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GraphQL over WebSocket · SvelteKit

Before you start

Start with an existing SvelteKit app. Keep its renderer, routes and plugins. These files add one live view; Spinetab does not create your API.

Your schema exposes Subscription.queue: Queue! with Queue.open: Int!. Each event contains the complete queue value. Serve the graphql-transport-ws protocol at /graphql. Queries and mutations, if used, go to /graphql. This is a GraphQL endpoint, not a plain SSE or WebSocket feed.

The examples use same-origin URLs and declare anonymous: true: no token is supplied, although cookies still flow. For a separate API origin, use its URL and configure CORS or your application's proxy. For private data, add credentials and user scopes; never put a secret in these files.

1. Install

pnpm add spinetab graphql@^17.0.2 graphql-ws@^6.3.0

Keep your framework's existing dependencies. See compatible versions if upgrading an older app.

2. Configure your app

Merge this addition into your configuration; preserve existing plugins and options. Restart the dev server afterwards. The plugin bundles the worker and discovers the adapters imported below.

vite.config.ts

import { sveltekit } from "@sveltejs/kit/vite";
import { spinetab } from "spinetab/vite";
import { defineConfig } from "vite";

export default defineConfig({ plugins: [sveltekit(), spinetab()] });

3. Connect and render

Save these files together in src/lib/recipe/.

reconcile: "latest" fits this full-state contract: the next complete event restores the displayed value after a gap. Use a refresh/merge policy for deltas or partial GraphQL results. Reconnecting alone does not reconstruct missed state.

src/lib/recipe/live.ts

import { createSpinetab } from "spinetab";

export const spinetab = createSpinetab({ anonymous: true });

src/lib/recipe/queue-types.ts

export type Queue = { open: number };
export type QueueView = { open?: number; problem?: string };

src/lib/recipe/source.ts

import { parse } from "graphql";
import {
  type GraphqlDocument,
  type GraphqlResult,
  graphqlWs,
} from "spinetab/graphql-ws";
import type { Queue, QueueView } from "./queue-types";

const document: GraphqlDocument<
  { queue: Queue },
  Record<string, never>
> = parse("subscription Queue { queue { open } }");

export const queueSource = graphqlWs("/graphql").subscription({
  query: document,
});

export function selectQueue(
  result: GraphqlResult<{ queue: Queue }>,
): QueueView {
  return {
    open: result.data?.queue?.open,
    problem:
      result.errors?.map((error) => error.message).join("; ") ||
      (result.data?.queue ? undefined : "The server returned no queue."),
  };
}

src/lib/recipe/Recipe.svelte

<script lang="ts">
import { bindClient } from "spinetab/svelte";
import { spinetab } from "./live";
import { queueSource, selectQueue } from "./source";

const { liveStore } = bindClient(spinetab);
const queue = liveStore(queueSource, { map: selectQueue, reconcile: "latest" });
</script>

{#if $queue.error || $queue.data?.problem}
  <p role="alert">{$queue.error?.message ?? $queue.data?.problem}</p>
{:else if $queue.data?.open === undefined}
  <p role="status">Loading queue…</p>
{:else}
  <p><output>{$queue.data.open}</output> open</p>
{/if}

4. Mount the view

src/routes/queue/+page.svelte

<script lang="ts">
import Recipe from "../../lib/recipe/Recipe.svelte";
</script>
<main><Recipe /></main>

Keep your existing SvelteKit deployment adapter. Component lifecycle keeps live work out of server rendering; do not disable SSR or subscribe in a server load function.

Check the result

Open /queue in two tabs of the same browser profile. Both should show advancing queue values. Matching subscriptions share upstream work when SharedWorker is available; fallback runs independently in each tab. Remove one view and the other should keep updating. Removing the last view releases its subscription; connection closure can follow the adapter's idle delay.

API options and advanced recovery · Authentication