use caching dialogs holder to reduce telegram api calls

src/main.ts

@@ -32,8 +32,7 @@ const user = await tg.start({
 
 console.log("Logged in as", user.username);
 
-registry.registerMetric(metrics.newStaticPeerInfoGauge(tg));
-registry.registerMetric(metrics.newUnreadCountGauge(tg));
+metrics.collectDialogMetrics(tg, registry);
 metrics.collectNewMessageMetrics(dp, registry);
 
 if (config.keywords) {

src/metrics.ts

@@ -1,6 +1,10 @@
 import type { Dispatcher } from "@mtcute/dispatcher";
-import type { TelegramClient } from "@mtcute/node";
+import type { Dialog, TelegramClient } from "@mtcute/node";
 import type { Registry } from "prom-client";
+
+import process from "node:process";
+import timers from "node:timers/promises";
+
 import { PropagationAction } from "@mtcute/dispatcher";
 import { Counter, Gauge } from "prom-client";
 
@@ -78,19 +82,52 @@ function collectNewMessageMetrics(dp: Dispatcher, registry: Registry) {
     registry.registerMetric(messages);
 }
 
-function newStaticPeerInfoGauge(tg: TelegramClient) {
-    const gauge = new Gauge({
+class DialogsHolder {
+    private lastUpdate = 0n;
+    private dialogs: Dialog[] = [];
+    private isUpdating = false;
+    private ttl: bigint;
+
+    constructor(private tg: TelegramClient, ttl: number, private timeout: number, private pollInterval = 10) {
+        this.ttl = BigInt(ttl) * 1000000n;
+    }
+
+    public async get() {
+        if (this.isUpdating) {
+            for (let i = 0; i < this.timeout && this.isUpdating; i += this.pollInterval) {
+                await timers.setTimeout(this.pollInterval);
+            }
+            if (this.isUpdating) {
+                throw new Error("Timed out fetching dialogs");
+            }
+        }
+        if (process.hrtime.bigint() - this.lastUpdate > this.ttl) {
+            this.isUpdating = true;
+            this.dialogs = [];
+            for await (const d of this.tg.iterDialogs()) {
+                if (!peersConfigBoolFilter(config, d.peer.id)) {
+                    continue;
+                }
+                this.dialogs.push(d);
+            }
+            this.lastUpdate = process.hrtime.bigint();
+            this.isUpdating = false;
+        }
+        return this.dialogs;
+    }
+}
+
+function collectDialogMetrics(tg: TelegramClient, registry: Registry) {
+    const dialogs = new DialogsHolder(tg, 1000, 5000);
+
+    const info = new Gauge({
         name: "messenger_dialog_info",
         help: "Dialog information exposed as labels",
         labelNames: ["peerId", "peerType", "displayName"],
         collect: async () => {
-            gauge.reset();
-            for await (const d of tg.iterDialogs()) {
-                if (!peersConfigBoolFilter(config, d.peer.id)) {
-                    continue;
-                }
-
-                gauge.set({
+            info.reset();
+            for (const d of await dialogs.get()) {
+                info.set({
                     peerId: d.peer.id,
                     peerType: d.peer.type,
                     displayName: d.peer.displayName,
@@ -98,28 +135,23 @@ function newStaticPeerInfoGauge(tg: TelegramClient) {
             }
         },
     });
-    return gauge;
-}
 
-function newUnreadCountGauge(tg: TelegramClient) {
-    const gauge = new Gauge({
+    const unread = new Gauge({
         name: "messenger_dialog_unread_messages_count",
         help: "Number of unread messages in dialogs",
         labelNames: ["peerId"],
         collect: async () => {
-            gauge.reset();
-            for await (const d of tg.iterDialogs()) {
-                if (!peersConfigBoolFilter(config, d.peer.id)) {
-                    continue;
-                }
-
-                gauge.set({
+            unread.reset();
+            for (const d of await dialogs.get()) {
+                unread.set({
                     peerId: d.peer.id,
                 }, d.unreadCount);
             }
         },
     });
-    return gauge;
+
+    registry.registerMetric(info);
+    registry.registerMetric(unread);
 }
 
 function newWordsCounter(dp: Dispatcher) {
@@ -142,9 +174,8 @@ function newWordsCounter(dp: Dispatcher) {
 }
 
 export {
+    collectDialogMetrics,
     collectNewMessageMetrics,
     KeywordsCounter,
-    newStaticPeerInfoGauge,
-    newUnreadCountGauge,
     newWordsCounter,
 };