Linux监控重要进程的实现方法
Linux监控重要进程的实现方法
不管后台服务程序写的多么健壮,还是可能会出现core dump等程序异常退出的情况,但是一般情况下需要在无
人为干预情况下,能够自动重新启动,保证服务进程能够服务用户。这时就需要一个监控程序来实现能够让服务进程自动重新启动。查阅相关资料及尝试一些方法之后,总结linux系统监控重要进程的实现方法:脚本检测和子进程替换。
1、脚本检测 (1) 基本思路: 通过shell命令(ps -e | grep "$1" | grep -v "grep" | wc -l) 获取 $1 ($1 代表进程的名字)的进程数,脚本根据进程数来决定下一步的操作。通过一个死循环,每隔几秒检查一次系统中的指定程序的进程数,这里也可使用crontab来实现。 (2) 具体实现过程的代码如下: [ supervisor.sh ]
- #! /bin/sh
- # supervisor process
- LOG_FILE=/var/log/supervisor_sh.log
- # log function
- function log() {
- local t=$(date +"%F %X")
- echo "[ $t ] $0 : $1 " >> ${LOG_FILE}
- }
- # check process number
- # $1 : process name
- function check_process() {
- if [ -z $1 ]; then
- log "Input parameter is empty."
- return 0
- fi
- p_num=$(ps -e | grep "$1" | grep -v "grep" | wc -l)
- log "p_num = $p_num"
- echo $p_num
- }
- # supervisor process
- while [ 1 ]
- do
- declare -i ch_num
- p_name="apache2"
- ch_num=$(check_process $p_name)
- if [ $ch_num -eq 0 ]; then
- killall $p_name
- service $p_name start
- fi
- sleep 3
- done
#! /bin/sh # supervisor process LOG_FILE=/var/log/supervisor_sh.log # log function function log() { local t=$(date +"%F %X") echo "[ $t ] $0 : $1 " >> ${LOG_FILE} } # check process number # $1 : process name function check_process() { if [ -z $1 ]; then log "Input parameter is empty." return 0 fi p_num=$(ps -e | grep "$1" | grep -v "grep" | wc -l) log "p_num = $p_num" echo $p_num } # supervisor process while [ 1 ] do declare -i ch_num p_name="apache2" ch_num=$(check_process $p_name) if [ $ch_num -eq 0 ]; then killall $p_name service $p_name start fi sleep 3 done
2、子进程替换 (1) 基本思路: a. 使用fork函数创建一个新的进程,在进程表中创建一个新的表项,而创建者(即父进程)按原来的流程继续执行,子进程执行自己的控制流程 b. 运用execv函数把当前进程替换为一个新的进程,新进程由path或file参数指定,可以使用execv函数将程序的执行从一个程序切换到另一个程序 c. 当fork启动一个子进程时,子进程就有了它自己的生命周期并将独立运行,此时可以在父进程中调用wait函数让父进程等待子进程的结束 (2) 基本的实现步骤: a. 首先使用fork系统调用,创建子进程 b. 在子进程中使用execv函数,执行需要自动重启的程序 c. 在父进程中执行wait函数等待子进程的结束,然后重新创建一个新的子进程 (3) 具体实现的代码如下: supervisor.c
- /**
- *
- * supervisor
- *
- * date: 2016-08-10
- *
- */
- #include <stdio.h>
- #include <unistd.h>
- #include <errno.h>
- #include <string.h>
- #include <sys/types.h>
- #include <sys/wait.h>
- #include <stdlib.h>
- #include <time.h>
- #define LOG_FILE "/var/log/supervisor.log"
- void s_log(char *text) {
- time_t t;
- struct tm *tm;
- char *log_file;
- FILE *fp_log;
- char date[128];
- log_file = LOG_FILE;
- fp_log = fopen(log_file, "a+");
- if (NULL == fp_log) {
- fprintf(stderr, "Could not open logfile '%s' for writing\n", log_file);
- }
- time(&t);
- tm = localtime(&t);
- strftime(date, 127, "%Y-%m-%d %H:%M:%S", tm);
- /* write the message to stdout and/or logfile */
- fprintf(fp_log, "[%s] %s\n", date, text);
- fflush(fp_log);
- fclose(fp_log);
- }
- int main(int argc, char **argv) {
- int ret, i, status;
- char *child_argv[100] = {0};
- pid_t pid;
- if (argc < 2) {
- fprintf(stderr, "Usage:%s <exe_path> <args...>", argv[0]);
- return -1;
- }
- for (i = 1; i < argc; ++i) {
- child_argv[i-1] = (char *)malloc(strlen(argv[i])+1);
- strncpy(child_argv[i-1], argv[i], strlen(argv[i]));
- //child_argv[i-1][strlen(argv[i])] = '0';
- }
- while(1) {
- pid = fork();
- if (pid == -1) {
- fprintf(stderr, "fork() error.errno:%d error:%s", errno, strerror(errno));
- break;
- }
- if (pid == 0) {
- s_log(child_argv[0]);
- ret = execv(child_argv[0], (char **)child_argv);
- s_log("execv return");
- if (ret < 0) {
- fprintf(stderr, "execv ret:%d errno:%d error:%s", ret, errno, strerror(errno));
- continue;
- }
- s_log("exit child process");
- exit(0);
- }
- if (pid > 0) {
- pid = wait(&status);
- fprintf(stdout, "Child process id: %d\n", pid);
