Canal简介 | 易学教程

以下内容主要摘自Canal 官方wiki和网友博客：https://www.jianshu.com/p/6299048fad66

一、背景

早期，阿里巴巴B2B公司因为存在杭州和美国双机房部署，存在跨机房同步的业务需求。不过早期的数据库同步业务，主要是基于trigger的方式获取增量变更，不过从2010年开始，阿里系公司开始逐步的尝试基于数据库的日志解析，获取增量变更进行同步，由此衍生出了增量订阅&消费的业务，从此开启了一段新纪元。
ps. 目前内部版本已经支持mysql和oracle部分版本的日志解析，当前的canal开源版本支持5.7及以下的版本(阿里内部mysql 5.7.13, 5.6.10, mysql 5.5.18和5.1.40/48)

基于日志增量订阅&消费支持的业务：

数据库镜像
数据库实时备份
多级索引 (卖家和买家各自分库索引)
search build
业务cache刷新
价格变化等重要业务消息

二、项目介绍

名称：canal [kə'næl]
译意：水道/管道/沟渠
语言：纯java开发
定位：基于数据库增量日志解析，提供增量数据订阅&消费，目前主要支持了mysql

三、工作原理

1、mysql主备复制实现

从上层来看，复制分成三步：
master将改变记录到二进制日志(binary log)中（这些记录叫做二进制日志事件，binary log events，可以通过show binlog events进行查看）；
slave将master的binary log events拷贝到它的中继日志(relay log)；
slave重做中继日志中的事件，将改变反映它自己的数据。

2、canal的工作原理：

原理相对比较简单：
canal模拟mysql slave的交互协议，伪装自己为mysql slave，向mysql master发送dump协议
mysql master收到dump请求，开始推送binary log给slave(也就是canal)
canal解析binary log对象(原始为byte流)

四、canal安装

1、下载并解压缩

[root@master1 canal]#wget https://github.com/alibaba/canal/releases/download/v1.0.23/canal.deployer-1.0.23.tar.gz
[root@master1 canal]#mkdir /root/canal
[root@master1 canal]#tar zxvf canal.deployer-1.0.23.tar.gz  -C /root/canal

2、创建mysql的canal用户

mysql> CREATE USER 'canal'@'localhost' IDENTIFIED BY 'canal';
Query OK, 0 rows affected (0.00 sec)
mysql> GRANT ALL PRIVILEGES ON *.* TO 'canal'@'localhost' WITH GRANT OPTION;
Query OK, 0 rows affected (0.01 sec)
mysql> CREATE USER 'canal'@'%' IDENTIFIED BY 'canal';
Query OK, 0 rows affected (0.00 sec)
mysql> GRANT ALL PRIVILEGES ON *.* TO 'canal'@'%' WITH GRANT OPTION;
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

3、修改canal配置文件(如果是访问本机，并且用户密码都为canal则不需要修改配置文件)

[root@master1 canal]# vi /root/canal/conf/example/instance.properties
#################################################
## mysql serverId
canal.instance.mysql.slaveId = 1234
# position info
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
#修改这两项
canal.instance.dbUsername = canal
canal.instance.dbPassword = canal
canal.instance.defaultDatabaseName =
canal.instance.connectionCharset = UTF-8
# table regex
canal.instance.filter.regex = .*\\..*
# table black regex
canal.instance.filter.black.regex =
#################################################

