一、canal的介绍
canal [kə'næl]，译意为水道/管道/沟渠，主要用途是基于 MySQL 数据库增量日志解析，提供增量数据订阅和消费
早期阿里巴巴因为杭州和美国双机房部署，存在跨机房同步的业务需求，实现方式主要是基于业务 trigger 获取增量变更。从 2010 年开始，业务逐步尝试数据库日志解析获取增量变更进行同步，由此衍生出了大量的数据库增量订阅和消费业务。
基于日志增量订阅和消费的业务包括
- 数据库镜像
- 数据库实时备份
- 索引构建和实时维护(拆分异构索引、倒排索引等)
- 业务 cache 刷新
- 带业务逻辑的增量数据处理
当前的 canal 支持源端 MySQL 版本包括 5.1.x , 5.5.x , 5.6.x , 5.7.x , 8.0.x
二、canal的工作原理
2.1、mysql的工作原理
- MySQL master 将数据变更写入二进制日志( binary log, 其中记录叫做二进制日志事件binary log events，可以通过 show binlog events 进行查看)
- MySQL slave 将 master 的 binary log events 拷贝到它的中继日志(relay log)
- MySQL slave 重放 relay log 中事件，将数据变更反映它自己的数据
2.2、canal 工作原理
- canal 模拟 MySQL slave 的交互协议，伪装自己为 MySQL slave ，向 MySQL master 发送dump 协议
- MySQL master 收到 dump 请求，开始推送 binary log 给 slave (即 canal )
- canal 解析 binary log 对象(原始为 byte 流)
三、canal安装配置
3.1、 mysql准备
mysql安装配置不在介绍，只列出canal需要的配置
在my.cnf配置中开启 Binlog ，配置 binlog-format 为 ROW 模式
[mysqld]
log-bin=mysql-bin # 开启 binlog
binlog-format=ROW # 选择 ROW 模式
server_id=1 # 配置 MySQL replaction 需要定义，不要和 canal 的 slaveId 重复创建canal用户，赋予作为mysql slave的连接master的权限
CREATE USER canal IDENTIFIED BY 'canal';
GRANT SELECT, REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO 'canal'@'%';
-- GRANT ALL PRIVILEGES ON *.* TO 'canal'@'%' ;
FLUSH PRIVILEGES;3.2、canal下载安装
-
下载 canal, 访问 release 页面 , 选择需要的包下载, 如以 1.0.17 版本为例
wget https://github.com/alibaba/canal/releases/download/canal-1.0.17/canal.deployer-1.0.17.tar.gz -
解压缩
mkdir /tmp/canal tar zxvf canal.deployer-$version.tar.gz -C /tmp/canal- 解压完成后，进入 /tmp/canal 目录，可以看到如下结构
drwxr-xr-x 2 jianghang jianghang 136 2013-02-05 21:51 bin drwxr-xr-x 4 jianghang jianghang 160 2013-02-05 21:51 conf drwxr-xr-x 2 jianghang jianghang 1.3K 2013-02-05 21:51 lib drwxr-xr-x 2 jianghang jianghang 48 2013-02-05 21:29 logs
- 解压完成后，进入 /tmp/canal 目录，可以看到如下结构
-
配置修改
vi conf/example/instance.properties## mysql serverId canal.instance.mysql.slaveId = 1234 #position info，需要改成自己的数据库信息 canal.instance.master.address = 127.0.0.1:3306 canal.instance.master.journal.name = canal.instance.master.position = canal.instance.master.timestamp = #canal.instance.standby.address = #canal.instance.standby.journal.name = #canal.instance.standby.position = #canal.instance.standby.timestamp = #username/password，需要改成自己的数据库信息 canal.instance.dbUsername = canal canal.instance.dbPassword = canal canal.instance.defaultDatabaseName = canal.instance.connectionCharset = UTF-8 #table regex canal.instance.filter.regex = .\*\\\\..\*- canal.instance.connectionCharset 代表数据库的编码方式对应到 java 中的编码类型，比如 UTF-8，GBK , ISO-8859-1
- 如果系统是1个 cpu，需要将 canal.instance.parser.parallel 设置为 false
-
启动
sh bin/startup.sh -
查看 server 日志
vi logs/canal/canal.log</pre>2013-02-05 22:45:27.967 [main] INFO com.alibaba.otter.canal.deployer.CanalLauncher - ## start the canal server. 2013-02-05 22:45:28.113 [main] INFO com.alibaba.otter.canal.deployer.CanalController - ## start the canal server[10.1.29.120:11111] 2013-02-05 22:45:28.210 [main] INFO com.alibaba.otter.canal.deployer.CanalLauncher - ## the canal server is running now ...... -
查看 instance 的日志
vi logs/example/example.log2013-02-05 22:50:45.636 [main] INFO c.a.o.c.i.spring.support.PropertyPlaceholderConfigurer - Loading properties file from class path resource [canal.properties] 2013-02-05 22:50:45.641 [main] INFO c.a.o.c.i.spring.support.PropertyPlaceholderConfigurer - Loading properties file from class path resource [example/instance.properties] 2013-02-05 22:50:45.803 [main] INFO c.a.otter.canal.instance.spring.CanalInstanceWithSpring - start CannalInstance for 1-example 2013-02-05 22:50:45.810 [main] INFO c.a.otter.canal.instance.spring.CanalInstanceWithSpring - start successful.... -
关闭
sh bin/stop.sh
四、canal的使用
4.1、maven引入pom依赖
<dependency>
<groupId>com.alibaba.otter</groupId>
<artifactId>canal.client</artifactId>
<version>1.1.0</version>
</dependency>4.2、java的client代码
