424 lines
19 KiB
Markdown
424 lines
19 KiB
Markdown
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# 34 | 自己动手写高性能HTTP服务器（三）：TCP字节流处理和HTTP协议实现
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你好，我是盛延敏，这里是网络编程实战第34讲，欢迎回来。
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这一讲，我们延续第33讲的话题，继续解析高性能网络编程框架的字节流处理部分，并为网络编程框架增加HTTP相关的功能，在此基础上完成HTTP高性能服务器的编写。
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## buffer对象
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你肯定在各种语言、各种框架里面看到过不同的buffer对象，buffer，顾名思义，就是一个缓冲区对象，缓存了从套接字接收来的数据以及需要发往套接字的数据。
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如果是从套接字接收来的数据，事件处理回调函数在不断地往buffer对象增加数据，同时，应用程序需要不断把buffer对象中的数据处理掉，这样，buffer对象才可以空出新的位置容纳更多的数据。
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如果是发往套接字的数据，应用程序不断地往buffer对象增加数据，同时，事件处理回调函数不断调用套接字上的发送函数将数据发送出去，减少buffer对象中的写入数据。
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可见，buffer对象是同时可以作为输入缓冲（input buffer）和输出缓冲（output buffer）两个方向使用的，只不过，在两种情形下，写入和读出的对象是有区别的。
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这张图描述了buffer对象的设计。
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下面是buffer对象的数据结构。
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```
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//数据缓冲区
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struct buffer {
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char *data; //实际缓冲
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int readIndex; //缓冲读取位置
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int writeIndex; //缓冲写入位置
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int total_size; //总大小
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};
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```
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buffer对象中的writeIndex标识了当前可以写入的位置；readIndex标识了当前可以读出的数据位置，图中红色部分从readIndex到writeIndex的区域是需要读出数据的部分，而绿色部分从writeIndex到缓存的最尾端则是可以写出的部分。
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随着时间的推移，当readIndex和writeIndex越来越靠近缓冲的尾端时，前面部分的front\_space\_size区域变得会很大，而这个区域的数据已经是旧数据，在这个时候，就需要调整一下整个buffer对象的结构，把红色部分往左侧移动，与此同时，绿色部分也会往左侧移动，整个缓冲区的可写部分就会变多了。
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make\_room函数就是起这个作用的，如果右边绿色的连续空间不足以容纳新的数据，而最左边灰色部分加上右边绿色部分一起可以容纳下新数据，就会触发这样的移动拷贝，最终红色部分占据了最左边，绿色部分占据了右边，右边绿色的部分成为一个连续的可写入空间，就可以容纳下新的数据。下面的一张图解释了这个过程。
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下面是make\_room的具体实现。
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```
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void make_room(struct buffer *buffer, int size) {
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if (buffer_writeable_size(buffer) >= size) {
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return;
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}
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//如果front_spare和writeable的大小加起来可以容纳数据，则把可读数据往前面拷贝
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if (buffer_front_spare_size(buffer) + buffer_writeable_size(buffer) >= size) {
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int readable = buffer_readable_size(buffer);
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int i;
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for (i = 0; i < readable; i++) {
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memcpy(buffer->data + i, buffer->data + buffer->readIndex + i, 1);
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}
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buffer->readIndex = 0;
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buffer->writeIndex = readable;
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} else {
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//扩大缓冲区
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void *tmp = realloc(buffer->data, buffer->total_size + size);
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if (tmp == NULL) {
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return;
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}
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buffer->data = tmp;
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buffer->total_size += size;
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}
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}
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```
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当然，如果红色部分占据过大，可写部分不够，会触发缓冲区的扩大操作。这里我通过调用realloc函数来完成缓冲区的扩容。
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下面这张图对此做了解释。
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## 套接字接收数据处理
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套接字接收数据是在tcp\_connection.c中的handle\_read来完成的。在这个函数里，通过调用buffer\_socket\_read函数接收来自套接字的数据流，并将其缓冲到buffer对象中。之后你可以看到，我们将buffer对象和tcp\_connection对象传递给应用程序真正的处理函数messageCallBack来进行报文的解析工作。这部分的样例在HTTP报文解析中会展开。
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```
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int handle_read(void *data) {
