From 6a41444c3ed98acbcc95e942d0998b933df2c046 Mon Sep 17 00:00:00 2001
From: Willem Kaufmann <willem.kaufmann@redpanda.com>
Date: Tue, 30 Apr 2024 15:25:31 -0400
Subject: [PATCH] http: add `to_reply()` in `httpd::redirect_exception`

This function allows for the creation of an `http::reply`
from a thrown `redirect_exception`, with a url for the `Location`
header and an optional `Retry-After` timeout value.
---
 include/seastar/http/exception.hh | 16 ++++++++++++++--
 src/http/routes.cc                |  6 ++++--
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/include/seastar/http/exception.hh b/include/seastar/http/exception.hh
index 048a9de42f7..f03ee42441c 100644
--- a/include/seastar/http/exception.hh
+++ b/include/seastar/http/exception.hh
@@ -65,10 +65,22 @@ private:
  */
 class redirect_exception : public base_exception {
 public:
-    redirect_exception(const std::string& url, http::reply::status_type status = http::reply::status_type::moved_permanently)
-            : base_exception("", status), url(url) {
+    redirect_exception(const std::string& url, http::reply::status_type status = http::reply::status_type::moved_permanently, const std::optional<int>& retry_after = std::nullopt)
+            : base_exception("", status), url(url), retry_after(retry_after) {
     }
+
+    http::reply to_reply() const {
+        http::reply reply{};
+	reply.add_header("Location", url);
+	if (retry_after.has_value()) {
+	    reply.add_header("Retry-After", std::to_string(retry_after.value()));
+	}
+	reply.set_status(status()).done("json");
+	return reply;
+    }
+
     std::string url;
+    std::optional<int> retry_after;
 };
 
 /**
diff --git a/src/http/routes.cc b/src/http/routes.cc
index 66d0f99e682..35135299131 100644
--- a/src/http/routes.cc
+++ b/src/http/routes.cc
@@ -73,8 +73,8 @@ std::unique_ptr<http::reply> routes::exception_reply(std::exception_ptr eptr) {
         }
         std::rethrow_exception(eptr);
     } catch (const redirect_exception& _e) {
-       rep.reset(new http::reply());
-       rep->add_header("Location", _e.url).set_status(_e.status());
+      *rep = _e.to_reply();
+      return rep;
     } catch (const base_exception& e) {
         rep->set_status(e.status(), json_exception(e).to_json());
     } catch (...) {
@@ -94,6 +94,8 @@ future<std::unique_ptr<http::reply> > routes::handle(const sstring& path, std::u
             handler->verify_mandatory_params(*req);
             auto r =  handler->handle(path, std::move(req), std::move(rep));
             return r.handle_exception(_general_handler);
+        } catch (const redirect_exception& _e) {
+	    *rep = _e.to_reply();
         } catch (...) {
             rep = exception_reply(std::current_exception());
         }