canal入门Demo | 易学教程

关于canal具体的原理，以及应用场景，可以参考开发文档：https://github.com/alibaba/canal

下面给出canal的入门Demo

（一）部署canal服务器

可以参考官方文档的QuickStart：https://github.com/alibaba/canal/wiki/QuickStart

为了完整性，下面重复给出如何配置canal服务器

开启mysql的binlog功能，并配置binlog模式为row

1. Windows环境下，是修改my.ini文件：

[mysqld]
log-bin=mysql-bin #添加这一行就ok
binlog-format=ROW #选择row模式
server_id=1 #配置mysql replaction需要定义，不能和canal的slaveId重复

2. 在mysql中配置canal数据库管理用户，配置相应权限（repication权限），运行mysql后依次运行这四条代码：

1 CREATE USER canal IDENTIFIED BY 'canal';  
2 GRANT SELECT, REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO 'canal'@'%';
3 -- GRANT ALL PRIVILEGES ON *.* TO 'canal'@'%' ;
4 FLUSH PRIVILEGES;

3. 下载好canal，修改配置 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_test
canal.instance.connectionCharset = UTF-8
 
# table regex
canal.instance.filter.regex = .*\\..*
 
#################################################

4. 启动startup.bat，并且查看日志log：

如果日志中有记录，证明canal服务器部署成功了。

（二）运行canal客户端

运行canal客户端代码时，一定要先启动canal服务器！！！

1. 建立实例maven工程：

不选择任何Maven模板

2. 添加pom依赖：

<dependency>
    <groupId>com.alibaba.otter</groupId>
    <artifactId>canal.client</artifactId>
    <version>1.0.12</version>
</dependency>

3. 更新依赖

4. canal客户端代码：

 1 import java.net.InetSocketAddress;
 2 import java.util.List;
 3 
 4 import com.alibaba.otter.canal.client.CanalConnector;
 5 import com.alibaba.otter.canal.protocol.Message;
 6 import com.alibaba.otter.canal.protocol.CanalEntry.Column;
 7 import com.alibaba.otter.canal.protocol.CanalEntry.Entry;
 8 import com.alibaba.otter.canal.protocol.CanalEntry.EntryType;
 9 import com.alibaba.otter.canal.protocol.CanalEntry.EventType;
10 import com.alibaba.otter.canal.protocol.CanalEntry.RowChange;
11 import com.alibaba.otter.canal.protocol.CanalEntry.RowData;
12 import com.alibaba.otter.canal.client.*;
13 
14 public class canal_client {
15 
16     public static void main(String args[]) {
17         // 创建链接
18         CanalConnector connector = CanalConnectors.newSingleConnector(new InetSocketAddress("127.0.0.1",
19                 11111), "example", "", "");
20         int batchSize = 1000;
21         int emptyCount = 0;
22         try {
23             connector.connect();
24             connector.subscribe(".*\\..*");
25             connector.rollback();
26             int totalEntryCount = 1200;
27             while (emptyCount < totalEntryCount) {
28                 Message message = connector.getWithoutAck(batchSize); // 获取指定数量的数据
29                 long batchId = message.getId();
30                 int size = message.getEntries().size();
31                 if (batchId == -1 || size == 0) {
32                     emptyCount++;
33                     System.out.println("empty count : " + emptyCount);
34                     try {
35                         Thread.sleep(5000);
36                     } catch (InterruptedException e) {
37                         e.printStackTrace();
38                     }
39                 } else {
40                     emptyCount = 0;
41                     printEntry(message.getEntries());
42                 }
43                 connector.ack(batchId); // 提交确认
44             }
45             System.out.println("empty too many times, exit");
46         }catch (Exception e){
47             //connector.rollback(batchId); // 处理失败, 回滚数据
48         }
49         finally {
50             connector.disconnect();
51         }
52     }
53 
54     private static void printEntry( List<Entry> entrys) {
55         for (Entry entry : entrys) {
56             if (entry.getEntryType() == EntryType.TRANSACTIONBEGIN || entry.getEntryType() == EntryType.TRANSACTIONEND) {
57                 continue;
58             }
59             RowChange rowChage = null;
60             try {
61                 rowChage = RowChange.parseFrom(entry.getStoreValue());
62             } catch (Exception e) {
63                 throw new RuntimeException("ERROR ## parser of eromanga-event has an error , data:" + entry.toString(), e);
64             }
65 
66             EventType eventType = rowChage.getEventType();
67             System.out.println(String.format("================> binlog[%s:%s] , name[%s,%s] , eventType : %s",
68                     entry.getHeader().getLogfileName(), entry.getHeader().getLogfileOffset(),
69                     entry.getHeader().getSchemaName(), entry.getHeader().getTableName(),
70                     eventType));
71             for (RowData rowData : rowChage.getRowDatasList()) {
72                 if (eventType == EventType.DELETE) {
73                     printColumn(rowData.getBeforeColumnsList());
74                 } else if (eventType == EventType.INSERT) {
75                     printColumn(rowData.getAfterColumnsList());
76                 } else {
77                     System.out.println("-------> before");
78                     printColumn(rowData.getBeforeColumnsList());
79                     System.out.println("-------> after");
80                     printColumn(rowData.getAfterColumnsList());
81                 }
82             }
83         }
84     }
85 
86     private static void printColumn( List<Column> columns) {
87         for (Column column : columns) {
88             System.out.println(column.getName() + " : " + column.getValue() + "    update=" + column.getUpdated());
89         }
90     }
91 }

View Code

5. 运行客户端实例：

6. 触发数据库变更：

总结：参考网上的资料，运行这个canal的Demo，对canal的机制有一点了解；当MySQL将binary log发送给canal服务器，然后canal client从服务器获取binary log，同时解析出来，尤其是解析的过程对于理解canal会更深刻一点。

建议运行的代码的过程中打断点调试处理！

来源：https://www.cnblogs.com/jayinnn/p/9606466.html

标签

canal

otter