（3.4）mysql基础深入——mysql.server启动脚本源码阅读与分析
my.server主要分为3大部分
【1】变量初始化部分 【2】函数声明部分 【3】具体执行部分
#!/bin/sh #【第1部分，变量初始化部分begin】 #【1.1】指定Mysql安装程序及数据目录的路径，默认是/usr/local/mysql，默认是空的 basedir=/mysql/app/mysql datadir=/mysql/data/3306/data # Default value, in seconds, afterwhich the script should timeout waiting # for server start. # Value here is overriden by value in my.cnf. # 0 means don't wait at all # Negative numbers mean to wait indefinitely
#【1.2】定义mysql服务启动时间的限制，如果超过900S没有启动，则退出 service_startup_timeout=900 # Lock directory for RedHat / SuSE.
#【1.3】操作系统默认在关闭过程一些服务进程的调用，
#【1.3】其实lockdir就是/etc/init.d/ 这个里面启动的，会慢慢一个一个关闭本行里面的进程 lockdir='/var/lock/subsys' lock_file_path="$lockdir/mysql" # The following variables are only set for letting mysql.server find things. # Set some defaults
#【1.4】判断mysql有没有启动 mysqld_pid_file_path=/mysql/data/3306/mysql.pid
#【1.5】判断文件是否存在，然后进行相应的赋值 if test -z "$basedir" then basedir=/mysql/app/mysql bindir=/mysql/app/mysql/bin if test -z "$datadir" then datadir=/mysql/data/3306/data fi sbindir=/mysql/app/mysql/bin libexecdir=/mysql/app/mysql/bin else bindir="$basedir/bin" if test -z "$datadir" then datadir="$basedir/data" fi sbindir="$basedir/sbin" libexecdir="$basedir/libexec" fi # datadir_set is used to determine if datadir was set (and so should be # *not* set inside of the --basedir= handler.) datadir_set=
#【第1部分，变量初始化部分end】
#【第2部分，函数声明部分begin】 # # Use LSB init script functions for printing messages, if possible #
#【2.1】本地文件，有些系统可能不存在该文件。可能会在/etc/init.d/init-functions lsb_functions="/lib/lsb/init-functions" if test -f $lsb_functions ; then . $lsb_functions else log_success_msg() { echo " SUCCESS! $@" } log_failure_msg() { echo " ERROR! $@" } fi
#设置path环境变量 PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin" export PATH
#传脚本运行时的参数 mode=$1 # start or stop [ $# -ge 1 ] && shift other_args="$*" # uncommon, but needed when called from an RPM upgrade action # Expected: "--skip-networking --skip-grant-tables" # They are not checked here, intentionally, as it is the resposibility # of the "spec" file author to give correct arguments only. case `echo "testingc"`,`echo -n testing` in *c*,-n*) echo_n= echo_c= ;; *c*,*) echo_n=-n echo_c= ;; *) echo_n= echo_c='c' ;; esac
#【2.1】参数解析函数（将参数值赋予变量）
#【2.1】主要涉及参数：--basedir --datadir --pid-file --service-startup-timeout parse_server_arguments() { for arg do case "$arg" in --basedir=*) basedir=`echo "$arg" | sed -e 's/^[^=]*=//'` bindir="$basedir/bin" if test -z "$datadir_set"; then datadir="$basedir/data" fi sbindir="$basedir/sbin" libexecdir="$basedir/libexec" ;; --datadir=*) datadir=`echo "$arg" | sed -e 's/^[^=]*=//'` datadir_set=1 ;; --pid-file=*) mysqld_pid_file_path=`echo "$arg" | sed -e 's/^[^=]*=//'` ;; --service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e 's/^[^=]*=//'` ;; esac done } wait_for_pid () { verb="$1" # created | removed pid="$2" # process ID of the program operating on the pid-file pid_file_path="$3" # path to the PID file. i=0 avoid_race_condition="by checking again" while test $i -ne $service_startup_timeout ; do case "$verb" in 'created') # wait for a PID-file to pop into existence. test -s "$pid_file_path" && i='' && break ;; 'removed') # wait for this PID-file to disappear test ! -s "$pid_file_path" && i='' && break ;; *) echo "wait_for_pid () usage: wait_for_pid created|removed pid pid_file_path" exit 1 ;; esac # if server isn't running, then pid-file will never be updated if test -n "$pid"; then if kill -0 "$pid" 2>/dev/null; then : # the server still runs else # The server may have exited between the last pid-file check and now. if test -n "$avoid_race_condition"; then avoid_race_condition="" continue # Check again. fi # there's nothing that will affect the file. log_failure_msg "The server quit without updating PID file ($pid_file_path)." return 1 # not waiting any more. fi fi echo $echo_n ".$echo_c" i=`expr $i + 1` sleep 1 done if test -z "$i" ; then log_success_msg return 0 else log_failure_msg return 1 fi } 【2.1】参数解析函数end
#【3】主体执行部分
#【3.1】判断my_print_defaults文件的位置
