Limit deadline split between attempts by a factor (#286)

* Limit deadline split between attempts by a factor

* Add to CHANGELOG.md

* Fix

* Fix review comments

* Add more docs

CHANGELOG.md

@@ -7,6 +7,7 @@
 * [Do not retry low timeout response](https://github.com/anna-money/aio-request/pull/276)
 * Refactoring around request enrichers and deprecation of setup_v2. Related PRs: [#277](https://github.com/anna-money/aio-request/pull/277), [#282](https://github.com/anna-money/aio-request/pull/282), [#285](https://github.com/anna-money/aio-request/pull/285)
 * [Deadline provider for sequential strategy](https://github.com/anna-money/aio-request/pull/284)
+* [Limit deadline split between attempts by a factor](https://github.com/anna-money/aio-request/pull/286)
 
 
 ## v0.1.34 (2024-11-05)

aio_request/deadline_provider.py

@@ -5,7 +5,7 @@
 DeadlineProvider = Callable[[Deadline, int, int], Deadline]
 
 
-def split_deadline_between_attempts() -> DeadlineProvider:
+def split_deadline_between_attempts(*, attempts_count_to_split: int | None = None) -> DeadlineProvider:
     """
     Split deadline between attempts.
 
@@ -16,17 +16,23 @@ def split_deadline_between_attempts() -> DeadlineProvider:
 
     2. 1 sec -> 1 sec -> 8 sec. Two attempts have spent 1 seconds each,
     the last one has received the remaining 8 seconds due to redistribution.
+
+    If attempts_count_to_split is not None, then the deadline will be split between the first attempts_count_to_split.
     """
 
+    if attempts_count_to_split is not None and attempts_count_to_split < 2:
+        raise ValueError("attempts_count_to_split should be greater or equal to 2")
+
     def __provider(deadline: Deadline, attempt: int, attempts_count: int) -> Deadline:
         if deadline.expired:
             return deadline
-
-        attempts_left = attempts_count - attempt
-        if attempts_left == 0:
-            raise ValueError("no attempts left")
-
-        return deadline / attempts_left
+        if attempts_count_to_split is None:
+            effective_attempts_left = attempts_count - attempt
+        else:
+            effective_attempts_left = min(attempts_count_to_split, attempts_count) - attempt
+        if effective_attempts_left <= 1:
+            return deadline
+        return deadline / effective_attempts_left
 
     return __provider
 

tests/test_deadline_provider.py

@@ -10,11 +10,29 @@ async def test_split_deadline_between_attempt():
     attempt_deadline = provider(deadline, 0, 3)
     assert 0.3 <= attempt_deadline.timeout <= 0.34
 
-    await asyncio.sleep(attempt_deadline.timeout)
+    await asyncio.sleep(0.33)
 
     attempt_deadline = provider(deadline, 1, 3)
     assert 0.3 <= attempt_deadline.timeout <= 0.34
-    await asyncio.sleep(attempt_deadline.timeout)
+    await asyncio.sleep(0.33)
+
+    attempt_deadline = provider(deadline, 2, 3)
+    assert 0.3 <= attempt_deadline.timeout <= 0.34
+
+
+async def test_split_deadline_between_attempt_with_split_factor():
+    provider = aio_request.split_deadline_between_attempts(attempts_count_to_split=2)
+    deadline = aio_request.Deadline.from_timeout(1)
+
+    attempt_deadline = provider(deadline, 0, 3)
+    assert 0.45 <= attempt_deadline.timeout <= 0.5
+
+    await asyncio.sleep(0.33)
+
+    attempt_deadline = provider(deadline, 1, 3)
+    assert 0.6 <= attempt_deadline.timeout <= 0.67
+
+    await asyncio.sleep(0.33)
 
     attempt_deadline = provider(deadline, 2, 3)
     assert 0.3 <= attempt_deadline.timeout <= 0.34
@@ -35,3 +53,21 @@ async def test_split_deadline_between_attempts_fast_attempt_failure():
 
     attempt_deadline = provider(deadline, 2, 3)
     assert 0.75 <= attempt_deadline.timeout <= 0.8
+
+
+async def test_split_deadline_between_attempts_fast_attempt_failure_with_split_factor():
+    provider = aio_request.split_deadline_between_attempts(attempts_count_to_split=2)
+    deadline = aio_request.Deadline.from_timeout(1)
+
+    attempt_deadline = provider(deadline, 0, 3)
+    assert 0.45 <= attempt_deadline.timeout <= 0.5
+
+    await asyncio.sleep(0.1)  # fast attempt failure
+
+    attempt_deadline = provider(deadline, 1, 3)
+    assert 0.85 <= attempt_deadline.timeout <= 0.9
+
+    await asyncio.sleep(0.1)  # fast attempt failure
+
+    attempt_deadline = provider(deadline, 2, 3)
+    assert 0.75 <= attempt_deadline.timeout <= 0.8