Server Events

The Node.js server after startup can emit a variety of different events that the app can listen to, eg. upgrade, listening, etc. As you know, streams are the main building block of Marble.js. @marblejs/core createServer function allows you to listen to emitted server events via event$ attribute, where you can hook your stream.

HttpServerEffect is used for dealing with stream of incoming server events, but in comparison to others, the interface doesn't specify what the output of the stream should be.

import { createServer, matchEvent, ServerEvent, HttpServerEffect } from '@marblejs/core';
import { merge } from 'rxjs';
import { map, tap } from 'rxjs/operators';

const listening$: HttpServerEffect = event$ =>
  event$.pipe(
    matchEvent(ServerEvent.listening),
    map(event => event.payload),
    tap(({ port, host }) => console.log(`Running @ http://${host}:${port}/`)),
  );

const server = createServer({
  // ...
  event$: (...args) => merge(
    listening$(...args),
  ),
});

As in the case of WebSocket or messaging module, you can match incoming events using the same matchEvent operator. ServerEvent contains a full list of events that you can match to, preserving at the same time type correctness of matched events.

Upgrading HTTP connections

The HTTP/1.1 protocol provides a special mechanism that can be used to upgrade an already established connection to a different protocol, using the Upgrade header field.

This mechanism is optional; it cannot be used to insist on a protocol change. Implementations can choose not to take advantage of an upgrade even if they support the new protocol, and in practice, this mechanism is used mostly to bootstrap a WebSockets connection.

--- source: MDN

import { createServer, matchEvent, ServerEvent, HttpServerEffect, bindEagerlyTo } from '@marblejs/core';
import { mapToServer } from '@marblejs/websockets';
import { merge } from 'rxjs';
import { WebSocketServerToken } from './tokens';
import { listener } from './http.listener';
import { webSocketServer } from './ws.listener';

const upgrade$: HttpServerEffect = (event$, ctx) =>
  event$.pipe(
    matchEvent(ServerEvent.upgrade),
    mapToServer({
      path: '/api/:version/ws',
      server: ctx.ask(WsServerToken),
    }),
  );

const server = createServer({
  port: 1337,
  httpListener,
  dependencies: [
    bindEageryTo(WebSocketServerToken)(async () =>
      await (await webSocketServer)()
    ),
  ],
  event$: (...args) => merge(
    upgrade$(...args),
  ),
});

You can upgrade running WebSocket server using dedicated mapToServer operator. This kind of mechanism allows you to hook multiple WebSocket servers into an already running HTTP server on different paths.

// `createServer`
bindEageryTo(WsServerToken_1)(async () => await (await webSocketServer_1)()),
bindEageryTo(WsServerToken_2)(async () => await (await webSocketServer_2)()),

// upgrade$
mapToServer({
  path: '/ws_1',
  server: ctx.ask(WsServerToken_1),
}, {
  path: '/ws_2',
  server: ctx.ask(WsServerToken_2),
}),