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canal是阿里巴巴旗下的一款开源项目,纯Java开发。基于数据库增量日志解析,提供增量数据订阅&消费,目前主要支持了Mysql(也支持mariaDB)。
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先了解下Mysql主备复制的工作原理:
master将改变记录到二进制日志(binary log)中(这些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);
slave将master的binary log events拷贝到它的中继日志(relay log);
slave重做中继日志中的事件,将改变反映它自己的数据。
- Canal的工作原理
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(也就是canal)
canal解析binary log对象(原始为byte流)
- Canal架构设计
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server代表一个canal运行实例,对应于一个jvm
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instance对应于一个数据队列 (1个server对应1…n个instance)
- Canal的instance模块
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eventParser (数据源接入,模拟slave协议和master进行交互,协议解析)
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eventSink (Parser和Store链接器,进行数据过滤,加工,分发的工作)
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eventStore (数据存储)
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metaManager (增量订阅&消费信息管理器)
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登录Mysql后使用
show variables like 'log_%';
查看是否开启binlog -
编辑配置文件
vim /etc/my.cnf
server_id=1 #配置 MySQL replaction 需要定义,不要和 canal 的 slaveId 重复
log-bin=mysql-bin #开启 binlog
binlog-format=ROW #选择 ROW模式
expire_logs_days=30
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重启Mysql服务
systemctl restart mysqld
,然后再次使用命令show variables like 'log_%';
进行查看,为ON
表明binlog已成功开启 -
授权 canal 链接 MySQL 账号具有作为 MySQL slave 的权限
CREATE USER canal IDENTIFIED BY 'canal';
GRANT SELECT, REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO 'canal'@'%';
FLUSH PRIVILEGES;
其中, /usr/local/mysql/data
为binlog日志文件存放路径,mysql-bin是日志文件系统的前缀名
#下载安装包
wget https://github.com/alibaba/canal/releases/download/canal-1.0.17/canal.deployer-1.0.17.tar.gz
#解压
tar zxvf canal.deployer-$version.tar.gz -C /usr/local/canal
修改配置vi conf/example/instance.properties
启动canal sh bin/startup.sh
查看server日志 vi logs/canal/canal.log
查看 instance 的日志vim logs/example/example.log
#配置pom文件
<dependency>
<groupId>com.alibaba.otter</groupId>
<artifactId>canal.client</artifactId>
<version>1.1.1</version>
</dependency>
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.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("120.27.233.226",
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]: 库名是[%s],表名是 [%s],eventType是[%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("字段名" + column.getName() + "值为" + column.getValue() + " ,更新状态是" + column.getUpdated());
}
}
}
触发数据库变更,可以从控制台看到
具体图片网页请移步:SimpleCanalClientSample