Webbench是一个在linux下使用的非常简单的网站压测工具。它使用fork()模拟多个客户端同时访问我们设定的URL，测试网站在压力下工作的性能，最多可以模拟3万个并发连接去测试网站的负载能力。Webbench使用C语言编写, 代码实在太简洁，源码加起来不到600行。

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注释代码如下：

webbench.c

#include "socket.c"
#include <unistd.h>
#include <sys/param.h>
#include <rpc/types.h>
#include <getopt.h>
#include <strings.h>
#include <time.h>
#include <signal.h>

/* values */
volatile int timerexpired=0;
int speed=0;
int failed=0;
int bytes=0;

/* globals */
int http10=1; /* 0 - http/0.9, 1 - http/1.0, 2 - http/1.1 */

/* Allow: GET, HEAD, OPTIONS, TRACE */
#define METHOD_GET 0
#define METHOD_HEAD 1
#define METHOD_OPTIONS 2
#define METHOD_TRACE 3

#define PROGRAM_VERSION "1.5"

int method=METHOD_GET;
int clients=1;
int force=0;
int force_reload=0;
int proxyport=80;
char *proxyhost=NULL;
int benchtime=30;

/* internal */
int mypipe[2];
char host[MAXHOSTNAMELEN];
#define REQUEST_SIZE 2048
char request[REQUEST_SIZE];

/* 选项结构定义 
 * staruct option:
 *  no_argument : 没有参数quir
 *  required    : 需要参数
 *  {“长选项”， 是否有参数， 参数， 短选项}
 * */
static const struct option long_options[]=
{
    {"force",no_argument,&force,1},
    {"reload",no_argument,&force_reload,1},
    {"time",required_argument,NULL,'t'},
    {"help",no_argument,NULL,'?'},
    {"http09",no_argument,NULL,'9'},
    {"http10",no_argument,NULL,'1'},
    {"http11",no_argument,NULL,'2'},
    {"get",no_argument,&method,METHOD_GET},
    {"head",no_argument,&method,METHOD_HEAD},
    {"options",no_argument,&method,METHOD_OPTIONS},
    {"trace",no_argument,&method,METHOD_TRACE},
    {"version",no_argument,NULL,'V'},
    {"proxy",required_argument,NULL,'p'},
    {"clients",required_argument,NULL,'c'},
    {NULL,0,NULL,0}
};

/* prototypes */
static void benchcore(const char* host,const int port, const char *request);
static int bench(void);
static void build_request(const char *url);

/* 闹钟中断函数 */
static void alarm_handler(int signal)
{
    timerexpired=1;
}   

static void usage(void)
{
    fprintf(stderr,
                "webbench [option]... URL\n"
                "  -f|--force               Don't wait for reply from server.\n"
                "  -r|--reload              Send reload request - Pragma: no-cache.\n"
                "  -t|--time <sec>          Run benchmark for <sec> seconds. Default 30.\n"
                "  -p|--proxy <server:port> Use proxy server for request.\n"
                "  -c|--clients <n>         Run <n> HTTP clients at once. Default one.\n"
                "  -9|--http09              Use HTTP/0.9 style requests.\n"
                "  -1|--http10              Use HTTP/1.0 protocol.\n"
                "  -2|--http11              Use HTTP/1.1 protocol.\n"
                "  --get                    Use GET request method.\n"
                "  --head                   Use HEAD request method.\n"
                "  --options                Use OPTIONS request method.\n"
                "  --trace                  Use TRACE request method.\n"
                "  -?|-h|--help             This information.\n"
                "  -V|--version             Display program version.\n"
           );
};
int main(int argc, char *argv[])
{
    int opt=0;
    int options_index=0;
    char *tmp=NULL;

    if(argc==1)
    {
        usage();
        return 2;
    } 
    /* 解析命令 
     * 需要参数的短选项后面需要：*/
    while((opt=getopt_long(argc,argv,"912Vfrt:p:c:?h",long_options,&options_index))!=EOF )
    {
        switch(opt)
        {
            case  0 : break;
            case 'f': force=1;break;
            case 'r': force_reload=1;break; 
            case '9': http10=0;break;
            case '1': http10=1;break;
            case '2': http10=2;break;
            case 'V': printf(PROGRAM_VERSION"\n");exit(0);
            case 't': benchtime=atoi(optarg);break; /* optarg 选项参数指针 */      
            case 'p': 
                      /* proxy server parsing server:port */
                      tmp=strrchr(optarg,':');
                      proxyhost=optarg;
                      if(tmp==NULL)
                      {
                          break;
                      }
                      if(tmp==optarg)
                      {
                          fprintf(stderr,"Error in option --proxy %s: Missing hostname.\n",optarg);
                          return 2;
                      }
                      if(tmp==optarg+strlen(optarg)-1)
                      {
                          fprintf(stderr,"Error in option --proxy %s Port number is missing.\n",optarg);
                          return 2;
                      }
                      *tmp='\0';
                      proxyport=atoi(tmp+1);break;
            case ':':
            case 'h':
            case '?': usage();return 2;break;
            case 'c': clients=atoi(optarg);break;
        }
    }
    /* optind 当前opt解析位置 
     * if optind == argc 表示解析完了*/
    if(optind==argc) {
        fprintf(stderr,"webbench: Missing URL!\n");
        usage();
        return 2;
    }

