Factor out stream rewind before retry

databricks/sdk/_base_client.py

@@ -159,16 +159,29 @@ def do(self,
         if isinstance(data, (str, bytes)):
             data = io.BytesIO(data.encode('utf-8') if isinstance(data, str) else data)
 
-        # Only retry if the request is not a stream or if the stream is seekable and
-        # we can rewind it. This is necessary to avoid bugs where the retry doesn't
-        # re-read already read data from the body.
-        if data is not None and not self._is_seekable_stream(data):
-            logger.debug(f"Retry disabled for non-seekable stream: type={type(data)}")
-            call = self._perform
-        else:
+        if not data:
+            # The request is not a stream.
             call = retried(timeout=timedelta(seconds=self._retry_timeout_seconds),
                            is_retryable=self._is_retryable,
                            clock=self._clock)(self._perform)
+        elif self._is_seekable_stream(data):
+            # Keep track of the initial position of the stream so that we can rewind to it
+            # if we need to retry the request.
+            initial_data_position = data.tell()
+
+            def rewind():
+                logger.debug(f"Rewinding input data to offset {initial_data_position} before retry")
+                data.seek(initial_data_position)
+
+            call = retried(timeout=timedelta(seconds=self._retry_timeout_seconds),
+                           is_retryable=self._is_retryable,
+                           clock=self._clock,
+                           before_retry=rewind)(self._perform)
+        else:
+            # Do not retry if the stream is not seekable. This is necessary to avoid bugs
+            # where the retry doesn't re-read already read data from the stream.
+            logger.debug(f"Retry disabled for non-seekable stream: type={type(data)}")
+            call = self._perform
 
         response = call(method,
                         url,
@@ -249,12 +262,6 @@ def _perform(self,
                  files=None,
                  data=None,
                  auth: Callable[[requests.PreparedRequest], requests.PreparedRequest] = None):
-        # Keep track of the initial position of the stream so that we can rewind it if
-        # we need to retry the request.
-        initial_data_position = 0
-        if self._is_seekable_stream(data):
-            initial_data_position = data.tell()
-
         response = self._session.request(method,
                                          url,
                                          params=self._fix_query_string(query),
@@ -266,16 +273,8 @@ def _perform(self,
                                          stream=raw,
                                          timeout=self._http_timeout_seconds)
         self._record_request_log(response, raw=raw or data is not None or files is not None)
-
         error = self._error_parser.get_api_error(response)
         if error is not None:
-            # If the request body is a seekable stream, rewind it so that it is ready
-            # to be read again in case of a retry.
-            #
-            # TODO: This should be moved into a "before-retry" hook to avoid one
-            # unnecessary seek on the last failed retry before aborting.
-            if self._is_seekable_stream(data):
-                data.seek(initial_data_position)
             raise error from None
 
         return response

databricks/sdk/retries.py

@@ -13,7 +13,8 @@ def retried(*,
             on: Sequence[Type[BaseException]] = None,
             is_retryable: Callable[[BaseException], Optional[str]] = None,
             timeout=timedelta(minutes=20),
-            clock: Clock = None):
+            clock: Clock = None,
+            before_retry: Callable = None):
     has_allowlist = on is not None
     has_callback = is_retryable is not None
     if not (has_allowlist or has_callback) or (has_allowlist and has_callback):
@@ -54,6 +55,9 @@ def wrapper(*args, **kwargs):
                         raise err
 
                     logger.debug(f'Retrying: {retry_reason} (sleeping ~{sleep}s)')
+                    if before_retry:
+                        before_retry()
+
                     clock.sleep(sleep + random())
                     attempt += 1
             raise TimeoutError(f'Timed out after {timeout}') from last_err