深度解析MySQL启动时报“TheserverquitwithoutupdatingPID。。。很多童鞋在启动mysql的时候，碰到过这个错误，
⾸先，澄清⼀点，出现这个错误的前提是：通过服务脚本来启动mysql。通过mysqld_safe或mysqld启动mysql实例并不会报这个错误。
那么，出现这个错误的原因具体是什么呢？
哈哈，对分析过程不care的童鞋可直接跳到⽂末的总结部分~
下⾯，来分析下mysql的服务启动脚本
脚本完整内容如下：
#!/bin/sh
# Copyright Abandoned 1996 TCX DataKonsult AB & Monty Program KB & Detron HB
# This file is public domain and comes with NO WARRANTY of any kind
# MySQL daemon start/stop script.
# Usually this is put in /etc/init.d (at least on machines SYSV R4 based
# systems) and linked to /etc/rc3.d/S99mysql and /etc/rc0.d/K01mysql.
# When this is done the mysql server will be started when the machine is
# started and shut down when the systems goes down.
# Comments to support chkconfig on RedHat Linux
# chkconfig: 23456436
# description: A very fast and reliable SQL database engine.
# Comments to support LSB init script conventions
### BEGIN INIT INFO
# Provides: mysql
# Required-Start: $local_fs $network $remote_fs
# Should-Start: ypbind nscd ldap ntpd xntpd
# Required-Stop: $local_fs $network $remote_fs
# Default-Start: 2345
# Default-Stop: 016
# Short-Description: start and stop MySQL
# Description: MySQL is a very fast and reliable SQL database engine.
### END INIT INFO
# If you install MySQL on some other places than /usr/local/mysql, then you
# have to do one of the following things for this script to work:
#
# - Run this script from within the MySQL installation directory
# - Create a /etc/myf file with the following information:
# [mysqld]
# basedir=<path-to-mysql-installation-directory>
# - Add the above to any other configuration file (for example ~/.my.ini)
# and copy my_print_defaults to /usr/bin
# - Add the path to the mysql-installation-directory to the basedir variable
# below.
#
# If you want to affect other MySQL variables, you should make your changes
# in the /etc/myf, ~/.myf or other MySQL configuration files.
# If you change base dir, you must also change datadir. These may get
# overwritten by settings in the MySQL configuration files.
basedir=
datadir=
# Default value, in seconds, afterwhich the script should timeout waiting
# for server start.
# Value here is overriden by value in myf.
# 0 means don't wait at all
# Negative numbers mean to wait indefinitely
service_startup_timeout=900
# Lock directory for RedHat / SuSE.
lockdir='/var/lock/subsys'
lock_file_path="$lockdir/mysql"
# The following variables are only set for letting mysql.server find things.
# Set some defaults
mysqld_pid_file_path=
if test -z "$basedir"
then
basedir=/usr/local/mysql
bindir=/usr/local/mysql/bin
if test -z "$datadir"
then
datadir=/usr/local/mysql/data
fi
sbindir=/usr/local/mysql/bin
libexecdir=/usr/local/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=
#
# Use LSB init script functions for printing messages, if possible
#
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! $@"
}
PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin"
export PATH
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"testing\c"`,`echo -n testing` in
*c*,-n*) echo_n= echo_c= ;;
*c*,*) echo_n=-n echo_c= ;;
*) echo_n= echo_c='\c' ;;
esac
parse_server_arguments() {
for arg do
case"$arg"in
--basedir=*) basedir=`echo"$arg" | sed -e 's/^[^=]*=//'`
bindir="$basedir/bin"exited
if test -z "$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 $i + 1`
sleep1
done
if test -z "$i" ; then
log_success_msg
return 0
else
log_failure_msg
return 1
fi
}
# Get arguments from the myf file,
# the only group, which is read from now on is [mysqld]
if test -x ./bin/my_print_defaults
then
print_defaults="./bin/my_print_defaults"
elif test -x $bindir/my_print_defaults
then
print_defaults="$bindir/my_print_defaults"
elif test -x $bindir/mysql_print_defaults
then
print_defaults="$bindir/mysql_print_defaults"
else
# Try to find basedir in /etc/myf
conf=/etc/myf
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="$d/bin/my_print_defaults"
fi
if test -x "$d/bin/mysql_print_defaults"
then
print_defaults="$d/bin/mysql_print_defaults"
break
fi
done
fi
# Hope it's in the PATH ... but I doubt it
test -z "$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
#
extra_args=""
if test -r "$basedir/myf"
then
extra_args="-e $basedir/myf"
else
if test -r "$datadir/myf"
then
extra_args="-e $datadir/myf"
fi
fi
parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`
#
# Set pid file if not given
#
if test -z "$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
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 myf file. This script
# may be overwritten at next upgrade.
$bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 & wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$?