# Get arguments from the my.cnf file, # the only group, which is read from now on is [mysqld] if test -x "$bindir/my_print_defaults"; then print_defaults="$bindir/my_print_defaults" else # Try to find basedir in /etc/my.cnf conf=/etc/my.cnf print_defaults= if test -r $conf then subpat='^[^=]*basedir[^=]*=(.*)$' dirs=`sed -e "/$subpat/!d" -e 's//1/' $conf` for d in $dirs do d=`echo $d | sed -e 's/[ ]//g'` if test -x "$d/bin/my_print_defaults" then print_defaults="$d/bin/my_print_defaults" break fi done fi # Hope it's in the PATH ... but I doubt it test -z "$print_defaults" && print_defaults="my_print_defaults" fi # # Read defaults file from 'basedir'. If there is no defaults file there # check if it's in the old (depricated) place (datadir) and read it from there #
#【3.2】查找默认的配置文件
extra_args="" if test -r "$basedir/my.cnf" then extra_args="-e $basedir/my.cnf" fi parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`
#【3.3】设置PID文件的路径 # # Set pid file if not given # if test -z "$mysqld_pid_file_path" then mysqld_pid_file_path=$datadir/`hostname`.pid else case "$mysqld_pid_file_path" in /* ) ;; * ) mysqld_pid_file_path="$datadir/$mysqld_pid_file_path" ;; esac fi
#【3.4】mysql服务脚本start选项 case "$mode" in 'start') # Start daemon # Safeguard (relative paths, core dumps..) cd $basedir echo $echo_n "Starting MySQL" if test -x $bindir/mysqld_safe then # Give extra arguments to mysqld with the my.cnf file. This script # may be overwritten at next upgrade. $bindir/mysqld_safe --defaults-file=/mysql/data/3306/my.cnf --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null & wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$? # Make lock for RedHat / SuSE if test -w "$lockdir" then touch "$lock_file_path" fi exit $return_value else log_failure_msg "Couldn't find MySQL server ($bindir/mysqld_safe)" fi ;;
#【3.5】 mysql服务停止操作 'stop') # Stop daemon. We use a signal here to avoid having to know the # root password. if test -s "$mysqld_pid_file_path" then # signal mysqld_safe that it needs to stop touch "$mysqld_pid_file_path.shutdown" mysqld_pid=`cat "$mysqld_pid_file_path"` if (kill -0 $mysqld_pid 2>/dev/null) then echo $echo_n "Shutting down MySQL" kill $mysqld_pid # mysqld should remove the pid file when it exits, so wait for it. wait_for_pid removed "$mysqld_pid" "$mysqld_pid_file_path"; return_value=$? else log_failure_msg "MySQL server process #$mysqld_pid is not running!" rm "$mysqld_pid_file_path" fi # Delete lock for RedHat / SuSE if test -f "$lock_file_path" then rm -f "$lock_file_path" fi exit $return_value else log_failure_msg "MySQL server PID file could not be found!" fi ;;
#【3.6】mysql服务重启 'restart') # Stop the service and regardless of whether it was # running or not, start it again. if $0 stop $other_args; then $0 start $other_args else log_failure_msg "Failed to stop running server, so refusing to try to start." exit 1 fi ;; #【3.7】重新加载mysql服务（重新加载复位服务文件，即mysql进程pid文件） 'reload'|'force-reload') if test -s "$mysqld_pid_file_path" ; then read mysqld_pid < "$mysqld_pid_file_path" kill -HUP $mysqld_pid && log_success_msg "Reloading service MySQL" touch "$mysqld_pid_file_path" else log_failure_msg "MySQL PID file could not be found!" exit 1 fi ;;
#【3.8】mysql服务脚本status选项，查看状态 'status') # First, check to see if pid file exists if test -s "$mysqld_pid_file_path" ; then read mysqld_pid < "$mysqld_pid_file_path" if kill -0 $mysqld_pid 2>/dev/null ; then log_success_msg "MySQL running ($mysqld_pid)" exit 0 else log_failure_msg "MySQL is not running, but PID file exists" exit 1 fi else # Try to find appropriate mysqld process mysqld_pid=`pidof $libexecdir/mysqld`
#【3.9】mysql多实例服务 # test if multiple pids exist pid_count=`echo $mysqld_pid | wc -w` if test $pid_count -gt 1 ; then log_failure_msg "Multiple MySQL running but PID file could not be found ($mysqld_pid)" exit 5 elif test -z $mysqld_pid ; then if test -f "$lock_file_path" ; then log_failure_msg "MySQL is not running, but lock file ($lock_file_path) exists" exit 2 fi log_failure_msg "MySQL is not running" exit 3 else log_failure_msg "MySQL is running but PID file could not be found" exit 4 fi fi ;; *)
#【3.10】其他情况，如果输入的命令不是如下命令，那么会给一条提示（即echo的提示） # usage basename=`basename "$0"` echo "Usage: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]" exit 1 ;; esac exit 0