/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ #include <my_global.h> #include <my_sys.h> #include <string.h> #include <signal.h> #include <sys/wait.h> #include "manager.h" #include "options.h" #include "log.h" /* Few notes about the Instance Manager architecture: Instance Manager consisits of two processes: the angel process, and the instance manager process. Responsibilities of the angel process is to monitor the instance manager process, and restart it in case of failure/shutdown. The angel process is started only if startup option '--run-as-service' is provided. The Instance Manager process consists of several subsystems (thread sets): - the signal handling thread: it's responsibilities are to handle user signals and propogate them to the other threads. All other threads are accounted in the signal handler thread Thread Repository. - the listener: listens all sockets. There is a listening socket for each (mysql, http, snmp, rendezvous (?)) subsystem. - mysql subsystem: Instance Manager acts like an ordinary MySQL Server, but with very restricted command set. Each MySQL client connection is handled in a separate thread. All MySQL client connections threads constitute mysql subsystem. - http subsystem: it is also possible to talk with Instance Manager via http. One thread per http connection is used. Threads are pooled. - 'snmp' connections (FIXME: I know nothing about it yet) - rendezvous threads */ static void init_environment(char *progname); static void daemonize(const char *log_file_name); static void angel(const Options &options); /* main, entry point - init environment - handle options - daemonize and run angel process (if necessary) - run manager process */ int main(int argc, char *argv[]) { init_environment(argv[0]); Options options; options.load(argc, argv); if (options.run_as_service) { daemonize(options.log_file_name); angel(options); } else manager(options.log_file_name); return 0; } /******************* Auxilary functions implementation **********************/ /* Init environment, common for daemon and non-daemon */ static void init_environment(char *progname) { MY_INIT(progname); log_init(); umask(0117); } /* Become a UNIX service SYNOPSYS daemonize() */ static void daemonize(const char *log_file_name) { pid_t pid= fork(); switch (pid) { case -1: // parent, fork error die("daemonize(): fork failed, %s", strerror(errno)); case 0: // child, fork ok int fd; /* Become a session leader: setsid should succeed because child is guaranteed not to be a process group leader (it belongs to the process group of the parent.) The goal is not to have a controlling terminal. */ if (setsid() == -1) die("daemonize(): setsid() failed, %s", strerror(errno)); /* As we now don't have a controlling terminal we will not receive tty-related signals - no need to ignore them. */ close(STDIN_FILENO); fd= open(log_file_name, O_WRONLY | O_CREAT | O_APPEND | O_NOCTTY, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP); if (fd < 0) die("daemonize(): failed to open log file %s, %s", log_file_name, strerror(errno)); dup2(fd, STDOUT_FILENO); dup2(fd, STDERR_FILENO); if (fd != STDOUT_FILENO && fd != STDERR_FILENO) close(fd); /* TODO: chroot() and/or chdir() here */ break; default: /* successfully exit from parent */ exit(0); } } enum { CHILD_OK= 0, CHILD_NEED_RESPAWN, CHILD_EXIT_ANGEL }; static volatile sig_atomic_t child_status= CHILD_OK; /* Signal handler for SIGCHLD: reap child, analyze child exit status, and set child_status appropriately. */ void reap_child(int __attribute__((unused)) signo) { int child_exit_status; /* As we have only one child, no need to cycle waitpid */ if (waitpid(0, &child_exit_status, WNOHANG) > 0) { if (WIFSIGNALED(child_exit_status)) child_status= CHILD_NEED_RESPAWN; else /* As we reap_child is not called for SIGSTOP, we should be here only if the child exited normally. */ child_status= CHILD_EXIT_ANGEL; } } /* Not static to reuse it in childs */ volatile sig_atomic_t is_terminated= 0; /* Signal handler for terminate signals - SIGTERM, SIGHUP, SIGINT. Set termination status and return. (q) do we need to handle SIGQUIT? */ void terminate(int signo) { is_terminated= signo; } /* Fork a child and monitor it. User can explicitly kill the angel process with SIGTERM/SIGHUP/SIGINT. Angel process will exit silently if mysqlmanager exits normally. */ static void angel(const Options &options) { /* install signal handlers */ sigset_t zeromask; // to sigsuspend in parent struct sigaction sa_chld, sa_term; struct sigaction sa_chld_out, sa_term_out, sa_int_out, sa_hup_out; if (sigemptyset(&zeromask) || sigemptyset(&sa_chld.sa_mask) || sigemptyset(&sa_term.sa_mask)) // how can it fail? die("angel(): sigemptyset() failed, %s", strerror(errno)); sa_chld.sa_handler= reap_child; sa_chld.sa_flags= SA_NOCLDSTOP; sa_term.sa_handler= terminate; sa_term.sa_flags= 0; if (sigaction(SIGCHLD, &sa_chld, &sa_chld_out) == -1 || sigaction(SIGTERM, &sa_term, &sa_term_out) == -1 || sigaction(SIGINT, &sa_term, &sa_int_out) == -1 || sigaction(SIGHUP, &sa_term, &sa_hup_out) == -1) die("angel(): sigaction() failed, %s", strerror(errno)); /* spawn a child */ spawn: pid_t pid= fork(); switch (pid) { case -1: die("angel(): fork failed, %s", strerror(errno)); case 0: // child, success /* restore default actions for signals to let the manager work with signals as he wishes */ if (sigaction(SIGCHLD, &sa_chld_out, 0) == -1 || sigaction(SIGTERM, &sa_term_out, 0) == -1 || sigaction(SIGINT, &sa_int_out, 0) == -1 || sigaction(SIGHUP, &sa_hup_out, 0) == -1) die("angel(): child failed to restore old signal actions, %s", strerror(errno)); manager(options.socket_file_name); default: // parent, success while (child_status == CHILD_OK && is_terminated == 0) { errno= 0; sigsuspend(&zeromask); if (errno != EINTR) die("angel(): sigsuspend failed, %s", strerror(errno)); } if (is_terminated) log_info("angel got signal %d (%s), exiting", is_terminated, sys_siglist[is_terminated]); else if (child_status == CHILD_NEED_RESPAWN) { child_status= CHILD_OK; log_error("angel(): mysqlmanager exited abnormally: respawning..."); sleep(1); /* don't respawn too fast */ goto spawn; } /* mysqlmanager successfully exited, let's silently evaporate */ } }