1 files changed, 31 insertions, 0 deletions
diff --git a/internal/middleware/requestid.go b/internal/middleware/requestid.go
new file mode 100644
index 0000000..6914137
--- /dev/null
+++ b/internal/middleware/requestid.go
@@ -0,0 +1,31 @@
+package middleware
+
+import (
+	"net/http"
+
+	"github.com/celrenheit/sandflake"
+	"within.website/ln"
+)
+
+// RequestID appends a unique (sandflake) request ID to each request's
+// X-Request-Id header field, much like Heroku's router does.
+func RequestID(next http.Handler) http.Handler {
+	var g sandflake.Generator
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		id := g.Next().String()
+
+		if rid := r.Header.Get("X-Request-Id"); rid != "" {
+			id = rid + "," + id
+		}
+
+		ctx := ln.WithF(r.Context(), ln.F{
+			"request_id": id,
+		})
+		r = r.WithContext(ctx)
+
+		w.Header().Set("X-Request-Id", id)
+		r.Header.Set("X-Request-Id", id)
+
+		next.ServeHTTP(w, r)
+	})
+}