基于Libevent的HTTP Server

基于Libevent的HTTP Server

简单的Http Server

使用Libevent内置的http相关接口，可以很容易的构建一个Http Server，一个简单的Http Server如下：

#include

#include

#include

#include

#include

#include

int init_win_socket()

{

WSADATA wsaData;

if(WSAStartup(MAKEWORD(2,2) , &wsaData) != 0)

{

return -1;

}

return0;

}

void generic_handler(struct evhttp_request *req, void *arg)

{

struct evbuffer *buf = evbuffer_new();

if(!buf)

{

puts("failed to create response buffer \n");

return;

}

evbuffer_add_printf(buf, "Server Responsed. Requested: %s\n", evhttp_request_get_uri(req));

evhttp_send_reply(req, HTTP_OK, "OK", buf);

evbuffer_free(buf);

}

int main(int argc, char* argv[])

{

#ifdef WIN32

init_win_socket();

#endif

short http_port = 8081;

char *http_addr = "127.0.0.1";

struct event_base * base = event_base_new();

struct evhttp * http_server = evhttp_new(base);

if(!http_server)

{

return -1;

}

int ret = evhttp_bind_socket(http_server,http_addr,http_port);

if(ret!=0)

{

return -1;

}

evhttp_set_gencb(http_server, generic_handler, NULL);

printf("http server start OK! \n");

event_base_dispatch(base);

evhttp_free(http_server);

WSACleanup();

return0;

}

通过Libevent的接口构建一个Http Server的过程如下：

（1）初始化：在event_base上新建一个evhttp，将这个evhttp绑定到监听的IP和端口号。

（2）设置Http回调函数：使用evhttp_set_gencb设置Http Server的处理请求的回调函数。

（3）启动Http Server：等待请求进入事件循环。

在Http Server中使用定时器提供更新服务

#include

#include

#include

#include

#include

#include

#include

#include

#include

#define DEFAULT_FILE "F:\\Libevent\\LibeventTest\\Debug\\sample.txt"

char *filedata;

time_t lasttime = 0;

char filename[80];

int counter = 0;

struct event *loadfile_event;

struct timeval tv;

void read_file()

{

unsigned long size = 0;

char *data;

struct stat buf;

if(stat(filename,&buf)<0)

{

printf("Read file error! \n");

return;

}

if (buf.st_mtime > lasttime)

{

if (counter++)

fprintf(stderr,"Reloading file: %s",filename);

else

fprintf(stderr,"Loading file: %s",filename);

FILE *f = fopen(filename, "rb");

if (f == NULL)

{

fprintf(stderr,"Couldn't open file\n");

return;

}

size = buf.st_size;

filedata = (char *)malloc(size+1);

memset(filedata,0,size+1);

fread(filedata, sizeof(char), size, f);

fclose(f);

fprintf(stderr," (%d bytes)\n",size);

lasttime = buf.st_mtime;

}

}

void read_file_timer_cb(evutil_socket_t listener, short event, void *arg)

{

if (!evtimer_pending(loadfile_event, NULL))

{

event_del(loadfile_event);

evtimer_add(loadfile_event, &tv);

}

read_file();

}

void load_file(struct event_base * base)

{

https://www.360docs.net/doc/6718896499.html,_sec = 5;

https://www.360docs.net/doc/6718896499.html,_usec = 0;

//loadfile_event = malloc(sizeof(struct event));

loadfile_event = evtimer_new(base,read_file_timer_cb,NULL);

//evtimer_set(loadfile_event,load_file,loadfile_event);

evtimer_add(loadfile_event,&tv);

}

void generic_handler(struct evhttp_request *req, void *arg)

{

struct evbuffer *buf = evbuffer_new();

if(!buf)

{

puts("failed to create response buffer \n");

return;

}

evbuffer_add_printf(buf,"%s",filedata);

evhttp_send_reply(req, HTTP_OK, "OK", buf);

evbuffer_free(buf);

}

int init_win_socket()

{

WSADATA wsaData;

if(WSAStartup(MAKEWORD(2,2) , &wsaData) != 0)

{

return -1;

}

return0;

}

int main(int argc, char* argv[])

{

#ifdef WIN32

init_win_socket();

#endif

short http_port = 8081;

char *http_addr = "127.0.0.1";

if (argc > 1)

