Recently, I have mainly invested in the Ping An Cloud MySQL DRDS project. I am mainly responsible for the configuration of the zookeeper module and the writing of background scripts. In order to deepen the understanding of the overall architecture of DRDS, I feel that it is necessary to manually build a Mysql distributed database cluster based on Mycat. Now I will share the construction process with you. I will do further research on various configurations of Mycat in the future, so stay tuned.
Mycat and MySQL instance deployment:
Mycat:
IP: 10.20.8.57, Port: 3310/3311
MySQL:
db1-M1, IP: 10.20.8.126, Port: 3306
db1-M2, IP: 10.20.8.126, Port: 3307
db2- M1, IP: 10.25.80.7, Port: 3307
The architecture diagram is as follows:
Deployment Mycat
server.xml:
<!DOCTYPE mycat:server SYSTEM "server.dtd">
<mycat:server xmlns:mycat="http://io.mycat/">
<system>
<property name="useSqlStat">1</property>
<property name="useGlobleTableCheck">0</property>
<property name="defaultSqlParser">druidparser</property>
<property name="sequnceHandlerType">2</property>
<property name="processorBufferPoolType">0</property>
<property name="serverPort">3310</property> <!-- mycat的使用端口 -->
<property name="managerPort">3311</property> <!-- mycat的管理端口 -->
<property name="handleDistributedTransactions">0</property>
<property name="useOffHeapForMerge">1</property>
<property name="memoryPageSize">1m</property>
<property name="spillsFileBufferSize">1k</property>
<property name="useStreamOutput">0</property>
<property name="systemReserveMemorySize">389m</property>
</system>
<user name="root">
<property name="password">123456</property>
<property name="schemas">db</property>
<property name="readOnly">false</property>
</user>
</mycat:server>schema.xml：
<?xml version="1.0"?>
<!DOCTYPE mycat:schema SYSTEM "schema.dtd">
<mycat:schema xmlns:mycat="http://io.mycat/">
<!-- 数据库配置，与server.xml中的数据库对应 -->
<schema name="db" checkSQLschema="false" sqlMaxLimit="100">
<table name="t1" dataNode="dn1,dn2" rule="mod-long" /> <!-- 对2取模，详见rule.xml -->
</schema>
<!-- 分片配置 -->
<dataNode name="dn1" dataHost="shard1" database="db1" />
<dataNode name="dn2" dataHost="shard2" database="db2" />
<!-- 物理数据库配置 -->
<dataHost name="shard1" maxCon="1000" minCon="10" balance="3" writeType="0" dbType="mysql" dbDriver="native" switchType="1" slaveThreshold="100">
<heartbeat>select user();</heartbeat>
<writeHost host="db1-M1" url="10.20.8.126:3306" user="root" password="123456">
<readHost host="db1-M2" url="10.20.8.126:3307" user="root" password="123456" />
</writeHost>
<!-- 配置standby writeHost -->
<writeHost host="db1-M2" url="10.20.8.126:3307" user="root" password="123456">
</writeHost>
</dataHost>
<dataHost name="shard2" maxCon="1000" minCon="10" balance="0" writeType="0" dbType="mysql" dbDriver="native" switchType="1" slaveThreshold="100">
<heartbeat>select user();</heartbeat>
<writeHost host="db2-M1" url="10.25.80.7:3307" user="root" password="123456">
</writeHost>
</dataHost>
</mycat:schema>Modify the following configuration items in rule.xml:
<tableRule name="mod-long">
<rule>
<columns>id</columns> <!-- t1的分片列 -->
<algorithm>mod-long</algorithm>
</rule>
</tableRule>
<function name="mod-long" class="io.mycat.route.function.PartitionByMod">
<!-- how many data nodes -->
<property name="count">2</property> <!-- count值与分片个数相同 -->
</function>For the meaning of each label in the configuration file, please refer to the article: MyCat key configuration instructions
Start Mycat:
[root@SZB-L0059021 bin]# ./mycat start
Starting Mycat-server...
[root@SZB-L0059021 bin]# ./mycat status
Mycat-server is running (27020).
[root@SZB-L0059021 bin]# mysql -uroot -p123456 -Ddb -h127.0.0.1 -P3310Sub-database sub-table verification:
mysql> show tables;
+--------------+
| Tables in db |
+--------------+
| t1 |
+--------------+
1 row in set (0.00 sec)
mysql> desc t1;
+---------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| db_name | varchar(20) | YES | | NULL | |
+---------+-------------+------+-----+---------+-------+
2 rows in set (0.01 sec)
mysql> insert into t1(id,db_name) values(1,database());
Query OK, 1 row affected (0.01 sec)
mysql> insert into t1(id,db_name) values(2,database());
Query OK, 1 row affected (0.03 sec)
mysql> select * from t1;
+------+---------+
| id | db_name |
+------+---------+
| 2 | db1 | --id=2，对2取模为0，所以插入dn1
| 1 | db2 | --id=1，对2取模为1，所以插入dn2
+------+---------+
2 rows in set (0.01 sec)
上述查询结果可知，两次插入的数据分落入了db1、db2上，实现了分库Read-write separation verification:
mysql> select * from t1;
+------+---------+
| id | db_name |
+------+---------+
| 2 | db1 | --来自shard1上的db1-M2
| 1 | db2 | --来自shard2上的db2-M1
+------+---------+
2 rows in set (0.01 sec)
查看日志可知，上述查询结果来自dn1中db1-M2（端口3307）和dn2中的db2-M1：
2018-05-08 15:03:39.385 DEBUG [$_NIOREACTOR-0-RW] (io.mycat.server.NonBlockingSession.execute(NonBlockingSession.java:110)) - ServerConnection [id=1, schema=db, host=127.0.0.1, user=root,txIsolation=3, autocommit=true, schema=db]select * from t1, route={
1 -> dn1{SELECT *
FROM t1
LIMIT 100}
2 -> dn2{SELECT *
FROM t1
LIMIT 100}
}
...
