feat(sdk): align linear retry strategy with exponential

Signed-off-by: Sai Asish Y <say.apm35@gmail.com>

Author: SAY-5

packages/aws-durable-execution-sdk-python/src/aws_durable_execution_sdk_python/retries.py

@@ -71,84 +71,135 @@ def max_delay_seconds(self) -> int:
         return self.max_delay.to_seconds()
 
 
+@dataclass
+class LinearRetryStrategyConfig:
+    max_attempts: int = 6
+    initial_delay: Duration = field(default_factory=lambda: Duration.from_seconds(1))
+    increment: Duration = field(default_factory=lambda: Duration.from_seconds(1))
+    max_delay: Duration = field(default_factory=lambda: Duration.from_minutes(5))
+    jitter_strategy: JitterStrategy = field(default=JitterStrategy.FULL)
+    retryable_errors: list[str | re.Pattern] | None = None
+    retryable_error_types: list[type[Exception]] | None = None
+
+    @property
+    def initial_delay_seconds(self) -> int:
+        """Get initial delay in seconds."""
+        return self.initial_delay.to_seconds()
+
+    @property
+    def increment_seconds(self) -> int:
+        """Get increment in seconds."""
+        return self.increment.to_seconds()
+
+    @property
+    def max_delay_seconds(self) -> int:
+        """Get max delay in seconds."""
+        return self.max_delay.to_seconds()
+
+
+def _resolve_retryable_errors(
+    retryable_errors: list[str | re.Pattern] | None,
+    retryable_error_types: list[type[Exception]] | None,
+) -> tuple[list[str | re.Pattern], list[type[Exception]]]:
+    """Resolve the error filters, applying the match-all default only when neither is set."""
+    should_use_default_errors: bool = (
+        retryable_errors is None and retryable_error_types is None
+    )
+    resolved_errors: list[str | re.Pattern] = (
+        retryable_errors
+        if retryable_errors is not None
+        else ([_DEFAULT_RETRYABLE_ERROR_PATTERN] if should_use_default_errors else [])
+    )
+    resolved_error_types: list[type[Exception]] = retryable_error_types or []
+    return resolved_errors, resolved_error_types
+
+
+def _is_error_retryable(
+    error: Exception,
+    retryable_errors: list[str | re.Pattern],
+    retryable_error_types: list[type[Exception]],
+) -> bool:
+    """Return True when the error matches one of the message patterns or types."""
+    is_retryable_error_message: bool = any(
+        pattern.search(str(error))
+        if isinstance(pattern, re.Pattern)
+        else pattern in str(error)
+        for pattern in retryable_errors
+    )
+    is_retryable_error_type: bool = any(
+        isinstance(error, error_type) for error_type in retryable_error_types
+    )
+    return is_retryable_error_message or is_retryable_error_type
+
+
+def _finalize_delay_seconds(base_delay: float, jitter_strategy: JitterStrategy) -> int:
+    """Apply jitter, round up, and clamp to a minimum of 1 second."""
+    delay_with_jitter: float = jitter_strategy.apply_jitter(base_delay)
+    return max(1, math.ceil(delay_with_jitter))
+
+
 def create_retry_strategy(
     config: RetryStrategyConfig | None = None,
 ) -> Callable[[Exception, int], RetryDecision]:
     if config is None:
         config = RetryStrategyConfig()
 
-    # Apply default retryableErrors only if user didn't specify either filter
-    should_use_default_errors: bool = (
-        config.retryable_errors is None and config.retryable_error_types is None
-    )
-
-    retryable_errors: list[str | re.Pattern] = (
-        config.retryable_errors
-        if config.retryable_errors is not None
-        else ([_DEFAULT_RETRYABLE_ERROR_PATTERN] if should_use_default_errors else [])
+    retryable_errors, retryable_error_types = _resolve_retryable_errors(
+        config.retryable_errors, config.retryable_error_types
     )
-    retryable_error_types: list[type[Exception]] = config.retryable_error_types or []
 
     def retry_strategy(error: Exception, attempts_made: int) -> RetryDecision:
         # Check if we've exceeded max attempts
         if attempts_made >= config.max_attempts:
             return RetryDecision.no_retry()
 
