Async poolify with dalayed requests

tshemsedinov · tshemsedinov · commit 4ca0f8211e5d · 2018-01-07T14:34:09.000+02:00
diff --git a/JavaScript/5-async.js b/JavaScript/5-async.js
@@ -0,0 +1,65 @@
+'use strict';
+
+const poolify = (factory, min, norm, max) => {
+
+  const duplicate = n => new Array(n).fill().map(() => factory());
+
+  const pool = (par) => {
+    if (typeof(par) !== 'function') {
+      if (pool.items.length < max) {
+        const delayed = pool.delayed.pop();
+        if (delayed) {
+          console.log('Recycle item, pass to delayed');
+          delayed(par);
+          return;
+        } else {
+          pool.items.push(par);
+        }
+      }
+      console.log('Recycle item, count =', pool.items.length);
+      return;
+    }
+    if (pool.items.length < min) {
+      const items = duplicate(norm - pool.items.length);
+      pool.items.push(...items);
+    }
+    const res = pool.items.pop();
+    console.log('Get from pool, count =', pool.items.length);
+    if (res) {
+      par(res);
+    } else {
+      pool.delayed.push(par);
+      console.log('Request delayed');
+    }
+    return pool;
+  };
+
+  return Object.assign(pool, {
+    items: duplicate(norm),
+    delayed: []
+  });
+
+};
+
+// Usage
+
+// Factory to allocate 4kb buffer
+const buffer = () => new Uint32Array(128);
+
+// Allocate pool of 10 buffers
+const pool = poolify(buffer, 0, 5, 10);
+
+let i = 0;
+
+const next = () => {
+  pool(item => {
+    console.log('Buffer size', item.length * 32);
+    i++;
+    if (i < 10) {
+      setTimeout(next, i * 10);
+      setTimeout(() => pool(item), i * 100);
+    }
+  });
+};
+
+next();
