canal入門
數據抽取簡單的來說,就是將一個表的數據提取到另一個表中。有很多的ETL工具可以幫助我們來進行數據的抽取和轉換,ETL工具能進行一次性或者定時作業抽取數據,不過canal作爲阿里巴巴提供的開源的數據抽取項目,能夠做到實時抽取,原理就是僞裝成mysql從節點,讀取mysql的binlog,生成消息,客戶端訂閱這些數據變更消息,處理並存儲。下面我們來一起搭建一下canal服務
配置mysql
mysql默認沒有開啓binlog,修改mysql的my.cnf文件,添加如下配置,注意binlog-format必須爲row,因爲binlog如果爲
STATEMENT或者MIXED,則binlog中記錄的是sql語句,不是具體的數據行,canal就無法解析到具體的數據變更了
log-bin=E:/mysql5.5/bin_log/mysql-bin.log
binlog-format=ROW
server-id=123
canal配置
下載並安裝canal,在conf目錄可以看到canal.properties文件,修改該文件爲
#設置要監聽的mysql服務器的地址和端口
canal.instance.master.address = 127.0.0.1:3306
#設置一個可訪問mysql的用戶名和密碼並具有相應的權限,本示例用戶名、密碼都爲canal
canal.instance.dbUsername = canal
canal.instance.dbPassword = canal
#連接的數據庫
canal.instance.defaultDatabaseName =test
#訂閱實例中所有的數據庫和表
canal.instance.filter.regex = .*\\..*
#連接canal的端口
canal.port= 11111
#監聽到的數據變更發送的隊列
canal.destinations= example
啓動 bin/startup.sh 或bin/startup.bat
客戶端代碼
添加canal依賴
<dependency>
<groupId>com.alibaba.otter</groupId>
<artifactId>canal.client</artifactId>
<version>1.0.21</version>
</dependency>
package com.cw.demo.canal;
import com.alibaba.otter.canal.client.CanalConnector;
import com.alibaba.otter.canal.client.CanalConnectors;
import com.alibaba.otter.canal.common.utils.AddressUtils;
import com.alibaba.otter.canal.protocol.CanalEntry;
import com.alibaba.otter.canal.protocol.Message;
import com.google.protobuf.InvalidProtocolBufferException;
import java.net.InetSocketAddress;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* Created by chenwei01 on 2017/4/9.
*/
public class CanalClient {
public static void main(String[] args) {
while (true) {
//連接canal
CanalConnector connector = CanalConnectors.newSingleConnector(new InetSocketAddress(AddressUtils.getHostIp(), 11111), "example", "canal", "canal");
connector.connect();
//訂閱 監控的 數據庫.表
connector.subscribe("demo_db.user_tab");
//一次取5條
Message msg = connector.getWithoutAck(5);
long batchId = msg.getId();
int size = msg.getEntries().size();
if (batchId < 0 || size == 0) {
System.out.println("沒有消息,休眠5秒");
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
} else {
//
CanalEntry.RowChange row = null;
for (CanalEntry.Entry entry : msg.getEntries()) {
try {
row = CanalEntry.RowChange.parseFrom(entry.getStoreValue());
List<CanalEntry.RowData> rowDatasList = row.getRowDatasList();
for (CanalEntry.RowData rowdata : rowDatasList) {
List<CanalEntry.Column> afterColumnsList = rowdata.getAfterColumnsList();
Map<String, Object> dataMap = transforListToMap(afterColumnsList);
if (row.getEventType() == CanalEntry.EventType.INSERT) {
//具體業務操作
System.out.println(dataMap);
} else if (row.getEventType() == CanalEntry.EventType.UPDATE) {
//具體業務操作
System.out.println(dataMap);
} else if (row.getEventType() == CanalEntry.EventType.DELETE) {
List<CanalEntry.Column> beforeColumnsList = rowdata.getBeforeColumnsList();
for (CanalEntry.Column column : beforeColumnsList) {
if ("id".equals(column.getName())) {
//具體業務操作
System.out.println("刪除的id:" + column.getValue());
}
}
} else {
System.out.println("其他操作類型不做處理");
}
}
} catch (InvalidProtocolBufferException e) {
e.printStackTrace();
}
}
//確認消息
connector.ack(batchId);
}
}
}
public static Map<String, Object> transforListToMap(List<CanalEntry.Column> afterColumnsList) {
Map map = new HashMap();
if (afterColumnsList != null && afterColumnsList.size() > 0) {
for (CanalEntry.Column column : afterColumnsList) {
map.put(column.getName(), column.getValue());
}
}
return map;
}
}