MOBILE-3036 core: Define different cache expiration times

src/classes/site.ts

@@ -117,11 +117,13 @@ export interface CoreSiteWSPreSets {
     /**
      * Wehther a pending request in the queue matching the same function and arguments can be reused instead of adding
      * a new request to the queue. Defaults to true for read requests.
+     * @type {boolean}
      */
     reusePending?: boolean;
 
     /**
      * Whether the request will be be sent immediately as a single request. Defaults to false.
+     * @type {boolean}
      */
     skipQueue?: boolean;
 
@@ -129,6 +131,14 @@ export interface CoreSiteWSPreSets {
      * Cache the response if it returns an errorcode present in this list.
      */
     cacheErrors?: string[];
+
+    /**
+     * Update frequency. This value determines how often the cached data will be updated. Possible values:
+     * CoreSite.FREQUENCY_USUALLY, CoreSite.FREQUENCY_OFTEN, CoreSite.FREQUENCY_SOMETIMES, CoreSite.FREQUENCY_RARELY.
+     * Defaults to CoreSite.FREQUENCY_USUALLY.
+     * @type {number}
+     */
+    updateFrequency?: number;
 }
 
 /**
@@ -184,6 +194,12 @@ export class CoreSite {
     // @todo Set REQUEST_QUEUE_FORCE_WS to false before the release.
     static REQUEST_QUEUE_FORCE_WS = true; // Use "tool_mobile_call_external_functions" even for calling a single function.
 
+    // Constants for cache update frequency.
+    static FREQUENCY_USUALLY = 0;
+    static FREQUENCY_OFTEN = 1;
+    static FREQUENCY_SOMETIMES = 2;
+    static FREQUENCY_RARELY = 3;
+
     // List of injected services. This class isn't injectable, so it cannot use DI.
     protected appProvider: CoreAppProvider;
     protected dbProvider: CoreDbProvider;
@@ -213,6 +229,14 @@ export class CoreSite {
         3.7: 2019052000
     };
 
+    // Possible cache update frequencies.
+    protected UPDATE_FREQUENCIES = [
+        CoreConfigConstants.cache_update_frequency_usually || 420000,
+        CoreConfigConstants.cache_update_frequency_often || 1200000,
+        CoreConfigConstants.cache_update_frequency_sometimes || 3600000,
+        CoreConfigConstants.cache_update_frequency_rarely || 43200000
+    ];
+
     // Rest of variables.
     protected logger;
     protected db: SQLiteDB;
@@ -1016,11 +1040,22 @@ export class CoreSite {
 
         return promise.then((entry) => {
             const now = Date.now();
+            let expirationTime;
 
             preSets.omitExpires = preSets.omitExpires || !this.appProvider.isOnline();
 
             if (!preSets.omitExpires) {
-                if (now > entry.expirationTime) {
+                let expirationDelay = this.UPDATE_FREQUENCIES[preSets.updateFrequency] ||
+                        this.UPDATE_FREQUENCIES[CoreSite.FREQUENCY_USUALLY];
+
+                if (this.appProvider.isNetworkAccessLimited()) {
+                    // Not WiFi, increase the expiration delay a 50% to decrease the data usage in this case.
+                    expirationDelay *= 1.5;
+                }
+
+                expirationTime = entry.expirationTime + expirationDelay;
+
+                if (now > expirationTime) {
                     this.logger.debug('Cached element found, but it is expired');
 
                     return Promise.reject(null);
@@ -1028,8 +1063,12 @@ export class CoreSite {
             }
 
             if (typeof entry != 'undefined' && typeof entry.data != 'undefined') {
-                const expires = (entry.expirationTime - now) / 1000;
-                this.logger.info(`Cached element found, id: ${id} expires in ${expires} seconds`);
+                if (!expirationTime) {
+                    this.logger.info(`Cached element found, id: ${id}. Expiration time ignored.`);
+                } else {
+                    const expires = (expirationTime - now) / 1000;
+                    this.logger.info(`Cached element found, id: ${id}. Expires in expires in ${expires} seconds`);
+                }
 
                 return this.textUtils.parseJSON(entry.data, {});
             }
@@ -1064,15 +1103,15 @@ export class CoreSite {
         }
 
         return promise.then(() => {
+            // Since 3.7, the expiration time contains the time the entry is modified instead of the expiration time.
+            // We decided to reuse this field to prevent modifying the database table.
             const id = this.getCacheId(method, data),
                 entry: any = {
                     id: id,
-                    data: JSON.stringify(response)
+                    data: JSON.stringify(response),
+                    expirationTime: Date.now()
                 };
-            let cacheExpirationTime = CoreConfigConstants.cache_expiration_time;
 
-            cacheExpirationTime = isNaN(cacheExpirationTime) ? 300000 : cacheExpirationTime;
-            entry.expirationTime = new Date().getTime() + cacheExpirationTime;
             if (preSets.cacheKey) {
                 entry.key = preSets.cacheKey;
             }

src/config.json

@@ -4,7 +4,10 @@
     "desktopappname": "Moodle Desktop",
     "versioncode": 3700,
     "versionname": "3.7.0-dev",
-    "cache_expiration_time": 300000,
+    "cache_update_frequency_usually": 420000,
+    "cache_update_frequency_often": 1200000,
+    "cache_update_frequency_sometimes": 3600000,
+    "cache_update_frequency_rarely": 43200000,
     "default_lang": "en",
     "languages": {
         "ar": "عربي",

upgrade.txt

@@ -4,6 +4,7 @@ information provided here is intended especially for developers.
 === 3.7.0 ===
 
 - The pushnotifications addon has been moved to core. All imports of that addon need to be fixed to use the right path and name.
+- Now the expirationTime of cache entries contains the time the entry was modified, not the expiration time. This is to allow calculating dynamic expiration times. We decided to reuse the same field to prevent modifying the database table.
 
 === 3.6.1 ===