{

strcpy(filename,argv[1]);

printf("Using %s\n",filename);

}

else

{

strcpy(filename,DEFAULT_FILE);

}

struct event_base * base = event_base_new();

struct evhttp * http_server = evhttp_new(base);

if(!http_server)

{

return -1;

}

int ret = evhttp_bind_socket(http_server,http_addr,http_port);

if(ret!=0)

{

return -1;

}

evhttp_set_gencb(http_server, generic_handler, NULL);

read_file();

load_file(base);

printf("http server start OK! \n");

event_base_dispatch(base);

evhttp_free(http_server);

WSACleanup();

return0;

}

在这个Http Server中提供了一个每5秒触发一次的定时器，读取一个文件，如果这个文件被更新过，则读取更新后的内容。

当访问这个Http Server时，提供这个文件中最新的内容。

多线程的Http Server

在上面的Http Server中，处理Http请求的回调函数generic_handler和定时器读取文件的回调函数read_file_timer_cb都在同一个event_base的dispatch中，并且都在同一个进程中，使用多线程可以改善程序的性能，下面是一个来自网络的多线程Http Server：

#include

#include

#include

#include

#include

#include

#include

#include

#include

int httpserver_bindsocket(int port, int backlog);

int httpserver_start(int port, int nthreads, int backlog);

void* httpserver_Dispatch(void *arg);

void httpserver_GenericHandler(struct evhttp_request *req, void *arg); void httpserver_ProcessRequest(struct evhttp_request *req);

int httpserver_bindsocket(int port, int backlog) {

int r;

int nfd;

nfd = socket(AF_INET, SOCK_STREAM, 0);

if (nfd < 0) return -1;

int one = 1;

r = setsockopt(nfd, SOL_SOCKET, SO_REUSEADDR, (char *)&one, sizeof(int));

struct sockaddr_in addr;

memset(&addr, 0, sizeof(addr));

addr.sin_family = AF_INET;

addr.sin_addr.s_addr = INADDR_ANY;

addr.sin_port = htons(port);

r = bind(nfd, (struct sockaddr*)&addr, sizeof(addr));

if (r < 0) return -1;

r = listen(nfd, backlog);

if (r < 0) return -1;

int flags;

if ((flags = fcntl(nfd, F_GETFL, 0)) < 0

|| fcntl(nfd, F_SETFL, flags | O_NONBLOCK) < 0) return -1;

return nfd;

}

int httpserver_start(int port, int nthreads, int backlog) {

int r, i;

int nfd = httpserver_bindsocket(port, backlog);

if (nfd < 0) return -1;

pthread_t ths[nthreads];

for (i = 0; i < nthreads; i++) {

struct event_base *base = event_init();

if (base == NULL) return -1;

struct evhttp *httpd = evhttp_new(base);

if (httpd == NULL) return -1;

r = evhttp_accept_socket(httpd, nfd);

if (r != 0) return -1;

evhttp_set_gencb(httpd, httpserver_GenericHandler, NULL);

r = pthread_create(&ths[i], NULL, httpserver_Dispatch, base);

if (r != 0) return -1;

}

for (i = 0; i < nthreads; i++) {

pthread_join(ths[i], NULL);

}

}

void* httpserver_Dispatch(void *arg) {

event_base_dispatch((struct event_base*)arg);

return NULL;

}

void httpserver_GenericHandler(struct evhttp_request *req, void*arg) { httpserver_ProcessRequest(req);

}

void httpserver_ProcessRequest(struct evhttp_request *req) { struct evbuffer *buf = evbuffer_new();

if (buf == NULL) return;

//here comes the magic

}

int main(void) {

httpserver_start(80, 10, 10240);

}

上面的代码基于Libevent 1.X版本的，不过很容易很看懂：在一个监听socket上创建了多个event_base实例和evhttp实例，在不同的线程中调度不同的event_base，继而可以在不同的线程中处理http请求。

这里还有一个基于Libevent的多线程Http Server：

https://https://www.360docs.net/doc/6718896499.html,/projects/libevent-thread/，看源代码处理的过程和上面类似，只是每次在监听的socket上accept一个连接请求时，将对应的处理放到一个工作队列里，在队列里由多线程处理相应的回调函数。