4、启动canal

[root@master1 canal]# sh /root/canal/bin/startup.sh
cd to /root/canal/bin for workaround relative path
LOG CONFIGURATION : /root/canal/bin/../conf/logback.xml
canal conf : /root/canal/bin/../conf/canal.properties
CLASSPATH :/root/canal/bin/../conf:/root/canal/bin/../lib/zookeeper-3.4.5.jar:/root/canal/bin/../lib/zkclient-0.1.jar:/root/canal/bin/../lib/spring-2.5.6.jar:/root/canal/bin/../lib/slf4j-api-1.7.12.jar:/root/canal/bin/../lib/protobuf-java-2.6.1.jar:/root/canal/bin/../lib/oro-2.0.8.jar:/root/canal/bin/../lib/netty-3.2.5.Final.jar:/root/canal/bin/../lib/logback-core-1.1.3.jar:/root/canal/bin/../lib/logback-classic-1.1.3.jar:/root/canal/bin/../lib/log4j-1.2.14.jar:/root/canal/bin/../lib/jcl-over-slf4j-1.7.12.jar:/root/canal/bin/../lib/guava-18.0.jar:/root/canal/bin/../lib/fastjson-1.1.35.jar:/root/canal/bin/../lib/commons-logging-1.1.1.jar:/root/canal/bin/../lib/commons-lang-2.6.jar:/root/canal/bin/../lib/commons-io-2.4.jar:/root/canal/bin/../lib/commons-beanutils-1.8.2.jar:/root/canal/bin/../lib/canal.store-1.0.23.jar:/root/canal/bin/../lib/canal.sink-1.0.23.jar:/root/canal/bin/../lib/canal.server-1.0.23.jar:/root/canal/bin/../lib/canal.protocol-1.0.23.jar:/root/canal/bin/../lib/canal.parse.driver-1.0.23.jar:/root/canal/bin/../lib/canal.parse.dbsync-1.0.23.jar:/root/canal/bin/../lib/canal.parse-1.0.23.jar:/root/canal/bin/../lib/canal.meta-1.0.23.jar:/root/canal/bin/../lib/canal.instance.spring-1.0.23.jar:/root/canal/bin/../lib/canal.instance.manager-1.0.23.jar:/root/canal/bin/../lib/canal.instance.core-1.0.23.jar:/root/canal/bin/../lib/canal.filter-1.0.23.jar:/root/canal/bin/../lib/canal.deployer-1.0.23.jar:/root/canal/bin/../lib/canal.common-1.0.23.jar:/root/canal/bin/../lib/aviator-2.2.1.jar:.:/usr/java/jdk1.8.0_121/lib
cd to /root/canal for continue

5、关闭canal

[root@master1 canal]# sh /root/canal/bin/stop.sh
master1: stopping canal 16062 ... 
Oook! cost:1

6、相关日志位置

[root@master1 canal]# cat /root/canal/logs/canal/canal.log
[root@master1 canal]# cat /root/canal/logs/example/example.log

五、编写代码读取binlog

1、创建maven项目

Paste_Image.png

2、pom.xml增加依赖

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

3、编写ClientSample类订阅binlog

>package com.chainfin.canal;
>
>import java.net.InetSocketAddress;
>import java.util.List;
>
>import com.alibaba.otter.canal.client.CanalConnector;
import com.alibaba.otter.canal.client.CanalConnectors;
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;
import com.alibaba.otter.canal.protocol.Message;
>
/**
 * 
 * @author jinxiaoxin
 *
 */
public class ClientSample {
    public static void main(String[] args) {
        // 创建链接
        CanalConnector connector = CanalConnectors.newSingleConnector(
                new InetSocketAddress("10.105.10.121", 11111), "example", "",
                "");// AddressUtils.getHostIp(),
        int batchSize = 1000;
        int emptyCount = 0;
        try {
            connector.connect();
            connector.subscribe("test\\..*");// .*代表database，..*代表table
            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());
        }
    }
}
>

4、MYSQL进行增删改查

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 (0.01 sec)
mysql> insert into xdual(id,x) values(1,now());
Query OK, 1 row affected (0.01 sec)

5、eclipse控制台可以看到如下输出

Paste_Image.png

六、canal集群搭建

1、需要安装zookeeper

自行了解安装及其使用，此处略过

2、修改canal配置文件

修改两个配置

[root@master1 canal]# vi /root/canal/conf/canal.properties
# 用逗号隔开且不留空格 
canal.zkServers=10.105.10.123:2181,10.105.10.124:2181,10.105.10.125:2181
canal.instance.global.spring.xml = classpath:spring/default-instance.xml

3、拷贝canal到另一台机器并解压缩(作为从节点)

[root@master1 canal]# scp canal.deployer-1.0.23.tar.gz root@10.105.10.122:/root
canal.deployer-1.0.23.tar.gz          100% 9586KB   9.4MB/s   00:00   
[root@master2 ~]# mkdir canal
[root@master2 ~]# tar -zxvf canal.deployer-1.0.23.tar.gz -C /root/canal

