zabbix_server代码分析--多进程创建

一、如果单纯的启动多个进程，那么代码如下：

//总体思路：父进程创建多个子进程，并且使用一个特殊标记值，使每个子进程这个数值都不同//父进程创建子进程之后，根据这个特殊数值依次给进程分配要执行的代码for(i = 0;i < thread_num;i++){if(0 == (thread_pid[i] = topo_fork())){        //每个子进程thread_mark都有一个唯一的数值，该值依次递增，从1开始。thread_mark = i + 1;break;}else{printf("thread(%d): %d\n",i,thread_pid[i]); }}    //根据thread_mark数值不同，设置条件，使不同的进程执行不同的代码。    //父进程的thread_mark为0if(0 == thread_mark){printf("This is parent process start\n");        //父进程执行的代码parent_main_loop();}    //第一个子进程的thread_mark为1else(thread_mark == 1){printf("This is snmp child process start\n");        //第一个进程执行的代码topo_main_loop();}    //第二个子进程的thread_mark为2else(thread_mark == 2){printf("This is watchdog child process start\n");        //第二个进程执行的代码watchdog_main_loop();}

这样做的缺点是要启动的进程个数是确定的，哪个功能要启动几个进程也是确定的，而zabbix里面启动多少个进程是不确定的，哪个功能要启动多少个进程也是不确定的，比如poller进程的个数，是可以配置文件配置个数的。

二、zabbix多进程实现

intCONFIG_ALERTER_FORKS= 1;intCONFIG_DISCOVERER_FORKS= 1;intCONFIG_HOUSEKEEPER_FORKS= 1;intCONFIG_NODEWATCHER_FORKS= 1;intCONFIG_PINGER_FORKS= 1;intCONFIG_POLLER_FORKS= 5;intCONFIG_UNREACHABLE_POLLER_FORKS= 1;intCONFIG_HTTPPOLLER_FORKS= 1;intCONFIG_IPMIPOLLER_FORKS= 0;intCONFIG_TIMER_FORKS= 1;intCONFIG_TRAPPER_FORKS= 5;intCONFIG_SNMPTRAPPER_FORKS= 0;intCONFIG_JAVAPOLLER_FORKS= 0;intCONFIG_ESCALATOR_FORKS= 1;intCONFIG_SELFMON_FORKS= 1;intCONFIG_WATCHDOG_FORKS= 1;intCONFIG_DATASENDER_FORKS= 0;intCONFIG_HEARTBEAT_FORKS= 0;intCONFIG_CONFSYNCER_FORKS= 1;intMAIN_ZABBIX_ENTRY(){pid_tpid;inti, server_num = 0, server_count = 0;//要启动的进程数量由这些变量的值决定，配置值为1就启动该进程，为0就不启动该进程。//这些值有的有默认值，有的根据配置文件决定。threads_num = CONFIG_CONFSYNCER_FORKS + CONFIG_WATCHDOG_FORKS + CONFIG_POLLER_FORKS+ CONFIG_UNREACHABLE_POLLER_FORKS + CONFIG_TRAPPER_FORKS + CONFIG_PINGER_FORKS+ CONFIG_ALERTER_FORKS + CONFIG_HOUSEKEEPER_FORKS + CONFIG_TIMER_FORKS+ CONFIG_NODEWATCHER_FORKS + CONFIG_HTTPPOLLER_FORKS + CONFIG_DISCOVERER_FORKS+ CONFIG_HISTSYNCER_FORKS + CONFIG_ESCALATOR_FORKS + CONFIG_IPMIPOLLER_FORKS+ CONFIG_JAVAPOLLER_FORKS + CONFIG_SNMPTRAPPER_FORKS + CONFIG_PROXYPOLLER_FORKS+ CONFIG_SELFMON_FORKS;threads = zbx_calloc(threads, threads_num, sizeof(pid_t));//使用fork()产生新的进程，thread_num是多少，就产生多少个进程。//fork()产生新进程的过程中，对于父进程，fork函数返回了子程序的进程号，而对于子程序，fork函数则返回零//所以此处使用if，else结构，会使父进程和子进程执行不同的代码for (i = 0; i < threads_num; i++){if (0 == (pid = zbx_child_fork())){//每个子进程都中的server_num都会有一个唯一的依次递增的值//根据server_num这个在每个进程中数值都不一样的特点，可以在下面实现每个子进程去执行不同的代码//子进程执行break，直接跳出循环，去执行进程之后的代码server_num = i + 1;/* child processes are numbered starting from 1 */break;}else//父进程返回的是子进程的进程号，父进程将每个子进程的进程号记录在thread[]结构中threads[i] = pid;}//父进程的server_num为0，每个子进程都有不同的server_num，根据server_num的不同，使不同的进程执行不同的代码。if (0 == server_num){zabbix_log(LOG_LEVEL_INFORMATION, "server #0 started [main process]");while (-1 == wait(&i))/* wait for any child to exit */{if (EINTR != errno){zabbix_log(LOG_LEVEL_ERR, "failed to wait on child processes: %s", zbx_strerror(errno));break;}}/* all exiting child processes should be caught by signal handlers */THIS_SHOULD_NEVER_HAPPEN;zbx_on_exit();}    //server_count是已启动的子进程的个数，CONFIG_CONFSYNCER_FORKS为本次要启动的子进程的个数，server_num为每个子进程的标记值，    //以server_num <= (server_count += CONFIG_CONFSYNCER_FORKS)为条件，可实现让子进程依次去执行相关的代码功能    //server_count初始值为0，第一个子进程的server_num数值为1，    //如果CONFIG_CONFSYNCER_FORKS为0，则server_count += CONFIG_CONFSYNCER_FORKS 数值为0，不满足1<=0，不执行main_dbconfig_loop()    //如果CONFIG_CONFSYNCER_FORKS为1，则server_count += CONFIG_CONFSYNCER_FORKS 数值为1，满足1 <= 1，把main_dbconfig_loop()作为子进程要执行的代码。    //如果CONFIG_CONFSYNCER_FORKS为2，则server_count += CONFIG_CONFSYNCER_FORKS 数值为2，第一个子进程执行时满足1<=2，执行main_dbconfig_loop()    //第二个子进程执行时，满足2<=2，执行main_dbconfig_loop()；由此可以实现同样的功能启动多个进程。CONFIG_CONFSYNCER_FORKS就是该功能启动进程的个数。else if (server_num <= (server_count += CONFIG_CONFSYNCER_FORKS)){INIT_SERVER(ZBX_PROCESS_TYPE_CONFSYNCER, CONFIG_CONFSYNCER_FORKS);main_dbconfig_loop();}else if (server_num <= (server_count += CONFIG_WATCHDOG_FORKS)){INIT_SERVER(ZBX_PROCESS_TYPE_WATCHDOG, CONFIG_WATCHDOG_FORKS);main_watchdog_loop();}return SUCCEED;}

