MySQL啟動(dòng)時(shí)報(bào)“The server quit without updating PID file”錯(cuò)誤解決辦法

本文主要介紹了mysql啟動(dòng)時(shí)報(bào)“the server quit without updating pid file”錯(cuò)誤的原因,需要的朋友可以參考下,希望能幫助到大家。

很多童鞋在啟動(dòng)mysql的時(shí)候,碰到過這個(gè)錯(cuò)誤,

首先,澄清一點(diǎn),出現(xiàn)這個(gè)錯(cuò)誤的前提是:通過服務(wù)腳本來啟動(dòng)mysql。通過mysqld_safe或mysqld啟動(dòng)mysql實(shí)例并不會(huì)報(bào)這個(gè)錯(cuò)誤。

那么,出現(xiàn)這個(gè)錯(cuò)誤的原因具體是什么呢?

哈哈,對(duì)分析過程不care的童鞋可直接跳到文末的總結(jié)部分~

總結(jié)

下面,來分析下mysql的服務(wù)啟動(dòng)腳本

腳本完整內(nèi)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: 2345 64 36  # 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 $remote_fs  # Default-Start: 2 3 4 5  # Default-Stop: 0 1 6  # Short-Description: start and stop MySQL  # Description: MySQL is a very fast and reliable SQL database engine.  ### END INIT INFO  # If you install MySQL on some other places than /usr/local/mysql, then you  # have to do one of the following things for this script to work:  #  # - Run this script from within the MySQL installation directory  # - Create a /etc/my.cnf file with the following information:  # [mysqld]  # basedir=<path-to-mysql-installation-directory>  # - Add the above to any other configuration file (for example ~/.my.ini)  # and copy my_print_defaults to /usr/bin  # - Add the path to the mysql-installation-directory to the basedir variable  # below.  #  # If you want to affect other MySQL variables, you should make your changes  # in the /etc/my.cnf, ~/.my.cnf or other MySQL configuration files.  # If you change base dir, you must also change datadir. These may get  # overwritten by settings in the MySQL configuration files.  basedir=  datadir=  # Default value, in seconds, afterwhich the script should timeout waiting  # for server start.   # Value here is overriden by value in my.cnf.   # 0 means don't wait at all  # Negative numbers mean to wait indefinitely  service_startup_timeout=900  # Lock directory for RedHat / SuSE.  lockdir='/var/lock/subsys'  lock_file_path="$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! $@"   }  fi  PATH="/sbin:/usr/sbin:/bin:/usr/bin:$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 "testingc"`,`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="$basedir/bin"     if test -z "$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  }  # Get arguments from the my.cnf 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/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="$d/bin/my_print_defaults"    break    fi    if test -x "$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/my.cnf"  then   extra_args="-e $basedir/my.cnf"  else   if test -r "$datadir/my.cnf"   then   extra_args="-e $datadir/my.cnf"   fi  fi  parse_server_arguments `$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 my.cnf 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   ;;   '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`    # 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

首先,定義相關(guān)參數(shù)

basedir=  datadir=  # 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  service_startup_timeout=900  # Lock directory for RedHat / SuSE.  lockdir='/var/lock/subsys'  lock_file_path="$lockdir/mysql"

其中,

basedir 指的二進(jìn)制壓縮包解壓后所在的目錄,譬如/usr/local/mysql。

datadir 指的是數(shù)據(jù)目錄

service_startup_timeout=900 定義mysql服務(wù)啟動(dòng)的時(shí)間限制,如果在900s中沒有啟動(dòng)成功,則該腳本會(huì)退出。

lockdir='/var/lock/subsys'

關(guān)于/var/lock/subsys,網(wǎng)上的解釋如下,后續(xù)會(huì)用到。

總的來說,系統(tǒng)關(guān)閉的過程(發(fā)出關(guān)閉信號(hào),調(diào)用服務(wù)自身的進(jìn)程)中會(huì)檢查/var/lock/subsys下的文件,逐一關(guān)閉每個(gè)服務(wù),如果某一運(yùn)行的服務(wù)在/var/lock/subsys下沒有相應(yīng)的選項(xiàng)。在系統(tǒng)關(guān)閉的時(shí)候,會(huì)像殺死普通進(jìn)程一樣殺死這個(gè)服務(wù)。

