Sadly, the presence API is worse than I hoped

package-lock.json

@@ -30,7 +30,7 @@
         "get-relative-path": "^1.0.2",
         "get-stream": "^6.0.1",
         "h3": "^1.12.0",
-        "heatsync": "^2.5.5",
+        "heatsync": "^2.6.0",
         "lru-cache": "^10.4.3",
         "minimist": "^1.2.8",
         "node-fetch": "^2.6.7",
@@ -1193,7 +1193,8 @@
     "node_modules/backtracker": {
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/backtracker/-/backtracker-4.0.0.tgz",
-      "integrity": "sha512-XG2ldN+WDRq9niJMnoZDjLLUnhDOQGhFZc6qZQotN59xj8oOa4KXSCu6YyZQawPqi6gG3HilGFt91zT6Hbdh1w=="
+      "integrity": "sha512-XG2ldN+WDRq9niJMnoZDjLLUnhDOQGhFZc6qZQotN59xj8oOa4KXSCu6YyZQawPqi6gG3HilGFt91zT6Hbdh1w==",
+      "license": "MIT"
     },
     "node_modules/balanced-match": {
       "version": "1.0.2",
@@ -1938,9 +1939,10 @@
       }
     },
     "node_modules/heatsync": {
-      "version": "2.5.5",
-      "resolved": "https://registry.npmjs.org/heatsync/-/heatsync-2.5.5.tgz",
-      "integrity": "sha512-Sy2/X2a69W2W1xgp7GBY81naHtWXxwV8N6uzPTJLQXgq4oTMJeL6F/AUlGS+fUa/Pt5ioxzi7gvd8THMJ3GpyA==",
+      "version": "2.6.0",
+      "resolved": "https://registry.npmjs.org/heatsync/-/heatsync-2.6.0.tgz",
+      "integrity": "sha512-UfemOt4Kg1hvhDj/Zz8sYa1pF73ul+tF19MYNisYoOymXoTo4iCZv2BDdCMFE1xvZ6YFjcMoekb/aeBU1uqFjQ==",
+      "license": "MIT",
       "dependencies": {
         "backtracker": "^4.0.0"
       }

package.json

@@ -39,7 +39,7 @@
     "get-relative-path": "^1.0.2",
     "get-stream": "^6.0.1",
     "h3": "^1.12.0",
-    "heatsync": "^2.5.5",
+    "heatsync": "^2.6.0",
     "lru-cache": "^10.4.3",
     "minimist": "^1.2.8",
     "node-fetch": "^2.6.7",

src/d2m/actions/create-space.js

@@ -32,7 +32,7 @@ async function createSpace(guild, kstate) {
 	assert(name)
 
 	const memberCount = guild["member_count"] ?? guild.approximate_member_count ?? 0
-	const enablePresenceByDefault = +(memberCount < 150) // could increase this later on if it doesn't cause any problems
+	const enablePresenceByDefault = +(memberCount < 50) // scary! all active users in a presence-enabled guild will be pinging the server every <30 seconds to stay online
 	const globalAdmins = select("member_power", "mxid", {room_id: "*"}).pluck().all()
 
 	const roomID = await createRoom.postApplyPowerLevels(kstate, async kstate => {

src/d2m/actions/set-presence.js

@@ -5,9 +5,28 @@ const {sync, select} = passthrough
 /** @type {import("../../matrix/api")} */
 const api = sync.require("../../matrix/api")
 
-// Adding a debounce to all updates because events are issued multiple times, once for each guild.
-// Sometimes a status update is even issued twice in a row for the same user+guild, weird!
+/*
+	We do this in two phases for optimisation reasons.
+	Discord sends us an event when the presence *changes.*
+	We need to keep the event data in memory because we need to *repeatedly* send it to Matrix using a long-lived loop.
+
+	There are two phases to get it from Discord to Matrix.
+	The first phase stores Discord presence data in memory.
+	The second phase loops over the memory and sends it on to Matrix.
+
+	In the first phase, for optimisation reasons, we want to do as little work as possible if the presence doesn't actually need to be sent all the way through.
+	* Presence can be deactivated per-guild in OOYE settings. If it's deactivated for all of a user's guilds, we shouldn't send them to the second phase.
+	* Presence can be sent for users without sims. In this case, we shouldn't send them to the second phase.
+	* Presence can be sent multiple times in a row for the same user for each guild we share. We want to batch these up so we only query the mxid and enter the second phase once per user.
+*/
+
+
+// ***** first phase *****
+
+
+// Delay before querying user details and putting them in memory.
 const presenceDelay = 1500
+
 /** @type {Map<string, NodeJS.Timeout>} user ID -> cancelable timeout */
 const presenceDelayMap = new Map()
 
