Queue events for later if homeserver is down

docs/developer-orientation.md

@@ -113,6 +113,7 @@ Total transitive production dependencies: 144
 * (0) ansi-colors: Helps with interactive prompting for the initial setup, and it's already pulled in by enquirer.
 * (1) chunk-text: It does what I want.
 * (0) cloudstorm: Discord gateway library with bring-your-own-caching that I trust.
+* (0) denque: Much faster than using arrays as a queue.
 * (0) discord-api-types: Bitfields needed at runtime and types needed for development.
 * (0) domino: DOM implementation that's already pulled in by turndown.
 * (2) enquirer: Interactive prompting for the initial setup rather than forcing users to edit YAML non-interactively.

src/d2m/actions/create-space.js

@@ -8,6 +8,8 @@ const {reg} = require("../../matrix/read-registration")
 
 const passthrough = require("../../passthrough")
 const {discord, sync, db, select} = passthrough
+/** @type {import("../../matrix/mreq")} */
+const mreq = sync.require("../../matrix/mreq")
 /** @type {import("../../matrix/api")} */
 const api = sync.require("../../matrix/api")
 /** @type {import("../../matrix/file")} */
@@ -237,8 +239,12 @@ async function syncSpaceExpressions(data, checkBeforeSync) {
 			try {
 				existing = await api.getStateEvent(spaceID, "im.ponies.room_emotes", eventKey)
 			} catch (e) {
+				if (e instanceof mreq.MatrixServerError && e.httpStatus < 400) {
 					// State event not found. This space doesn't have any existing emojis. We create a dummy empty event for comparison's sake.
 					existing = fn([], guild)
+				} else {
+					throw e
+				}
 			}
 			if (isDeepStrictEqual(existing, content)) return
 		}

src/d2m/discord-packets.js

@@ -1,18 +1,18 @@
 // @ts-check
 
-// Discord library internals type beat
+const assert = require("assert")
-
-const DiscordTypes = require("discord-api-types/v10")
 const passthrough = require("../passthrough")
-const {sync, db} = passthrough
+const {sync} = passthrough
+
+/** @type {import("../matrix/homeserver-status")} */
+const homeserverStatus = sync.require("../matrix/homeserver-status")
 
-const utils = {
 /**
  * @param {import("./discord-client")} client
  * @param {import("cloudstorm").IGatewayMessage} message
  * @param {string} listen "full", "half", "no" - whether to set up the event listeners for OOYE to operate
  */
-	async onPacket(client, message, listen) {
+async function onPacket(client, message, listen) {
 	// requiring this later so that the client is already constructed by the time event-dispatcher is loaded
 	/** @type {typeof import("./event-dispatcher")} */
 	const eventDispatcher = sync.require("./event-dispatcher")
@@ -152,6 +152,28 @@ const utils = {
 
 	// Event dispatcher for OOYE bridge operations
 	if (listen === "full" && message.t) {
+		const alwaysRealTimeEvents = ["PRESENCE_UPDATE"]
+		if (alwaysRealTimeEvents.includes(message.t) || homeserverStatus.homeserverStatus.isRealTime()) {
+			dispatchPacketToBridge(client, message)
+		} else {
+			homeserverStatus.homeserverStatus.queuePacket(message)
+		}
+	}
+}
+
+/**
+ * @param {import("./discord-client")} client
+ * @param {import("cloudstorm").IGatewayMessage} message
+ */
+async function dispatchPacketToBridge(client, message) {
+	// requiring this later so that the client is already constructed by the time event-dispatcher is loaded
+	/** @type {typeof import("./event-dispatcher")} */
+	const eventDispatcher = sync.require("./event-dispatcher")
+	/** @type {import("../discord/register-interactions")} */
+	const interactions = sync.require("../discord/register-interactions")
+
+	assert(message.t) // checked above
+
 	try {
 		if (message.t === "MESSAGE_REACTION_REMOVE" || message.t === "MESSAGE_REACTION_REMOVE_EMOJI" || message.t === "MESSAGE_REACTION_REMOVE_ALL") {
 			await eventDispatcher.onSomeReactionsRemoved(client, message.d)
@@ -167,7 +189,6 @@ const utils = {
 		await eventDispatcher.onError(client, e, message)
 	}
 }
-	}
-}
 
