feat: add functionality to stream or poll events from the build process (#5940)

* refactor: simplify TaskService by removing Celery integration

* refactor: enhance AnyIO backend task management and error handling

* refactor: restructure flow building process and enhance event handling

* feat: implement QueueService for managing job queues and tasks

* feat: Add QueueService for managing job queues and task lifecycle

* feat!: Enhance flow building with QueueService integration for job management

* revert changes to async session

* feat: Integrate QueueService into lifespan management for task handling

* refactor: Enhance QueueService with robust lifecycle management and cleanup mechanisms

* refactor: Simplify docstring for get_queue_service function

* refactor: Update import statements in queue factory for clarity

* test: Improve chat endpoint tests with comprehensive build flow scenarios

* refactor: Streamline flow build event generation and queue management

* refactor: Improve flow build process with modular event handling and URL parameter management

* test: Enhance loop component tests with flow build and event handling utilities

* fix: Improve transaction logging with null flow_id handling and debug logging

* fix: Remove unnecessary db.refresh() in transaction logging

* feat: Add polling mode for build events with optional streaming

* feat: Add event delivery configuration option to settings

* feat: Implement polling for build events with configuration-driven streaming

* refactor: Enhance queue cleanup with improved logging and error handling

* test: Improve build event stream assertion with detailed error reporting

* test: Add benchmark test for build flow polling mechanism

* refactor: Remove redundant end event in flow event generation

* test: Update test_component_tool_with_api_key to use async flow

* Convert test method to async
* Update graph start method to use async_start()
* Add client parameter to test method
* Modify tool retrieval to use async method

* test: Add session ID generation in agent component test

* fix: Enhance error handling in LCAgentComponent for ExceptionWithMessageError

Add null checks to prevent potential AttributeError when handling agent message deletion

* test: Refactor test assertion for model name options in agent component

Simplify the assertion for checking "sonnet" in model name options by extracting the options to a variable first

* refactor: Improve type hints and imports in AnyIOTaskResult

* Add `__future__` import for type annotations
* Use conditional import for `Callable` and `TracebackType`
* Explicitly type `_traceback` attribute with `TracebackType | None`

* fix: Add null checks for event task in build events streaming

* refactor: Extract build and disconnect handling into separate modules

This commit separates the build and disconnect handling logic from the chat API module into dedicated files:

- Created `langflow/api/build.py` to house the flow generation and vertex building logic
- Created `langflow/api/disconnect.py` to manage the custom streaming response with disconnect handling
- Removed duplicate code from `langflow/api/v1/chat.py`
- Improved code organization and modularity

* refactor: Extract flow build and event handling methods in build API

This commit introduces two new methods in the build API to improve code organization and reusability:

- `start_flow_build()`: Centralizes the logic for creating a queue and starting a flow build task
- `get_flow_events_response()`: Handles retrieving flow events for both streaming and polling modes

The changes simplify the chat API endpoint implementations and reduce code duplication

* refactor: Deprecate /task endpoint and add informative error message

This commit marks the /task endpoint as deprecated and raises an HTTP 400 error with a clear message indicating the endpoint will be removed in a future version. The changes improve API clarity and guide users towards the recommended /run endpoint.

* refactor: Update log_transaction function return type annotation

Modify the return type hint for log_transaction to allow for potential None return, improving type safety and clarity in the transactions logging method.

* feat: Add configurable event delivery streaming option

Introduce support for configurable event delivery mode (streaming/polling) across frontend components:

- Add `shouldStreamEvents()` method in NodeStatus and IOModal
- Update flowStore to accept a `stream` parameter
- Modify buildFlowVerticesWithFallback to use the stream parameter directly
- Remove hardcoded polling logic in buildUtils

* fix: Add null check for flow_id in log_transaction function

Prevent logging transactions without a flow_id by returning None, ensuring data integrity and avoiding potential database errors

* chore: Update changes-filter to include chat API path

* fix: Add error handling and null checks in flow transaction deletion

Improve robustness of transaction and vertex build deletion by:
- Adding a null check for flow_id in delete_transactions_by_flow_id
- Wrapping deletion operations in try-except blocks to prevent failures
- Logging debug messages for any deletion errors

* fix: Remove redundant commit in vertex builds deletion

Remove unnecessary db.commit() from delete_vertex_builds_by_flow_id to prevent duplicate commits and simplify database transaction handling

* fix: Improve transaction logging with debug message and return value

Move debug logging from CRUD layer to utils to provide more context about logged transactions and ensure proper error handling

* fix: Improve error handling and transaction cleanup in active_user fixture

Enhance user and transaction cleanup process in test fixture by:
- Adding separate try-except blocks for transaction/vertex build deletion and user deletion
- Adding debug logging for potential errors during cleanup
- Ensuring proper session commits for each operation

* propagate parent task CancelledError instead of supressing it

Co-authored-by: Christophe Bornet <cbornet@hotmail.com>

* refactor: Rename queue service to job queue service

Restructure job queue management by:
- Renaming QueueService to JobQueueService
- Moving queue-related files to a new job_queue directory
- Updating import paths and service type references
- Enhancing job queue service with more robust async job management

* fix: Correct ServiceType enum reference for job queue service

Update the service type constant to match the recently renamed JobQueueService, ensuring consistent service type referencing across the application.