@@ -20,8 +39,9 @@ function checkPresenceEnabledGuilds() {
 checkPresenceEnabledGuilds()
 
 /**
+ * This function is called for each Discord presence packet.
  * @param {string} userID Discord user ID
- * @param {string} guildID Discord guild ID that this presence applies to (really, the same presence applies to every single guild, but is delivered separately)
+ * @param {string} guildID Discord guild ID that this presence applies to (really, the same presence applies to every single guild, but is delivered separately by Discord for some reason)
  * @param {string} status status field from Discord's PRESENCE_UPDATE event
  */
 function setPresence(userID, guildID, status) {
@@ -47,11 +67,38 @@ function setPresenceCallback(user_id, status) {
 		( status === "online" ? "online"
 		: status === "offline" ? "offline"
 		: "unavailable") // idle, dnd, and anything else they dream up in the future
-	api.setPresence(presence, mxid).catch(e => {
-		console.error("d->m: Skipping presence update failure:")
-		console.error(e)
-	})
+	if (presence === "offline") {
+		userPresence.delete(mxid) // stop syncing next cycle
+	} else {
+		const delay = userPresence.get(mxid)?.delay || presenceLoopInterval * Math.random() // distribute the updates across the presence loop
+		userPresence.set(mxid, {data: {presence}, delay}) // will be synced next cycle
+	}
 }
 
+
+// ***** second phase *****
+
+
+// Synapse expires each user's presence after 30 seconds and makes them offline, so we have loop every 28 seconds and update each user again.
+const presenceLoopInterval = 28e3
+
+/** @type {Map<string, {data: {presence: "online" | "offline" | "unavailable", status_msg?: string}, delay: number}>} mxid -> presence data to send to api */
+const userPresence = new Map()
+
+sync.addTemporaryInterval(() => {
+	for (const [mxid, memory] of userPresence.entries()) {
+		// I haven't tried, but assuming Synapse explodes if you try to update too many presences at the same time,
+		// I'll space them out over the whole 28 second cycle.
+		setTimeout(() => {
+			const d = new Date().toISOString().slice(0, 19)
+			api.setPresence(memory.data, mxid).catch(e => {
+				console.error("d->m: Skipping presence update failure:")
+				console.error(e)
+			})
+		}, memory.delay)
+	}
+}, presenceLoopInterval)
+
+
 module.exports.setPresence = setPresence
 module.exports.checkPresenceEnabledGuilds = checkPresenceEnabledGuilds

src/matrix/api.js

@@ -409,11 +409,11 @@ async function setAccountData(type, content, mxid) {
 }
 
 /**
- * @param {"online" | "offline" | "unavailable"} presence
+ * @param {{presence: "online" | "offline" | "unavailable", status_msg?: string}} data
  * @param {string} mxid
  */
-async function setPresence(presence, mxid) {
-	await mreq.mreq("PUT", path(`/client/v3/presence/${mxid}/status`, mxid), {presence})
+async function setPresence(data, mxid) {
+	await mreq.mreq("PUT", path(`/client/v3/presence/${mxid}/status`, mxid), data)
 }
 
 module.exports.path = path

src/passthrough.js

@@ -4,7 +4,7 @@
  * @typedef {Object} Passthrough
  * @property {import("repl").REPLServer} repl
  * @property {import("./d2m/discord-client")} discord
- * @property {import("heatsync").default} sync
+ * @property {import("heatsync")} sync
  * @property {import("better-sqlite3/lib/database")} db
  * @property {import("@cloudrac3r/in-your-element").AppService} as
  * @property {import("./db/orm").from} from

start.js

@@ -1,6 +1,7 @@
 #!/usr/bin/env node
 // @ts-check
 
+const fs = require("fs")
 const sqlite = require("better-sqlite3")
 const migrate = require("./src/db/migrate")
 const HeatSync = require("heatsync")
@@ -9,7 +10,7 @@ const {reg} = require("./src/matrix/read-registration")
 const passthrough = require("./src/passthrough")
 const db = new sqlite("ooye.db")
 
-const sync = new HeatSync()
+const sync = new HeatSync({watchFunction: fs.watchFile})
 
 Object.assign(passthrough, {sync, db})