Merge pull request #156 from MRuy/147-add-cache-for-gettopusers

Add cache for getTopUsers

config.json.example

@@ -23,6 +23,7 @@
     "readOnly": false,
     "webhooks": [],
     "categoryList": ["sponsor", "intro", "outro", "interaction", "selfpromo", "music_offtopic"], // List of supported categories any other category will be rejected
+    "getTopUsersCacheTimeMinutes": 5, // cacheTime for getTopUsers result in minutes
     "maxNumberOfActiveWarnings": 3, // Users with this number of warnings will be blocked until warnings expire
     "hoursAfterWarningExpire": 24,
     "rateLimit": {

src/routes/getTopUsers.js

@@ -1,34 +1,18 @@
 var db = require('../databases/databases.js').db;
+const logger = require('../utils/logger.js');
+const createMemoryCache = require('../utils/createMemoryCache.js');
+const config = require('../config.js');
 
-module.exports = function getTopUsers (req, res) {
-  let sortType = req.query.sortType;
-  let categoryStatsEnabled = req.query.categoryStats;
+const MILLISECONDS_IN_MINUTE = 60000;
+const getTopUsersWithCache = createMemoryCache(generateTopUsersStats, config.getTopUsersCacheTimeMinutes * MILLISECONDS_IN_MINUTE);
 
-  if (sortType == undefined) {
-      //invalid request
-      res.sendStatus(400);
-      return;
-  }
-
-  //setup which sort type to use
-  let sortBy = "";
-  if (sortType == 0) {
-      sortBy = "minutesSaved";
-  } else if (sortType == 1) {
-      sortBy = "viewCount";
-  } else if (sortType == 2) {
-      sortBy = "totalSubmissions";
-  } else {
-      //invalid request
-      res.sendStatus(400);
-      return;
-  }
-
-  let userNames = [];
-  let viewCounts = [];
-  let totalSubmissions = [];
-  let minutesSaved = [];
-  let categoryStats = categoryStatsEnabled ? [] : undefined;
+function generateTopUsersStats(sortBy, categoryStatsEnabled = false) {
+  return new Promise((resolve, reject) => {
+    const userNames = [];
+    const viewCounts = [];
+    const totalSubmissions = [];
+    const minutesSaved = [];
+    const categoryStats = categoryStatsEnabled ? [] : undefined;
     
     let additionalFields = '';
     if (categoryStatsEnabled) {
@@ -40,7 +24,7 @@ module.exports = function getTopUsers (req, res) {
                           "SUM(CASE WHEN category = 'music_offtopic' THEN 1 ELSE 0 END) as categoryMusicOfftopic, ";
     }
 
-  let rows = db.prepare('all', "SELECT COUNT(*) as totalSubmissions, SUM(views) as viewCount," + 
+    const rows = db.prepare('all', "SELECT COUNT(*) as totalSubmissions, SUM(views) as viewCount," + 
                     "SUM((sponsorTimes.endTime - sponsorTimes.startTime) / 60 * sponsorTimes.views) as minutesSaved, " +
                     "SUM(votes) as userVotes, " +
                     additionalFields +
@@ -68,12 +52,41 @@ module.exports = function getTopUsers (req, res) {
         }
     }
     
-  //send this result
-  res.send({
+    resolve({
       userNames,
       viewCounts,
       totalSubmissions,
       minutesSaved,
       categoryStats
     });
+  });
+}
+
+module.exports = async function getTopUsers (req, res) {
+  let sortType = req.query.sortType;
+  let categoryStatsEnabled = req.query.categoryStats;
+
+  if (sortType == undefined) {
+      //invalid request
+      res.sendStatus(400);
+      return;
+  }
+  
+  //setup which sort type to use
+  let sortBy = '';
+  if (sortType == 0) {
+    sortBy = 'minutesSaved';
+  } else if (sortType == 1) {
+    sortBy = 'viewCount';
+  } else if (sortType == 2) {
+    sortBy = 'totalSubmissions';
+  } else {
+    //invalid request
+    return res.sendStatus(400);
+  }
+  
+  const stats = await getTopUsersWithCache(sortBy, categoryStatsEnabled);
+  
+  //send this result
+  res.send(stats);
 }

src/utils/createMemoryCache.js

@@ -0,0 +1,42 @@
+module.exports = function createMemoryCache(memoryFn, cacheTimeMs) {
+  // holds the promise results
+  const cache = new Map();
+  // holds the promises that are not fulfilled
+  const promiseMemory = new Map();
+  return (...args) => {
+    // create cacheKey by joining arguments as string
+    const cacheKey = args.join('.');
+    // check if promising is already running
+    if (promiseMemory.has(cacheKey)) {
+      return promiseMemory.get(cacheKey);
+    }
+    else {
+      // check if result is in cache
+      if (cache.has(cacheKey)) {
+        const cacheItem = cache.get(cacheKey);
+        const now = Date.now();
+        // check if cache is valid
+        if (!(cacheItem.cacheTime + cacheTimeMs < now)) {
+          return Promise.resolve(cacheItem.result);
+        }
+      }
+      // create new promise
+      const promise = new Promise(async (resolve, reject) => {
+        resolve((await memoryFn(...args)));
+      });
+      // store promise reference until fulfilled
+      promiseMemory.set(cacheKey, promise);
+      return promise.then(result => {
+        // store promise result in cache
+        cache.set(cacheKey, {
+          result,
+          cacheTime: Date.now(),
+        });
+        // remove fulfilled promise from memory
+        promiseMemory.delete(cacheKey);
+        // return promise result
+        return result;
+      });
+    }
+  };
+};