add headers to websocket connection

handshake.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"net/http"
+	"runtime/debug"
+	"sync"
+)
+
+const (
+	clientName       = "schematic-datastream-replicator"
+	clientModulePath = "github.com/schematichq/schematic-datastream-replicator"
+)
+
+var (
+	clientVersionOnce sync.Once
+	clientVersion     string
+)
+
+// ClientVersion returns the replicator version reported on the DataStream
+// handshake. It prefers the ldflag-injected `main.version` used by the
+// Dockerfile build, then falls back to module build info (a tag for
+// `go install …@v1.2.3` builds, "(devel)" for local `go build .`), and
+// finally "unknown".
+func ClientVersion() string {
+	clientVersionOnce.Do(func() {
+		clientVersion = resolveClientVersion()
+	})
+	return clientVersion
+}
+
+func resolveClientVersion() string {
+	if version != "" {
+		return version
+	}
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return "unknown"
+	}
+	if info.Main.Path == clientModulePath && info.Main.Version != "" {
+		return info.Main.Version
+	}
+	for _, dep := range info.Deps {
+		if dep == nil || dep.Path != clientModulePath {
+			continue
+		}
+		if dep.Replace != nil && dep.Replace.Version != "" {
+			return dep.Replace.Version
+		}
+		if dep.Version != "" {
+			return dep.Version
+		}
+	}
+	return "unknown"
+}
+
+// datastreamHandshakeHeaders returns the HTTP headers attached to the
+// outbound DataStream WebSocket handshake so the backend can distinguish
+// replicator connections from direct-SDK connections and correlate them to a
+// release.
+func datastreamHandshakeHeaders() http.Header {
+	h := http.Header{}
+	h.Set("X-Schematic-Datastream-Mode", "replicator")
+	h.Set("X-Schematic-Client", clientName)
+	h.Set("X-Schematic-Client-Version", ClientVersion())
+	return h
+}

main.go

@@ -21,6 +21,20 @@ import (
 	"github.com/schematichq/schematic-go/option"
 )
 
+// Populated at build time via -ldflags="-X main.version=... -X main.commit=... -X main.buildTime=..."
+var (
+	version   string
+	commit    string
+	buildTime string
+)
+
+func valueOrUnknown(s string) string {
+	if s == "" {
+		return "unknown"
+	}
+	return s
+}
+
 const (
 	defaultAPIURL               = "https://api.schematichq.com"
 	apiKeyEnvVar                = "SCHEMATIC_API_KEY"
@@ -286,6 +300,7 @@ func main() {
 		MaxReconnectAttempts: 10,
 		MinReconnectDelay:    1 * time.Second,
 		MaxReconnectDelay:    30 * time.Second,
+		ExtraHeaders:         datastreamHandshakeHeaders(),
 	}
 
 	// Get WebSocket ping/pong intervals from environment (optional)
@@ -309,6 +324,7 @@ func main() {
 	}
 
 	logger.Info(context.Background(), "Starting Schematic Datastream Replicator...")
+	logger.Info(context.Background(), fmt.Sprintf("Version: %s, Commit: %s, Build time: %s", ClientVersion(), valueOrUnknown(commit), valueOrUnknown(buildTime)))
 	logger.Info(context.Background(), fmt.Sprintf("API URL: %s", apiBaseURL))
 	if os.Getenv("SCHEMATIC_DATASTREAM_URL") != "" {
 		logger.Info(context.Background(), fmt.Sprintf("Datastream URL: %s (explicit)", datastreamURL))