Register and report User-Agents used in Lantern session

src/github.com/getlantern/flashlight/client/handler.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 
 	"github.com/getlantern/detour"
+	"github.com/getlantern/flashlight/logging"
 )
 
 const (
@@ -21,6 +22,8 @@ const (
 // handler available from getHandler() and latest ReverseProxy available from
 // getReverseProxy().
 func (client *Client) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
+	logging.RegisterUserAgent(req.Header.Get("User-Agent"))
+
 	if req.Method == httpConnectMethod {
 		// CONNECT requests are often used for HTTPS requests.
 		log.Tracef("Intercepting CONNECT %s", req.URL)

src/github.com/getlantern/flashlight/logging/logging.go

@@ -215,14 +215,15 @@ func (w logglyErrorWriter) Write(b []byte) (int, error) {
 	}
 
 	extra := map[string]string{
-		"logLevel":  "ERROR",
-		"osName":    runtime.GOOS,
-		"osArch":    runtime.GOARCH,
-		"osVersion": "",
-		"language":  w.lang,
-		"country":   geolookup.GetCountry(),
-		"timeZone":  w.tz,
-		"version":   w.versionToLoggly,
+		"logLevel":          "ERROR",
+		"osName":            runtime.GOOS,
+		"osArch":            runtime.GOARCH,
+		"osVersion":         "",
+		"language":          w.lang,
+		"country":           geolookup.GetCountry(),
+		"timeZone":          w.tz,
+		"version":           w.versionToLoggly,
+		"sessionUserAgents": getSessionUserAgents(),
 	}
 
 	// extract last 2 (at most) chunks of fullMessage to message, without prefix,

src/github.com/getlantern/flashlight/logging/useragents.go

@@ -0,0 +1,48 @@
+package logging
+
+import (
+	"bytes"
+	"fmt"
+	"regexp"
+	"sync"
+)
+
+var (
+	userAgents  = make(map[string]int)
+	agentsMutex = &sync.Mutex{}
+	reg         = regexp.MustCompile("^Go.*package http$")
+)
+
+// registerUserAgent tries to find the User-Agent in the HTTP request
+// and keep track of the applications using Lantern during this session
+func RegisterUserAgent(agent string) {
+	// Do this asynchronously because it is not a critical operation,
+	// so there is no wait for the mutex in the caller goroutine
+	go func() {
+		if agent != "" {
+			agentsMutex.Lock()
+			defer agentsMutex.Unlock()
+			if n, ok := userAgents[agent]; ok {
+				userAgents[agent] = n + 1
+			} else {
+				userAgents[agent] = 1
+			}
+		}
+	}()
+}
+
+// getSessionUserAgents returns the
+func getSessionUserAgents() string {
+	agentsMutex.Lock()
+	defer agentsMutex.Unlock()
+
+	var buffer bytes.Buffer
+
+	for key, val := range userAgents {
+		if !reg.MatchString(key) {
+			buffer.WriteString(key)
+			buffer.WriteString(fmt.Sprintf(": %d requests; ", val))
+		}
+	}
+	return string(buffer.String())
+}