2018-05-08 15:03:39.391 DEBUG [$_NIOREACTOR-0-RW] (io.mycat.backend.mysql.nio.handler.MultiNodeQueryHandler.rowEofResponse(MultiNodeQueryHandler.java:311)) - on row end reseponse MySQLConnection [id=29, lastTime=1525763019368, user=root, schema=db1, old shema=db1, borrowed=true, fromSlaveDB=true, threadId=511, charset=utf8, txIsolation=3, autocommit=true, attachment=dn1{SELECT *
FROM t1
LIMIT 100}, respHandler=io.mycat.backend.mysql.nio.handler.MultiNodeQueryHandler@66328ec4, host=10.20.8.126, port=3307, statusSync=null, writeQueue=0, modifiedSQLExecuted=false]
...
2018-05-08 15:03:39.392 DEBUG [$_NIOREACTOR-0-RW] (io.mycat.backend.mysql.nio.handler.MultiNodeQueryHandler.rowEofResponse(MultiNodeQueryHandler.java:311)) - on row end reseponse MySQLConnection [id=3, lastTime=1525763019387, user=root, schema=db2, old shema=db2, borrowed=true, fromSlaveDB=false, threadId=28, charset=utf8, txIsolation=3, autocommit=true, attachment=dn2{SELECT *
FROM t1
LIMIT 100}, respHandler=io.mycat.backend.mysql.nio.handler.MultiNodeQueryHandler@66328ec4, host=10.25.80.7, port=3307, statusSync=null, writeQueue=0, modifiedSQLExecuted=false]
...Master-slave switching:
By viewing the dnindex.properties file in the mycat/conf directory, you can know the writeHost that mycat is using, 0 means the first writeHost under the dataHost tag in schema.xml.
[root@SZB-L0059021 conf]# cat dnindex.properties
#update
#Tue May 08 12:59:24 CST 2018
shard2=0
shard1=0 --此时状态正常，mycat选取每个dataHost标签中的第一个writeHost作为写入入口Switch to the 10.20.8.126 host and manually stop db1-M1
10.20.8.126:3306:Master > mysqladmin -uroot -p123456 shutdownGo back to 10.20.8.57 (mycat host) and look at dnindex.properties again
[root@SZB-L0059021 conf]# cat dnindex.properties
#update
#Tue May 08 15:12:12 CST 2018
shard2=0
shard1=1 --db1-M1被shutdown后，mycat在shard1上的writeHost切换至db1-M2Switch to 10.20.8.57 (the host where mycat is located) and execute the following insert command
mysql> insert into t1(id,db_name) values(4,database());
Query OK, 1 row affected (0.01 sec)
查看日志可知，Mycat此时选择通过db1-M2（端口3307）写入数据：
2018-05-08 15:13:44.987 DEBUG [$_NIOREACTOR-0-RW] (io.mycat.server.NonBlockingSession.releaseConnection(NonBlockingSession.java:341)) - release connection MySQLConnection [id=24, lastTime=1525763624968, user=root, schema=db1, old shema=db1, borrowed=true, fromSlaveDB=false, threadId=506, charset=utf8, txIsolation=3, autocommit=true, attachment=dn1{insert into t1(id,db_name) values(4,database())}, respHandler=SingleNodeHandler [node=dn1{insert into t1(id,db_name) values(4,database())}, packetId=1], host=10.20.8.126, port=3307, statusSync=null, writeQueue=0, modifiedSQLExecuted=true]Since writeType="0" is configured in dataHost, Mycat will still choose db1-M2 as the writeHost of
shard1 even after db1-M1 restarts and recovers.
verify:
切换至10.20.8.126主机，并手动启动db1-M1
10.20.8.126:3306:Master > mysqld_safe &
在Mycat中插入验证数据
mysql> insert into t1(id,db_name) values(6,database());
Query OK, 1 row affected (0.02 sec)
查看日志可知，数据仍通过db1-M2（端口3307）写入：
2018-05-08 15:16:09.579 DEBUG [$_NIOREACTOR-0-RW] (io.mycat.server.NonBlockingSession.releaseConnection(NonBlockingSession.java:341)) - release connection MySQLConnection [id=32, lastTime=1525763769548, user=root, schema=db1, old shema=db1, borrowed=true, fromSlaveDB=false, threadId=514, charset=utf8, txIsolation=3, autocommit=true, attachment=dn1{insert into t1(id,db_name) values(6,database())}, respHandler=SingleNodeHandler [node=dn1{insert into t1(id,db_name) values(6,database())}, packetId=1], host=10.20.8.126, port=3307, statusSync=null, writeQueue=0, modifiedSQLExecuted=true]At this point, to change the writeHost of Mycat on shard1 to db1-M1 again, just change shard1=1 in dnindex.properties to shard1=0, and restart Mycat.