From 73f10ed5ab21fc78e97206001b9d3f067407c8d4 Mon Sep 17 00:00:00 2001
From: Alex Unger <6905948+refs@users.noreply.github.com>
Date: Fri, 3 Sep 2021 09:50:54 +0200
Subject: [PATCH] Create exporter based on agent endpoint configuration (#2029)

---
 changelog/unreleased/tracing-agent-config.md |  5 ++
 cmd/revad/runtime/runtime.go                 |  2 +-
 pkg/trace/trace.go                           | 61 ++++++++++++++++++--
 3 files changed, 63 insertions(+), 5 deletions(-)
 create mode 100644 changelog/unreleased/tracing-agent-config.md

diff --git a/changelog/unreleased/tracing-agent-config.md b/changelog/unreleased/tracing-agent-config.md
new file mode 100644
index 0000000000..12b0088f0f
--- /dev/null
+++ b/changelog/unreleased/tracing-agent-config.md
@@ -0,0 +1,5 @@
+Enhancement: Tracing agent configuration
+
+Earlier we could only use the collector URL directly, but since an agent can be deployed as a sidecar process it makes much more sense to use it instead of the collector directly.
+
+https://github.com/cs3org/reva/pull/2029
\ No newline at end of file
diff --git a/cmd/revad/runtime/runtime.go b/cmd/revad/runtime/runtime.go
index bac257454b..458caf401d 100644
--- a/cmd/revad/runtime/runtime.go
+++ b/cmd/revad/runtime/runtime.go
@@ -149,7 +149,7 @@ func initServers(mainConf map[string]interface{}, log *zerolog.Logger) map[strin
 }
 
 func initTracing(conf *coreConf) {
-	rtrace.SetTraceProvider(conf.TracingCollector)
+	rtrace.SetTraceProvider(conf.TracingCollector, conf.TracingEndpoint)
 }
 
 func initCPUCount(conf *coreConf, log *zerolog.Logger) {
diff --git a/pkg/trace/trace.go b/pkg/trace/trace.go
index c610131711..bc506d9e58 100644
--- a/pkg/trace/trace.go
+++ b/pkg/trace/trace.go
@@ -19,6 +19,10 @@
 package trace
 
 import (
+	"fmt"
+	"net/url"
+	"strings"
+
 	"go.opentelemetry.io/otel/exporters/jaeger"
 	"go.opentelemetry.io/otel/propagation"
 	"go.opentelemetry.io/otel/sdk/resource"
@@ -36,10 +40,35 @@ var (
 )
 
 // SetTraceProvider sets the TracerProvider at a package level.
-func SetTraceProvider(url string) {
-	exp, err := jaeger.New(jaeger.WithCollectorEndpoint(jaeger.WithEndpoint(url)))
-	if err != nil {
-		panic(err)
+func SetTraceProvider(collectorEndpoint string, agentEndpoint string) {
+	var exp *jaeger.Exporter
+	var err error
+
+	if agentEndpoint != "" {
+		var agentHost string
+		var agentPort string
+
+		agentHost, agentPort, err = parseAgentConfig(agentEndpoint)
+		if err != nil {
+			panic(err)
+		}
+
+		exp, err = jaeger.New(
+			jaeger.WithAgentEndpoint(
+				jaeger.WithAgentHost(agentHost),
+				jaeger.WithAgentPort(agentPort),
+			),
+		)
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	if collectorEndpoint != "" {
+		exp, err = jaeger.New(jaeger.WithCollectorEndpoint(jaeger.WithEndpoint(collectorEndpoint)))
+		if err != nil {
+			panic(err)
+		}
 	}
 
 	Provider = sdktrace.NewTracerProvider(
@@ -50,3 +79,27 @@ func SetTraceProvider(url string) {
 		)),
 	)
 }
+
+func parseAgentConfig(ae string) (string, string, error) {
+	u, err := url.Parse(ae)
+	// as per url.go:
+	// [...] Trying to parse a hostname and path
+	// without a scheme is invalid but may not necessarily return an
+	// error, due to parsing ambiguities.
+	if err == nil && u.Hostname() != "" && u.Port() != "" {
+		return u.Hostname(), u.Port(), nil
+	}
+
+	p := strings.Split(ae, ":")
+	if len(p) != 2 {
+		return "", "", fmt.Errorf(fmt.Sprintf("invalid agent endpoint `%s`. expected format: `hostname:port`", ae))
+	}
+
+	switch {
+	case p[0] == "" && p[1] == "": // case ae = ":"
+		return "", "", fmt.Errorf(fmt.Sprintf("invalid agent endpoint `%s`. expected format: `hostname:port`", ae))
+	case p[0] == "":
+		return "", "", fmt.Errorf(fmt.Sprintf("invalid agent endpoint `%s`. expected format: `hostname:port`", ae))
+	}
+	return p[0], p[1], nil
+}