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pipecat/examples/multi-worker/ui-worker/async-tasks/README.md
Mark Backman 07725429b2 Add async-tasks UIWorker example
A UIWorker with a custom reply tool fans research out to three BaseWorker peers
via start_user_job_group; their progress streams to the client as ui-task cards
and the user can cancel a group mid-flight.
2026-05-21 23:20:40 -04:00

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# async-tasks
The UIWorker fans out long-running work to multiple peer workers in
parallel, streams their progress to an in-flight panel on the page, and
lets the user cancel mid-flight.
## What it shows
- The **`user_job_group` / `start_user_job_group`** API: dispatching
parallel work to multiple peer workers and automatically forwarding
every job lifecycle event to the client. The `reply` tool calls
`start_user_job_group("wikipedia", "news", "scholar", payload=...,
label=...)` and the `UIWorker` does the rest.
- The four **`ui-task` envelopes** the worker forwards (`group_started`,
`task_update`, `task_completed`, `group_completed`) and the
client-side `RTVIEvent.UITask` event for consuming them. The client
keeps a state map keyed by `task_id` and renders per-worker progress.
- **Cancellation**: the in-flight card's Cancel button calls
`client.cancelUITask(task_id, reason)`. The reserved `__cancel_task`
event is translated by the `UIWorker` into `cancel_job_group(task_id)`
on the registered group; cancelled workers report status `cancelled`.
- **Background dispatch from a tool**: `start_user_job_group` returns
immediately so the `reply` tool can speak its acknowledgement
("Researching the Mariana Trench now") while the workers run — the
main LLM is free to take follow-up turns.
## What it adds vs. the prior demos
The other examples use the request/response half of the bus protocol
(main LLM → UIWorker → reply). This one adds the streaming job-group
half: UIWorker → peer workers → progress events forwarded to the client.
The architecture grows from "one delegate" to "one delegate plus a
worker pool" — the peers are plain `BaseWorker`s launched on the runner.
## Run
Two terminals.
**Terminal 1 — bot:**
```bash
cd examples/multi-worker/ui-worker/async-tasks
uv run python bot.py
```
The bot starts on `http://localhost:7860`.
**Terminal 2 — client:**
```bash
cd examples/multi-worker/ui-worker/async-tasks/client
npm install # one-time
npm run dev
```
Open `http://localhost:5173` and click **Connect**.
## What to try
The workers are simulated (canned summaries, randomized `asyncio.sleep`
delays) so the demo focuses on the protocol, not the AI. Each research
call takes a few seconds.
- _"Research the Mariana Trench."_ — the worker spawns three peers,
acknowledges in one short reply, and a card appears showing each
peer's status as it progresses (searching → found N results →
summarizing → completed).
- _"Look up octopus cognition."_ — same flow; a second card stacks.
- _"Research the moon, then research Mars."_ — two groups run
concurrently.
- _"How are you?"_ (no research) — quick reply, no job group.
- **Click Cancel on an in-flight card** — the cancellation routes
through, the peers' tasks raise `CancelledError`, and their responses
come back as `cancelled`.
## Requirements
- `OPENAI_API_KEY`
- `DEEPGRAM_API_KEY`
- `CARTESIA_API_KEY`
A `.env` in the example folder is the easiest way to set these (see
`examples/multi-worker/env.example`).
## What this example _doesn't_ show
Real worker integrations (the peers are simulated), LLM-driven peers
(these are pure data-fetch — a peer can itself be an `LLMWorker`),
streaming chunks (`send_job_stream_data` for progressive output), or
worker-to-worker fan-out (nested job groups).