Improve LRU cache behavior

src/source/source_cache.js

@@ -409,6 +409,7 @@ class SourceCache extends Evented {
         if (!tile) {
             tile = this._cache.get(wrapped.id);
             if (tile) {
+                this._cache.remove(wrapped.id);
                 tile.redoPlacement(this._source);
                 if (this._cacheTimers[wrapped.id]) {
                     clearTimeout(this._cacheTimers[wrapped.id]);
@@ -446,7 +447,7 @@ class SourceCache extends Evented {
         const tileExpires = tile.getExpiry();
         if (tileExpires) {
             this._cacheTimers[id] = setTimeout(() => {
-                this._cache.remove(id);
+                this._cache.remove(id, true);
                 this._cacheTimers[id] = undefined;
             }, tileExpires - new Date().getTime());
         }

src/util/lru_cache.js

@@ -62,8 +62,7 @@ class LRUCache<T> {
             this.order.push(key);
 
             if (this.order.length > this.max) {
-                const removedData = this.get(this.order[0]);
-                if (removedData) this.onRemove(removedData);
+                this.remove(this.order[0], true);
             }
         }
 
@@ -104,8 +103,8 @@ class LRUCache<T> {
 
         const data = this.data[key];
 
-        delete this.data[key];
         this.order.splice(this.order.indexOf(key), 1);
+        this.order.push(key);
 
         return data;
     }
@@ -117,12 +116,16 @@ class LRUCache<T> {
      * @returns {LRUCache} this cache
      * @private
      */
-    remove(key: string) {
+    remove(key: string, expired: boolean) {
         if (!this.has(key)) { return this; }
 
         const data = this.data[key];
         delete this.data[key];
-        this.onRemove(data);
+
+        if (expired) {
+            this.onRemove(data);
+        }
+
         this.order.splice(this.order.indexOf(key), 1);
 
         return this;
@@ -139,8 +142,7 @@ class LRUCache<T> {
         this.max = max;
 
         while (this.order.length > this.max) {
-            const removedData = this.get(this.order[0]);
-            if (removedData) this.onRemove(removedData);
+            this.remove(this.order[0], true);
         }
 
         return this;

test/unit/source/source_cache.test.js

@@ -871,7 +871,7 @@ test('SourceCache#findLoadedParent', (t) => {
         t.equal(sourceCache.findLoadedParent(new TileCoord(2, 3, 3), 0, retain), undefined);
         t.equal(sourceCache.findLoadedParent(new TileCoord(2, 0, 0), 0, retain), tile);
         t.deepEqual(retain, expectedRetain);
-        t.equal(sourceCache._cache.order.length, 0);
+        t.equal(sourceCache._cache.order.length, 1);
 
         t.end();
     });

test/unit/util/lru_cache.test.js

@@ -12,9 +12,22 @@ test('LRUCache', (t) => {
     t.deepEqual(cache.keys(), ['washington'], '.keys()');
     t.equal(cache.has('washington'), true, '.has()');
     t.equal(cache.get('washington'), 'dc', '.get()');
-    t.equal(cache.get('washington'), null, '.get()');
-    t.equal(cache.has('washington'), false, '.has()');
-    t.deepEqual(cache.keys(), [], '.keys()');
+    t.equal(cache.get('washington'), 'dc', '.get()');
+    t.equal(cache.has('washington'), true, '.has()');
+    t.deepEqual(cache.keys(), ['washington'], '.keys()');
+    t.end();
+});
+
+test('LRUCache - get moves key to top of order stack', (t) => {
+    const cache = new LRUCache(10, (removed) => {
+        t.equal(removed, 'dc');
+    });
+    t.equal(cache.add('washington', 'dc'), cache, '.add()');
+    t.equal(cache.add('san francisco', 'ca'), cache, '.add()');
+    t.deepEqual(cache.keys(), ['washington', 'san francisco'], '.keys()');
+    t.equal(cache.has('washington'), true, '.has()');
+    t.equal(cache.get('washington'), 'dc', '.get()');
+    t.deepEqual(cache.keys(), ['san francisco', 'washington'], '.keys()');
     t.end();
 });
 
@@ -33,7 +46,11 @@ test('LRUCache - duplicate add', (t) => {
 });
 
 test('LRUCache - remove', (t) => {
-    const cache = new LRUCache(10, () => {});
+    let called;
+    const cache = new LRUCache(10, (removed) => {
+        t.equal(removed, 'dc');
+        called = true;
+    });
 
     cache.add('washington', 'dc');
     cache.add('baltimore', 'md');
@@ -49,6 +66,10 @@ test('LRUCache - remove', (t) => {
 
     t.ok(cache.remove('baltimore'));
 
+    t.notOk(called);
+    cache.remove('washington', true);
+    t.ok(called);
+
     t.end();
 });