From 6196a68239afbf946448c0ffd1f7c602f26a6ad0 Mon Sep 17 00:00:00 2001
From: Willem Kaufmann <willem.kaufmann@redpanda.com>
Date: Mon, 6 May 2024 19:55:10 -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 | 15 +++++++++++++--
 src/http/routes.cc                |  6 ++++--
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/seastar/http/exception.hh b/include/seastar/http/exception.hh
index 048a9de42f7..759516464d8 100644
--- a/include/seastar/http/exception.hh
+++ b/include/seastar/http/exception.hh
@@ -65,10 +65,21 @@ 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());
+	return reply;
     }
     std::string url;
+    std::optional<int> retry_after;
 };
 
 /**
diff --git a/src/http/routes.cc b/src/http/routes.cc
index 66d0f99e682..bd0cd08795d 100644
--- a/src/http/routes.cc
+++ b/src/http/routes.cc
@@ -73,8 +73,7 @@ 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();
     } catch (const base_exception& e) {
         rep->set_status(e.status(), json_exception(e).to_json());
     } catch (...) {
@@ -94,6 +93,9 @@ 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();
+            rep->done("json");
         } catch (...) {
             rep = exception_reply(std::current_exception());
         }