通過察看/etc/rc.d/init.d下的腳本,可以發(fā)現(xiàn)每個(gè)服務(wù)自己操縱時(shí)都會(huì)去查看/var/lock/subsys下相應(yīng)的服務(wù)。

很多程序需要判斷是否當(dāng)前已經(jīng)有一個(gè)實(shí)例在運(yùn)行,這個(gè)目錄就是讓程序判斷是否有實(shí)例運(yùn)行的標(biāo)志,比如說xinetd,如果存在這個(gè)文件,表示已經(jīng)有xinetd在運(yùn)行了,否則就是沒有,當(dāng)然程序里面還要有相應(yīng)的判斷措施來真正確定是否有實(shí)例在運(yùn)行。通常與該目錄配套的還有/var/run目錄,用來存放對(duì)應(yīng)實(shí)例的PID,如果你寫腳本的話,會(huì)發(fā)現(xiàn)這2個(gè)目錄結(jié)合起來可以很方便的判斷出許多服務(wù)是否在運(yùn)行,運(yùn)行的相關(guān)信息等等。?

判斷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文件的路徑

-z string 判斷字符串是否為空

如果basedir沒有顯示設(shè)置,則默認(rèn)為/usr/local/mysql,這也是為什么很多mysql安裝教程都推薦將mysql相關(guān)文件放到/usr/local/mysql下。

如果datadir沒有顯示設(shè)置,則默認(rèn)為$basedir/data。

定義log_success_msg()和log_failure_msg()函數(shù)

首先,判斷/lib/lsb/init-functions文件是否存在,如果存在,則使定義在init-functions文件中的所有shell函數(shù)在當(dāng)前腳本中生效。

如果沒有,則定義兩個(gè)函數(shù),一個(gè)用于打印成功日志,一個(gè)是打印錯(cuò)誤日志。

在RHCS 6.7中,該文件并不存在,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

傳遞參數(shù)

將第一個(gè)參數(shù)傳遞給mode,剩下的參數(shù)傳遞給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 "testingc"`,`echo -n testing` in   *c*,-n*) echo_n= echo_c=  ;;   *c*,*) echo_n=-n echo_c=  ;;   *)  echo_n= echo_c='c' ;;  esac

解析配置文件中的參數(shù)

這個(gè)函數(shù)在腳本后面會(huì)涉及到。

主要涉及如下參數(shù):–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  }

判斷my_print_defaults的位置

首先,它判斷當(dāng)前路徑下的bin目錄中是否存在該可執(zhí)行文件,如果不存在,則再判斷$bindir(通常指的是$basedir/bin)目錄下是否存在。

如果還是沒有,則會(huì)判斷/etc/my.cnf是否存在并且可讀,如果是,則判斷該配置文件中是否指定了basedir參數(shù),

如果指定了,則取出該參數(shù)的值,并判斷該值對(duì)應(yīng)的目錄中是否存在bin/my_print_defaults可執(zhí)行文件

最后一步,如果在上述目錄中實(shí)在沒發(fā)現(xiàn)my_print_defaults文件,

索性就將print_defaults設(shè)置為”my_print_defaults”,寄希望于該命令在當(dāng)前的PATH環(huán)境中。

# Get arguments from the my.cnf 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/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="$d/bin/my_print_defaults"    break    fi    if test -x "$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

查找默認(rèn)的配置文件

-r file 如果文件可讀,則為真

#  # 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/my.cnf"  then   extra_args="-e $basedir/my.cnf"  else   if test -r "$datadir/my.cnf"   then   extra_args="-e $datadir/my.cnf"   fi  fi

