langflow-ai/langflow · error · HTTPException

Job not found: {exc!s}

Error message

Job not found: {exc!s}

What it means

Raised when JobQueueService.get_queue_data(job_id) raises JobQueueNotFoundError — the build job id is unknown to the queue service. With the in-memory queue this means the job never existed, finished and was evicted, or lived in a different worker process. With the Redis-backed queue it means the key expired or was flushed. 404.

Source

Thrown at src/backend/base/langflow/api/build.py:322

                    if event_task is not None:
                        event_task.cancel()
                    event_manager.on_end(data={})
                else:
                    events.append(_project_event_to_v1(value.decode("utf-8")))

            # Return as NDJSON format - each line is a complete JSON object
            content = "\n".join([event for event in events if event is not None])
            return Response(content=content, media_type="application/x-ndjson")
        except asyncio.CancelledError as exc:
            await logger.ainfo(f"Event polling was cancelled for job {job_id}")
            raise HTTPException(status_code=499, detail="Event polling was cancelled") from exc
        except asyncio.TimeoutError:
            await logger.awarning(f"Timeout while waiting for events for job {job_id}")
            return Response(content="", media_type="application/x-ndjson")  # Return empty response instead of error

    except JobQueueNotFoundError as exc:
        await logger.aerror(f"Job not found: {job_id}. Error: {exc!s}")
        raise HTTPException(status_code=404, detail=f"Job not found: {exc!s}") from exc
    except Exception as exc:
        if isinstance(exc, HTTPException):
            raise
        await logger.aexception(f"Unexpected error processing flow events for job {job_id}")
        raise HTTPException(status_code=500, detail=f"Unexpected error: {exc!s}") from exc


async def create_flow_response(
    queue: asyncio.Queue,
    event_manager: EventManager,
    event_task: asyncio.Task | None,
    *,
    queue_service: JobQueueService | None = None,
    job_id: str | None = None,
) -> DisconnectHandlerStreamingResponse:
    """Create a streaming response for the flow build process.

    When *queue_service* and *job_id* are provided and the service exposes a

View on GitHub (pinned to 976ec789d2)

Solutions

1. Start a fresh build to obtain a new job_id, then immediately attach the events consumer.
2. In multi-worker deployments, configure the Redis-backed queue so any worker can serve any job.
3. Consume events promptly after starting the build rather than much later.

Example fix

# before
job_id = load_cached_job_id()  # stale from previous run
await get_flow_events(job_id)

# after
job_id = await start_build(flow_id)
await get_flow_events(job_id)

async def job_alive(client, job_id: str) -> bool:
    res = await client.get(f"/api/v1/build/{job_id}/events")
    return res.status_code != 404

try:
    events = await get_flow_events(job_id)
except HTTPError as e:
    if e.response.status_code == 404:
        job_id = await start_build(flow_id)  # stale job — start a new one
        events = await get_flow_events(job_id)
    else:
        raise

When it happens

Trigger: GET the events endpoint with a job_id that was never issued by the build endpoint; polling a job after it completed and its queue entry was garbage-collected; a load balancer routing the events request to a worker without that in-memory job.

Common situations: Client persisting a job_id across restarts of a memory-queue backend; multi-worker deployment without Redis so jobs are worker-local; long-polling after the retention window elapsed.

Related errors

• str(e)
• Job not found: {exc!s}
• Flow not found
• Build job not found
• Refusing to start with {num_workers} workers and the default

AI-assisted analysis of langflow-ai/langflow@976ec789d2 (2026-08-14). Data as JSON: /api/errors/b5b3dc3c8afbb7dd. Report an issue: GitHub.