From b52fdb0867d5d6319890bc4c4a92fdc16b3bb476 Mon Sep 17 00:00:00 2001
From: Felipe Fumero <ffumero@backblaze.com>
Date: Wed, 30 Sep 2026 13:19:12 -0600
Subject: [PATCH] Honor Retry-After on 5xx responses, not just 429

A 5xx carrying Retry-After was ignored: the client retried on its default
backoff instead of waiting the requested time, unlike 429. Give ServiceError a
retry_after_seconds slot (mirroring TooManyRequests) and pass the header from the
5xx branch of interpret_b2_error; b2http already honors a non-None value.
---
 b2sdk/_internal/exception.py | 11 ++++++++++-
 changelog.d/606.fixed.md     |  1 +
 test/unit/test_exception.py  |  9 +++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 changelog.d/606.fixed.md

diff --git a/b2sdk/_internal/exception.py b/b2sdk/_internal/exception.py
index aef410f37..d692a778c 100644
--- a/b2sdk/_internal/exception.py
+++ b/b2sdk/_internal/exception.py
@@ -433,6 +433,12 @@ class ServiceError(TransientErrorMixin, B2Error):
     Used for HTTP status codes 500 through 599.
     """
 
+    def __init__(self, *args, retry_after_seconds=None):
+        super().__init__(*args)
+
+        if retry_after_seconds is not None:
+            self.retry_after_seconds = int(retry_after_seconds)
+
 
 class CapExceeded(B2Error):
     def __str__(self):
@@ -753,5 +759,8 @@ def interpret_b2_error(
     elif status == 429:
         return TooManyRequests(retry_after_seconds=response_headers.get('retry-after'))
     elif 500 <= status < 600:
-        return ServiceError('%d %s %s' % (status, code, message))
+        return ServiceError(
+            '%d %s %s' % (status, code, message),
+            retry_after_seconds=response_headers.get('retry-after'),
+        )
     return UnknownError('%d %s %s' % (status, code, message))
diff --git a/changelog.d/606.fixed.md b/changelog.d/606.fixed.md
new file mode 100644
index 000000000..bd710ff39
--- /dev/null
+++ b/changelog.d/606.fixed.md
@@ -0,0 +1 @@
+Fixed honoring the Retry-After header on 5xx service errors.
diff --git a/test/unit/test_exception.py b/test/unit/test_exception.py
index 258e301a4..f4f6e8c96 100644
--- a/test/unit/test_exception.py
+++ b/test/unit/test_exception.py
@@ -147,6 +147,15 @@ def test_too_many_requests_without_retry_after_header(self):
         error = self._check_one(TooManyRequests, 429, '', '', {})
         assert error.retry_after_seconds is None
 
+    def test_service_error_with_retry_after_header(self):
+        retry_after = 200
+        error = self._check_one(ServiceError, 503, '', '', {'retry-after': retry_after})
+        assert error.retry_after_seconds == retry_after
+
+    def test_service_error_without_retry_after_header(self):
+        error = self._check_one(ServiceError, 503, '', '', {})
+        assert error.retry_after_seconds is None
+
     @pytest.mark.apiver(
         from_ver=3
     )  # previous apivers throw this as well, but BucketIdNotFound is a different class in them