解析配置文件中的參數(shù)

my_print_defaults的用法如下:

my_print_defaults –defaults-file=example.cnf client mysql

即讀取配置文件中,client和mysql部分的參數(shù)配置,

具體在本腳本中,是讀取mysqld,server,mysql_server,mysql.server四個(gè)部分的配置參數(shù)。

parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`

設(shè)置pid file的路徑

-z string 判斷字符串是否為空

如果–pid-file沒有在讀取到的配置文件中設(shè)置或者腳本剛開始的mysqld_pid_file_path參數(shù)沒有設(shè)置,

則pid file默認(rèn)設(shè)置在datadir下,以主機(jī)名.pid命名。

如果該參數(shù)設(shè)置了,還需要進(jìn)一步判斷

如果該參數(shù)中帶有斜杠,則代表給定的值帶有路徑,可直接使用。

如果該參數(shù)中沒帶路徑,則代表給定的值只是pid的文件名,可將其設(shè)在datadir下。

#  # 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

服務(wù)腳本start選項(xiàng)

首先,切換到$basedir中

其次,判斷$basedir/bin中的mysqld_safe是否是可執(zhí)行文件,如果是,則啟動(dòng)mysqld實(shí)例,如果不是,則報(bào)錯(cuò)退出。

那么,啟動(dòng)流程又是如何實(shí)現(xiàn)的呢?

首先,執(zhí)行$bindir/mysqld_safe –datadir=”$datadir” –pid-file=”$mysqld_pid_file_path” $other_args >/dev/null 2>&1 &命令,啟動(dòng)mysqld實(shí)例。

注意到?jīng)]有,mysqld_safe其實(shí)是在basedir中執(zhí)行的,包括mysql初始化腳本mysql_install_db,也建議在basedir中執(zhí)行,具體可參考:

分析MariaDB初始化腳本mysql_install_db

然后通過wait_for_pid函數(shù)進(jìn)行判斷,具體可見下文對(duì)于wait_for_pid函數(shù)的分析

判斷完畢后,

查看$lockdir目錄是否可寫,可寫的話,則在目錄上創(chuàng)建一個(gè)文件。

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.    $bindir/mysqld_safe --datadir="$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   ;;

wait_for_pid函數(shù)

在利用mysqld_safe啟動(dòng)mysql實(shí)例后,會(huì)調(diào)用該參數(shù)

wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$?

其中$!在shell中用于獲取最后運(yùn)行的后臺(tái)Process的PID,具體在本例中,是mysqld_safe進(jìn)程的pid。

因?yàn)榈谝粋€(gè)參數(shù)是created,所以會(huì)執(zhí)行test -s “$pid_file_path” && i=” && break命令。

-s file 如果文件的長(zhǎng)度不為零,則為真

該命令的意思是如果pid文件存在,則將變量i設(shè)置為空,并退出while循環(huán)。

然后執(zhí)行如下判斷,

if test -z "$i" ; then   log_success_msg   return 0   else   log_failure_msg   return 1   fi

如果$i為空,則打印成功日志,并退出腳本,很顯然,在pid文件存在的情況下,會(huì)將變量i設(shè)置為空。

再來看看pid文件不存在的情況

首先,會(huì)判斷$pid是否不為空(即if test -n “$pid”)

如果不為空,則代表在執(zhí)行完mysqld_safe后,已經(jīng)捕捉到了該進(jìn)程的pid。

在這種情況下,進(jìn)一步通過kill -0 “$pid”確認(rèn)該進(jìn)程是否存在。

kill -0就是不發(fā)送任何信號(hào),但是系統(tǒng)會(huì)進(jìn)行錯(cuò)誤檢查,所以經(jīng)常用來檢查一個(gè)進(jìn)程是否存在,當(dāng)進(jìn)程不存在時(shí), kill -0 pid會(huì)返回錯(cuò)誤