-        # Check if error is retryable based on error message
-        is_retryable_error_message: bool = any(
-            pattern.search(str(error))
-            if isinstance(pattern, re.Pattern)
-            else pattern in str(error)
-            for pattern in retryable_errors
-        )
-
-        # Check if error is retryable based on error type
-        is_retryable_error_type: bool = any(
-            isinstance(error, error_type) for error_type in retryable_error_types
-        )
-
-        if not is_retryable_error_message and not is_retryable_error_type:
+        if not _is_error_retryable(error, retryable_errors, retryable_error_types):
             return RetryDecision.no_retry()
 
         # Calculate delay with exponential backoff
         base_delay: float = min(
             config.initial_delay_seconds * (config.backoff_rate ** (attempts_made - 1)),
             config.max_delay_seconds,
         )
-        # Apply jitter to get final delay
-        delay_with_jitter: float = config.jitter_strategy.apply_jitter(base_delay)
-        # Round up and ensure minimum of 1 second
-        final_delay: int = max(1, math.ceil(delay_with_jitter))
+        final_delay: int = _finalize_delay_seconds(base_delay, config.jitter_strategy)
 
         return RetryDecision.retry(Duration(seconds=final_delay))
 
     return retry_strategy
 
 
 def create_linear_retry_strategy(
-    max_attempts: int = 6,
-    initial_delay: Duration | None = None,
-    increment: Duration | None = None,
+    config: LinearRetryStrategyConfig | None = None,
 ) -> Callable[[Exception, int], RetryDecision]:
-    """Linearly increasing delay between retries: initial + increment * (attempts_made - 1).
+    """Linearly increasing delay between retries.
 
-    Mirrors the JS SDK's ``createLinearRetryStrategy``. With the defaults this
-    yields delays of 1s, 2s, 3s, 4s, 5s. No jitter is applied and there is no
-    upper cap on the delay; callers who need either can build their own
-    strategy via ``create_retry_strategy``.
+    The base delay is ``initial_delay + increment * (attempts_made - 1)``,
+    capped at ``max_delay``, with jitter and error filtering applied the same
+    way as :func:`create_retry_strategy`. Mirrors the JS SDK's
+    ``createLinearRetryStrategy``.
     """
-    initial: Duration = (
-        initial_delay if initial_delay is not None else Duration.from_seconds(1)
+    if config is None:
+        config = LinearRetryStrategyConfig()
+
+    retryable_errors, retryable_error_types = _resolve_retryable_errors(
+        config.retryable_errors, config.retryable_error_types
     )
-    step: Duration = increment if increment is not None else Duration.from_seconds(1)
 
-    def linear_retry_strategy(_error: Exception, attempts_made: int) -> RetryDecision:
-        if attempts_made >= max_attempts:
+    def linear_retry_strategy(error: Exception, attempts_made: int) -> RetryDecision:
+        if attempts_made >= config.max_attempts:
+            return RetryDecision.no_retry()
+
+        if not _is_error_retryable(error, retryable_errors, retryable_error_types):
             return RetryDecision.no_retry()
-        delay_seconds: int = initial.to_seconds() + step.to_seconds() * (
-            attempts_made - 1
+
+        base_delay: float = min(
+            config.initial_delay_seconds
+            + config.increment_seconds * (attempts_made - 1),
+            config.max_delay_seconds,
         )
-        return RetryDecision.retry(Duration(seconds=delay_seconds))
+        final_delay: int = _finalize_delay_seconds(base_delay, config.jitter_strategy)
+
+        return RetryDecision.retry(Duration(seconds=final_delay))
 
     return linear_retry_strategy
 
@@ -212,9 +263,12 @@ def critical(cls) -> Callable[[Exception, int], RetryDecision]:
     def linear(cls) -> Callable[[Exception, int], RetryDecision]:
         """Linearly increasing delay between retries: 1s, 2s, 3s, 4s, 5s."""
         return create_linear_retry_strategy(
-            max_attempts=6,
-            initial_delay=Duration.from_seconds(1),
-            increment=Duration.from_seconds(1),
+            LinearRetryStrategyConfig(
+                max_attempts=6,
+                initial_delay=Duration.from_seconds(1),
+                increment=Duration.from_seconds(1),
+                jitter_strategy=JitterStrategy.NONE,
+            )
         )
 
