feat(api): Introduce workflow pause state management (#27298)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/core/workflow/entities/__init__.py

@@ -4,6 +4,7 @@ from .agent import AgentNodeStrategyInit
 from .graph_init_params import GraphInitParams
 from .workflow_execution import WorkflowExecution
 from .workflow_node_execution import WorkflowNodeExecution
+from .workflow_pause import WorkflowPauseEntity
 
 __all__ = [
     "AgentNodeStrategyInit",
@@ -12,4 +13,5 @@ __all__ = [
     "VariablePool",
     "WorkflowExecution",
     "WorkflowNodeExecution",
+    "WorkflowPauseEntity",
 ]

api/core/workflow/entities/pause_reason.py

@@ -0,0 +1,49 @@
+from enum import StrEnum, auto
+from typing import Annotated, Any, ClassVar, TypeAlias
+
+from pydantic import BaseModel, Discriminator, Tag
+
+
+class _PauseReasonType(StrEnum):
+    HUMAN_INPUT_REQUIRED = auto()
+    SCHEDULED_PAUSE = auto()
+
+
+class _PauseReasonBase(BaseModel):
+    TYPE: ClassVar[_PauseReasonType]
+
+
+class HumanInputRequired(_PauseReasonBase):
+    TYPE = _PauseReasonType.HUMAN_INPUT_REQUIRED
+
+
+class SchedulingPause(_PauseReasonBase):
+    TYPE = _PauseReasonType.SCHEDULED_PAUSE
+
+    message: str
+
+
+def _get_pause_reason_discriminator(v: Any) -> _PauseReasonType | None:
+    if isinstance(v, _PauseReasonBase):
+        return v.TYPE
+    elif isinstance(v, dict):
+        reason_type_str = v.get("TYPE")
+        if reason_type_str is None:
+            return None
+        try:
+            reason_type = _PauseReasonType(reason_type_str)
+        except ValueError:
+            return None
+        return reason_type
+    else:
+        # return None if the discriminator value isn't found
+        return None
+
+
+PauseReason: TypeAlias = Annotated[
+    (
+        Annotated[HumanInputRequired, Tag(_PauseReasonType.HUMAN_INPUT_REQUIRED)]
+        | Annotated[SchedulingPause, Tag(_PauseReasonType.SCHEDULED_PAUSE)]
+    ),
+    Discriminator(_get_pause_reason_discriminator),
+]

api/core/workflow/entities/workflow_pause.py

@@ -0,0 +1,61 @@
+"""
+Domain entities for workflow pause management.
+
+This module contains the domain model for workflow pause, which is used
+by the core workflow module. These models are independent of the storage mechanism
+and don't contain implementation details like tenant_id, app_id, etc.
+"""
+
+from abc import ABC, abstractmethod
+from datetime import datetime
+
+
+class WorkflowPauseEntity(ABC):
+    """
+    Abstract base class for workflow pause entities.
+
+    This domain model represents a paused workflow execution state,
+    without implementation details like tenant_id, app_id, etc.
+    It provides the interface for managing workflow pause/resume operations
+    and state persistence through file storage.
+
+    The `WorkflowPauseEntity` is never reused. If a workflow execution pauses multiple times,
+    it will generate multiple `WorkflowPauseEntity` records.
+    """
+
+    @property
+    @abstractmethod
+    def id(self) -> str:
+        """The identifier of current WorkflowPauseEntity"""
+        pass
+
+    @property
+    @abstractmethod
+    def workflow_execution_id(self) -> str:
+        """The identifier of the workflow execution record the pause associated with.
+        Correspond to `WorkflowExecution.id`.
+        """
+
+    @abstractmethod
+    def get_state(self) -> bytes:
+        """
+        Retrieve the serialized workflow state from storage.
+
+        This method should load and return the workflow execution state
+        that was saved when the workflow was paused. The state contains
+        all necessary information to resume the workflow execution.
+
+        Returns:
+            bytes: The serialized workflow state containing
+            execution context, variable values, node states, etc.
+
+        """
+        ...
+
+    @property
+    @abstractmethod
+    def resumed_at(self) -> datetime | None:
+        """`resumed_at` return the resumption time of the current pause, or `None` if
+        the pause is not resumed yet.
+        """
+        pass