    if(clients==0) clients=1;
    if(benchtime==0) benchtime=60;
    /* Copyright */
    fprintf(stderr,"Webbench - Simple Web Benchmark "PROGRAM_VERSION"\n"
                "Copyright (c) Radim Kolar 1997-2004, GPL Open Source Software.\n"
           );
    /* argv[optind] 表示url */
    build_request(argv[optind]);
    /* print bench info */
    printf("\nBenchmarking: ");
    switch(method)
    {
        case METHOD_GET:
        default:
            printf("GET");break;
        case METHOD_OPTIONS:
            printf("OPTIONS");break;
        case METHOD_HEAD:
            printf("HEAD");break;
        case METHOD_TRACE:
            printf("TRACE");break;
    }
    printf(" %s",argv[optind]);
    switch(http10)
    {
        case 0: printf(" (using HTTP/0.9)");break;
        case 2: printf(" (using HTTP/1.1)");break;
    }
    printf("\n");
    if(clients==1) printf("1 client");
    else
      printf("%d clients",clients);

    printf(", running %d sec", benchtime);
    if(force) printf(", early socket close");
    if(proxyhost!=NULL) printf(", via proxy server %s:%d",proxyhost,proxyport);
    if(force_reload) printf(", forcing reload");
    printf(".\n");

    /*开始测试 */
    return bench();
}

void build_request(const char *url)
{
    char tmp[10];
    int i;

    bzero(host,MAXHOSTNAMELEN);
    bzero(request,REQUEST_SIZE);

    if(force_reload && proxyhost!=NULL && http10<1) http10=1;
    if(method==METHOD_HEAD && http10<1) http10=1;
    if(method==METHOD_OPTIONS && http10<2) http10=2;
    if(method==METHOD_TRACE && http10<2) http10=2;

    /* 构建headers 头 */
    switch(method)
    {
        default:
        case METHOD_GET: strcpy(request,"GET");break;
        case METHOD_HEAD: strcpy(request,"HEAD");break;
        case METHOD_OPTIONS: strcpy(request,"OPTIONS");break;
        case METHOD_TRACE: strcpy(request,"TRACE");break;
    }

    strcat(request," ");
    /* 检测URL格式合法性 */
    if(NULL==strstr(url,"://"))
    {
        fprintf(stderr, "\n%s: is not a valid URL.\n",url);
        exit(2);
    }
    if(strlen(url)>1500)
    {
        fprintf(stderr,"URL is too long.\n");
        exit(2);
    }
    if(proxyhost==NULL)
      if (0!=strncasecmp("http://",url,7)) 
      {
          fprintf(stderr,"\nOnly HTTP protocol is directly supported, set --proxy for others.\n");
          exit(2);
      }
    /* protocol/host delimiter */
    /* url 开始位置 http为7*/
    i=strstr(url,"://")-url+3;
    /* printf("%d\n",i); */
    
    /* 如果url中没有字符/ */
    if(strchr(url+i,'/')==NULL) {
        fprintf(stderr,"\nInvalid URL syntax - hostname don't ends with '/'.\n");
        exit(2);
    }
    /* 如果没有代理 */
    if(proxyhost==NULL)
    {
        /* get port from hostname */
        if(index(url+i,':')!=NULL &&
                    index(url+i,':')<index(url+i,'/'))
        {
            /* 获取Host 长度：strchr(url+i, ':') - (url+i) */
            strncpy(host,url+i,strchr(url+i,':')-url-i);
            bzero(tmp,10);
            /* 获取port */
            strncpy(tmp,index(url+i,':')+1,strchr(url+i,'/')-index(url+i,':')-1);
            /* printf("tmp=%s\n",tmp); */
            proxyport=atoi(tmp);
            if(proxyport==0) proxyport=80;
        } else
        {
            strncpy(host,url+i,strcspn(url+i,"/"));
        }
         printf("Host=%s\n",host);
        strcat(request+strlen(request),url+i+strcspn(url+i,"/"));
    } else /* 使用代理 */
    {
        printf("ProxyHost=%s\nProxyPort=%d\n",proxyhost,proxyport);
        /*将url放到request里面*/
        strcat(request,url);
        printf("request:%s\n", request);
    }
    /* 设置http协议版本 */
    if(http10==1)
      strcat(request," HTTP/1.0");
    else if (http10==2)
      strcat(request," HTTP/1.1");
    strcat(request,"\r\n");
    if(http10>0)
      strcat(request,"User-Agent: WebBench "PROGRAM_VERSION"\r\n");
    if(proxyhost==NULL && http10>0)
    {
        strcat(request,"Host: ");
        strcat(request,host);
        strcat(request,"\r\n");
    }
    if(force_reload && proxyhost!=NULL)
    {
        strcat(request,"Pragma: no-cache\r\n");
    }
    if(http10>1)
      strcat(request,"Connection: close\r\n");
    /* add empty line at end */
    /* 添加一空行 */
    if(http10>0) strcat(request,"\r\n"); 
    // printf("Req=%s\n",request);
}