     @classmethod

packages/aws-durable-execution-sdk-python/tests/retries_test.py

@@ -8,6 +8,7 @@
 from aws_durable_execution_sdk_python.config import Duration
 from aws_durable_execution_sdk_python.retries import (
     JitterStrategy,
+    LinearRetryStrategyConfig,
     RetryDecision,
     RetryPresets,
     RetryStrategyConfig,
@@ -580,8 +581,10 @@ def test_mixed_error_types_and_patterns():
 # region create_linear_retry_strategy
 
 
-def test_linear_retry_strategy_uses_additive_formula():
-    """Default config yields delays of 1s, 2s, 3s, 4s, 5s with no jitter."""
+@patch("random.random")
+def test_linear_retry_strategy_uses_additive_formula(mock_random):
+    """Default config yields additive delays of 1s, 2s, 3s, 4s, 5s."""
+    mock_random.return_value = 1.0  # FULL jitter at the upper bound keeps the base
     strategy = create_linear_retry_strategy()
 
     delays = [
@@ -593,7 +596,7 @@ def test_linear_retry_strategy_uses_additive_formula():
 
 def test_linear_retry_strategy_stops_at_max_attempts():
     """No retry once attempts_made reaches max_attempts."""
-    strategy = create_linear_retry_strategy(max_attempts=3)
+    strategy = create_linear_retry_strategy(LinearRetryStrategyConfig(max_attempts=3))
 
     assert strategy(Exception("e"), 1).should_retry is True
     assert strategy(Exception("e"), 2).should_retry is True
@@ -603,9 +606,12 @@ def test_linear_retry_strategy_stops_at_max_attempts():
 def test_linear_retry_strategy_respects_custom_initial_and_increment():
     """Custom initial_delay and increment shift the additive sequence."""
     strategy = create_linear_retry_strategy(
-        max_attempts=10,
-        initial_delay=Duration.from_seconds(2),
-        increment=Duration.from_seconds(3),
+        LinearRetryStrategyConfig(
+            max_attempts=10,
+            initial_delay=Duration.from_seconds(2),
+            increment=Duration.from_seconds(3),
+            jitter_strategy=JitterStrategy.NONE,
+        )
     )
 
     delays = [
@@ -616,6 +622,61 @@ def test_linear_retry_strategy_respects_custom_initial_and_increment():
     assert delays == [2, 5, 8, 11]
 
 
+def test_linear_retry_strategy_caps_at_max_delay():
+    """The additive delay is capped at max_delay before jitter."""
+    strategy = create_linear_retry_strategy(
+        LinearRetryStrategyConfig(
+            max_attempts=10,
+            initial_delay=Duration.from_seconds(10),
+            increment=Duration.from_seconds(10),
+            max_delay=Duration.from_seconds(25),
+            jitter_strategy=JitterStrategy.NONE,
+        )
+    )
+
+    # 10, 20, then capped at 25 for the third attempt (would be 30).
+    delays = [
+        strategy(Exception("e"), attempt).delay_seconds for attempt in range(1, 4)
+    ]
+    assert delays == [10, 20, 25]
+
+
+@patch("random.random")
+def test_linear_retry_strategy_applies_jitter(mock_random):
+    """FULL jitter scales the additive base delay by random()."""
+    mock_random.return_value = 0.5
+    strategy = create_linear_retry_strategy(
+        LinearRetryStrategyConfig(
+            initial_delay=Duration.from_seconds(4),
+            increment=Duration.from_seconds(4),
+            jitter_strategy=JitterStrategy.FULL,
+        )
+    )
+
+    # base = 4 + 4*1 = 8, full jitter = 0.5 * 8 = 4
+    assert strategy(Exception("e"), 2).delay_seconds == 4
+
+
+def test_linear_retry_strategy_filters_by_error_message():
+    """Only errors matching retryable_errors are retried."""
+    strategy = create_linear_retry_strategy(
+        LinearRetryStrategyConfig(retryable_errors=["timeout"])
+    )
+
+    assert strategy(Exception("connection timeout"), 1).should_retry is True
+    assert strategy(Exception("permission denied"), 1).should_retry is False
+
+
+def test_linear_retry_strategy_filters_by_error_type():
+    """Only errors matching retryable_error_types are retried."""
+    strategy = create_linear_retry_strategy(
+        LinearRetryStrategyConfig(retryable_error_types=[ValueError])
+    )
+
+    assert strategy(ValueError("bad"), 1).should_retry is True
+    assert strategy(KeyError("missing"), 1).should_retry is False
+
+
 # endregion