY=
 github.com/cespare/xxhash/v2 v2.1.1/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/cheekybits/genny v1.0.0/go.mod h1:+tQajlRqAUrPI7DOSpB0XAqZYtQakVtB7wXkRAgjxjQ=
 github.com/cheggaaa/pb v1.0.28/go.mod h1:pQciLPpbU0oxA0h+VJYYLxO+XeDQb5pZijXscXHm81s=

pkg/command/server.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"strconv"
 	"strings"
 	"time"
 
@@ -42,6 +43,8 @@ func Server(cfg *config.Config) *cli.Command {
 		Usage: "Start integrated server",
 		Flags: flagset.ServerWithConfig(cfg),
 		Before: func(ctx *cli.Context) error {
+			l := NewLogger(cfg)
+			l.Debug().Str("tracing", strconv.FormatBool(cfg.Tracing.Enabled)).Msg("init: before")
 			if cfg.HTTP.Root != "/" {
 				cfg.HTTP.Root = strings.TrimSuffix(cfg.HTTP.Root, "/")
 			}

pkg/flagset/flagset.go

@@ -77,7 +77,7 @@ func ServerWithConfig(cfg *config.Config) []cli.Flag {
 		},
 		&cli.StringFlag{
 			Name:        "tracing-collector",
-			Value:       "",
+			Value:       "http://localhost:14268/api/traces",
 			Usage:       "Endpoint for the collector",
 			EnvVars:     []string{"PROXY_TRACING_COLLECTOR"},
 			Destination: &cfg.Tracing.Collector,

pkg/proxy/proxy.go

@@ -1,13 +1,17 @@
 package proxy
 
 import (
-	"github.com/owncloud/ocis-proxy/pkg/proxy/policy"
+	"context"
 	"net/http"
 	"net/http/httputil"
 	"net/url"
 	"regexp"
 	"strings"
 
+	"github.com/owncloud/ocis-proxy/pkg/proxy/policy"
+	"go.opencensus.io/plugin/ochttp/propagation/tracecontext"
+	"go.opencensus.io/trace"
+
 	"github.com/owncloud/ocis-pkg/v2/log"
 	"github.com/owncloud/ocis-proxy/pkg/config"
 )
@@ -18,6 +22,8 @@ type MultiHostReverseProxy struct {
 	Directors      map[string]map[config.RouteType]map[string]func(req *http.Request)
 	PolicySelector policy.Selector
 	logger         log.Logger
+	propagator     tracecontext.HTTPFormat
+	config         *config.Config
 }
 
 // NewMultiHostReverseProxy undocummented
@@ -27,6 +33,7 @@ func NewMultiHostReverseProxy(opts ...Option) *MultiHostReverseProxy {
 	rp := &MultiHostReverseProxy{
 		Directors: make(map[string]map[config.RouteType]map[string]func(req *http.Request)),
 		logger:    options.Logger,
+		config:    options.Config,
 	}
 
 	if options.Config.Policies == nil {
@@ -140,6 +147,16 @@ func (p *MultiHostReverseProxy) ServeHTTP(w http.ResponseWriter, r *http.Request
 			Msgf("policy %v is not configured", pol)
 	}
 
+	ctx := context.Background()
+	var span *trace.Span
+
+	// Start root span.
+	if p.config.Tracing.Enabled {
+		ctx, span = trace.StartSpan(context.Background(), r.URL.String())
+		defer span.End()
+		p.propagator.SpanContextToRequest(span.SpanContext(), r)
+	}
+
 Loop:
 	for _, rt := range config.RouteTypes {
 		var handler func(string, url.URL) bool
@@ -175,7 +192,7 @@ Loop:
 	}
 
 	// Call upstream ServeHTTP
-	p.ReverseProxy.ServeHTTP(w, r)
+	p.ReverseProxy.ServeHTTP(w, r.WithContext(ctx))
 }
 
 func (p MultiHostReverseProxy) queryRouteMatcher(endpoint string, target url.URL) bool {