4、修改slave配置文件

[root@master2 canal]# vi /root/canal/conf/example/instance.properties
## mysql serverId修改与master不同即可
canal.instance.mysql.slaveId = 1235
# position info修改成mysql地址即可
canal.instance.master.address = 10.105.10.121:3306
[root@master2 canal]# vi /root/canal/conf/canal.properties
# 用逗号隔开且不留空格 
canal.zkServers=10.105.10.123:2181,10.105.10.124:2181,10.105.10.125:2181
canal.instance.global.spring.xml = classpath:spring/default-instance.xml

5、两台机器分别启动canal

[root@master2 canal]#  sh /root/canal/bin/startup.sh

6、查看canal在zk中的状态

[zk: localhost:2181(CONNECTED) 11] get /otter/canal/destinations/example/running
{"active":true,"address":"10.105.10.121:11111","cid":1}
cZxid = 0x250000f037
ctime = Thu Apr 13 13:42:04 CST 2017
mZxid = 0x250000f037
mtime = Thu Apr 13 13:42:04 CST 2017
pZxid = 0x250000f037
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x15b5b11e9cd16e1
dataLength = 55
numChildren = 0

10.105.10.121为active，所以10.105.10.122位stangby节点

7、测试HA是否配置成功

stop掉10.105.10.121这台机器

[root@master1 canal]# sh /root/canal/bin/stop.sh
master1: stopping canal 6107 ... 
Oook! cost:1

[zk: localhost:2181(CONNECTED) 28] get /otter/canal/destinations/example/running
{"active":true,"address":"10.105.10.122:11111","cid":1}
cZxid = 0x250000f0a7
ctime = Thu Apr 13 13:46:10 CST 2017
mZxid = 0x250000f0a7
mtime = Thu Apr 13 13:46:10 CST 2017
pZxid = 0x250000f0a7
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x35b5b11e9d816cb
dataLength = 55

很明显active已经切换到10.105.10.122上了

8、客户端代码

//创建connector 为集群connector 
CanalConnector connector = CanalConnectors.newClusterConnector("10.105.10.123:2181,10.105.10.124:2181,10.105.10.125:2181","example", "", "");

启动代码

Paste_Image.png

9、错误解决

当这个配置的ip不配成127.0.0.1时(也就是本地)
canal.instance.master.address = 10.105.10.121:3306
查看canal配置文件，会报如下错误导致，无法读取binlog

[root@master1 example]# tail -f example.log
2017-04-13 14:29:23.646 [destination = example , address = master1/10.105.10.121:3306 , EventParser] ERROR c.a.o.canal.parse.inbound.mysql.dbsync.DirectLogFetcher - I/O error while reading from client socket
java.io.IOException: Received error packet: errno = 1236, sqlstate = HY000 errmsg = Could not find first log file name in binary log index file
    at com.alibaba.otter.canal.parse.inbound.mysql.dbsync.DirectLogFetcher.fetch(DirectLogFetcher.java:95) ~[canal.parse-1.0.23.jar:na]
    at com.alibaba.otter.canal.parse.inbound.mysql.MysqlConnection.dump(MysqlConnection.java:121) [canal.parse-1.0.23.jar:na]
    at com.alibaba.otter.canal.parse.inbound.AbstractEventParser$3.run(AbstractEventParser.java:209) [canal.parse-1.0.23.jar:na]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]

解决办法：
登录mysql

mysql> show variables like "%sum%";
+---------------------------+-------+
| Variable_name             | Value |
+---------------------------+-------+
| binlog_checksum           | CRC32 |
| innodb_checksum_algorithm | crc32 |
| innodb_checksums          | ON    |
| innodb_log_checksums      | ON    |
| master_verify_checksum    | OFF   |
| slave_sql_verify_checksum | ON    |
+---------------------------+-------+
6 rows in set (0.00 sec)

查询资料发现mysql版本为5.6时，
这个错误一般出现在master5.6,slave在低版本的情况下。这是由于5.6使用了crc32做binlog的checksum；
当一个event被写入binary log(二进制日志)的时候，checksum也同时写入binary log，然后在event通过网络传输到从服务器(slave)之后，再在从服务器中对其进行验证并写入从服务器的relay log.
由于每一步都记录了event和checksum，所以我们可以很快地找出问题所在。
在master1中设置binlog_checksum =none；

mysql> set global binlog_checksum='NONE';
Query OK, 0 rows affected (0.00 sec)
mysql>  show variables like "%sum%";
+---------------------------+-------+
| Variable_name             | Value |
+---------------------------+-------+
| binlog_checksum           | NONE  |
| innodb_checksum_algorithm | crc32 |
| innodb_checksums          | ON    |
| innodb_log_checksums      | ON    |
| master_verify_checksum    | OFF   |
| slave_sql_verify_checksum | ON    |
+---------------------------+-------+
6 rows in set (0.01 sec)

