Enhanced GraphEngine Pause Handling (#28196)

This commit: 

1. Convert `pause_reason` to `pause_reasons` in `GraphExecution` and relevant classes. Change the field from a scalar value to a list that can contain multiple `PauseReason` objects, ensuring all pause events are properly captured.
2. Introduce a new `WorkflowPauseReason` model to record reasons associated with a specific `WorkflowPause`.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: -LAN- <laipz8200@outlook.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

api/core/workflow/entities/__init__.py

@@ -1,17 +1,11 @@
-from ..runtime.graph_runtime_state import GraphRuntimeState
-from ..runtime.variable_pool import VariablePool
 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",
     "GraphInitParams",
-    "GraphRuntimeState",
-    "VariablePool",
     "WorkflowExecution",
     "WorkflowNodeExecution",
-    "WorkflowPauseEntity",
 ]

api/core/workflow/entities/pause_reason.py

@@ -1,49 +1,26 @@
 from enum import StrEnum, auto
-from typing import Annotated, Any, ClassVar, TypeAlias
+from typing import Annotated, Literal, TypeAlias
 
-from pydantic import BaseModel, Discriminator, Tag
+from pydantic import BaseModel, Field
 
 
-class _PauseReasonType(StrEnum):
+class PauseReasonType(StrEnum):
     HUMAN_INPUT_REQUIRED = auto()
     SCHEDULED_PAUSE = auto()
 
 
-class _PauseReasonBase(BaseModel):
-    TYPE: ClassVar[_PauseReasonType]
+class HumanInputRequired(BaseModel):
+    TYPE: Literal[PauseReasonType.HUMAN_INPUT_REQUIRED] = PauseReasonType.HUMAN_INPUT_REQUIRED
+
+    form_id: str
+    # The identifier of the human input node causing the pause.
+    node_id: str
 
 
-class HumanInputRequired(_PauseReasonBase):
-    TYPE = _PauseReasonType.HUMAN_INPUT_REQUIRED
-
-
-class SchedulingPause(_PauseReasonBase):
-    TYPE = _PauseReasonType.SCHEDULED_PAUSE
+class SchedulingPause(BaseModel):
+    TYPE: Literal[PauseReasonType.SCHEDULED_PAUSE] = 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),
-]
+PauseReason: TypeAlias = Annotated[HumanInputRequired | SchedulingPause, Field(discriminator="TYPE")]

api/core/workflow/entities/workflow_pause.py

@@ -1,61 +0,0 @@
-"""
-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