fix(api): Fix resetting sys var causing internal server error (#21604)

and sorts draft variables by their creation time, ensures a consist order.

api/core/workflow/entities/workflow_node_execution.py

@@ -66,11 +66,21 @@ class WorkflowNodeExecution(BaseModel):
     but they are not stored in the model.
     """
 
-    # Core identification fields
-    id: str  # Unique identifier for this execution record
-    node_execution_id: Optional[str] = None  # Optional secondary ID for cross-referencing
+    # --------- Core identification fields ---------
+
+    # Unique identifier for this execution record, used when persisting to storage.
+    # Value is a UUID string (e.g., '09b3e04c-f9ae-404c-ad82-290b8d7bd382').
+    id: str
+
+    # Optional secondary ID for cross-referencing purposes.
+    #
+    # NOTE: For referencing the persisted record, use `id` rather than `node_execution_id`.
+    # While `node_execution_id` may sometimes be a UUID string, this is not guaranteed.
+    # In most scenarios, `id` should be used as the primary identifier.
+    node_execution_id: Optional[str] = None
     workflow_id: str  # ID of the workflow this node belongs to
     workflow_execution_id: Optional[str] = None  # ID of the specific workflow run (null for single-step debugging)
+    # --------- Core identification fields ends ---------
 
     # Execution positioning and flow
     index: int  # Sequence number for ordering in trace visualization

api/core/workflow/nodes/http_request/executor.py

@@ -333,7 +333,7 @@ class Executor:
         try:
             response = getattr(ssrf_proxy, self.method.lower())(**request_args)
         except (ssrf_proxy.MaxRetriesExceededError, httpx.RequestError) as e:
-            raise HttpRequestNodeError(str(e))
+            raise HttpRequestNodeError(str(e)) from e
         # FIXME: fix type ignore, this maybe httpx type issue
         return response  # type: ignore
 

api/core/workflow/repositories/draft_variable_repository.py

@@ -0,0 +1,32 @@
+import abc
+from collections.abc import Mapping
+from typing import Any, Protocol
+
+from sqlalchemy.orm import Session
+
+from core.workflow.nodes.enums import NodeType
+
+
+class DraftVariableSaver(Protocol):
+    @abc.abstractmethod
+    def save(self, process_data: Mapping[str, Any] | None, outputs: Mapping[str, Any] | None):
+        pass
+
+
+class DraftVariableSaverFactory(Protocol):
+    @abc.abstractmethod
+    def __call__(
+        self,
+        session: Session,
+        app_id: str,
+        node_id: str,
+        node_type: NodeType,
+        node_execution_id: str,
+        enclosing_node_id: str | None = None,
+    ) -> "DraftVariableSaver":
+        pass
+
+
+class NoopDraftVariableSaver(DraftVariableSaver):
+    def save(self, process_data: Mapping[str, Any] | None, outputs: Mapping[str, Any] | None):
+        pass