* refactor: Enhance JobQueueService with comprehensive logging and documentation

Improve the JobQueueService implementation by:
- Adding detailed docstrings with clear explanations of methods and attributes
- Implementing comprehensive logging throughout the service
- Enhancing error handling and logging for queue and task management
- Providing more context in log messages for debugging and monitoring

* docs: Improve stop method docstring for JobQueueService

Enhance the documentation for the stop method by:
- Providing a more detailed and precise description of the shutdown process
- Clarifying the steps involved in gracefully stopping the service
- Improving the explanation of resource cleanup and task cancellation

* fix: Properly handle task cancellation and propagate exceptions in JobQueueService

* fix: Enhance error handling and raise appropriate exceptions in JobQueueService methods

* improve docstring

Co-authored-by: Christophe Bornet <cbornet@hotmail.com>

* fix: Remove redundant exception raises in JobQueueService methods and improve cleanup logic

* fix: Improve logging during job cleanup and handle exceptions more appropriately

* feat: add utility to run tests with multiple event delivery modes

* feat: integrate withEventDeliveryModes utility in multiple test files

* refactor: replace status code assertions with httpx codes for clarity

* remove noqa comment and change argument name

Co-authored-by: Christophe Bornet <cbornet@hotmail.com>

* refactor: streamline event polling logic in get_flow_events_response

* refactor: use getattr for safer session attribute access

Co-author: @cbornet

* feat: add is_started method to JobQueueService

* refactor: modify JobQueueService start method and main.py queue service initialization

* feat: add ready state and teardown method to JobQueueService

* refactor: simplify job queue cleanup logic in JobQueueService

* refactor: improve error logging in active_user fixture

* refactor: improve AnyIO task management with TaskGroup and CancelScope

* refactor: Implement LimitedBackgroundTasks for controlled vertex build logging (#6312)

* feat: implement LimitedBackgroundTasks for controlled vertex build logging

* refactor: replace BackgroundTasks with LimitedBackgroundTasks in build_flow endpoint

* refactor: improve task cancellation error handling in JobQueueService

* refactor: Rename LimitedBackgroundTasks to LimitVertexBuildBackgroundTasks

* feat: Add EventDeliveryType enum for event delivery methods

* feat: Add polling constants for endpoint and streaming status

* refactor: Update buildFlowVerticesWithFallback to use polling constants

* refactor: Update event delivery handling to use EventDeliveryType enum

* [autofix.ci] apply automated fixes

* fix: Improve error handling for cancelled build tasks

Refactor generate_flow_events to properly handle and propagate CancelledError
- Remove unnecessary task creation and manual cancellation
- Directly await _build_vertex instead of creating a separate task
- Improve exception logging for cancelled tasks
- Ensure CancelledError is raised instead of being silently handled

* fix: trigger event_manager.on_end after error handling in generate_flow_events

---------

Co-authored-by: Christophe Bornet <cbornet@hotmail.com>
Co-authored-by: anovazzi1 <otavio2204@gmail.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

src/backend/tests/conftest.py

@@ -135,11 +135,12 @@ def get_text():
 
 
 async def delete_transactions_by_flow_id(db: AsyncSession, flow_id: UUID):
+    if not flow_id:
+        return
     stmt = select(TransactionTable).where(TransactionTable.flow_id == flow_id)
     transactions = await db.exec(stmt)
     for transaction in transactions:
         await db.delete(transaction)
-    await db.commit()
 
 
 async def _delete_transactions_and_vertex_builds(session, flows: list[Flow]):
@@ -147,8 +148,14 @@ async def _delete_transactions_and_vertex_builds(session, flows: list[Flow]):
     for flow_id in flow_ids:
         if not flow_id:
             continue
-        await delete_vertex_builds_by_flow_id(session, flow_id)
-        await delete_transactions_by_flow_id(session, flow_id)
+        try:
+            await delete_vertex_builds_by_flow_id(session, flow_id)
+        except Exception as e:  # noqa: BLE001
+            logger.debug(f"Error deleting vertex builds for flow {flow_id}: {e}")
+        try:
+            await delete_transactions_by_flow_id(session, flow_id)
+        except Exception as e:  # noqa: BLE001
+            logger.debug(f"Error deleting transactions for flow {flow_id}: {e}")
 
 
 @pytest.fixture
@@ -433,12 +440,21 @@ async def active_user(client):  # noqa: ARG001
     yield user
     # Clean up
     # Now cleanup transactions, vertex_build
-    async with db_manager.with_session() as session:
-        user = await session.get(User, user.id, options=[selectinload(User.flows)])
-        await _delete_transactions_and_vertex_builds(session, user.flows)
-        await session.delete(user)
+    try:
+        async with db_manager.with_session() as session:
+            user = await session.get(User, user.id, options=[selectinload(User.flows)])
+            await _delete_transactions_and_vertex_builds(session, user.flows)
+            await session.commit()
+    except Exception as e:  # noqa: BLE001
+        logger.exception(f"Error deleting transactions and vertex builds for user: {e}")
 
-        await session.commit()
+    try:
+        async with db_manager.with_session() as session:
+            user = await session.get(User, user.id)
+            await session.delete(user)
+            await session.commit()
+    except Exception as e:  # noqa: BLE001
+        logger.exception(f"Error deleting user: {e}")
 
 
 @pytest.fixture