SolidStart SSE Chat

Updated for SolidStart v1.0.0-rc.0

Basic Chat demonstration with server-sent events (SSE) for server to client communication.

If HTTP/1.1 compatibility is desired a client application shouldn't use more that one SSE connection as there is a limit of 6 connections per domain on a browser (the limit is significantly higher with HTTP/2). Typically SSE is less resource intensive compared to WebSockets (which aren't part of the HTTP spec either).

With HTTP/3 both will likely be replaced with WebTransport (MDN, web.dev).

For EventSources the HTML Living Standard recommends:

Clients that support HTTP's per-server connection limitation might run into trouble when opening multiple pages from a site if each page has an EventSource to the same domain. Authors can avoid this using the relatively complex mechanism of using unique domain names per connection, or by allowing the user to enable or disable the EventSource functionality on a per-page basis, or by sharing a single EventSource object using a shared worker.

From that perspective it's likely a mistake to create an EventSource inside an ordinary component as it may be construed from the remix-utils useEventSource() example (the example does actually only use it in the top-level App component though that detail is easily missed.).

Here the EventSource is centrally handled in history-context where the messages are staged and expose via cache async access points which are made accessible via a context to the rest of the application. A component can then use createAsync (or in this case createAsyncStore) to get reactive access to the messages.

Ideally in a larger application with multiple server-to-client information streams, the streams should be multiplexed onto a single SSE connection and demultiplexed client-side into the appropriate parts of client state.

cd solid-start-sse-chat

pnpm install

    Lockfile is up to date, resolution step is skipped
    Packages: +572
    +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    Progress: resolved 572, reused 572, downloaded 0, added 572, done

    dependencies:
    + @solidjs/meta 0.29.3
    + @solidjs/router 0.13.2
    + @solidjs/start 1.0.0-rc.0
    + nanoid 5.0.7
    + solid-js 1.8.17
    + vinxi 0.3.11

    devDependencies:
    + @typescript-eslint/eslint-plugin 7.8.0
    + @typescript-eslint/parser 7.8.0
    + eslint 8.57.0
    + eslint-config-prettier 9.1.0
    + prettier 3.2.5
    + typescript 5.4.5

    Done in 1.7s

cp .env.example .env

pnpm run dev

    > solid-start-sse-chat@0.0.0 dev
    > vinxi dev

    vinxi v0.3.11
    vinxi starting dev server

        ➜ Local:    http://localhost:3000/
        ➜ Network:  use --host to expose

---

Notes

• To force the application to use the long polling fallback instead of SSE:

// file: src/components/history-context/index.tsx
// …

// To start with long polling, set to: connectStatus.LONGPOLL;
let status: ConnectStatus = connectStatus.IDLE;

// …

• The messages streamed to the browser are handled via the /api/messages API route. Messages sent to the server are handled with the broadcast server action. Server functions and route handling seem to operate in isolated memory spaces on the server. This lead to BroadcastChannel being used for communication between the publish and subscription portion of the server logic.

• Concurrent (SSR) requests share the same memory space and thereby JS modules and their globals. This made it necessary to isolate the context values used during SSR in app-store.