# `@livestore/sync-cf`

## Goals

- Flexible: Leverage the strenghts of Cloudflare abstractions and let app developers choose right setup for their use case (configurable transports/storage)
- Efficient: Let's Durable Objects hibernate when not possible to avoid CPU billing while still staying fully reactive
- Cloudflare idiomatic: Embrace Cloudflare's APIs and abstractions so using LiveStore on Cloudflare feels right at home

## Transports

| Transport          | Connection | Encoding | Runtime Env                                  |
| ------------------ | ---------- | -------- | -------------------------------------------- |
| WebSocket          | Stateful   | JSON     | Anywhere                                     |
| HTTP               | Stateless  | JSON     | Anywhere                                     |
| Durable Object RPC | Stateful   | MsgPack  | Only available between Durable Objects (DOs) |

### WebSocket

```
┌─────────────┐  WS (hibernated) ┌─────────────┐
│   Client    │ ──────────────── │  Sync DO    │
└─────────────┘                  └─────────────┘
```

- Support hibernated WebSockets (i.e. client DO doesn't need to stay alive during pull streaming)

### HTTP

```
┌─────────────┐      HTTP       ┌─────────────┐
│   Client    │ ─────────────── │  Sync DO    │
└─────────────┘                 └─────────────┘
```

- Request-response model for each RPC call
- Streaming responses are implemented via HTTP streaming
  - Requires `enable_request_signal` compatibility flag to properly support `pull` streaming responses
  - Keeps DO alive for the duration of the stream (which causes CPU billing)

### Durable Object RPC

```
┌─────────────┐     DO RPC      ┌─────────────┐
│ DO Client   │ ─────────────── │  Sync DO    │
└─────────────┘                 └─────────────┘
```

- Only supported in combination with `@livestore/adapter-cloudflare`
- RPC streams are implement via `ReadableStream` which is billed for the entire duration of the stream, not just the time it takes to send the data

## Storage

- D1
- Cloudflare Durable Objects SQLite

## TODO (in readme)

- possibly add a CF Queue based transport mechanism for pull streaming responses
- alternative for DO RPC streams: poke to pull (let server callback client DO via client-side RPC endpoint)