From 524737a579d4dccfa205d87ba99d9db1326acbab Mon Sep 17 00:00:00 2001
From: Ernest Zaslavsky <ernest.zaslavsky@scylladb.com>
Date: Tue, 21 Oct 2025 17:48:05 +0300
Subject: [PATCH] retry_strategy: introduce Seastar-based retry strategy

Add a new class derived from Seastar's `default_retry_strategy`.
Relocate the `should_retry` implementation from Scylla's
`default_retry_strategy` into the new class to centralize and
standardize retry behavior.
---
 utils/s3/default_aws_retry_strategy.cc | 30 ++++++++++++--------------
 utils/s3/default_aws_retry_strategy.hh | 26 ++++------------------
 2 files changed, 18 insertions(+), 38 deletions(-)

diff --git a/utils/s3/default_aws_retry_strategy.cc b/utils/s3/default_aws_retry_strategy.cc
index 5d459f1258..5235795f1e 100644
--- a/utils/s3/default_aws_retry_strategy.cc
+++ b/utils/s3/default_aws_retry_strategy.cc
@@ -8,40 +8,38 @@
 
 #include "default_aws_retry_strategy.hh"
 #include "aws_error.hh"
+#include "seastar/http/exception.hh"
+#include "seastar/util/short_streams.hh"
 #include "utils/log.hh"
 
+namespace seastar::http::experimental {
+extern logging::logger rs_logger;
+}
+
 using namespace std::chrono_literals;
+using namespace seastar::http::experimental;
 
 namespace aws {
 
-static logging::logger rs_logger("default_retry_strategy");
-
-default_aws_retry_strategy::default_aws_retry_strategy(unsigned max_retries, unsigned scale_factor) : _max_retries(max_retries), _scale_factor(scale_factor) {
+default_aws_retry_strategy::default_aws_retry_strategy(unsigned max_retries) : _max_retries(max_retries) {
 }
 
-seastar::future<bool> default_aws_retry_strategy::should_retry(const aws_error& error, unsigned attempted_retries) const {
+seastar::future<bool> default_aws_retry_strategy::should_retry(std::exception_ptr error, unsigned attempted_retries) const {
     if (attempted_retries >= _max_retries) {
         rs_logger.warn("Retries exhausted. Retry# {}", attempted_retries);
         co_return false;
     }
-    bool should_retry = error.is_retryable() == retryable::yes;
+    auto err = aws_error::from_exception_ptr(error);
+    bool should_retry = err.is_retryable() == retryable::yes;
     if (should_retry) {
-        rs_logger.debug("AWS HTTP client request failed. Reason: {}. Retry# {}", error.get_error_message(), attempted_retries);
+        rs_logger.debug("AWS HTTP client request failed. Reason: {}. Retry# {}", err.get_error_message(), attempted_retries);
     } else {
         rs_logger.warn("AWS HTTP client encountered non-retryable error. Reason: {}. Code: {}. Retry# {}",
-                       error.get_error_message(),
-                       std::to_underlying(error.get_error_type()),
+                       err.get_error_message(),
+                       std::to_underlying(err.get_error_type()),
                        attempted_retries);
     }
     co_return should_retry;
 }
 
-std::chrono::milliseconds default_aws_retry_strategy::delay_before_retry(const aws_error&, unsigned attempted_retries) const {
-    if (attempted_retries == 0) {
-        return 0ms;
-    }
-
-    return std::chrono::milliseconds((1UL << attempted_retries) * _scale_factor);
-}
-
 } // namespace aws
diff --git a/utils/s3/default_aws_retry_strategy.hh b/utils/s3/default_aws_retry_strategy.hh
index d6dee8279c..deeab7c21f 100644
--- a/utils/s3/default_aws_retry_strategy.hh
+++ b/utils/s3/default_aws_retry_strategy.hh
@@ -7,38 +7,20 @@
  */
 
 #pragma once
-#include <chrono>
-#include <seastar/core/future.hh>
+#include <seastar/http/retry_strategy.hh>
 
 namespace aws {
 
 class aws_error;
 
-class retry_strategy {
-public:
-    virtual ~retry_strategy() = default;
-    // Returns true if the error can be retried given the error and the number of times already tried.
-    virtual seastar::future<bool> should_retry(const aws_error& error, unsigned attempted_retries) const = 0;
-
-    // Calculates the time in milliseconds the client should wait before attempting another request based on the error and attemptedRetries count.
-    [[nodiscard]] virtual std::chrono::milliseconds delay_before_retry(const aws_error& error, unsigned attempted_retries) const = 0;
-
-    [[nodiscard]] virtual unsigned get_max_retries() const = 0;
-};
-
-class default_aws_retry_strategy : public retry_strategy {
+class default_aws_retry_strategy : public seastar::http::experimental::retry_strategy {
 protected:
     unsigned _max_retries;
-    unsigned _scale_factor;
 
 public:
-    explicit default_aws_retry_strategy(unsigned max_retries = 10, unsigned scale_factor = 25);
+    explicit default_aws_retry_strategy(unsigned max_retries = 10);
 
-    seastar::future<bool> should_retry(const aws_error& error, unsigned attempted_retries) const override;
-
-    [[nodiscard]] std::chrono::milliseconds delay_before_retry(const aws_error& error, unsigned attempted_retries) const override;
-
-    [[nodiscard]] unsigned get_max_retries() const override { return _max_retries; }
+    seastar::future<bool> should_retry(std::exception_ptr error, unsigned attempted_retries) const override;
 };
 
 } // namespace aws