remove batched release, replace hash with cyrb53

server/server.ts

@@ -25,7 +25,6 @@ import { deleteUser, validateUserToken } from './utils/firebase';
 import path from 'path';
 import { getStartOfDay } from './utils/time';
 import { getBgVMManagers, getSessionLimitSeconds } from './vm/utils';
-import { hashString } from './utils/string';
 import { postgres, insertObject, upsertObject } from './utils/postgres';
 import axios from 'axios';
 import crypto from 'crypto';
@@ -51,7 +50,6 @@ if (process.env.NODE_ENV === 'development') {
 const gzip = util.promisify(zlib.gzip);
 
 const releaseInterval = 5 * 60 * 1000;
-const releaseBatches = config.NODE_ENV === 'development' ? 1 : 10;
 const app = express();
 let server: any = null;
 if (config.SSL_KEY_FILE && config.SSL_CRT_FILE) {
@@ -89,7 +87,7 @@ async function init() {
   server.listen(config.PORT, config.HOST);
   // Following functions iterate over in-memory rooms
   setInterval(minuteMetrics, 60 * 1000);
-  setInterval(release, releaseInterval / releaseBatches);
+  setInterval(release, releaseInterval);
   setInterval(freeUnusedRooms, 5 * 60 * 1000);
   saveRooms();
   if (process.env.NODE_ENV === 'development') {
@@ -607,15 +605,12 @@ async function saveRooms() {
   }
 }
 
-let currBatch = 0;
 async function release() {
   // Reset VMs in rooms that are:
   // older than the session limit
   // assigned to a room with no users
-  const roomArr = Array.from(rooms.values()).filter((room) => {
-    return hashString(room.roomId) % releaseBatches === currBatch;
-  });
-  console.log('[RELEASE][%s] %s rooms in batch', currBatch, roomArr.length);
+  const roomArr = Array.from(rooms.values());
+  console.log('[RELEASE] %s rooms in batch', roomArr.length);
   for (let i = 0; i < roomArr.length; i++) {
     const room = roomArr[i];
     if (room.vBrowser && room.vBrowser.assignTime) {
@@ -628,7 +623,7 @@ async function release() {
       const isRoomIdle =
         Date.now() - Number(room.lastUpdateTime) > 5 * 60 * 1000;
       if (isTimedOut || (isRoomEmpty && isRoomIdle)) {
-        console.log('[RELEASE][%s] VM in room:', currBatch, room.roomId);
+        console.log('[RELEASE] VM in room:', room.roomId);
         room.stopVBrowserInternal();
         if (isTimedOut) {
           room.addChatMessage(null, {
@@ -650,8 +645,11 @@ async function release() {
         });
       }
     }
+    // We want to spread out the jobs over about half the release interval
+    // This gives other jobs some CPU time
+    const waitTime = releaseInterval / 2 / roomArr.length;
+    await new Promise((resolve) => setTimeout(resolve, waitTime));
   }
-  currBatch = (currBatch + 1) % releaseBatches;
 }
 
 async function minuteMetrics() {

src/utils/hash.ts

@@ -0,0 +1,40 @@
+// Extremely simple function to convert a string to a number for bucketing
+// Will return the same value for the same letters, regardless of order (collisions very likely)
+export function hashString(input: string) {
+  var hash = 0;
+  for (var i = 0; i < input.length; i++) {
+    var charCode = input.charCodeAt(i);
+    hash += charCode;
+  }
+  return hash;
+}
+
+// An improved alternative:
+// cyrb53 (c) 2018 bryc (github.com/bryc). License: Public domain. Attribution appreciated.
+// A fast and simple 64-bit (or 53-bit) string hash function with decent collision resistance.
+// Largely inspired by MurmurHash2/3, but with a focus on speed/simplicity.
+// See https://stackoverflow.com/questions/7616461/generate-a-hash-from-string-in-javascript/52171480#52171480
+// https://github.com/bryc/code/blob/master/jshash/experimental/cyrb53.js
+export const cyrb53 = (str: string, seed = 0) => {
+  let h1 = 0xdeadbeef ^ seed,
+    h2 = 0x41c6ce57 ^ seed;
+  for (let i = 0, ch; i < str.length; i++) {
+    ch = str.charCodeAt(i);
+    h1 = Math.imul(h1 ^ ch, 2654435761);
+    h2 = Math.imul(h2 ^ ch, 1597334677);
+  }
+  h1 = Math.imul(h1 ^ (h1 >>> 16), 2246822507);
+  h1 ^= Math.imul(h2 ^ (h2 >>> 13), 3266489909);
+  h2 = Math.imul(h2 ^ (h2 >>> 16), 2246822507);
+  h2 ^= Math.imul(h1 ^ (h1 >>> 13), 3266489909);
+
+  return 4294967296 * (2097151 & h2) + (h1 >>> 0);
+};
+// If we want all 64 bits of the output:
+/*
+return [h2>>>0, h1>>>0];
+// or
+return (h2>>>0).toString(16).padStart(8,0)+(h1>>>0).toString(16).padStart(8,0);
+// or 
+return 4294967296n * BigInt(h2) + BigInt(h1);
+*/

src/utils/index.ts

@@ -4,6 +4,7 @@ import { MD5 } from './md5';
 import firebase from 'firebase/compat/app';
 import { XMLParser } from 'fast-xml-parser';
 import config from '../config';
+import { cyrb53 } from './hash';
 
 export function formatTimestamp(input: any, wallClock?: boolean): string {
   if (
@@ -54,15 +55,6 @@ export function formatSize(input: number) {
   return input + ' B';
 }
 
-export function hashString(input: string) {
-  var hash = 0;
-  for (var i = 0; i < input.length; i++) {
-    var charCode = input.charCodeAt(i);
-    hash += charCode;
-  }
-  return hash;
-}
-
 export const colorMappings: StringDict = {
   red: 'B03060',
   orange: 'FE9A76',
@@ -98,7 +90,7 @@ export function getColorForString(id: string) {
   if (colorCache[id]) {
     return colors[colorCache[id]];
   }
-  colorCache[id] = Math.abs(hashString(id)) % colors.length;
+  colorCache[id] = Math.abs(cyrb53(id)) % colors.length;
   return colors[colorCache[id]];
 }