/* vraci system rc error kod */
static int bench(void)
{
    int i,j,k;    
    pid_t pid=0;
    FILE *f;

    /* check avaibility of target server */
    /* 测试是否可以连接这个url */
    i=Socket(proxyhost==NULL?host:proxyhost,proxyport);
    if(i<0) { 
        fprintf(stderr,"\nConnect to server failed. Aborting benchmark.\n");
        return 1;
    }
    /* 关闭连接 */
    close(i);
    /* create pipe 创建管道 
     * 将文件描述符由mypipe[]数组返回
     * mypipe[0] 为管道读取端
     * mypipe[1] 为管道写入端
     * 成功返回0 否则返回-1*/
    if(pipe(mypipe))
    {
        perror("pipe failed.");
        return 3;
    }

    /* not needed, since we have alarm() in childrens */
    /* wait 4 next system clock tick */
    /*
       cas=time(NULL);
       while(time(NULL)==cas)
       sched_yield();
       */

    /* fork childs */
    for(i=0;i<clients;i++)
    {
        /* 复制一个进程 */
        pid=fork();
        /* 进程创建失败 */
        if(pid <= (pid_t) 0)
        {
            /* child process or error*/
            sleep(1); /* make childs faster */
            break;
        }
    }

    if( pid< (pid_t) 0)
    {
        fprintf(stderr,"problems forking worker no. %d\n",i);
        perror("fork failed.");
        return 3;
    }
    /* 子进程 */
    if(pid== (pid_t) 0)
    {
        /* I am a child */
        /* 连接 */
        if(proxyhost==NULL)
          benchcore(host,proxyport,request);
        else
          benchcore(proxyhost,proxyport,request);

        /* write results to pipe */
        f=fdopen(mypipe[1],"w");
        if(f==NULL)
        {
            perror("open pipe for writing failed.");
            return 3;
        }
        /* fprintf(stderr,"Child - %d %d\n",speed,failed); */
        fprintf(f,"%d %d %d\n",speed,failed,bytes);
        fclose(f);
        return 0;
    } else /* 父进程 */
    {
        /* 读取结果 */
        f=fdopen(mypipe[0],"r");
        if(f==NULL) 
        {
            perror("open pipe for reading failed.");
            return 3;
        }
        /* 设置文件流缓冲区 缓冲类型为__IONBF, 0字节*/
        /* 清空缓冲区及各项数据 */
        setvbuf(f,NULL,_IONBF,0);
        speed=0;
        failed=0;
        bytes=0;
        
        /* 循环读取 */
        while(1)
        {
            pid=fscanf(f,"%d %d %d",&i,&j,&k);
            if(pid<2)
            {
                fprintf(stderr,"Some of our childrens died.\n");
                break;
            }
            speed+=i;
            failed+=j;
            bytes+=k;
            /* fprintf(stderr,"*Knock* %d %d read=%d\n",speed,failed,pid); */
            if(--clients==0) break;
        }
        fclose(f);
        /* 所有任务完成输出结果 */
        printf("\nSpeed=%d pages/min, %d bytes/sec.\nRequests: %d susceed, %d failed.\n",
                    (int)((speed+failed)/(benchtime/60.0f)),
                    (int)(bytes/(float)benchtime),
                    speed,
                    failed);
    }
    return i;
}

void benchcore(const char *host,const int port,const char *req)
{
    int rlen;
    char buf[1500];
    int s,i;
    /* Linux中信号机制 */
    struct sigaction sa;

    /* setup alarm signal handler */
    /* 配置中断函数 */
    sa.sa_handler=alarm_handler;
    sa.sa_flags=0;
    if(sigaction(SIGALRM,&sa,NULL))
      exit(3);
    alarm(benchtime);

    rlen=strlen(req);
    nexttry:
        while(1)
        {
            if(timerexpired)/* 闹钟时间到 */
            {
                if(failed>0)
                {
                    /* fprintf(stderr,"Correcting failed by signal\n"); */
                    failed--;
                }
                return;
            }
            /* 开始连接 */
            s=Socket(host,port);                          
            if(s<0) { failed++;continue;}
            /* 发送header */
            if(rlen!=write(s,req,rlen)) {failed++;close(s);continue;}
            if(http10==0)/* 关闭连接 HTTP0.9*/ 
              if(shutdown(s,1)) { failed++;close(s);continue;}
            if(force==0) 
            {
                /* read all available data from socket */
                while(1)
                {
                    if(timerexpired) break; 
                    i=read(s,buf,1500);
                    /* fprintf(stderr,"%d\n",i); */
                    if(i<0) 
                    { 
                        failed++;
                        close(s);
                        goto nexttry;
                    }
                    else
                      if(i==0) break;
                      else
                        bytes+=i;
                }
            }
            if(close(s)) {failed++;continue;}
            /* 循环次数 */
            speed++;
        }