From 09719cf3b7401c7d76cc226c9ca38d9085e023e6 Mon Sep 17 00:00:00 2001
From: Kegan Dougal <kegan@matrix.org>
Date: Thu, 5 Mar 2020 11:48:24 +0000
Subject: [PATCH] breaking: Add Tracing.Enabled to toggle whether we do
 opentracing

Defaults to false, which is why this is a breaking change. We need
this flag because WASM builds cannot do opentracing.
---
 common/basecomponent/base.go | 14 ++++++--------
 common/config/config.go      |  5 +++++
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/common/basecomponent/base.go b/common/basecomponent/base.go
index 83be5ff52..d1d953f7b 100644
--- a/common/basecomponent/base.go
+++ b/common/basecomponent/base.go
@@ -64,11 +64,10 @@ func NewBaseDendrite(cfg *config.Dendrite, componentName string) *BaseDendrite {
 	common.SetupStdLogging()
 	common.SetupHookLogging(cfg.Logging, componentName)
 
-	// TODO: Make this optional
-	//closer, err := cfg.SetupTracing("Dendrite" + componentName)
-	//if err != nil {
-	//	logrus.WithError(err).Panicf("failed to start opentracing")
-	//}
+	closer, err := cfg.SetupTracing("Dendrite" + componentName)
+	if err != nil {
+		logrus.WithError(err).Panicf("failed to start opentracing")
+	}
 
 	var kafkaConsumer sarama.Consumer
 	var kafkaProducer sarama.SyncProducer
@@ -80,7 +79,7 @@ func NewBaseDendrite(cfg *config.Dendrite, componentName string) *BaseDendrite {
 
 	return &BaseDendrite{
 		componentName: componentName,
-		//tracerCloser:  closer,
+		tracerCloser:  closer,
 		Cfg:           cfg,
 		APIMux:        mux.NewRouter().UseEncodedPath(),
 		KafkaConsumer: kafkaConsumer,
@@ -90,8 +89,7 @@ func NewBaseDendrite(cfg *config.Dendrite, componentName string) *BaseDendrite {
 
 // Close implements io.Closer
 func (b *BaseDendrite) Close() error {
-	return nil
-	// return b.tracerCloser.Close()
+	return b.tracerCloser.Close()
 }
 
 // CreateHTTPAppServiceAPIs returns the QueryAPI for hitting the appservice
diff --git a/common/config/config.go b/common/config/config.go
index 22991036f..bd83cbf8b 100644
--- a/common/config/config.go
+++ b/common/config/config.go
@@ -224,6 +224,8 @@ type Dendrite struct {
 
 	// The config for tracing the dendrite servers.
 	Tracing struct {
+		// Set to true to enable tracer hooks. If false, no tracing is set up.
+		Enabled bool `yaml:"enabled"`
 		// The config for the jaeger opentracing reporter.
 		Jaeger jaegerconfig.Configuration `yaml:"jaeger"`
 	} `yaml:"tracing"`
@@ -703,6 +705,9 @@ func (config *Dendrite) FederationSenderURL() string {
 
 // SetupTracing configures the opentracing using the supplied configuration.
 func (config *Dendrite) SetupTracing(serviceName string) (closer io.Closer, err error) {
+	if !config.Tracing.Enabled {
+		return ioutil.NopCloser(bytes.NewReader([]byte{})), nil
+	}
 	return config.Tracing.Jaeger.InitGlobalTracer(
 		serviceName,
 		jaegerconfig.Logger(logrusLogger{logrus.StandardLogger()}),