docs(workerpool): bring up

README.md

@@ -41,6 +41,7 @@ Utilities for [Hexo].
 - [truncate](#truncatestr-options)
 - [unescapeHTML](#unescapehtmlstr)
 - [url_for](#url_forpath-option)
+- [WorkerPool](#workerpool)
 - [bind(hexo)](#bindhexo)
 
 ## Installation
@@ -665,6 +666,64 @@ url_for('/css/style.css', {relative: false})
 // /css/style.css
 ```
 
+## WorkerPool
+
+A worker management utility designed for multi-core job running.
+
+**`new WorkerPool(workerPath[, numberOfThreads])`**
+
+initializing a WorkerPool.
+
+- `workerPath`: `<string>` The path to `worker.js` file
+- `numberOfThreads`: `<number>` The number of workers will be created. Default value is `require('os').cpus().length`.
+
+```js
+const { WorkerPool } = require('hexo-util');
+const pool = new WorkerPool(workerPath, 2);
+```
+
+**`workerpool.run(data)`**
+
+Add tasks to the queue and execute when there is an inactive worker.
+
+- `data`: `<any>` The parameter will be passed to `worker.js` function.
+- Return: `<Promise>`
+
+```js
+async () => {
+  const result = await pool.run();
+}
+```
+
+**`workerpool.destroy(force)`**
+
+Destroy the WorkerPool by terminating every workers created under the WorkerPool.
+
+- `force`: `<boolean>`. Default is `false`.
+
+```js
+pool.destroy();
+```
+
+If there is a worker is still executing, an Error will be thrown:
+
+```
+The worker [id of the worker] is still runing!
+```
+
+You can force destroy a workerpool by passing a `true` to it:
+
+```js
+pool.destroy(true);
+```
+
+----
+
+Also, there are other internal functions. Avoid using them directly.
+
+- `workerpool.getInactiveWorkerId()` - Rerturn the id of the first incactive worker in the workerpool. Return `-1` if no incactive worker is found.
+- `workerpool.runWorker(workerId, taskObj)` - Run given task in a specific worker.
+
 ## bind(hexo)
 
 Following utilities require `bind(hexo)` / `bind(this)` / `call(hexo, input)` / `call(this, input)` to parse the user config when initializing: