from:http://blog.csdn.net/signmem/article/details/17379427
特色
MySQL/Galera 是一种多主同步集群，但只限于使用 MySQL/InnoDB 引擎，并具有下面特点
同步复制
多个主服务器的拓扑结构
可以在任意节点上进行读写
自动控制成员，自动删除故障节点
自动加入节点
真正给予行级别的并发复制
调度客户连接
优势
参考下面基于 DBMS 集群的解决方法
不存在从服务器角色
不存在事务丢失
读写操作可根据需要进行随意扩展
更少的闩操作
知识点
MySQL/Galera 集群使用 Galera 库执行复制，对应 Galera 复制接口，我们需要MySQL 服务器支持 wsrep API 接口
http://www.codership.com/products/mysql-write-set-replication-project
是否可以使用 MySQL 而不使用 mariadb?
不可以，因为 mysql 中没有支持 wsrep_ 数据复制的参数，当然代码级别上也具有很大差别
工作原理
mariadb 可以看做是常见的数据库，负责连接应用(web, API 等）
单纯的 mariadb 无法实现多个主服务器数据同步
多台数据库中数据同步由 wsrep 接口实现
最终目标，实现多个 MySQL 同时读写
wsrep API
wsrep API 是一种数据库插件接口，比较类似一种应用程序，主要针对写复制
该程序主要用于定义应用程序如何调用复制库实现回写
wsrep API 由支持改库的应用程序动态装载
全局事务ID(GTID)
wsrep API 描述下面复制模型，一个应用程序，如数据库当前的一个对象，当前被客户端修改，对象改变导致事务产生一系列的原子性改变， 在集群中所有的节点都具备相同的对象，并由同步复制应用都各自节点，按照相同的顺序产生相同变化从而实现数据同步
到最后，wsrep API 将会分配一个全局事务ID 该 ID 具有下面功能
标识对象的改变
标识对象自身 ID 最后状态（正常情况下，ID 是连续不中断的）
GTID 包含
一个 UUID 作为对象标识及经历改变的序号，序号会发生连续的改变
GTID 允许比较应用程序状态，建立对象改变的顺序，决定对象的变化是否需要更新 GTID
通常 GTID 会卑记录成下面格式
45eec521-2f34-11e0-0800-2a36050b826b:94530586304
言归正传，我们需要编译 mariadb-mysql 及 galera 插件
galera/mysql 编译步骤
https://downloads.mariadb.org/interstitial/mariadb-galera-5.5.33a/kvm-tarbake-jaunty-x86/mariadb-galera-5.5.33a.tar.gz/from/http://mirrors.scie.in/mariadb
yum install -y cmake
tar xf mariadb-galera-5.5.33a.tar.gz
cd mariadb-5.5.33a/
cmake -LAH
参考 CMakeCache.txt 文件中的配置信息
- cmake -DINSTALL_MYSQLDATADIR:STRING=/mdb -DINSTALL_UNIX_ADDRDIR:STRING=/var/run/mysqld/mysql5.socket
- make
- make install
默认情况下， mariadb 安装在 /usr/local/mysql
galera 编译
https://launchpad.net/galera/2.x/23.2.7/+download/galera-23.2.7-src.tar.gz
添加数据源
- baseurl=http://mirror.neu.edu.cn/fedora/epel//6Server/x86_64/
添加下面软件包
- yum erase -y mysql.x86_64 mysql-devel.x86_64 mysql-libs.x86_64
- yum install -y boost-devel.x86_64 libodb-boost-devel.x86_64 bzr scons
解压 galera-23.2.7-src.tar.gz 并进行编译
- cd /usr/src
- tar xf galera-23.2.7-src.tar.gz
- cd galera-23.2.7-src
- scons
注: scons 为编译命令
编译后能生成 libgalera_smm.so
复制编译好的库至下面位置 /usr/local/galera/lib/libgalera_smm.so
- mkdir /usr/local/galera/lib -p
- cp /usr/src/galera-23.2.7-src/libgalera_smm.so /usr/local/galera/lib/libgalera_smm.so
复制 启动脚本 /usr/src/galera-23.2.7-src/scripts/mysql/mysql-galera 到 /usr/local
- cp /usr/src/galera-23.2.7-src/scripts/mysql/mysql-galera /usr/local
创建 /usr/local/mysql/etc/my.cnf
- [mysqld]
- basedir=/usr/local/mysql
- big-tables
- bind-address=0.0.0.0
- character-set-server=utf8
- datadir=/mdb
- log-error=/var/log/mysqld/mysql5-error.log
- socket=/var/run/mysqld/mysql5.socket
- pid-file=/var/run/mysqld/mysql5.pid
- port=3306
- user=mysql
-
- binlog_format = ROW
- binlog_cache_size = 1M
- character_set_server = utf8
- collation_server = utf8_general_ci
-
- default-storage-engine = InnoDB
-
- expire_logs_days = 10
-
- innodb_buffer_pool_size = 300M
- innodb_thread_concurrency = 16
- innodb_log_buffer_size = 8M
-
- innodb_doublewrite = 1
- innodb_file_per_table = 1
- innodb_flush_log_at_trx_commit = 2
-
- server-id = 1
- max_connections = 1000
-
- net_buffer_length = 8K
- open-files-limit = 65535
-
- wsrep_cluster_address = 'gcomm://192.168.200.163,192.168.200.171,172.18.8.49，172.18.8.50'
- wsrep_provider = /usr/local/galera/lib/libgalera_smm.so
- wsrep_retry_autocommit = 0
- wsrep_sst_method = rsync
- wsrep_provider_options="gcache.size=256m; gcache.page_size=256m"
- wsrep_slave_threads=16
-
- wsrep_cluster_name='my_cluster'
- wsrep_node_name='db5'
-
- wsrep_sst_auth=tt:tt123
maridb 启动测试
初始化数据库
- mkdir /mdb
- cd /usr/local/mysql
- ./scripts/install_mysql_db --datadir=/mdb
启动脚本 /etc/rc.d/init.d/mysql5 确保文件可执行权限
- #!/bin/sh
- # chkconfig: 2345 64 36
- # description: A very fast and reliable SQL database engine.
- <p>basedir=/usr/local/mysql
- datadir=/mdb</p><p># 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
- startup_sleep=1</p><p># Lock directory for RedHat / SuSE.
- lockdir='/var/lock/subsys'
- lock_file_path="$lockdir/mysql"</p><p># The following variables are only set for letting mysql.server find things.</p><p># Set some defaults
- mysqld_pid_file_path=/var/run/mysqld/mysql5.pid
- if test -z "$basedir"
- then
- basedir=/usr/local/mysql
- bindir=/usr/local/mysql/bin
- if test -z "$datadir"
- then
- datadir=/usr/local/mysql/data
- fi
- sbindir=/usr/local/mysql/bin
- libexecdir=/usr/local/mysql/bin
- </p><p>else
- bindir="$basedir/bin"
- if test -z "$datadir"
- then
- datadir="$basedir/data"
- fi
- sbindir="$basedir/sbin"
- if test -f "$basedir/bin/mysqld"
- then
- libexecdir="$basedir/bin"
- else
- libexecdir="$basedir/libexec"
- fi
- fi</p><p># datadir_set is used to determine if datadir was set (and so should be
- # *not* set inside of the --basedir= handler.)
- datadir_set=</p><p>#
- # 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! $@"
- }
- fi</p><p>PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin"
- </p><p>export PATH</p><p>mode=$1 # start or stop</p><p>[ $# -ge 1 ] && shift</p><p>
- other_args="$*" # 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.</p><p>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</p><p>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"
- if test -f "$basedir/bin/mysqld"
- then
- libexecdir="$basedir/bin"
- else
- libexecdir="$basedir/libexec"
- fi
- libexecdir="$basedir/libexec"
- ;;
- --datadir=*) datadir=`echo "$arg" | sed -e 's/^[^=]*=//'`
- datadir_set=1
- </p><p> ;;
- --pid-file=*) mysqld_pid_file_path=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;
- --service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;
- esac
- done
- }</p><p>wait_for_pid () {
- verb="$1" # created | removed
- pid="$2" # process ID of the program operating on the pid-file
- pid_file_path="$3" # path to the PID file.</p><p> sst_progress_file=$datadir/sst_in_progress
- i=0
- avoid_race_condition="by checking again"</p><p> while test $i -ne $service_startup_timeout ; do</p><p> case "$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</p><p> # 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
- </p><p> else
- # The server may have exited between the last pid-file check and now.
- if test -n "$avoid_race_condition"; then
- avoid_race_condition=""
- continue # Check again.
- fi</p><p> # there's nothing that will affect the file.
- log_failure_msg "The server quit without updating PID file ($pid_file_path)."
- return 1 # not waiting any more.
- fi
- fi</p><p> if test -e $sst_progress_file && [ $startup_sleep -ne 100 ];then
- echo $echo_n "SST in progress, setting sleep higher"
- startup_sleep=100
- fi</p><p> echo $echo_n ".$echo_c"
- i=`expr $i + 1`
- sleep $startup_sleep</p><p> done</p><p> if test -z "$i" ; then
- log_success_msg
- return 0
- else
- log_failure_msg
- return 1
- fi
- }</p><p># 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
- </p><p> 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=/usr/local/mysql/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="$d/bin/mysql_print_defaults"
- break
- fi
- done
- fi</p><p> # Hope it's in the PATH ... but I doubt it
- test -z "$print_defaults" && print_defaults="my_print_defaults"
- fi</p><p>#
- # Read defaults file from 'basedir'. If there is no defaults file there
- </p><p># check if it's in the old (depricated) place (datadir) and read it from there
- #</p><p>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 $datadir/my.cnf"
- fi
- fi</p><p>parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`</p><p>#
- # Set pid file if not given
- #
- if test -z "$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</p><p>case "$mode" in
- 'start')
- # Start daemon</p><p> # Safeguard (relative paths, core dumps..)
- cd $basedir</p><p> echo $echo_n "Starting MySQL"
- </p><p> 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" $other_args >/dev/null 2>&1 &
- wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$?</p><p> # Make lock for RedHat / SuSE
- if test -w "$lockdir"
- then
- touch "$lock_file_path"
- fi</p><p> exit $return_value
- else
- log_failure_msg "Couldn't find MySQL server ($bindir/mysqld_safe)"
- fi
- ;;</p><p> 'stop')
- # Stop daemon. We use a signal here to avoid having to know the
- # root password.</p><p> if test -s "$mysqld_pid_file_path"
- then
- mysqld_pid=`cat "$mysqld_pid_file_path"`</p><p> 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
- </p><p> # 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
- ;;</p><p> 'restart')
- # Stop the service and regardless of whether it was
- # running or not, start it again.
- if $0 stop $other_args; then
- $0 start $other_args
- else
- log_failure_msg "Failed to stop running server, so refusing to try to start."
- exit 1
- fi
- ;;</p><p> 'reload'|'force-reload')
- if test -s "$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"
- </p><p> 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`</p><p> # 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
- ;;
- 'configtest')
- # Safeguard (relative paths, core dumps..)
- cd $basedir
- echo $echo_n "Testing MySQL configuration syntax"
- daemon=$bindir/mysqld
- if test -x $libexecdir/mysqld
- then
- daemon=$libexecdir/mysqld
- elif test -x $sbindir/mysqld
- then
- daemon=$sbindir/mysqld
- elif test -x `which mysqld`
- then
- daemon=`which mysqld`
- else
- log_failure_msg "Unable to locate the mysqld binary!"
- exit 1
- fi
- help_out=`$daemon --help 2>&1`; r=$?
- if test "$r" != 0 ; then
- log_failure_msg "$help_out"
- log_failure_msg "There are syntax errors in the server configuration. Please fix them!"
- else
- log_success_msg "Syntax OK"
- fi
- exit $r
- ;;
- 'bootstrap')
- # Bootstrap the cluster, start the first node
- # that initiate the cluster
- echo $echo_n "Bootstrapping the cluster"
- $0 start $other_args --wsrep-new-cluster
- ;;
- *)
- # usage
- basename=`basename "$0"`
- echo "Usage: $basename {start|stop|restart|reload|force-reload|status|configtest|bootstrap} [ MySQL server options ]"
- exit 1
- ;;
- esac</p><p>exit 0
- </p>
启动每一台数据库
在每台数据库中建立下面用户， 用于 sst 认证 (以 root 登入 mysql 数据库后执行下面的 SQL 语句)