这样错误就可以解决了

七、properties配置文件参数解释

properties配置分为两部分：

canal.properties  (系统根配置文件)
instance.properties  (instance级别的配置文件，每个instance一份)

1、canal.properties

canal.destinations  #当前server上部署的instance列表 
canal.conf.dir  #conf/目录所在的路径   
canal.auto.scan #开启instance自动扫描
#如果配置为true，canal.conf.dir目录下的instance配置变化会自动触发：
#a. instance目录新增： 触发instance配置载入，lazy为true时则自动启动
#b. instance目录删除：卸载对应instance配置，如已启动则进行关闭
#c. instance.properties文件变化：reload instance配置，如已启动自动进行重启操作
canal.auto.scan.interval    #instance自动扫描的间隔时间，单位秒  
canal.instance.global.mode  #全局配置加载方式   
canal.instance.global.lazy  #全局lazy模式   
canal.instance.global.manager.address   #全局的manager配置方式的链接信息    无
canal.instance.global.spring.xml    #全局的spring配置方式的组件文件 
canal.instance.example.mode
canal.instance.example.lazy
canal.instance.example.spring.xml
#instance级别的配置定义，如有配置，会自动覆盖全局配置定义模式
#命名规则：canal.instance.{name}.xxx 无

2、instance.properties

canal.id    #每个canal server实例的唯一标识，暂无实际意义   
canal.ip    #canal server绑定的本地IP信息，如果不配置，默认选择一个本机IP进行启动服务   
canal.port  #canal server提供socket服务的端口  
canal.zkServers #canal server链接zookeeper集群的链接信息
#例子：10.20.144.22:2181,10.20.144.51:2181 
canal.zookeeper.flush.period    #canal持久化数据到zookeeper上的更新频率，单位毫秒    
canal.instance.memory.batch.mode    #canal内存store中数据缓存模式
#1. ITEMSIZE : 根据buffer.size进行限制，只限制记录的数量
#2. MEMSIZE : 根据buffer.size  * buffer.memunit的大小，限制缓存记录的大小  
canal.instance.memory.buffer.size   #canal内存store中可缓存buffer记录数，需要为2的指数  
canal.instance.memory.buffer.memunit    #内存记录的单位大小，默认1KB，和buffer.size组合决定最终的内存使用大小  
canal.instance.transactionn.size    最大事务完整解析的长度支持
超过该长度后，一个事务可能会被拆分成多次提交到canal store中，无法保证事务的完整可见性
canal.instance.fallbackIntervalInSeconds    #canal发生mysql切换时，在新的mysql库上查找binlog时需要往前查找的时间，单位秒
#说明：mysql主备库可能存在解析延迟或者时钟不统一，需要回退一段时间，保证数据不丢
canal.instance.detecting.enable #是否开启心跳检查
canal.instance.detecting.sql    #心跳检查sql    insert into retl.xdual values(1,now()) on duplicate key update x=now()
canal.instance.detecting.interval.time  #心跳检查频率，单位秒
canal.instance.detecting.retry.threshold    #心跳检查失败重试次数
canal.instance.detecting.heartbeatHaEnable  #心跳检查失败后，是否开启自动mysql自动切换
#说明：比如心跳检查失败超过阀值后，如果该配置为true，canal就会自动链到mysql备库获取binlog数据
canal.instance.network.receiveBufferSize    #网络链接参数，SocketOptions.SO_RCVBUF 
canal.instance.network.sendBufferSize   #网络链接参数，SocketOptions.SO_SNDBUF 
canal.instance.network.soTimeout    #网络链接参数，SocketOptions.SO_TIMEOUT

作者：献给记性不好的自己
链接：https://www.jianshu.com/p/6299048fad66
來源：简书
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

来源：https://www.cnblogs.com/maxigang/p/9134523.html

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