当我们需要对数据库的修改做监听的时候，可以使用阿里的canal。例如，可以实现将mysql中修改的数据更新到redis中，而不用每个service都分两步去先操作mysql再操作redis。

配置mysql

启用mysql的binlog

# vim /etc/my.cnf

添加：
[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

添加canal数据库用户

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

配置canal

解压

mkdir /tmp/canal  
tar zxvf canal.deployer-$version.tar.gz  -C /tmp/canal

修改配置文件

vi conf/example/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.instance.connectionCharset = UTF-8  
  
# table regex  
canal.instance.filter.regex = .*\\..*  
  
#################################################

启动

sh bin/startup.sh

public class ClientSample {
  
    public static void main(String args[]) {  
        // 创建链接  
        CanalConnector connector = CanalConnectors.newSingleConnector(new InetSocketAddress("10.0.0.2",
                11111), "example", "", "");  
        int batchSize = 1000;  
        int emptyCount = 0;  
        try {  
            connector.connect();  
            connector.subscribe(".*\\..*");  
            connector.rollback();  
            int totalEmtryCount = 1200;  
            while (emptyCount < totalEmtryCount) {  
                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) {  
                        e.printStackTrace();  
                    }  
                } 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());
                    //redisDelete(rowData.getBeforeColumnsList());
                } else if (eventType == EventType.INSERT) {  
                    printColumn(rowData.getAfterColumnsList());  
                } else {  
                    System.out.println("-------> before");
                    //修改之前每个字段的值
                    printColumn(rowData.getBeforeColumnsList());  
                    System.out.println("-------> after");
                    //修改之后每个字段的值
                    printColumn(rowData.getAfterColumnsList());  
                }  
            }  
        }  
    }  
  
    private static void printColumn(List<Column> columns) {
        for (Column column : columns) {
            System.out.println(column.getName() + " : " + column.getValue() + "    update=" + column.getUpdated());
        }  
    }  
}

注意

canal每次会记录客户端消费的位置。如果canal挂掉，mysql在不断更新，redis更新滞后。重启canal后，会自动同步redis更新。

HA

server端可参考官方文档

client也是靠zookeeper实现ha

CanalConnector connector = CanalConnectors.newClusterConnector("192.168.213.44:4180", "example", "", "");  //client连接zookeeper地址
  
        int batchSize = 1;  
        int emptyCount = 0;  
        //启动多个实例，不断尝试连接zookeeper实现HA。
        while(true) {  
            try {  
                connector.connect();  
                connector.subscribe(".*\\..*");  
                ...
        }

Reference

来源：oschina

链接：https://my.oschina.net/u/1245414/blog/1556049

标签

canal

canal记录