# 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
;;
'stop')
# Stop daemon. We use a signal here to avoid having to know the
# root password.
if test -s "$mysqld_pid_file_path"
then
mysqld_pid=`cat "$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
;;
'restart')
# Stop the service and regardless of whether it was
# running or not, start it again.
if $0 stop $other_args; then
$0 start $other_args
else
log_failure_msg "Failed to stop running server, so refusing to try to start."
exit 1
fi
;;
'reload'|'force-reload')
if test -s "$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
;;
# 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`
# 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
;;
*)
# usage
basename=`basename "$0"`
echo "Usage: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]"
exit 1
;
;
esac
exit 0
View Code
⾸先，定义相关参数
basedir=
datadir=
# Default value, in seconds, afterwhich the script should timeout waiting
# for server start.
# Value here is overriden by value in myf.
# 0 means don't wait at all
# Negative numbers mean to wait indefinitely
service_startup_timeout=900
# Lock directory for RedHat / SuSE.
lockdir='/var/lock/subsys'
lock_file_path="$lockdir/mysql"
其中，
basedir 指的⼆进制压缩包解压后所在的⽬录，譬如/usr/local/mysql。
datadir 指的是数据⽬录
service_startup_timeout=900 定义mysql服务启动的时间限制，如果在900s中没有启动成功，则该脚本会退出。
lockdir='/var/lock/subsys'
关于/var/lock/subsys，⽹上的解释如下，后续会⽤到。
总的来说，系统关闭的过程（发出关闭信号，调⽤服务⾃⾝的进程）中会检查/var/lock/subsys下的⽂件，逐⼀关闭每个服务，如果某⼀运⾏的服务在/var/lock/subsys下没有相应的选项。在系统关闭的时候，会像杀死普通进程⼀样杀死这个服务。
通过察看/etc/rc.d/init.d下的脚本，可以发现每个服务⾃⼰操纵时都会去查看/var/lock/subsys下相应的服务。
很多程序需要判断是否当前已经有⼀个实例在运⾏，这个⽬录就是让程序判断是否有实例运⾏的标志，⽐如说xinetd，如果存在这个⽂件，表⽰已经有xinetd在运⾏了，否则就是没有，当然程序⾥⾯还要有相应的判断措施来真正确定是否有实例在运⾏
判断basedir和datadir
# Set some defaults
mysqld_pid_file_path=
if test -z "$basedir"
then
basedir=/usr/local/mysql
bindir=/usr/local/mysql/bin
if test -z "$datadir"
then
datadir=/usr/local/mysql/data
fi
sbindir=/usr/local/mysql/bin
libexecdir=/usr/local/mysql/bin
else
bindir="$basedir/bin"
if test -z "$datadir"
then
datadir="$basedir/data"
fi
sbindir="$basedir/sbin"
libexecdir="$basedir/libexec"
fi
其中，
mysqld_pid_file_path 指定pid⽂件的路径
-z string 判断字符串是否为空
如果basedir没有显⽰设置，则默认为/usr/local/mysql，这也是为什么很多mysql安装教程都推荐将mysql相关⽂件放到/usr/local/mysql下。
如果datadir没有显⽰设置，则默认为$basedir/data。
定义log_success_msg()和log_failure_msg()函数
⾸先，判断/lib/lsb/init-functions⽂件是否存在，如果存在，则使定义在init-functions⽂件中的所有shell函数在当前脚本中⽣效。
如果没有，则定义两个函数，⼀个⽤于打印成功⽇志，⼀个是打印错误⽇志。
在RHCS 6.7中，该⽂件并不存在，已被/etc/init.d/functions所替代。
#
# Use LSB init script functions for printing messages, if possible
#
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! $@"
}
fi
传递参数
将第⼀个参数传递给mode，剩下的参数传递给other_args
PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin"
export PATH
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"testing\c"`,`echo -n testing` in
*c*,-n*) echo_n= echo_c= ;;
*c*,*) echo_n=-n echo_c= ;;
*) echo_n= echo_c='\c' ;;
esac
解析配置⽂件中的参数
这个函数在脚本后⾯会涉及到。
主要涉及如下参数：--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
}
判断my_print_defaults的位置
⾸先，它判断当前路径下的bin⽬录中是否存在该可执⾏⽂件，如果不存在，则再判断$bindir（通常指的是$basedir/bin）⽬录下是否存在。如果还是没有，则会判断/etc/myf是否存在并且可读，如果是，则判断该配置⽂件中是否指定了basedir参数，
如果指定了，则取出该参数的值，并判断该值对应的⽬录中是否存在bin/my_print_defaults可执⾏⽂件
最后⼀步，如果在上述⽬录中实在没发现my_print_defaults⽂件，
索性就将print_defaults设置为"my_print_defaults"，寄希望于该命令在当前的PATH环境中。
# Get arguments from the myf file,
# the only group, which is read from now on is [mysqld]
if test -x ./bin/my_print_defaults
then
print_defaults="./bin/my_print_defaults"
elif test -x $bindir/my_print_defaults
then
print_defaults="$bindir/my_print_defaults"
elif test -x $bindir/mysql_print_defaults
then
print_defaults="$bindir/mysql_print_defaults"
else
# Try to find basedir in /etc/myf
conf=/etc/myf
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
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