There are numerous advantages to run multiple database instances on the save physical server. Here are some reasons that I would like to point out :
1. Utilize existing hardware properly
2. Long lead times to provide physical hardware
3. Reduce Licensing Hardware / OS costs
4. Smaller/manageable data center foot print
5. Reduced overhead
To run multiple instances using MysqL we need to have a couple of things separate from the initial install on MysqL like data directory,init script and config file. It is quite that simple and here is how we do it,I will subscript 2 for all the files/directories that I am going to create to indicate this new second instance:
1. Create a new data directory [/var/lib/MysqL2] and make MysqL user own it.
mkdir /var/lib/MysqL2
chown MysqL.MysqL /var/lib/MysqL2/
cp /etc/my.cnf /etc/my2.cnf
vi /etc/my2.cnfUpdate the lines as shown in the screenshot above [If you have a custom path,use it]:
datadir=/var/lib/MysqL2 port=33073. Create/copy existing MysqL init file to start/stop/reload etc on this new instance
cp /etc/init.d/MysqL /etc/init.d/MysqL24. Edit the init file and make some minor changes to make it this instance specific [Four edits required]
vi /etc/init.d/MysqL2
Edit 1 : Add the following line after line 138 for the init script to handle ports
--port=*) port=`echo "$arg" sed -e 's/^[^=]*=//'` ;;
Edit 2 : At line 215 update my.cnf to point to the new config file my2.cnf for this instance
conf=/etc/my2.cnf
Edit 3: At line 257 add -c flag to the arguments to read this config file while parsing server arguments
parse_server_arguments `$print_defaults $extra_args MysqLd server MysqL_server MysqL.server -c/etc/my2.cnf`
Edit 4: Add port argument to MysqL_safe command on line 284
$bindir/MysqLd_safe --defaults-file=/etc/my2.cnf --datadir="$datadir" --pid-file="$MysqLd_pid_file_path" --port="$port" --socket="$datadir"/MysqL2.sock $other_args >/dev/null 2>&1 &
You final init script looks like the following:
#!/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: MysqLs # required-Start: $local_fs $network $remote_fs # Should-Start: ypbind nscd ldap ntpd xntpd # required-Stop: $local_fs $network $remote_fs # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6 # Short-Description: start and stop MysqL # Description: MysqL is a very fast and reliable sql database engine. ### END INIT INFO # If you change base dir,you must also change datadir. These may get # overwritten by settings in the MysqL configuration files. basedir= datadir= # Default value,in seconds,afterwhich the script should timeout waiting # for server start. # Value here is overriden by value in my.cnf. # 0 means don't wait at all # Negative numbers mean to wait indefinitely service_startup_timeout=900 # Lock directory for RedHat / SuSE. lockdir='/var/lock/subsys' lock_file_path="$lockdir/MysqL" # The following variables are only set for letting MysqL.server find things. # Set some defaults MysqLd_pid_file_path= if test -z "$basedir" then basedir=/usr bindir=/usr/bin if test -z "$datadir" then datadir=/var/lib/MysqL fi sbindir=/usr/sbin libexecdir=/usr/sbin 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 "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="$basedir/bin" if test -z "$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 "$arg" | sed -e 's/^[^=]*=//'` ;; --port=*) port=`echo "$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/my2.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 $extra_args MysqLd server MysqL_server MysqL.server -c/etc/my2.cnf` # # Set pid file if not given # if test -z "$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. $bindir/MysqLd_safe --defaults-file=/etc/my2.cnf --datadir="$datadir" --pid-file="$MysqLd_pid_file_path" --port="$port" --socket="$datadir"/MysqL2.sock $other_args >/dev/null 2>&1 & wait_for_pid created "$!" "$MysqLd_pid_file_path"; return_value=$? # 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` if 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
If you plan on deploying more instances you just need to work through edit 2 and 3 mentioned above after you copy the above init file.
5. Install default tables for this new database instance
MysqL_install_db --datadir=/var/lib/MysqL2 --defaults-file=/etc/my2.cnf --user=MysqL
6. Start the new instance
/usr/bin/MysqLadmin -u root -h127.0.0.1 -P3307 password 'opensourcedbmsadmin' MysqL -uroot -h127.0.0.1 -P3307 -p
8. Finally add it to server start-up list
chkconfig --add MysqL2chkconfig MysqL2 --level 2345 on
If you want to deploy more instances change the subscript and follow above. Make sure that you properly manage memory and processor allocations when running multiple MysqL instances on the same server. Please post any questions below and I will answer as soon as I can.