如果該進(jìn)程存在,則不執(zhí)行任何操作,直接跳到如下操作

echo $echo_n ".$echo_c"  i=`expr $i + 1`  sleep 1

將變量i加1,并sleep 1s。

然后,繼續(xù)while循環(huán),之所以這樣做,是考慮到mysqld_safe已經(jīng)執(zhí)行,但是mysqld實(shí)例還在啟動(dòng)過程中,還沒創(chuàng)建好pid文件。

一直到$1達(dá)到$service_startup_timeout定義的時(shí)長(zhǎng)。

如果在while循環(huán)的過程中,通過kill -0 “$pid”判斷到進(jìn)程已經(jīng)不存在了,

則會(huì)再判斷一次,如果這次判斷的結(jié)果依舊是pid file不存在,且進(jìn)程不存在,則會(huì)執(zhí)行

log_failure_msg "The server quit without updating PID file ($pid_file_path)."

這就是大名鼎鼎的“The server quit without updating PID file”的由來。

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  }

服務(wù)腳本stop選項(xiàng)

首先,判斷pid文件的長(zhǎng)度是否不為零。

-s file 如果文件的長(zhǎng)度不為零,則為真

此時(shí),會(huì)通過pid文件獲取mysqld進(jìn)程的pid,注意,不是mysqld_safe進(jìn)程的pid

然后,判斷mysqld進(jìn)程是否在正常運(yùn)行,

如果是,則通過kill $mysqld_pid的方式來關(guān)閉mysqld進(jìn)程

殺死進(jìn)程最安全的方法是單純使用kill命令,不加修飾符,不帶標(biāo)志。

標(biāo)準(zhǔn)的kill命令通常會(huì)終止有問題的進(jìn)程,并把進(jìn)程的資源釋放給系統(tǒng)。然而,如果進(jìn)程啟動(dòng)了子進(jìn)程,只殺死父進(jìn)程,子進(jìn)程仍在運(yùn)行,因此仍消耗資源。為了防止這些所謂的“僵尸進(jìn)程”,應(yīng)確保在殺死父進(jìn)程之前,先殺死其所有的子進(jìn)程。

然后,調(diào)用wait_for_pid函數(shù)進(jìn)行判斷,其實(shí),wait_for_pid函數(shù)中設(shè)置avoid_race_condition變量的目的是為了stop選項(xiàng),確實(shí)有可能出現(xiàn),mysqld是在檢查pid file之后,檢查進(jìn)程是否存活之前退出的。

如果mysqld進(jìn)程沒有正常運(yùn)行,在會(huì)打印“MySQL server process #$mysqld_pid is not running!”信息,并刪除pid文件。

如果在執(zhí)行stop的時(shí)候,判斷pid文件的長(zhǎng)度為0,則會(huì)打印”MySQL server PID file could not be found!”信息。

所以,在pid文件不存在的情況下,通過服務(wù)腳本執(zhí)行stop選項(xiàng)并不會(huì)關(guān)閉mysqld進(jìn)程,這個(gè)時(shí)候,就可通過kill $mysqld_pid的方式來關(guān)閉mysqld進(jìn)程。

'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   ;;

服務(wù)腳本restart選項(xiàng)

首先,先執(zhí)行stop操作,如果stop操作成功的話,則繼續(xù)執(zhí)行start操作。

如果stop操作失敗的話,則會(huì)輸出”Failed to stop running server, so refusing to try to start.”信息,并退出腳本。

 '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   ;;

服務(wù)腳本reload選項(xiàng)

首先,判斷pid文件的長(zhǎng)度是否為0,如果不為0,則將該文件中的值設(shè)置為mysqld_pid變量的值。

然后對(duì)該進(jìn)程執(zhí)行kill -HUP操作。

kill -HUP pid

pid 是進(jìn)程標(biāo)識(shí)。如果想要更改配置而不需停止并重新啟動(dòng)服務(wù),請(qǐng)使用該命令。在對(duì)配置文件作必要的更改后,發(fā)出該命令以動(dòng)態(tài)更新服務(wù)配置。