    进程要有描述，这样才知道是哪个进程在执行哪个功能。有利于程序调试。

//对进程的描述，记录哪个进程执行的是什么功能//get_process_type_string根据传入的参数，执行switch case结构，返回对进程的描述。传入的参数为程序中宏定义的变量//server_num为第几个进程，et_process_type_string(process_type)为对进程执行功能的描述，process_num为该功能启动进程的计数（因为有的功能要启动多个进程）#define INIT_SERVER(type, count)\process_type = type;\process_num = server_num - server_count + count;\zabbix_log(LOG_LEVEL_INFORMATION, "server #%d started [%s #%d]",\server_num, get_process_type_string(process_type), process_num)#define ZBX_PROCESS_TYPE_POLLER0#define ZBX_PROCESS_TYPE_UNREACHABLE1#define ZBX_PROCESS_TYPE_IPMIPOLLER2#define ZBX_PROCESS_TYPE_PINGER3#define ZBX_PROCESS_TYPE_JAVAPOLLER4#define ZBX_PROCESS_TYPE_HTTPPOLLER5#define ZBX_PROCESS_TYPE_TRAPPER6#define ZBX_PROCESS_TYPE_SNMPTRAPPER7#define ZBX_PROCESS_TYPE_PROXYPOLLER8#define ZBX_PROCESS_TYPE_ESCALATOR9#define ZBX_PROCESS_TYPE_HISTSYNCER10#define ZBX_PROCESS_TYPE_DISCOVERER11#define ZBX_PROCESS_TYPE_ALERTER12#define ZBX_PROCESS_TYPE_TIMER13#define ZBX_PROCESS_TYPE_NODEWATCHER14#define ZBX_PROCESS_TYPE_HOUSEKEEPER15#define ZBX_PROCESS_TYPE_WATCHDOG16#define ZBX_PROCESS_TYPE_DATASENDER17#define ZBX_PROCESS_TYPE_CONFSYNCER18#define ZBX_PROCESS_TYPE_HEARTBEAT19#define ZBX_PROCESS_TYPE_SELFMON20#define ZBX_PROCESS_TYPE_COUNT21/* number of process types */#define ZBX_PROCESS_TYPE_UNKNOWN255            const char*get_process_type_string(unsigned char process_type){switch (process_type){case ZBX_PROCESS_TYPE_POLLER:return "poller";case ZBX_PROCESS_TYPE_UNREACHABLE:return "unreachable poller";case ZBX_PROCESS_TYPE_IPMIPOLLER:return "ipmi poller";case ZBX_PROCESS_TYPE_PINGER:return "icmp pinger";case ZBX_PROCESS_TYPE_JAVAPOLLER:return "java poller";case ZBX_PROCESS_TYPE_HTTPPOLLER:return "http poller";case ZBX_PROCESS_TYPE_TRAPPER:return "trapper";case ZBX_PROCESS_TYPE_SNMPTRAPPER:return "snmp trapper";case ZBX_PROCESS_TYPE_PROXYPOLLER:return "proxy poller";case ZBX_PROCESS_TYPE_ESCALATOR:return "escalator";case ZBX_PROCESS_TYPE_HISTSYNCER:return "history syncer";case ZBX_PROCESS_TYPE_DISCOVERER:return "discoverer";case ZBX_PROCESS_TYPE_ALERTER:return "alerter";case ZBX_PROCESS_TYPE_TIMER:return "timer";case ZBX_PROCESS_TYPE_NODEWATCHER:return "node watcher";case ZBX_PROCESS_TYPE_HOUSEKEEPER:return "housekeeper";case ZBX_PROCESS_TYPE_WATCHDOG:return "db watchdog";case ZBX_PROCESS_TYPE_DATASENDER:return "data sender";case ZBX_PROCESS_TYPE_CONFSYNCER:return "configuration syncer";case ZBX_PROCESS_TYPE_HEARTBEAT:return "heartbeat sender";case ZBX_PROCESS_TYPE_SELFMON:return "self-monitoring";}assert(0);}