Linux网络编程-自己动手写进程池

来源：互联网发布：知入与知出阅读答案编辑：程序博客网时间：2024/04/30 10:03

并发服务器的实现中，可以通过动态的创建子进程（或子线程）来实现。这样有几个缺点：

1、动态创建进程（或线程）比较耗时间，将导致客户响应较慢

2、动态创建的子进程或子线程通常只用来为一个客户服务，这导致系统中产生了很多进程或线程，使进程或线程之间的切换消耗很多CPU时间

3、动态创建子进程是当前进程的完整映像，当前进程需要谨慎管理其分配的文件描述符，否则子进程可能复制这些资源，导致系统可用资源急剧下降，进而影响服务器性能

以上的几个缺点可以通过进程池来规避，进程池是由服务器预先创建一组子进程，一般数目在3-10之间，进程池中的所有子进程运行着相同的代码，应具有相同的属性，比如优先级、PGID等。当有新任务来时，主进程选择进程池中的一个子进程来为之服务，相比于动态创建子进程，选择一个已经存在子进程显然来得跟快。

以下是我自己参考网络资料写的一个简单的进程池示例，进程间通信使用的是管道。

该程序说明：主进程先创建两个管道，一个用于向子进程写数据，另一个用于子进程向主进程写数据。然后主进程再创建4个子进程，让4个子进程来进程处理客户的连接请求，然后给主进程发送信息，同时主进程也给子进程发送应答信息。

运行程序后的输出结果(比如端口设为60000)：

在浏览器中输入http://192.168.1.2:60000（192.168.1.2运行该程序的主机）后就可以看到

源代码：

#include <stdio.h>#include <stdlib.h>#include <sys/types.h>#include <sys/socket.h>#include <sys/stat.h>#include <netinet/in.h>#include <string.h>#include <strings.h>#include <unistd.h>#include <signal.h>#include <fcntl.h>#define err_sys(msg) \    do { perror(msg); exit(-1); } while(0)#define err_exit(msg) \    do { fprintf(stderr, msg); exit(-1); } while(0)#define head200 "HTTP/1.1 200 OK \r\n"#define head404 "HTTP/1.1 404 Not Found\r\n"#define head503 "HTTP/1.1 503 Service unabailiable\r\n"#define MAXCHILD 4#define BUFFSIZE 1024typedef struct{    pid_t pid;    char status;}sReport;int len200, len404, len503;int pipe_fd1[2], pipe_fd2[2];void process_child(int listenfd, char* filename){    int connfd;    int cnt, len;    struct sockaddr_in cliaddr;    socklen_t clilen = sizeof(cliaddr);    sReport req;    char comm = '\0';    int running = 1;    char head_buf[1024];    req.pid = getpid();    while(running)    {        connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &clilen);        if(connfd < 0)            err_sys("accept");        req.status = 'n';        /* send message to parent process that got a new accept */        if(write(pipe_fd1[1], &req, sizeof(req)) < 0)            err_sys("write");        int fd;        struct stat file_stat;        if((fd = open(filename, O_RDONLY)) < 0)            err_sys("open");        if(stat(filename, &file_stat) < 0)            err_sys("stat");        bzero(head_buf, sizeof(head_buf));        len = 0;        cnt = snprintf(head_buf, BUFFSIZE - 1, head200);        len += cnt;        cnt = snprintf(head_buf + len, BUFFSIZE - 1 - len, "Coontent-Length: %lu\r\n", file_stat.st_size);        len += cnt;        cnt = snprintf(head_buf + len, BUFFSIZE - 1 - len, "\r\n");        char *file_buf;        struct iovec iv[2];        if((file_buf = (char *)malloc(file_stat.st_size)) == NULL)            err_sys("malloc");        bzero(file_buf, file_stat.st_size);        if(read(fd, file_buf, file_stat.st_size) < 0)            err_sys("read");        iv[0].iov_base = head_buf;        iv[0].iov_len = strlen(head_buf);        iv[1].iov_base = file_buf;        iv[1].iov_len = strlen(file_buf);        writev(connfd, iv, 2); /* send the file to client host */        free(file_buf);        close(fd);        close(connfd);        req.status = 'f';        /* tell parent process that finish the request */        if(write(pipe_fd1[1], &req, sizeof(req)) < 0)            err_sys("write");        /* wait for commond from parent process */        if(read(pipe_fd2[0], &comm, 1) < 1)            err_sys("read");        if('e' == comm)        {            printf("[%d] exit\n", req.pid);            running = 0;        }        else if('c' == comm)            printf("[%d] continue\n", req.pid);        else            printf("[%d]: comm: %c illeagle\n", req.pid, comm);    }}void handle_sigchld(int sig){    printf("the child process exit.\n");}int main(int argc, char *argv[]){    int listenfd;    struct sockaddr_in servaddr;    pid_t pid;    if(argc != 2)        err_exit("Usage: http-server port\n");    int port = atoi(argv[1]);    len200 = strlen(head200);    len404 = strlen(head404);    len503 = strlen(head503);    if(signal(SIGCHLD, handle_sigchld) < 0)        err_sys("signal");    if(pipe(pipe_fd1) < 0)        err_sys("pipe pipe_fd1");    if(pipe(pipe_fd2) < 0)        err_sys("pipe piep_fd2");    bzero(&servaddr, sizeof(servaddr));    servaddr.sin_family = AF_INET;    servaddr.sin_port = htons(port);    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);    if((listenfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)        err_sys("socket");    if(bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0)        err_sys("bind");    if(listen(listenfd, 10) < 0)        err_sys("listen");    int i;    for(i = 0; i < MAXCHILD; i++)    {        if((pid = fork()) < 0)            err_sys("fork");        else if(0 == pid)        {            process_child(listenfd, "test.txt"); //test.txt为测试文件，内容为 Hello World!!!        }        else        {            printf("have create child %d\n", pid);        }    }    close(pipe_fd1[1]);    close(pipe_fd2[0]);    close(listenfd);    char c = 'c';    int req_num = 0;    sReport req;    while(1)    {        if(read(pipe_fd1[0], &req, sizeof(req)) < 0)            err_sys("read pipe_fd1");        /* a new request come */        if(req.status == 'n') //子进程收到一个连接请求        {            req_num++;            printf("parent: %d have receive new request\n", req.pid);        }        else if(req.status == 'f') /* just finish a accept */        {            req_num--;            if(write(pipe_fd2[1], &c, sizeof(c)) < sizeof(c))                err_sys("write");        }    }    printf("Done\n");    return 0;}

参考资料：

1、《Linux高性能服务器编程》第15章进程池和线程池

2、一个进程池的服务器程序

0 0