MySQL Deamon少量解读

此文是Mysql 5.7的 Deamon 文件，配置多实例遇到pid不生效的问题，通读了下，贴出来，有少量自己加的注释。

#!/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 $remote_fs# Default-Start:  2 3 4 5# Default-Stop: 0 1 6# Short-Description: start and stop MySQL# Description: MySQL is a very fast and reliable SQL database engine.### END INIT INFO # If you install MySQL on some other places than /usr/local/mysql, then you# have to do one of the following things for this script to work:## - Run this script from within the MySQL installation directory# - Create a /etc/my.cnf file with the following information:#   [mysqld]#   basedir=<path-to-mysql-installation-directory># - Add the above to any other configuration file (for example ~/.my.ini)#   and copy my_print_defaults to /usr/bin# - Add the path to the mysql-installation-directory to the basedir variable#   below.## If you want to affect other MySQL variables, you should make your changes# in the /etc/my.cnf, ~/.my.cnf or other MySQL configuration files.# If you change base dir, you must also change datadir. These may get# overwritten by settings in the MySQL configuration files.basedir=/data/opt/mysqldatadir=/data/opt/mysql/data3307# Default value, in seconds, afterwhich the script should timeout waiting# for server start. # Value here is overriden by value in my.cnf. # 0 means don't wait at all# Negative numbers mean to wait indefinitelyservice_startup_timeout=900# Lock directory for RedHat / SuSE.lockdir='/var/lock/subsys'lock_file_path="$lockdir/mysql"# The following variables are only set for letting mysql.server find things.# Set some defaultsmysqld_pid_file_path=#如果$basedir 字符串为空 #则定位到默认位置#basedir=/usr/local/mysql#datadir=/usr/local/mysql/data#bindir=/usr/local/mysql/bin#sbindir=/usr/local/mysql/bin#libexecdir=/usr/local/mysql/binif test -z "$basedir"  then  basedir=/usr/local/mysql  bindir=/usr/local/mysql/bin  if test -z "$datadir"  then    datadir=/usr/local/mysql/data  fi  sbindir=/usr/local/mysql/bin  libexecdir=/usr/local/mysql/binelse  bindir="$basedir/bin"     #ok  if test -z "$datadir"  then    datadir="$basedir/data"  fi  sbindir="$basedir/sbin" #ok  libexecdir="$basedir/libexec" #okfi# 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 #文件存在,且是正规文件  . $lsb_functionselse  log_success_msg()  {    echo " SUCCESS! $@"  #$@ 所有参数列表  }  log_failure_msg()  {    echo " ERROR! $@"  }fiPATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin"  #启动加载环境变量export PATHmode=$1    # start or stop[ $# -ge 1 ] && shift   # $#:参数个数 遍历参数other_args="$*"   # 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' ;;esacparse_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 "$bindir/my_print_defaults";  then  print_defaults="$bindir/my_print_defaults"  #okelse  # 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#extra_args=""if test -r "$basedir/my.cnf"then  extra_args="-e $basedir/my.cnf"fiparse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`## Set pid file if not given 设置pid#if test -z "$mysqld_pid_file_path"  #如果mysqld_pid_file_path没设置then  mysqld_pid_file_path=$datadir/`hostname`.pid else  case "$mysqld_pid_file_path" in    /* ) ;;    * )  mysqld_pid_file_path="$datadir/$mysqld_pid_file_path" ;;  esacficase "$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.  #--defaults-file要作为第一个参数出现      $bindir/mysqld_safe --defaults-file="$datadir/my3307.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    ;;  '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    ;;  '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 $mysqld_pid && log_success_msg "Reloading service MySQL" #平滑更新服务配置      touch "$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    ;;esacexit 0