JavaScript SDK

Package: @fastpubsub-sdk/client

npm install @fastpubsub-sdk/client

Works in the browser and in Node.js over WebSocket. Browser WebTransport is implemented. Node.js without a WebTransport global is not supported.

Session, token, socket

import {
  CreateAccessTokenBuilder,
  TenantGrant,
  open,
} from "@fastpubsub-sdk/client";

const session = open("globaltest");

const token = await session.createAccessToken(
  process.env.FPS_MASTER_TOKEN,
  new CreateAccessTokenBuilder()
    .createdBy("backend")
    .expiresAt("+1h")
    .addTenantGrant(
      new TenantGrant(["app"])
        .allowPub(["public.#"])
        .allowSub(["public.#"])
    )
    .build()
);

const client = await session.webSocket(token.token)
  .pingIntervalSec(3)
  .build();

const queue = await client.subscribe("app", "public.#");
await client.publish("app", "public.chat", "hello");
const message = await queue.recv();

Mint tokens on the backend. Browsers should receive only AT_....

createAccessToken and webSocket(...).build() resolve a nearby edge when needed. To pre-warm discovery:

const edge = await session.resolveEdge({ cache: "prefer" });

Cached edges live up to 24 hours. About once per hour the SDK re-checks RTT; if latency grew more than 50%, it rediscovers (typical after a VPN change).

Publish modes

publish() sends a broadcast (legacy v1 frame).

await client.publishWithOptions("app", "public.chat", data, {
  delivery: "deliverOneLowLatency",
});

`delivery`	Behaviour
`"broadcast"`	All matching subscribers
`"deliverOneLowLatency"`	One overlay node with the lowest inter-node latency among nodes that have subscribers, then one local connection
`"deliverOneRandom"`	One random overlay node with subscribers, then one local connection

If there are no subscribers, deliver-one does nothing.

Link quality

GET /ping during edge selection measures which edge to use.
After connect, .pingIntervalSec(1 | 3 | 5) sends application PING and reads PONG. Omit it to disable.

client.linkQuality(30); // { lastRttMs, medianRttMs }

The edge only answers PONG. It does not store your RTT.

Refresh and revoke

Backend only. Needs the master token.

import { accessTokenId } from "@fastpubsub-sdk/client";

await session.refreshAccessTokenFromAt(masterToken, token.token, "+23h");
await session.revokeAccessToken(masterToken, token.token);

Filters and WebTransport

Import a single filter when you want a smaller bundle:

import { CompressedFilter } from "@fastpubsub-sdk/client/filters/compressed";

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