前段時間有一個實時獲取某個表結構數據變動的需求,簡單對canal做了個瞭解,現將當時做demo的過程記錄下來。
canal工作原理
- canal模擬mysql slave的交互協議,僞裝自己爲mysql slave,向mysql master發送dump協議
- mysql master收到dump請求,開始推送binary log給slave(也就是canal)
- canal解析binary log對象(原始爲byte流)
1. 數據庫準備
開啓 Binlog 寫入功能
[mysqld]
log-bin=mysql-bin # 開啓 binlog
binlog-format=ROW # 選擇 ROW 模式
server_id=1 # 配置 MySQL replaction 需要定義,不要和 canal 的 slaveId 重複
創建canal用戶並授權
CREATE USER canal IDENTIFIED BY 'canal';
GRANT ALL PRIVILEGES ON *.* TO 'canal'@'%' ;
FLUSH PRIVILEGES;
2. canal-server準備
docker大法好,懶人首選。。。。
拉取docker鏡像
docker pull canal/canal-server:v1.1.4
啓動canal-server的docker容器
docker run --name canal-server \
-e canal.instance.master.address=127.0.0.1:3306 \
-e canal.instance.dbUsername=canal \
-e canal.instance.dbPassword=canal \
-p 998:11111 \
-d canal/canal-server:v1.1.4
3. 客戶端demo代碼
pom依賴
<dependency>
<groupId>com.alibaba.otter</groupId>
<artifactId>canal.client</artifactId>
<version>1.1.4</version>
</dependency>
代碼
import com.alibaba.otter.canal.client.CanalConnector;
import com.alibaba.otter.canal.client.CanalConnectors;
import com.alibaba.otter.canal.protocol.CanalEntry;
import com.alibaba.otter.canal.protocol.Message;
import java.net.InetSocketAddress;
import java.util.List;
public class ClientTest {
public static void main(String args[]) {
// 創建鏈接
CanalConnector connector = CanalConnectors.newSingleConnector(new InetSocketAddress("127.0.0.1",
998), "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); // 獲取指定數量的數據
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;
printEntry(message.getEntries());
}
connector.ack(batchId); // 提交確認
}
System.out.println("empty too many times, exit");
} finally {
connector.disconnect();
}
}
private static void printEntry(List<CanalEntry.Entry> entrys) {
for (CanalEntry.Entry entry : entrys) {
if (entry.getEntryType() == CanalEntry.EntryType.TRANSACTIONBEGIN || entry.getEntryType() == CanalEntry.EntryType.TRANSACTIONEND) {
continue;
}
CanalEntry.RowChange rowChage = null;
try {
rowChage = CanalEntry.RowChange.parseFrom(entry.getStoreValue());
} catch (Exception e) {
throw new RuntimeException("ERROR ## parser of eromanga-event has an error , data:" + entry.toString(),
e);
}
CanalEntry.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 (CanalEntry.RowData rowData : rowChage.getRowDatasList()) {
if (eventType == CanalEntry.EventType.DELETE) {
printColumn(rowData.getBeforeColumnsList());
} else if (eventType == CanalEntry.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<CanalEntry.Column> columns) {
for (CanalEntry.Column column : columns) {
System.out.println(column.getName() + " : " + column.getValue() + " update=" + column.getUpdated());
}
}
}
新增、更新、刪除數據後日志的打印情況
================> binlog[mysql-bin.000002:6862] , name[panda_big_data,sys_role] , eventType : INSERT
role_id : 3 update=true
role_name : 角色1 update=true
remark : update=true
dept_id : update=true
create_time : update=true
================> binlog[mysql-bin.000002:7098] , name[panda_big_data,sys_role] , eventType : UPDATE
-------> before
role_id : 3 update=false
role_name : 角色1 update=false
remark : update=false
dept_id : update=false
create_time : update=false
-------> after
role_id : 3 update=false
role_name : 角色1 update=false
remark : 2 update=true
dept_id : update=false
create_time : update=false
================> binlog[mysql-bin.000002:7356] , name[panda_big_data,sys_role] , eventType : DELETE
role_id : 3 update=false
role_name : 角色1 update=false
remark : 2 update=false
dept_id : update=false
create_time : update=false
如打印的日誌所示,canal可以獲取到數據插入、更新前後、刪除前等操作的數據詳情,在一些需要了解數據實時變動的場景下,還是很有用的。