阿里巴巴Canal Client接入

参考：https://github.com/alibaba/canal/wiki

首先启动Canal Server

创建mvn标准工程

mvn archetype:generate -DgroupId=com.alibaba.otter -DartifactId=canal.sample

pom.xml依赖配置

<dependency>
    <groupId>com.alibaba.otter</groupId>
    <artifactId>canal.client</artifactId>
    <version>1.1.4</version>
</dependency>

ClientSample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), "test", "", "");
        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());
        }
    }
}

运行Client

启动Canal Client后，可以从控制台看到类似消息：

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

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)

可以从控制台中看到：

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

更多能力

如果需要更详细的exmpale例子，请下载canal当前最新源码包，里面有个example工程

• Simple客户端例子：SimpleCanalClientTest
• Cluster客户端例子：ClusterCanalClientTest

server/client交互协议

get/ack/rollback协议介绍：

（1）Message getWithoutAck(int batchSize)

允许指定batchSize，一次可以获取多条，每次返回的对象为Message，包含的内容为：

• batch id 唯一标识
• entries 具体的数据对象

（2）getWithoutAck(int batchSize, Long timeout, TimeUnit unit)

相比于getWithoutAck(int batchSize)，允许设定获取数据的timeout超时时间

• 拿够batchSize条记录或者超过timeout时间
• timeout=0，阻塞等到足够的batchSize

（3）void rollback(long batchId)

顾命思议，回滚上次的get请求，重新获取数据。基于get获取的batchId进行提交，避免误操作

（4）void ack(long batchId)

顾命思议，确认已经消费成功，通知server删除数据。基于get获取的batchId进行提交，避免误操作

canal的get/ack/rollback协议和常规的jms协议有所不同，允许get/ack异步处理，比如可以连续调用get多次，后续异步按顺序提交ack/rollback，项目中称之为流式api

数据对象格式

Entry  
    Header  
        logfileName   [binlog文件名]  
        logfileOffset [binlog position]  
        executeTime   [binlog里记录变更发生的时间戳,精确到秒]  
        schemaName   
        tableName  
        eventType [insert/update/delete类型]  
    entryType     [事务头BEGIN/事务尾END/数据ROWDATA]  
    storeValue    [byte数据,可展开，对应的类型为RowChange]  

RowChange

isDdl       [是否是ddl变更操作，比如create table/drop table]

sql         [具体的ddl sql]

rowDatas    [具体insert/update/delete的变更数据，可为多条，1个binlog event事件可对应多条变更，比如批处理]

beforeColumns [Column类型的数组，变更前的数据字段]

afterColumns  [Column类型的数组，变更后的数据字段]

Column

index

sqlType     [jdbc type]

name        [column name]

isKey       [是否为主键]

updated     [是否发生过变更]

isNull      [值是否为null]

value       [具体的内容，注意为string文本]  

说明：

• 可以提供数据库变更前和变更后的字段内容，针对binlog中没有的name,isKey等信息进行补全
• 可以提供ddl的变更语句
• insert只有after columns，delete只有before columns，而update则会有before/after columns数据

创建Connector

• 创建SimpleCanalConnector(直连ip，不支持server/client的failover机制)

CanalConnector connector = CanalConnectors.newSingleConnector(new InetSocketAddress(AddressUtils.getHostIp(),11111), destination, "", "");

• 创建ClusterCanalConnector(基于zookeeper获取canal server ip，支持server/client的failover机制)

CanalConnector connector = CanalConnectors.newClusterConnector("10.20.144.51:2181", destination, "", "");

• 创建ClusterCanalConnector(基于固定canal server的地址，支持固定的server ip的failover机制，不支持client的failover机制

CanalConnector connector = CanalConnectors.newClusterConnector(Arrays.asList(new InetSocketAddress(AddressUtils.getHostIp(),11111)), destination,"", "");