74 lines
2.5 KiB
TypeScript
74 lines
2.5 KiB
TypeScript
 
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import { MatrixClient, MatrixError } from 'matrix-js-sdk';
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/**
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* Synapse rate-limits `PUT /presence/{user}/status` to ONE request per 10 s per
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* user by default (`rc_presence.per_user`: 0.1/s, burst 1) — and the limit is
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* shared across all of a user's devices. Our presence heartbeat (online/away on
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* visibility and activity changes) can therefore make a manual status save 429.
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*
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* `setPresenceWithRetry` waits out `Retry-After` (bounded) instead of failing,
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* and `PresenceDeduper` lets the heartbeat skip writes that would not change
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* anything, so it stops spending the budget in the first place.
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*/
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export type PresenceWrite = { presence: 'online' | 'offline' | 'unavailable'; status_msg?: string };
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const sleep = (ms: number) =>
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new Promise<void>((r) => {
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setTimeout(r, ms);
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});
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export async function setPresenceWithRetry(
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mx: Pick<MatrixClient, 'setPresence'>,
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write: PresenceWrite,
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opts: { maxWaitMs?: number; sleepFn?: (ms: number) => Promise<void> } = {},
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): Promise<void> {
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const maxWaitMs = opts.maxWaitMs ?? 25_000;
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const sleepFn = opts.sleepFn ?? sleep;
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let waited = 0;
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for (;;) {
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try {
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// eslint-disable-next-line no-await-in-loop
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await mx.setPresence(write);
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return;
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} catch (e) {
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if (!(e instanceof MatrixError) || e.httpStatus !== 429) throw e;
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const wait = Math.min(e.getRetryAfterMs() ?? 10_500, 15_000);
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if (waited + wait > maxWaitMs) throw e;
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waited += wait;
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// eslint-disable-next-line no-await-in-loop
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await sleepFn(wait);
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}
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}
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}
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const presenceKey = (write: PresenceWrite): string => `${write.presence}|${write.status_msg ?? ''}`;
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/** Remembers the last write that succeeded so identical heartbeats are skipped. */
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export class PresenceDeduper {
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private last: string | null = null;
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shouldSend(write: PresenceWrite): boolean {
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return presenceKey(write) !== this.last;
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}
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sent(write: PresenceWrite): void {
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this.last = presenceKey(write);
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}
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reset(): void {
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this.last = null;
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}
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}
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/** A user-facing sentence for a failed status save. */
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export const describePresenceError = (e: unknown): string => {
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if (e instanceof MatrixError) {
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if (e.httpStatus === 429) {
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return 'The server limits how often presence can change (once every 10 seconds, shared by all your devices). Please wait a moment and try again.';
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}
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const serverText = (e.data as { error?: string } | undefined)?.error;
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if (serverText) return `Failed to save status: ${serverText}`;
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}
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return "Failed to save status — couldn't reach the server. Try again.";
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};
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