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struct tcp_connection *tcpConnection = (struct tcp_connection *) data;
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struct buffer *input_buffer = tcpConnection->input_buffer;
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struct channel *channel = tcpConnection->channel;
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if (buffer_socket_read(input_buffer, channel->fd) > 0) {
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//应用程序真正读取Buffer里的数据
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if (tcpConnection->messageCallBack != NULL) {
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tcpConnection->messageCallBack(input_buffer, tcpConnection);
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}
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} else {
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handle_connection_closed(tcpConnection);
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}
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}
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```
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在buffer\_socket\_read函数里，调用readv往两个缓冲区写入数据，一个是buffer对象，另外一个是这里的additional\_buffer，之所以这样做，是担心buffer对象没办法容纳下来自套接字的数据流，而且也没有办法触发buffer对象的扩容操作。通过使用额外的缓冲，一旦判断出从套接字读取的数据超过了buffer对象里的实际最大可写大小，就可以触发buffer对象的扩容操作，这里buffer\_append函数会调用前面介绍的make\_room函数，完成buffer对象的扩容。
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```
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int buffer_socket_read(struct buffer *buffer, int fd) {
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char additional_buffer[INIT_BUFFER_SIZE];
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struct iovec vec[2];
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int max_writable = buffer_writeable_size(buffer);
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vec[0].iov_base = buffer->data + buffer->writeIndex;
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vec[0].iov_len = max_writable;
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vec[1].iov_base = additional_buffer;
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vec[1].iov_len = sizeof(additional_buffer);
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int result = readv(fd, vec, 2);
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if (result < 0) {
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return -1;
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} else if (result <= max_writable) {
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buffer->writeIndex += result;
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} else {
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buffer->writeIndex = buffer->total_size;
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buffer_append(buffer, additional_buffer, result - max_writable);
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}
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return result;
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}
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```
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## 套接字发送数据处理
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当应用程序需要往套接字发送数据时，即完成了read-decode-compute-encode过程后，通过往buffer对象里写入encode以后的数据，调用tcp\_connection\_send\_buffer，将buffer里的数据通过套接字缓冲区发送出去。
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```
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int tcp_connection_send_buffer(struct tcp_connection *tcpConnection, struct buffer *buffer) {
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int size = buffer_readable_size(buffer);
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int result = tcp_connection_send_data(tcpConnection, buffer->data + buffer->readIndex, size);
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buffer->readIndex += size;
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return result;
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}
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```
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如果发现当前channel没有注册WRITE事件，并且当前tcp\_connection对应的发送缓冲无数据需要发送，就直接调用write函数将数据发送出去。如果这一次发送不完，就将剩余需要发送的数据拷贝到当前tcp\_connection对应的发送缓冲区中，并向event\_loop注册WRITE事件。这样数据就由框架接管，应用程序释放这部分数据。
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```
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//应用层调用入口
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int tcp_connection_send_data(struct tcp_connection *tcpConnection, void *data, int size) {
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size_t nwrited = 0;
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size_t nleft = size;
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int fault = 0;
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struct channel *channel = tcpConnection->channel;
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struct buffer *output_buffer = tcpConnection->output_buffer;
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//先往套接字尝试发送数据
