(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//data # Default value, in seconds, afterwhich the script should timeout waiting
# for server start.
# Value here is overriden by value in my.cnf.
# 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= # 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="$lockdir/mysql" # The following variables are only set for letting mysql.server find things. # Set some defaults
#【1.4】判断mysql有没有启动
mysqld_pid_file_path=/mysql/data//mysql.pid
#【1.5】判断文件是否存在,然后进行相应的赋值
if test -z "$basedir"
then
basedir=/mysql/app/mysql
bindir=/mysql/app/mysql/bin
if test -z "$datadir"
then
datadir=/mysql/data//data
fi
sbindir=/mysql/app/mysql/bin
libexecdir=/mysql/app/mysql/bin
else
bindir="$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=$ # start or stop [ $# -ge ] && shift other_args="$*" # 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 "testing\c"`,`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=
;;
--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=
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
;;
esac # if server isn't running, then pid-file will never be updated
if test -n "$pid"; then
if kill - "$pid" >/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 # not waiting any more.
fi
fi echo $echo_n ".$echo_c"
i=`expr $i + `
sleep done if test -z "$i" ; then
log_success_msg
return
else
log_failure_msg
return
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

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