package com.alibaba.otter.canal.sample;
import java.net.InetSocketAddress;
import java.util.List;
import com.alibaba.otter.canal.client.CanalConnectors;
import com.alibaba.otter.canal.client.CanalConnector;
import com.alibaba.otter.canal.common.utils.AddressUtils;
import com.alibaba.otter.canal.protocol.Message;
import com.alibaba.otter.canal.protocol.CanalEntry.Column;
import com.alibaba.otter.canal.protocol.CanalEntry.Entry;
import com.alibaba.otter.canal.protocol.CanalEntry.EntryType;
import com.alibaba.otter.canal.protocol.CanalEntry.EventType;
import com.alibaba.otter.canal.protocol.CanalEntry.RowChange;
import com.alibaba.otter.canal.protocol.CanalEntry.RowData;
public class SimpleCanalClientExample {
public static void main(String args[]) {
// 创建链接
CanalConnector connector = CanalConnectors.newSingleConnector(new InetSocketAddress(AddressUtils.getHostIp(),
11111), "example", "", "");
int batchSize = 1000;
int emptyCount = 0;
try {
connector.connect();
connector.subscribe(".*\\..*");
connector.rollback();
int totalEmptyCount = 120;
while (emptyCount < totalEmptyCount) {
Message message = connector.getWithoutAck(batchSize); // 获取指定数量的数据
long batchId = message.getId();
int size = message.getEntries().size();
if (batchId == -1 || size == 0) {
emptyCount++;
System.out.println("empty count : " + emptyCount);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}
} else {
emptyCount = 0;
// System.out.printf("message[batchId=%s,size=%s] \n", batchId, size);
printEntry(message.getEntries());
}
connector.ack(batchId); // 提交确认
// connector.rollback(batchId); // 处理失败, 回滚数据
}
System.out.println("empty too many times, exit");
} finally {
connector.disconnect();
}
}
private static void printEntry(List<Entry> entrys) {
for (Entry entry : entrys) {
if (entry.getEntryType() == EntryType.TRANSACTIONBEGIN || entry.getEntryType() == EntryType.TRANSACTIONEND) {
continue;
}
RowChange rowChage = null;
try {
rowChage = RowChange.parseFrom(entry.getStoreValue());
} catch (Exception e) {
throw new RuntimeException("ERROR ## parser of eromanga-event has an error , data:" + entry.toString(),
e);
}
EventType eventType = rowChage.getEventType();
System.out.println(String.format("================> binlog[%s:%s] , name[%s,%s] , eventType : %s",
entry.getHeader().getLogfileName(), entry.getHeader().getLogfileOffset(),
entry.getHeader().getSchemaName(), entry.getHeader().getTableName(),
eventType));
for (RowData rowData : rowChage.getRowDatasList()) {
if (eventType == EventType.DELETE) {
printColumn(rowData.getBeforeColumnsList());
} else if (eventType == EventType.INSERT) {
printColumn(rowData.getAfterColumnsList());
} else {
System.out.println("-------> before");
printColumn(rowData.getBeforeColumnsList());
System.out.println("-------> after");
printColumn(rowData.getAfterColumnsList());
}
}
}
}
private static void printColumn(List<Column> columns) {
for (Column column : columns) {
System.out.println(column.getName() + " : " + column.getValue() + " update=" + column.getUpdated());
}
}
}4.3、启动运行client
运行前首先在启动Canal Server
启动Canal Client后，可以从控制台从看到类似消息：
empty count : 1
empty count : 2
empty count : 3
empty count : 4
此时代表当前数据库无变更数据4.4、触发数据库变更
mysql> use test;
Database changed
mysql> CREATE TABLE `xdual` (
-> `ID` int(11) NOT NULL AUTO_INCREMENT,
-> `X` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
-> PRIMARY KEY (`ID`)
-> ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 ;
Query OK, 0 rows affected (0.06 sec)
mysql> insert into xdual(id,x) values(null,now());Query OK, 1 row affected (0.06 sec)执行数据库变更后，观察client的控制台，可以看到master主库的变更数据已经经过canal了
empty count : 1
empty count : 2
empty count : 3
empty count : 4
================> binlog[mysql-bin.001946:313661577] , name[test,xdual] , eventType : INSERT
ID : 4 update=true
X : 2013-02-05 23:29:46 update=true
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