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if (!channel_write_event_registered(channel) && buffer_readable_size(output_buffer) == 0) {
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nwrited = write(channel->fd, data, size);
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if (nwrited >= 0) {
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nleft = nleft - nwrited;
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} else {
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nwrited = 0;
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if (errno != EWOULDBLOCK) {
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if (errno == EPIPE || errno == ECONNRESET) {
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fault = 1;
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}
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}
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}
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}
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if (!fault && nleft > 0) {
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//拷贝到Buffer中，Buffer的数据由框架接管
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buffer_append(output_buffer, data + nwrited, nleft);
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if (!channel_write_event_registered(channel)) {
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channel_write_event_add(channel);
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}
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}
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return nwrited;
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}
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```
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## HTTP协议实现
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下面，我们在TCP的基础上，加入HTTP的功能。
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为此，我们首先定义了一个http\_server结构，这个http\_server本质上就是一个TCPServer，只不过暴露给应用程序的回调函数更为简单，只需要看到http\_request和http\_response结构。
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```
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typedef int (*request_callback)(struct http_request *httpRequest, struct http_response *httpResponse);
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struct http_server {
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struct TCPserver *tcpServer;
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request_callback requestCallback;
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};
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```
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在http\_server里面，重点是需要完成报文的解析，将解析的报文转化为http\_request对象，这件事情是通过http\_onMessage回调函数来完成的。在http\_onMessage函数里，调用的是parse\_http\_request完成报文解析。
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```
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// buffer是框架构建好的，并且已经收到部分数据的情况下
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// 注意这里可能没有收到全部数据，所以要处理数据不够的情形
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int http_onMessage(struct buffer *input, struct tcp_connection *tcpConnection) {
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yolanda_msgx("get message from tcp connection %s", tcpConnection->name);
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struct http_request *httpRequest = (struct http_request *) tcpConnection->request;
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struct http_server *httpServer = (struct http_server *) tcpConnection->data;
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if (parse_http_request(input, httpRequest) == 0) {
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char *error_response = "HTTP/1.1 400 Bad Request\r\n\r\n";
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tcp_connection_send_data(tcpConnection, error_response, sizeof(error_response));
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tcp_connection_shutdown(tcpConnection);
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}
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//处理完了所有的request数据，接下来进行编码和发送
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if (http_request_current_state(httpRequest) == REQUEST_DONE) {
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struct http_response *httpResponse = http_response_new();
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//httpServer暴露的requestCallback回调
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if (httpServer->requestCallback != NULL) {
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httpServer->requestCallback(httpRequest, httpResponse);
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}
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//将httpResponse发送到套接字发送缓冲区中
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struct buffer *buffer = buffer_new();
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http_response_encode_buffer(httpResponse, buffer);
