Context原理及其适用场景 随手记 李帅(飞雪无情) n 常见并发模式 n Context实现原理 n TLS VS Context n 典型适用场景 大纲 Channel Fan-in func fanIn(sum1, sum2 <-chan int) <-chan int { sum := make(chan int) go func() { for {sum <- <-sum1} } } Context l 一个任务，需要多个goroutine完成 l 一个请求，会触发好多个goroutine做不同的事情 l 如果我们的任务终止了，请求取消了，这些正在运行 的goroutine怎么办？ l 使用Context来简化这些操作 Context能做什么 u 手动、定时、超时发出取消信号 u 跨API传值 u 控制生成Context树结构（Context链） Context main() { rootCtx := context.Background() ctx, cancel := context.WithCancel(rootCtx) go watch(ctx) go watch(ctx) time.Sleep(1 * time.Second) cancel() } func watch(ctx context.Context) { for { select {

响应对象 响应对象功能和方法 HTTP 响应的内容 在 Web 服务器接收请求处理后，向客户端发送 HTTP 响应 （Response）。 O 响应的内容 ▶ 响应状态（Status Code） ▶ 响应头（Response Header） ▶ 响应体（Response Body） 大纲 HTTP 响应的内容 HTTP 响应对象 响应对象功能和方法 ‚ HTTP 响应状态行 表明响应的状态信息，如成功、失败、错误。 告知客户可以接收的字符集：Accept-Charset 3. 响应的字符编码集：Accept-Encoding 4. 响应体的 MIME 类型：Content-Type 5. 响应体的语言类型：Context-Language 6. 响应体的长度和字节数：Content-Length 7. 通知客户端到期时间：Expires 8. 缓存情况：Cache-Control 9. 重定向到另一个 URL 向客户端发送指定的错误信息码，可以是任意定义的整数。 1 response.setCharacterEncoding("GBK"); 2 response.sendError(580); O public void sendError(int sc, String msg) throws IOException 向客户端发送指定的错误信息码和自定义状态消息。 1 response.setCharacterEncoding("GBK");

. . . . . . . . 86 1.14 The Application Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 1.15 The Request Context . . . . . . . . . . . . . . . . . . . . a request in order to stay threadsafe. This approach is convenient, but requires a valid request context for dependency injection or when attempting to reuse code which uses a value pegged to the request use the test_request_context() method to try out url_for(). test_request_context() tells Flask to behave as though it’s handling a request even while we use a Python shell. See Context Locals. from flask

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 5.4.2 Request & Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 5.4.3 WebSocket Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 5.4.2 Request & Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 5.4.3 WebSocket Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 5.4.2 Request & Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.4.3 WebSocket Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 5.4.2 Request & Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.4.3 WebSocket Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 5.4.2 Request & Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.4.3 WebSocket Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 5.4.2 Request & Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 5.4.3 WebSocket Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 5.4.2 Request & Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.4.3 WebSocket Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs Highly-optimized, extensible code base • Easy access to headers and bodies through request and response objects • DRY request processing via middleware components and hooks • Strict adherence to RFCs