20 Building a Multithreaded Web Server.md

经过漫长的旅程，我们终于快到了书的终点。这章中，我将会创建一个项目来展示我们曾经学过的知识，并且也可以回顾我们之前学过的知识

下面是我们创建web服务器的计划

1. 学习一些关于TCP和HTTP的知识。
2. 在socket上监听TCP的连接。
3. 解析少量的HTTP请求。
4. 创建一个适当的 response
5. 用线程池来提供吞吐量。

在实现之前，我们需要说一个细节，我们实现的方法不是最好的实现web服务器的方法。在 crate.io中有很多产品级的库，可以提供更多完整的web服务以及线程池。

因为Rust是个系统编程语言呢，我们可以达到更低的抽象级别，而且是别的编程语言达不到的级别。我们将会手续底层的HTTP服务器，还有线程池，这样你可以学习到总体的思想核技术，在以后你可能会用到这些。

1 Building a Single-Threaded Web Server

1.1 Listening to the TCP Connection

1.2 Reading the Request

1.3 A Closer Look at an HTTP Request

1.4 Writing a Response

1.5 Returning Real HTML

1.5 Validating the Request and Selectively Responding

1.6 A Touch of Refactoring

2 Turning Our Single-Threaded Server into a Multithreaded Server

2.1 Simulating a Slow Request in the Current Server Implementation

2.2 Improving Throughput with a Thread Pool

2.2.1 Code Structure If We Could Spawn a Thread for Each Request

2.2.2 Creating a Similar Interface for a Finite Number of Threads

2.2.3 building the threadpool struct using compiler driven development

2.2.4 Validating the Number of Threads in new

2.2.5 Creating Space to Store the Threads

2.2.6 A Worker Struct Responsible for Sending Code from the ThreadPool to a Thread

2.2.7 Sending Requests to Threads via Channels

3 Graceful Shutdown and Cleanup

3.1 Implementing the Drop Trait on ThreadPool

The error tells us we can’t call join because we only have a mutable borrow of each worker and join takes ownership of its argument. We did this in Listing 17-15: if Worker holds an Option<thread::JoinHandle<()>> instead, we can call the take method on the Option to move the value out of the Some variant and leave a None variant in its place.

3.2 Signaling to the Threads to Stop Listening for Jobs

We could do more here! If you want to continue enhancing this project, here are some ideas:

• Add more documentation to ThreadPool and its public methods.
• Add tests of the library’s functionality.
• Change calls to unwrap to more robust error handling.
• Use ThreadPool to perform some task other than serving web requests.
• Find a thread pool crate on crates.io and implement a similar web server using the crate instead. Then compare its API and robustness to the thread pool we implemented.

4 Summary