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tcp_connection_send_buffer(tcpConnection, buffer);
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if (http_request_close_connection(httpRequest)) {
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tcp_connection_shutdown(tcpConnection);
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http_request_reset(httpRequest);
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}
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}
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}
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```
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还记得[第16讲中](https://time.geekbang.org/column/article/132443)讲到的HTTP协议吗？我们从16讲得知，HTTP通过设置回车符、换行符作为HTTP报文协议的边界。
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parse\_http\_request的思路就是寻找报文的边界，同时记录下当前解析工作所处的状态。根据解析工作的前后顺序，把报文解析的工作分成REQUEST\_STATUS、REQUEST\_HEADERS、REQUEST\_BODY和REQUEST\_DONE四个阶段，每个阶段解析的方法各有不同。
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在解析状态行时，先通过定位CRLF回车换行符的位置来圈定状态行，进入状态行解析时，再次通过查找空格字符来作为分隔边界。
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在解析头部设置时，也是先通过定位CRLF回车换行符的位置来圈定一组key-value对，再通过查找冒号字符来作为分隔边界。
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最后，如果没有找到冒号字符，说明解析头部的工作完成。
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parse\_http\_request函数完成了HTTP报文解析的四个阶段:
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```
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int parse_http_request(struct buffer *input, struct http_request *httpRequest) {
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int ok = 1;
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while (httpRequest->current_state != REQUEST_DONE) {
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if (httpRequest->current_state == REQUEST_STATUS) {
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char *crlf = buffer_find_CRLF(input);
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if (crlf) {
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int request_line_size = process_status_line(input->data + input->readIndex, crlf, httpRequest);
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if (request_line_size) {
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input->readIndex += request_line_size; // request line size
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input->readIndex += 2; //CRLF size
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httpRequest->current_state = REQUEST_HEADERS;
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}
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}
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} else if (httpRequest->current_state == REQUEST_HEADERS) {
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char *crlf = buffer_find_CRLF(input);
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if (crlf) {
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/**
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* <start>-------<colon>:-------<crlf>
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*/
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char *start = input->data + input->readIndex;
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int request_line_size = crlf - start;
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char *colon = memmem(start, request_line_size, ": ", 2);
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if (colon != NULL) {
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char *key = malloc(colon - start + 1);
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strncpy(key, start, colon - start);
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key[colon - start] = '\0';
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char *value = malloc(crlf - colon - 2 + 1);
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strncpy(value, colon + 1, crlf - colon - 2);
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value[crlf - colon - 2] = '\0';
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http_request_add_header(httpRequest, key, value);
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input->readIndex += request_line_size; //request line size
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input->readIndex += 2; //CRLF size
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} else {
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//读到这里说明:没找到，就说明这个是最后一行
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input->readIndex += 2; //CRLF size
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httpRequest->current_state = REQUEST_DONE;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
return ok;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
处理完了所有的request数据，接下来进行编码和发送的工作。为此，创建了一个http\_response对象，并调用了应用程序提供的编码函数requestCallback，接下来，创建了一个buffer对象，函数http\_response\_encode\_buffer用来将http\_response中的数据，根据HTTP协议转换为对应的字节流。
|
|||
|
|
|
|||
|
|
可以看到，http\_response\_encode\_buffer设置了如Content-Length等http\_response头部，以及http\_response的body部分数据。
