@liveflux/sse

The Server-Sent Events adapter for Liveflux — works with any backend that exposes an SSE endpoint, in any language. Turns a standard EventSource into a normalized, reconnect-safe event stream for @liveflux/core.

New to Liveflux? Start with pnpm create liveflux@latest — it picks your framework binding and transport and wires everything up for you.

• Backend-agnostic. The downstream stream is a plain EventSource; bring your own encode/decode.
• Zero runtime dependencies, tree-shakeable, tiny.
• Reconnect-safe. The core owns reconnect (one backoff policy, not the browser's opaque retry); the active subscription set is replayed on every reopen.
• Cursor resume. resume(subId, cursor) sends a gap-recovery frame, and the default decoder threads the SSE lastEventId through as the cursor.
• Configurable & secure by default. Injectable EventSource/fetch, an inbound size cap, and a decoder that only accepts well-formed events.

Why a control channel?

SSE is one-way (server → client). Subscribe / unsubscribe / resume therefore go upstream over a separate channel — by default an HTTP POST alongside the stream (override with control, or hand it your own transport function).

import { LivefluxClient } from '@liveflux/core';
import { sse } from '@liveflux/sse';

const client = new LivefluxClient({
  adapter: sse('/events', { control: '/events/control' }),
});
client.connect();

Options

| Option | Description | | --- | --- | | control | Upstream target for subscribe/unsubscribe/resume: a URL (POSTed as JSON), a function (your own transport), or omitted (POST to the stream URL). | | withCredentials | Send cookies with the stream request. | | EventSource | Inject an EventSource implementation (Node / tests). | | fetch | Inject fetch for the default control POST. | | encode / decode | Override the control-frame encoder and the inbound decoder. | | maxMessageBytes | Drop inbound frames larger than this before decoding (default 1 MiB; 0 disables). |

Pass url as a function to re-resolve it (e.g. a rotated token) on every reconnect.

License

MIT