User agent update (#328)

- Standalone indicates that the beat is not running under agent.
- Unmanaged indicates that the beat is running under agent but not managed by Fleet.
- Managed indicates that the beat is running under agent and managed by Fleet.

Author: graphaelli

useragent/useragent.go

@@ -18,22 +18,27 @@
 package useragent
 
 import (
-	"errors"
 	"runtime"
 	"strings"
 )
 
 type AgentManagementMode int
 
 const (
-	// AgentManagementModeManaged indicates that the beat is managed by Fleet.
-	AgentManagementModeManaged AgentManagementMode = iota
-	// AgentManagementModeStandalone indicates that the beat is running in standalone mode.
+	// AgentManagementModeUnknown indicates that the management mode is unknown.
+	AgentManagementModeUnknown AgentManagementMode = iota
+	// AgentManagementModeStandalone indicates that the beat is not running under agent.
 	AgentManagementModeStandalone
+	// AgentManagementModeUnmanaged indicates that the beat is running under agent but not managed by Fleet.
+	AgentManagementModeUnmanaged
+	// AgentManagementModeManaged indicates that the beat is running under agent and managed by Fleet.
+	AgentManagementModeManaged
 )
 
 func (m AgentManagementMode) String() string {
 	switch m {
+	case AgentManagementModeUnmanaged:
+		return "Unmanaged"
 	case AgentManagementModeManaged:
 		return "Managed"
 	case AgentManagementModeStandalone:
@@ -44,20 +49,26 @@ func (m AgentManagementMode) String() string {
 }
 
 // AgentUnprivilegedMode indicates whether the beat is running in unprivileged mode.
-type AgentUnprivilegedMode bool
+type AgentUnprivilegedMode int8
 
 const (
+	// AgentUnprivilegedModeUnknown indicates privilege mode is unknown.
+	AgentUnprivilegedModeUnknown AgentUnprivilegedMode = iota
 	// AgentUnprivilegedModeUnprivileged indicates that the beat is running in unprivileged mode.
-	AgentUnprivilegedModeUnprivileged AgentUnprivilegedMode = true
+	AgentUnprivilegedModeUnprivileged
 	// AgentUnprivilegedModePrivileged indicates that the beat is running in privileged mode.
-	AgentUnprivilegedModePrivileged AgentUnprivilegedMode = false
+	AgentUnprivilegedModePrivileged
 )
 
 func (m AgentUnprivilegedMode) String() string {
-	if m {
+	switch m {
+	case AgentUnprivilegedModeUnprivileged:
 		return "Unprivileged"
+	case AgentUnprivilegedModePrivileged:
+		return "Privileged"
+	default:
+		return "Unknown"
 	}
-	return "Privileged"
 }
 
 // UserAgent takes the capitalized name of the current beat and returns
@@ -82,23 +93,22 @@ func UserAgent(binaryNameCapitalized string, version, commit, buildTime string,
 	return builder.String()
 }
 
-func UserAgentWithBeatTelemetry(binaryNameCapitalized string, version string, mode AgentManagementMode, unprivileged AgentUnprivilegedMode) (string, error) {
+func UserAgentWithBeatTelemetry(binaryNameCapitalized string, version string, mode AgentManagementMode, unprivileged AgentUnprivilegedMode) string {
 	var builder strings.Builder
 	builder.WriteString("Elastic-" + binaryNameCapitalized + "/" + version + " ")
 	uaValues := []string{
 		runtime.GOOS,
 		runtime.GOARCH,
-		mode.String(),
-		unprivileged.String(),
+	}
+	if mode != AgentManagementModeUnknown {
+		uaValues = append(uaValues, mode.String())
+	}
+	if unprivileged != AgentUnprivilegedModeUnknown {
+		uaValues = append(uaValues, unprivileged.String())
 	}
 	builder.WriteByte('(')
 	builder.WriteString(strings.Join(uaValues, "; "))
 	builder.WriteByte(')')
 
-	// Ensure the user agent string does not exceed 100 characters
-	userAgent := builder.String()
-	if len(userAgent) > 100 {
-		return userAgent, errors.New("user agent string exceeds 100 characters")
-	}
-	return userAgent, nil
+	return builder.String()
 }

useragent/useragent_test.go

@@ -41,9 +41,10 @@ func TestUserAgent(t *testing.T) {
 }
 
 func TestUserAgentWithBeatTelemetry(t *testing.T) {
-	ua2, err := UserAgentWithBeatTelemetry("FakeBeat", v, mode, unprivileged)
+	ua2 := UserAgentWithBeatTelemetry("FakeBeat", v, mode, unprivileged)
 	assert.Regexp(t, regexp.MustCompile(`^Elastic-FakeBeat`), ua2)
 	assert.Regexp(t, regexp.MustCompile(`; Managed; Unprivileged\)$`), ua2)
+
+	// Require deliberate update in case we want to extend the User Agent later
 	assert.LessOrEqual(t, len(ua2), 100, "User agent string should be less than 100 characters")
-	assert.NoError(t, err)
 }