fix: backoff and jitter in new http wrapper (#418)

This behavior was present in the old decorator, and is needed for some
providers.

Signed-off-by: Will Murphy <[email protected]>

src/vunnel/utils/http.py

@@ -1,4 +1,5 @@
 import logging
+import random
 import time
 from collections.abc import Callable
 from typing import Any, Optional
@@ -42,9 +43,12 @@ def get(  # noqa: PLR0913
     """
     logger.debug(f"http GET {url}")
     last_exception: Exception | None = None
+    sleep_interval = backoff_in_seconds
     for attempt in range(retries + 1):
         if last_exception:
-            time.sleep(backoff_in_seconds)
+            time.sleep(sleep_interval)
+            sleep_interval = backoff_in_seconds * 2**attempt + random.uniform(0, 1)  # noqa: S311
+            # explanation of S311 disable: rng is not used cryptographically
         try:
             response = requests.get(url, timeout=timeout, **kwargs)
             if status_handler:
@@ -56,17 +60,17 @@ def get(  # noqa: PLR0913
             last_exception = e
             will_retry = ""
             if attempt < retries:
-                will_retry = f" (will retry in {backoff_in_seconds} seconds) "
+                will_retry = f" (will retry in {int(backoff_in_seconds)} seconds) "
             # HTTPError includes the attempted request, so don't include it redundantly here
-            logger.warning(f"attempt {attempt + 1} of {retries} failed:{will_retry}{e}")
+            logger.warning(f"attempt {attempt + 1} of {retries + 1} failed:{will_retry}{e}")
         except Exception as e:
             last_exception = e
             will_retry = ""
             if attempt < retries:
-                will_retry = f" (will retry in {backoff_in_seconds} seconds) "
+                will_retry = f" (will retry in {int(sleep_interval)} seconds) "
             # this is an unexpected exception type, so include the attempted request in case the
             # message from the unexpected exception doesn't.
-            logger.warning(f"attempt {attempt + 1} of {retries}{will_retry}: unexpected exception during GET {url}: {e}")
+            logger.warning(f"attempt {attempt + 1} of {retries + 1}{will_retry}: unexpected exception during GET {url}: {e}")
     if last_exception:
         logger.error(f"last retry of GET {url} failed with {last_exception}")
         raise last_exception

tests/unit/utils/test_http.py

@@ -36,6 +36,20 @@ def test_raises_when_out_of_retries(self, mock_requests, mock_sleep, mock_logger
             http.get("http://example.com/some-path", mock_logger, retries=2, backoff_in_seconds=3)
         mock_logger.error.assert_called()
 
+    @patch("time.sleep")
+    @patch("requests.get")
+    def test_correct_number_of_retria(self, mock_requests, mock_sleep, mock_logger, error_response):
+        mock_requests.side_effect = [
+            error_response,
+            error_response,
+            error_response,
+            error_response,
+            error_response,
+        ]  # more than enough
+        with pytest.raises(requests.HTTPError):
+            http.get("http://example.com/some-path", mock_logger, retries=2, backoff_in_seconds=3)
+        assert len(mock_requests.call_args_list) == 3  # once for initial plus two retries
+
     @patch("time.sleep")
     @patch("requests.get")
     def test_succeeds_if_retries_succeed(self, mock_requests, mock_sleep, mock_logger, error_response, success_response):
@@ -53,10 +67,14 @@ def test_timeout_is_passed_in(self, mock_requests, mock_logger):
 
     @patch("time.sleep")
     @patch("requests.get")
-    def test_sleeps_right_amount_between_retries(self, mock_requests, mock_sleep, mock_logger, error_response, success_response):
+    @patch("random.uniform")
+    def test_exponential_backoff_and_jitter(
+        self, mock_uniform_random, mock_requests, mock_sleep, mock_logger, error_response, success_response
+    ):
         mock_requests.side_effect = [error_response, error_response, error_response, success_response]
-        http.get("http://example.com/some-path", mock_logger, backoff_in_seconds=123, retries=3)
-        assert mock_sleep.call_args_list == [call(123), call(123), call(123)]
+        mock_uniform_random.side_effect = [0.5, 0.4, 0.1]
+        http.get("http://example.com/some-path", mock_logger, backoff_in_seconds=10, retries=3)
+        assert mock_sleep.call_args_list == [call(10), call(10 * 2 + 0.5), call(10 * 4 + 0.4)]
 
     @patch("time.sleep")
     @patch("requests.get")