-module.exports = utils
+module.exports.onPacket = onPacket
+module.exports.dispatchPacketToBridge = dispatchPacketToBridge

src/m2d/event-dispatcher.js

@@ -24,6 +24,8 @@ const vote = sync.require("./actions/vote")
 const matrixCommandHandler = sync.require("../matrix/matrix-command-handler")
 /** @type {import("../matrix/utils")} */
 const utils = sync.require("../matrix/utils")
+/** @type {import("../matrix/mreq")}) */
+const mreq = sync.require("../matrix/mreq")
 /** @type {import("../matrix/api")}) */
 const api = sync.require("../matrix/api")
 /** @type {import("../d2m/actions/create-room")} */
@@ -32,6 +34,8 @@ const createRoom = sync.require("../d2m/actions/create-room")
 const roomUpgrade = require("../matrix/room-upgrade")
 /** @type {import("../d2m/actions/retrigger")} */
 const retrigger = sync.require("../d2m/actions/retrigger")
+/** @type {import("../matrix/homeserver-status")} */
+const homeserverStatus = sync.require("../matrix/homeserver-status")
 const {reg} = require("../matrix/read-registration")
 
 let lastReportedEvent = 0
@@ -166,7 +170,12 @@ async function sendError(roomID, source, type, e, payload) {
 				key: "🔁"
 			}
 		})
-	} catch (e) {}
+	} catch (e) {
+		if (e instanceof mreq.MatrixServerError && [502, 503].includes(e.httpStatus)) {
+			// Matrix homeserver is down (reverse proxy indicated failure; synapse doesn't generate 502/503 when posting an event to a room)
+			homeserverStatus.homeserverStatus.setErrorWithPacket(payload)
+		}
+	}
 }
 
 function guard(type, fn) {

src/matrix/api.js

@@ -452,7 +452,8 @@ async function ping() {
 		headers: {
 			Authorization: `Bearer ${reg.as_token}`
 		},
-		body: "{}"
+		body: "{}",
+		signal: AbortSignal.timeout(15e3)
 	})
 	const root = await res.json()
 	return {

src/matrix/homeserver-status.js

@@ -0,0 +1,94 @@
+// @ts-check
+
+const assert = require("assert")
+const Denque = require("denque")
+const StateMachine = require("snowtransfer").StateMachine
+
+const passthrough = require("../passthrough")
+const {sync} = passthrough
+/** @type {import("../d2m/discord-packets")} */
+const discordPackets = sync.require("../d2m/discord-packets")
+/** @type {import("../matrix/api")} */
+const api = sync.require("../matrix/api")
+
+const DEBUG_HOMESERVER_STATUS = true
+
+function debugHomeserverStatus(message) {
+	if (DEBUG_HOMESERVER_STATUS) {
+		console.log(message)
+	}
+}
+
+const homeserverStatus = new class HomeserverStatus {
+	constructor() {
+		/** @private */
+		this.queue = new Denque()
+
+		/** @private */
+		this.pingInterval = undefined
+
+		/** @private */
+		this.sm = new StateMachine("online")
+			.defineState("online")
+
+			.defineState("offline", {
+				onEnter: [() => {
+					this.pingInterval = setInterval(async () => {
+						const pingResult = await api.ping().catch(e => ({ok: false, status: "net", root: e.message}))
+						if (pingResult.ok) {
+							this.sm.doTransition("ping ok")
+						}
+					}, 15e3)
+				}],
+				onLeave: [() => {
+					clearInterval(this.pingInterval)
+				}],
+				transitions: new Map()
+			})
+
+			.defineState("recovering", {
+				onEnter: [async () => { // Drain queue.
+					while (!this.queue.isEmpty()) {
+						const packet = this.queue.peekFront() // same position as .shift()
+						debugHomeserverStatus(`homeserver status: ${new Date().toISOString()} dq packet ${packet.t} ${packet.d?.content}`)
+						await discordPackets.dispatchPacketToBridge(passthrough.discord, packet)
+						if (this.sm.currentStateName !== "recovering") return // got kicked out due to another error
+						this.queue.shift()
+					}
+					this.sm.doTransition("recovered")
+				}],
+				onLeave: [],
+				transitions: new Map()
+			})
+
+			.defineUniversalTransition("error", "offline")
+			.defineTransition("offline", "ping ok", "recovering")
+			.defineTransition("recovering", "recovered", "online")
+
+		this.sm.on("enter", st => debugHomeserverStatus(`homeserver status: ${st}`))
+
+		this.sm.freeze()
+	}
+
+	isRealTime() {
+		return this.sm.currentStateName === "online"
+	}
+
+	/**
+	 * When offline or recovering, call this for incoming packets to queue them to be sent in order later.
+	 */
+	queuePacket(packet) {
+		assert(["offline", "recovering"].includes(this.sm.currentStateName))
+		this.queue.push(packet)
+	}
+
+	setErrorWithPacket(packet) {
+		const wasRecovering = this.sm.currentStateName === "recovering"
+		this.sm.doTransition("error")
+		if (!wasRecovering) { // if was recovering then packet is already in the right place in queue
+			this.queuePacket(packet)
+		}
+	}
+}
+
+module.exports.homeserverStatus = homeserverStatus