From d7ad6c44bda05c6c262a87b0a0592ca6b61c7e68 Mon Sep 17 00:00:00 2001
From: ston1th <ston1th@giftfish.de>
Date: Sun, 4 Aug 2019 21:51:11 +0200
Subject: [PATCH] added request tracing

---
 testapp/api/main.go | 35 +++++++++++++++++++++++++++++++----
 testapp/db/main.go  | 33 ++++++++++++++++++++++++++++++---
 testapp/srv/main.go | 35 +++++++++++++++++++++++++++++++----
 3 files changed, 92 insertions(+), 11 deletions(-)

diff --git a/testapp/api/main.go b/testapp/api/main.go
index 58f2f38..b95c887 100644
--- a/testapp/api/main.go
+++ b/testapp/api/main.go
@@ -12,8 +12,35 @@ import (
 
 var version string
 
-func get(c *http.Client, url string) (body string, err error) {
-	resp, err := c.Get(url)
+var tracer = []string{
+	"x-request-id",
+	"x-b3-traceid",
+	"x-b3-spanid",
+	"x-b3-parentspanid",
+	"x-b3-sampled",
+	"x-b3-flags",
+	"x-ot-span-context",
+}
+
+func trace(rd, rs *http.Request) {
+	if rd == nil || rs == nil {
+		return
+	}
+	for _, t := range tracer {
+		v := rs.Header.Get(t)
+		if v != "" {
+			rd.Header.Set(t, v)
+		}
+	}
+}
+
+func get(c *http.Client, req *http.Request, url string) (body string, err error) {
+	r, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return
+	}
+	trace(r, req)
+	resp, err := c.Do(r)
 	if err != nil {
 		return
 	}
@@ -39,11 +66,11 @@ func main() {
 				Timeout: 5 * time.Second,
 			}).DialContext,
 		}}
-		health, err := get(c, "http://testapp-db:8080/healthz")
+		health, err := get(c, r, "http://testapp-db:8080/healthz")
 		if err != nil {
 			health = err.Error()
 		}
-		ext, err := get(c, "http://httpbin.org/robots.txt")
+		ext, err := get(c, nil, "http://httpbin.org/robots.txt")
 		if err != nil {
 			ext = err.Error()
 		}
diff --git a/testapp/db/main.go b/testapp/db/main.go
index d6c8c56..b35759c 100644
--- a/testapp/db/main.go
+++ b/testapp/db/main.go
@@ -12,8 +12,35 @@ import (
 
 var version string
 
-func get(c *http.Client, url string) (body string, err error) {
-	resp, err := c.Get(url)
+var tracer = []string{
+	"x-request-id",
+	"x-b3-traceid",
+	"x-b3-spanid",
+	"x-b3-parentspanid",
+	"x-b3-sampled",
+	"x-b3-flags",
+	"x-ot-span-context",
+}
+
+func trace(rd, rs *http.Request) {
+	if rd == nil || rs == nil {
+		return
+	}
+	for _, t := range tracer {
+		v := rs.Header.Get(t)
+		if v != "" {
+			rd.Header.Set(t, v)
+		}
+	}
+}
+
+func get(c *http.Client, req *http.Request, url string) (body string, err error) {
+	r, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return
+	}
+	trace(r, req)
+	resp, err := c.Do(r)
 	if err != nil {
 		return
 	}
@@ -39,7 +66,7 @@ func main() {
 				Timeout: 5 * time.Second,
 			}).DialContext,
 		}}
-		body, err := get(c, "http://testapp-api:8080/healthz")
+		body, err := get(c, r, "http://testapp-api:8080/healthz")
 		if err != nil {
 			body = err.Error()
 		}
diff --git a/testapp/srv/main.go b/testapp/srv/main.go
index 1b3d940..b2587c4 100644
--- a/testapp/srv/main.go
+++ b/testapp/srv/main.go
@@ -14,8 +14,35 @@ import (
 
 var version string
 
-func get(c *http.Client, url string) (body string, err error) {
-	resp, err := c.Get(url)
+var tracer = []string{
+	"x-request-id",
+	"x-b3-traceid",
+	"x-b3-spanid",
+	"x-b3-parentspanid",
+	"x-b3-sampled",
+	"x-b3-flags",
+	"x-ot-span-context",
+}
+
+func trace(rd, rs *http.Request) {
+	if rd == nil || rs == nil {
+		return
+	}
+	for _, t := range tracer {
+		v := rs.Header.Get(t)
+		if v != "" {
+			rd.Header.Set(t, v)
+		}
+	}
+}
+
+func get(c *http.Client, req *http.Request, url string) (body string, err error) {
+	r, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return
+	}
+	trace(r, req)
+	resp, err := c.Do(r)
 	if err != nil {
 		return
 	}
@@ -49,12 +76,12 @@ func main() {
 			}).DialContext,
 		}}
 		dbUrl := "http://testapp-db:8080"
-		dbBody, err := get(c, dbUrl)
+		dbBody, err := get(c, r, dbUrl)
 		if err != nil {
 			dbBody = err.Error()
 		}
 		apiUrl := "http://testapp-api:8080"
-		apiBody, err := get(c, apiUrl)
+		apiBody, err := get(c, r, apiUrl)
 		if err != nil {
 			apiBody = err.Error()
 		}