- //fprintf(stdout, "wait return");
- s_log("Wait child process return");
- }
- }
- return 0;
- }
/** * * supervisor * * date: 2016-08-10 * */ #include <stdio.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/wait.h> #include <stdlib.h> #include <time.h> #define LOG_FILE "/var/log/supervisor.log" void s_log(char *text) { time_t t; struct tm *tm; char *log_file; FILE *fp_log; char date[128]; log_file = LOG_FILE; fp_log = fopen(log_file, "a+"); if (NULL == fp_log) { fprintf(stderr, "Could not open logfile '%s' for writing\n", log_file); } time(&t); tm = localtime(&t); strftime(date, 127, "%Y-%m-%d %H:%M:%S", tm); /* write the message to stdout and/or logfile */ fprintf(fp_log, "[%s] %s\n", date, text); fflush(fp_log); fclose(fp_log); } int main(int argc, char **argv) { int ret, i, status; char *child_argv[100] = {0}; pid_t pid; if (argc < 2) { fprintf(stderr, "Usage:%s <exe_path> <args...>", argv[0]); return -1; } for (i = 1; i < argc; ++i) { child_argv[i-1] = (char *)malloc(strlen(argv[i])+1); strncpy(child_argv[i-1], argv[i], strlen(argv[i])); //child_argv[i-1][strlen(argv[i])] = '0'; } while(1) { pid = fork(); if (pid == -1) { fprintf(stderr, "fork() error.errno:%d error:%s", errno, strerror(errno)); break; } if (pid == 0) { s_log(child_argv[0]); ret = execv(child_argv[0], (char **)child_argv); s_log("execv return"); if (ret < 0) { fprintf(stderr, "execv ret:%d errno:%d error:%s", ret, errno, strerror(errno)); continue; } s_log("exit child process"); exit(0); } if (pid > 0) { pid = wait(&status); fprintf(stdout, "Child process id: %d\n", pid); //fprintf(stdout, "wait return"); s_log("Wait child process return"); } } return 0; }
(4) 测试验证 a. 假设需要自动重启的程序为demo.c,其代码实现如下所示:
- /*
- *
- * demo
- *
- */
- #include <stdio.h>
- #include <unistd.h>
- #include <errno.h>
- #include <string.h>
- #include <sys/types.h>
- #include <sys/wait.h>
- #include <stdlib.h>
- #include <time.h>
- #define LOG_FILE "/var/log/demo.log"
- void demo_log(int num) {
- time_t t;
- struct tm *tm;
- char *log_file;
- FILE *fp_log;
- char date[128];
- log_file = LOG_FILE;
- fp_log = fopen(log_file, "a+");
- if (NULL == fp_log) {
- fprintf(stderr, "Could not open logfile '%s' for writing\n", log_file);
- }
- time(&t);
- tm = localtime(&t);
- strftime(date,127,"%Y-%m-%d %H:%M:%S",tm);
- /* write the message to stdout and/or logfile */
- fprintf(fp_log, "[%s] num = %d\n", date, num);
- fflush(fp_log);
- fclose(fp_log);
- }
- int main(int argc, char **argv[]) {
- int num = 0;
- while(1) {
- sleep(10);
- num++;
- demo_log(num);
- }
- }
/* * * demo * */ #include <stdio.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/wait.h> #include <stdlib.h> #include <time.h> #define LOG_FILE "/var/log/demo.log" void demo_log(int num) { time_t t; struct tm *tm; char *log_file; FILE *fp_log; char date[128]; log_file = LOG_FILE; fp_log = fopen(log_file, "a+"); if (NULL == fp_log) { fprintf(stderr, "Could not open logfile '%s' for writing\n", log_file); } time(&t); tm = localtime(&t); strftime(date,127,"%Y-%m-%d %H:%M:%S",tm); /* write the message to stdout and/or logfile */ fprintf(fp_log, "[%s] num = %d\n", date, num); fflush(fp_log); fclose(fp_log); } int main(int argc, char **argv[]) { int num = 0; while(1) { sleep(10); num++; demo_log(num); } }
b. 测试准备和说明:
b1. 以上相关服务程序编译后的二进制文件为: supervisor 和 demo
b2. 执行如下测试命令 ./supervisor ./demo
c. 测试的结果:
c1. execv(progname, arg) 执行成功后,其后的代码不会执行;只有当执行错误时,才会返回 -1。原来调用execv进程的代码段会被progname应用程序的代码段替换。
c2. 当kill掉子进程时,父进程wait函数会接收到子进程退出的信号,进而循环再启动子进程,此过程实时性非常高。
c3. 当kill掉父进程时,子进程会被init进程接管,如果此时再kill掉子进程,则子进程会退出。
c4. 当同时kill掉父子进程,则父子进程都会退出。