MM-21898: Part 2. Add opentracing (#13904)

* initial implementation of opentracing

* app layer

* Revert Makefile

* .

* cleanup

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* [ci]

* autogenerate interface

* .

* missed vendor files

* updated interfaces

* updated store layers

* lint fixes

* .

* finishing layer generators and nested spans

* added errors and b3 support

* code review

* .

* .

* fixed build error due to misplased flag.Parse()

* code review addressed

web/handlers.go

@@ -5,6 +5,7 @@ package web
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"net/http"
 	"reflect"
@@ -13,10 +14,15 @@ import (
 	"time"
 
 	"github.com/NYTimes/gziphandler"
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	spanlog "github.com/opentracing/opentracing-go/log"
 
 	"github.com/mattermost/mattermost-server/v5/app"
 	"github.com/mattermost/mattermost-server/v5/mlog"
 	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v5/services/tracing"
+	"github.com/mattermost/mattermost-server/v5/store"
 	"github.com/mattermost/mattermost-server/v5/utils"
 )
 
@@ -93,6 +99,33 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	c.Params = ParamsFromRequest(r)
 	c.Log = c.App.Log()
 
+	if *c.App.Config().ServiceSettings.EnableOpenTracing {
+		span, ctx := tracing.StartRootSpanByContext(context.Background(), "web:ServeHTTP")
+		carrier := opentracing.HTTPHeadersCarrier(r.Header)
+		_ = opentracing.GlobalTracer().Inject(span.Context(), opentracing.HTTPHeaders, carrier)
+		ext.HTTPMethod.Set(span, r.Method)
+		ext.HTTPUrl.Set(span, c.App.Path())
+		ext.PeerAddress.Set(span, c.App.IpAddress())
+		span.SetTag("request_id", c.App.RequestId())
+		span.SetTag("user_agent", c.App.UserAgent())
+
+		defer func() {
+			if c.Err != nil {
+				span.LogFields(spanlog.Error(c.Err))
+				ext.HTTPStatusCode.Set(span, uint16(c.Err.StatusCode))
+				ext.Error.Set(span, true)
+			}
+			span.Finish()
+		}()
+		c.App.SetContext(ctx)
+
+		tmpSrv := app.Server{}
+		tmpSrv = *c.App.Srv()
+		tmpSrv.Store = store.NewOpenTracingLayer(c.App.Srv().Store, ctx)
+		c.App.SetServer(&tmpSrv)
+		c.App = app.NewOpenTracingAppLayer(c.App, ctx)
+	}
+
 	// Set the max request body size to be equal to MaxFileSize.
 	// Ideally, non-file request bodies should be smaller than file request bodies,
 	// but we don't have a clean way to identify all file upload handlers.