根據(jù)約定,當(dāng)您發(fā)送一個(gè)掛起信號(hào)(信號(hào) 1 或 HUP)時(shí),大多數(shù)服務(wù)器進(jìn)程(所有常用的進(jìn)程)都會(huì)進(jìn)行復(fù)位操作并重新加載它們的配置文件。

如果pid文件的長(zhǎng)度為0,則輸出”MySQL PID file could not be found!”。

 '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   ;;

服務(wù)腳本status選項(xiàng)

首先,判斷pid文件長(zhǎng)度是否為0,如果不是,則讀取該文件中的值,并判斷pid對(duì)應(yīng)的進(jìn)程是否運(yùn)行正常,

如果運(yùn)行正常,則輸出”MySQL running”

如果不正常,則輸出”MySQL is not running, but PID file exists”

如果pid文件的長(zhǎng)度為0,則試圖通過mysqld的啟動(dòng)命令來獲取其pid,

這個(gè)時(shí)候,可能存在一個(gè)mysqld程序啟動(dòng)了多個(gè)實(shí)例,這會(huì)導(dǎo)致pid_count=`echo $mysqld_pid | wc -w`大于1。

這個(gè)時(shí)候,會(huì)輸出”Multiple MySQL running but PID file could not be found”信息,并退出腳本。

如果mysqld_pid為空,則會(huì)繼續(xù)判斷”$lock_file_path”是否存在,如果存在,

則會(huì)輸出”MySQL is not running, but lock file ($lock_file_path) exists”信息。

如果”$lock_file_path”不存在,則會(huì)輸出”MySQL is not running”信息。

如果mysqld_pid等于1,則會(huì)輸出”MySQL is running but PID file could not be found”信息。

 '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`    # 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   ;;

服務(wù)腳本其它選項(xiàng)

如果腳本的第一個(gè)參數(shù)不是上述幾個(gè)選項(xiàng),則會(huì)輸出Usage信息。

 *)    # usage    basename=`basename "$0"`    echo "Usage: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]"    exit 1   ;;

至此,mysql的服務(wù)腳本分析完畢~

總結(jié)

在通過服務(wù)腳本啟動(dòng)mysql的過程中,報(bào)“The server quit without updating PID file”錯(cuò)誤,有兩個(gè)條件

首先,pid文件不存在

其次,通過kill -0 $pid檢查到進(jìn)程并不存在

這個(gè)時(shí)候,只能通過mysql數(shù)據(jù)庫的錯(cuò)誤日志來定位。

服務(wù)腳本如果不做任何調(diào)整的話,默認(rèn)的basedir是/usr/local/mysql,datadir是/usr/local/mysql/data

如果自己的mysql服務(wù)均不是默認(rèn)路徑,

則需要在該腳本中顯式設(shè)置

經(jīng)測(cè)試,需設(shè)置如下幾處:

1. 設(shè)置basedir和添加conf變量

其中,conf指的是mysqld的配置文件,建議配置文件中顯式指定basedir和datadir的值。

在這里,datadir可不設(shè)置,因?yàn)閐atadir可通過配置文件來獲取。

但是basedir必須要指定,因?yàn)橐紫雀鶕?jù)basedir來判斷my_print_deefauts命令

basedir=/usr/local/mysql-advanced-5.6.23-linux-glibc2.5-x86_64  datadir=  conf=/usr/local/mysql-advanced-5.6.23-linux-glibc2.5-x86_64/my_3308.cnf

2. 第256行,添加extra_args=” -c $conf”

extra_args=" -e $basedir/my.cnf.bak"  if test -r "$basedir/my.cnf"  then   extra_args="-e $basedir/my.cnf"  else   if test -r "$datadir/my.cnf"   then   extra_args="-e $datadir/my.cnf"   fi  fi  extra_args=" -c $conf"

3. 修改285行mysqld_safe的啟動(dòng)參數(shù)

 $bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &

修改為,

  $bindir/mysqld_safe --defaults-file="$conf" --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &

主要是添加了–defaults-file選項(xiàng)

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