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
void http_response_encode_buffer(struct http_response *httpResponse, struct buffer *output) {
|
|||
|
|
char buf[32];
|
|||
|
|
snprintf(buf, sizeof buf, "HTTP/1.1 %d ", httpResponse->statusCode);
|
|||
|
|
buffer_append_string(output, buf);
|
|||
|
|
buffer_append_string(output, httpResponse->statusMessage);
|
|||
|
|
buffer_append_string(output, "\r\n");
|
|||
|
|
|
|||
|
|
if (httpResponse->keep_connected) {
|
|||
|
|
buffer_append_string(output, "Connection: close\r\n");
|
|||
|
|
} else {
|
|||
|
|
snprintf(buf, sizeof buf, "Content-Length: %zd\r\n", strlen(httpResponse->body));
|
|||
|
|
buffer_append_string(output, buf);
|
|||
|
|
buffer_append_string(output, "Connection: Keep-Alive\r\n");
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
if (httpResponse->response_headers != NULL && httpResponse->response_headers_number > 0) {
|
|||
|
|
for (int i = 0; i < httpResponse->response_headers_number; i++) {
|
|||
|
|
buffer_append_string(output, httpResponse->response_headers[i].key);
|
|||
|
|
buffer_append_string(output, ": ");
|
|||
|
|
buffer_append_string(output, httpResponse->response_headers[i].value);
|
|||
|
|
buffer_append_string(output, "\r\n");
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
buffer_append_string(output, "\r\n");
|
|||
|
|
buffer_append_string(output, httpResponse->body);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
## 完整的HTTP服务器例子
|
|||
|
|
|
|||
|
|
现在，编写一个HTTP服务器例子就变得非常简单。
|
|||
|
|
|
|||
|
|
在这个例子中，最主要的部分是onRequest callback函数，这里，onRequest方法已经在parse\_http\_request之后，可以根据不同的http\_request的信息，进行计算和处理。例子程序里的逻辑非常简单，根据http request的URL path，返回了不同的http\_response类型。比如，当请求为根目录时，返回的是200和HTML格式。
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
#include <lib/acceptor.h>
|
|||
|
|
#include <lib/http_server.h>
|
|||
|
|
#include "lib/common.h"
|
|||
|
|
#include "lib/event_loop.h"
|
|||
|
|
|
|||
|
|
//数据读到buffer之后的callback
|
|||
|
|
int onRequest(struct http_request *httpRequest, struct http_response *httpResponse) {
|
|||
|
|
char *url = httpRequest->url;
|
|||
|
|
char *question = memmem(url, strlen(url), "?", 1);
|
|||
|
|
char *path = NULL;
|
|||
|
|
if (question != NULL) {
|
|||
|
|
path = malloc(question - url);
|
|||
|
|
strncpy(path, url, question - url);
|
|||
|
|
} else {
|
|||
|
|
path = malloc(strlen(url));
|
|||
|
|
strncpy(path, url, strlen(url));
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
if (strcmp(path, "/") == 0) {
|
|||
|
|
httpResponse->statusCode = OK;
|
|||
|
|
httpResponse->statusMessage = "OK";
|
|||
|
|
httpResponse->contentType = "text/html";
|
|||
|
|
httpResponse->body = "<html><head><title>This is network programming</title></head><body><h1>Hello, network programming</h1></body></html>";
|
|||
|
|
} else if (strcmp(path, "/network") == 0) {
|
|||
|
|
httpResponse->statusCode = OK;
|
|||
|
|
httpResponse->statusMessage = "OK";
|
|||
|
|
httpResponse->contentType = "text/plain";
|
|||
|
|
httpResponse->body = "hello, network programming";
|
|||
|
|
} else {
|
|||
|
|
httpResponse->statusCode = NotFound;
|
|||
|
|
httpResponse->statusMessage = "Not Found";
|
|||
|
|
httpResponse->keep_connected = 1;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return 0;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
|
|||
|
|
int main(int c, char **v) {
|
|||
|
|
//主线程event_loop
|
|||
|
|
struct event_loop *eventLoop = event_loop_init();
|
|||
|
|
|
|||
|
|
//初始tcp_server，可以指定线程数目，如果线程是0，就是在这个线程里acceptor+i/o；如果是1，有一个I/O线程
|
|||
|
|
//tcp_server自己带一个event_loop
|
|||
|
|
struct http_server *httpServer = http_server_new(eventLoop, SERV_PORT, onRequest, 2);
|
|||
|
|
http_server_start(httpServer);
|
|||
|
|
|
|||
|
|
// main thread for acceptor
|
|||
|
|
event_loop_run(eventLoop);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
运行这个程序之后，我们可以通过浏览器和curl命令来访问它。你可以同时开启多个浏览器和curl命令，这也证明了我们的程序是可以满足高并发需求的。
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
$curl -v http://127.0.0.1:43211/
|
|||
|
|
* Trying 127.0.0.1...
|
|||
|
|
* TCP_NODELAY set
|
|||
|
|
* Connected to 127.0.0.1 (127.0.0.1) port 43211 (#0)
|
|||
|
|
> GET / HTTP/1.1
|
|||
|
|
> Host: 127.0.0.1:43211
|
|||
|
|
> User-Agent: curl/7.54.0
|
|||
|
|
> Accept: */*
|
|||
|
|
>
|
|||
|
|
< HTTP/1.1 200 OK
|
|||
|
|
< Content-Length: 116
|
|||
|
|
< Connection: Keep-Alive
|
|||
|
|
<
|
|||
|
|
* Connection #0 to host 127.0.0.1 left intact
|
|||
|
|
<html><head><title>This is network programming</title></head><body><h1>Hello, network programming</h1></body></html>%
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
## 总结
|
|||
|
|
|
|||
|
|
这一讲我们主要讲述了整个编程框架的字节流处理能力，引入了buffer对象，并在此基础上通过增加HTTP的特性，包括http\_server、http\_request、http\_response，完成了HTTP高性能服务器的编写。实例程序利用框架提供的能力，编写了一个简单的HTTP服务器程序。
|
|||
|
|
|
|||
|
|
## 思考题
|
|||
|
|
|
|||
|
|
和往常一样，给你布置两道思考题：
|
|||
|
|
|
|||
|
|
第一道， 你可以试着在HTTP服务器中增加MIME的处理能力，当用户请求/photo路径时，返回一张图片。
|
|||
|
|
|
|||
|
|
第二道，在我们的开发中，已经有很多面向对象的设计，你可以仔细研读代码，说说你对这部分的理解。
|
|||
|
|
|
|||
|
|
欢迎你在评论区写下你的思考，也欢迎把这篇文章分享给你的朋友或者同事，一起交流一下。
|
|||
|
|
|