- GRANT USAGE ON *.* to tt@'%' IDENTIFIED BY 'tt123';
- GRANT ALL PRIVILEGES on *.* to tt@'%';
- GRANT USAGE ON *.* to tt@'localhost' IDENTIFIED BY 'tt123';
- GRANT ALL PRIVILEGES on *.* to tt@'localhost';
- flush privileges;
关闭所有数据库, 集群启动前， 不需要启动任何一台的数据库
创建并加入集群
集群中第一个节点启动 (192.168.200.163)
创建软链接，并启动集群，集群启动过程中会自动启动 mariadb
- ln -s /usr/local/mysql/bin/ /usr/local/mysql/sbin
- cd /usr/local/
- ./mysql-galera -g gcomm:// start
测试是否成功启动方法, 查询是否会自动启动 4567 端口
- [root@db2 local]# netstat -ntl
- Active Internet connections (only servers)
- Proto Recv-Q Send-Q Local Address Foreign Address State
- tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN
- tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN
- tcp 0 0 0.0.0.0:4567 0.0.0.0:* LISTEN
登录 mysql 之后，查询当前是否启用 galera 插件
- MariaDB [(none)]> show status like 'wsrep_ready';
- +---------------+-------+
- | Variable_name | Value |
- +---------------+-------+
- | wsrep_ready | ON |
- +---------------+-------+
- 1 row in set (0.00 sec)
注，on 为已经启动插件状态
关闭方法
- cd /usr/local
- ./mysql-galera stop
其他节点加入集群方法
第一台 (192.168.200.163) 节点已经启动成功
第二台 (192.168.200.171) 需要加入集群
- cd /usr/local/
- ./mysql-galera -g gcomm://192.168.200.163 start
可按上述方法进行集群启动测试, 也可以参照下面方法, 观察集群地址是否增加两个服务器地址
- MariaDB [(none)]> show status like 'wsrep_incoming_addresses';
- +--------------------------+-------------------------------------------+
- | Variable_name | Value |
- +--------------------------+-------------------------------------------+
- | wsrep_incoming_addresses | 192.168.200.171:3306,192.168.200.163:3306 |
- +--------------------------+-------------------------------------------+
- 1 row in set (0.00 sec)
第三台 (172.18.8.49) 需要加入集群
- cd /usr/local/
- ./mysql-galera -g gcomm://192.168.200.163,192.168.200.171 start
第四台 (172.18.8.50) 需要加入集群
- cd /usr/local/
- ./mysql-galera -g gcomm://192.168.200.163,192.168.200.171,172.18.8.49 start
- 注: 每次集群启动， 将会启用数据同步机制，令每个集群中的数据同步
-
- 假如，集群工作期间，节点 3(172.18.8.49) 脱离集群，重启，发生故障
- 而脱机期间，节点1,2,4 仍可继续工作
- 当节点3 重新在线时，加入集群前，将会自动进行数据同步
-
- 重新在线方法与上文中加入节点方法一致
-
- 另外，假如觉得要定义所有的服务器地址麻烦，可以加入集群时候只定义其中一台的地址，如 gcomm://192.168.200.163 集群也能够自动在加入后添加其他集群 url地址
常见 wsrep 参数注释
- MariaDB [terry]> show status like 'wsrep%';
- +----------------------------+--------------------------------------+
- | Variable_name | Value |
- +----------------------------+--------------------------------------+
- | wsrep_local_state_uuid | bb5b9e17-66c8-11e3-86ba-96854521d205 | uuid 集群唯一标记
- | wsrep_protocol_version | 4 |
- | wsrep_last_committed | 16 | sql 提交记录
- | wsrep_replicated | 4 | 随着复制发出的次数
- | wsrep_replicated_bytes | 692 | 数据复制发出的字节数
- | wsrep_received | 18 | 数据复制接收次数
- | wsrep_received_bytes | 3070 | 数据复制接收的字节数
- | wsrep_local_commits | 4 | 本地执行的 sql
- | wsrep_local_cert_failures | 0 | 本地失败事务
- | wsrep_local_bf_aborts | 0 |从执行事务过程被本地中断
- | wsrep_local_replays | 0 |
- | wsrep_local_send_queue | 0 | 本地发出的队列
- | wsrep_local_send_queue_avg | 0.142857 | 队列平均时间间隔
- | wsrep_local_recv_queue | 0 | 本地接收队列
- | wsrep_local_recv_queue_avg | 0.000000 | 本地接收时间间隔
- | wsrep_flow_control_paused | 0.000000 |
- | wsrep_flow_control_sent | 0 |
- | wsrep_flow_control_recv | 0 |
- | wsrep_cert_deps_distance | 0.000000 | 并发数量
- | wsrep_apply_oooe | 0.000000 |
- | wsrep_apply_oool | 0.000000 |
- | wsrep_apply_window | 1.000000 |
- | wsrep_commit_oooe | 0.000000 |
- | wsrep_commit_oool | 0.000000 |
- | wsrep_commit_window | 1.000000 |
- | wsrep_local_state | 4 |
- | wsrep_local_state_comment | Synced |
- | wsrep_cert_index_size | 0 |
- | wsrep_causal_reads | 0 |
- | wsrep_incoming_addresses | 172.18.8.50:3306,172.18.8.49:3306 | 连接中的数据库
