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worker-pools.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: 工作池</title>
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</head>
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<body>
<div class="example" id="worker-pools">
<h2><a href="./">Go by Example 中文版</a>: 工作池</h2>
<table>
<tr>
<td class="docs">
<p>在这个例子中，我们将看到如何使用协程与通道实现一个_工作池_。</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://play.studygolang.com/p/Ai3RKixtXs9"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>
<span class="s">"fmt"</span>
<span class="s">"time"</span>
<span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这是 worker 程序，我们会并发的运行多个 worker。
worker 将在 <code>jobs</code> 频道上接收工作，并在 <code>results</code> 上发送相应的结果。
每个 worker 我们都会 sleep 一秒钟，以模拟一项昂贵的（耗时一秒钟的）任务。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">func</span> <span class="nf">worker</span><span class="p">(</span><span class="nx">id</span> <span class="kt">int</span><span class="p">,</span> <span class="nx">jobs</span> <span class="o"><-</span><span class="kd">chan</span> <span class="kt">int</span><span class="p">,</span> <span class="nx">results</span> <span class="kd">chan</span><span class="o"><-</span> <span class="kt">int</span><span class="p">)</span> <span class="p">{</span>
<span class="k">for</span> <span class="nx">j</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">jobs</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"worker"</span><span class="p">,</span> <span class="nx">id</span><span class="p">,</span> <span class="s">"started job"</span><span class="p">,</span> <span class="nx">j</span><span class="p">)</span>
<span class="nx">time</span><span class="p">.</span><span class="nf">Sleep</span><span class="p">(</span><span class="nx">time</span><span class="p">.</span><span class="nx">Second</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"worker"</span><span class="p">,</span> <span class="nx">id</span><span class="p">,</span> <span class="s">"finished job"</span><span class="p">,</span> <span class="nx">j</span><span class="p">)</span>
<span class="nx">results</span> <span class="o"><-</span> <span class="nx">j</span> <span class="o">*</span> <span class="mi">2</span>
<span class="p">}</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>为了使用 worker 工作池并且收集其的结果，我们需要 2 个通道。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">const</span> <span class="nx">numJobs</span> <span class="p">=</span> <span class="mi">5</span>
<span class="nx">jobs</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">int</span><span class="p">,</span> <span class="nx">numJobs</span><span class="p">)</span>
<span class="nx">results</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">int</span><span class="p">,</span> <span class="nx">numJobs</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这里启动了 3 个 worker，
初始是阻塞的，因为还没有传递任务。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="k">for</span> <span class="nx">w</span> <span class="o">:=</span> <span class="mi">1</span><span class="p">;</span> <span class="nx">w</span> <span class="o"><=</span> <span class="mi">3</span><span class="p">;</span> <span class="nx">w</span><span class="o">++</span> <span class="p">{</span>
<span class="k">go</span> <span class="nf">worker</span><span class="p">(</span><span class="nx">w</span><span class="p">,</span> <span class="nx">jobs</span><span class="p">,</span> <span class="nx">results</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这里我们发送 5 个 <code>jobs</code>，
然后 <code>close</code> 这些通道，表示这些就是所有的任务了。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="k">for</span> <span class="nx">j</span> <span class="o">:=</span> <span class="mi">1</span><span class="p">;</span> <span class="nx">j</span> <span class="o"><=</span> <span class="nx">numJobs</span><span class="p">;</span> <span class="nx">j</span><span class="o">++</span> <span class="p">{</span>
<span class="nx">jobs</span> <span class="o"><-</span> <span class="nx">j</span>
<span class="p">}</span>
<span class="nb">close</span><span class="p">(</span><span class="nx">jobs</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>最后，我们收集所有这些任务的返回值。
这也确保了所有的 worker 协程都已完成。
另一个等待多个协程的方法是使用<a href="waitgroups">WaitGroup</a>。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="k">for</span> <span class="nx">a</span> <span class="o">:=</span> <span class="mi">1</span><span class="p">;</span> <span class="nx">a</span> <span class="o"><=</span> <span class="nx">numJobs</span><span class="p">;</span> <span class="nx">a</span><span class="o">++</span> <span class="p">{</span>
<span class="o"><-</span><span class="nx">results</span>
<span class="p">}</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
<p>运行程序，显示 5 个任务被多个 worker 执行。
尽管所有的工作总共要花费 5 秒钟，但该程序只花了 2 秒钟，
因为 3 个 worker 是并行的。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="gp">$</span> time go run worker-pools.go
<span class="go">worker 1 started job 1
</span><span class="go">worker 2 started job 2
</span><span class="go">worker 3 started job 3
</span><span class="go">worker 1 finished job 1
</span><span class="go">worker 1 started job 4
</span><span class="go">worker 2 finished job 2
</span><span class="go">worker 2 started job 5
</span><span class="go">worker 3 finished job 3
</span><span class="go">worker 1 finished job 4
</span><span class="go">worker 2 finished job 5</span></pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code">
<pre class="chroma"><span class="go">real 0m2.358s</span></pre>
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="waitgroups">WaitGroup</a>
</p>
<p class="footer">
<a href="https://twitter.com/mmcgrana">@mmcgrana</a> 和<a href="https://eli.thegreenplace.net">Eli Bendersky</a>编写 | <a href="https://github.com/gobyexample-cn">gobyexample-cn</a> 翻译 | <a href="https://github.com/gobyexample-cn/gobyexample/issues">反馈</a> | <a href="https://github.com/gobyexample-cn/gobyexample">源码</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a> </p>
</p>
</div>
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