- | wsrep_cluster_conf_id | 18 |
- | wsrep_cluster_size | 2 | 集群成员个数
- | wsrep_cluster_state_uuid | bb5b9e17-66c8-11e3-86ba-96854521d205 | 集群 ID
- | wsrep_cluster_status | Primary | 主服务器
- | wsrep_connected | ON | 当前是否连接中
- | wsrep_local_index | 1 |
- | wsrep_provider_name | Galera |
- | wsrep_provider_vendor | Codership Oy <info@codership.com> |
- | wsrep_provider_version | 2.7(rXXXX) |
- | wsrep_ready | ON | 插件是否应用中
- +----------------------------+--------------------------------------+
- 40 rows in set (0.05 sec)
时间关系，还没有时间进行压力测试，也没有比对 galera 与 Percona XtraDB Cluster 集群之间区别
另，如使用 rpm 则十分方便，网路很多教程， 不详细描述
auto_increment
当更多的 MariaDB 加入到集群之后，集群中的数据库会自动进行协调，并且自动定义偏移量， 这个比较人性化，自动化，如下描述
db1:
- MariaDB [(none)]> show variables like 'auto_increment%';
- +--------------------------+-------+
- | Variable_name | Value |
- +--------------------------+-------+
- | auto_increment_increment | 4 |
- | auto_increment_offset | 3 |
- +--------------------------+-------+
- 2 rows in set (0.00 sec)
db2:
- MariaDB [(none)]> show variables like 'auto_increment%';
- +--------------------------+-------+
- | Variable_name | Value |
- +--------------------------+-------+
- | auto_increment_increment | 4 |
- | auto_increment_offset | 4 |
- +------------------------
db3:
- MariaDB [(none)]> show variables like 'auto_increment%';
- +--------------------------+-------+
- | Variable_name | Value |
- +--------------------------+-------+
- | auto_increment_increment | 4 |
- | auto_increment_offset | 2 |
- +--------------------------+-------+
- 2 rows in set (0.00 sec)
db4:
- MariaDB [(none)]> show variables like 'auto_increment%';
- +--------------------------+-------+
- | Variable_name | Value |
- +--------------------------+-------+
- | auto_increment_increment | 4 |
- | auto_increment_offset | 1 |
- +--------------------------+-------+
- 2 rows in set (0.00 sec)
当前加入集群中共 4 个节点， 如上所见，每个集群中都会每次在数字递增时候递增 4 位， 而数字起始值为加入集群的顺序
模拟测试1
创建测试表
- MariaDB [(none)]> desc terry.t2;
- +-------+-------------+------+-----+-------------------+-----------------------------+
- | Field | Type | Null | Key | Default | Extra |
- +-------+-------------+------+-----+-------------------+-----------------------------+
- | id | int(11) | NO | PRI | NULL | auto_increment |
- | name | varchar(20) | YES | | NULL | |
- | time | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
- +-------+-------------+------+-----+-------------------+-----------------------------+
- 3 rows in set (0.00 sec)
在每台电脑中创建对应的数据插入脚本 (太大量的并发插入会导致服务器不断脱离集群，最终只剩下一次，因此减少数据插入量)
- [root@db6 mdb]# cat /tmp/in.sh
- #!/bin/bash
- for (( a=1 ; a<=1000 ; a++ ))
- do
- name="db6.$a"
- mysql -u terry -p123 -e "insert into terry.t2 (name, time) values (\"$name\", now())"
- done
目的：同时在 4 台电脑中进行数据插入，每台插入 1000 行（并发执行)
插入过程中, 会出现锁，有一个数据库集群会自动脱离集群 >_<"
- MySQL thread id 16, OS thread handle 0x7f2f2019a700, query id 4666 applied write set 183192
- TABLE LOCK table `terry`.`t2` trx id 2D3EF lock mode IX
- ---TRANSACTION 2D3EE, ACTIVE 0 sec
- mysql tables in use 1, locked 1
- 1 lock struct(s), heap size 376, 0 row lock(s), undo log entries 1
- MySQL thread id 633, OS thread handle 0x7f2f20076700, query id 4664 localhost terry query end
- insert into terry.t2 (name, time) values ("db5.603", now())
- TABLE LOCK table `terry`.`t2` trx id 2D3EE lock mode IX
- ---TRANSACTION 2D3ED, ACTIVE (PREPARED) 0 sec preparing
- 1 lock struct(s), heap size 376, 0 row lock(s), undo log entries 1
- MySQL thread id 3, OS thread handle 0x7f2f3be4e700, query id 4662 committing 183190
参考其他三台 时间返回值
db1 (使用 13 秒)
db2 (使用 24秒)
db3(使用14秒)
db4(写入 35 条数据后 crash)