1. 背景
canal [kə'næl] ，译意为水道/管道/沟渠，主要用途是基于 MySQL 数据库增量日志解析，提供增量数据订阅和消费。其诞生的背景是早期阿里巴巴因为杭州和美国双机房部署，存在跨机房同步的业务需求，实现方式主要是基于业务 trigger 获取增量变更。从 2010 年开始，业务逐步尝试数据库日志解析获取增量变更进行同步，由此衍生出了大量的数据库增量订阅和消费业务。所以其核心功能如下：
数据实时备份
异构数据源(elasticsearch、Hbase)与数据库数据增量同步
业务缓存cache 刷新，保证缓存一致性
带业务逻辑的增量数据处理，如监听某个数据的变化做一定的逻辑处理
canal是借助于MySQL主从复制原理实现
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。
canal的工作原理：
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)
2. Windows系统安装canal
Github下载链接：Releases · alibaba/canal · GitHub
解压
进入/conf/example，修改instance.properties
# 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.master.gtid= # rds oss binlog canal.instance.rds.accesskey= canal.instance.rds.secretkey= canal.instance.rds.instanceId= # table meta tsdb info canal.instance.tsdb.enable=true #canal.instance.tsdb.url=jdbc:mysql://127.0.0.1:3306/canal_tsdb #canal.instance.tsdb.dbUsername=canal #canal.instance.tsdb.dbPassword=canal #canal.instance.standby.address = #canal.instance.standby.journal.name = #canal.instance.standby.position = #canal.instance.standby.timestamp = #canal.instance.standby.gtid= # username/password canal.instance.dbUsername=root canal.instance.dbPassword=123456 canal.instance.connectionCharset = UTF-8 # enable druid Decrypt database password canal.instance.enableDruid=false #canal.instance.pwdPublicKey=MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBALK4BUxdDltRRE5/zXpVEVPUgunvscYFtEip3pmLlhrWpacX7y7GCMo2/JM6LeHmiiNdH1FWgGCpUfircSwlWKUCAwEAAQ== # table regex canal.instance.filter.regex=.*\\..* # table black regex canal.instance.filter.black.regex=mysql\\.slave_.* # table field filter(format: schema1.tableName1:field1/field2,schema2.tableName2:field1/field2) #canal.instance.filter.field=test1.t_product:id/subject/keywords,test2.t_company:id/name/contact/ch # table field black filter(format: schema1.tableName1:field1/field2,schema2.tableName2:field1/field2) #canal.instance.filter.black.field=test1.t_product:subject/product_image,test2.t_company:id/name/contact/ch # mq config canal.mq.topic=example # dynamic topic route by schema or table regex #canal.mq.dynamicTopic=mytest1.user,mytest2\\..*,.*\\..* canal.mq.partition=0 # hash partition config #canal.mq.partitionsNum=3 #canal.mq.partitionHash=test.table:id^name,.*\\..* #canal.mq.dynamicTopicPartitionNum=test.*:4,mycanal:6 #################################################
之后进入到bin目录下启动startup就可以了。
3.Mysql准备工作
/* SQLyog Community v13.2.0 (64 bit) MySQL - 8.0.33 : Database - shop ********************************************************************* */ /*!40101 SET NAMES utf8 */; /*!40101 SET SQL_MODE=''*/; /*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */; /*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */; /*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */; /*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */; CREATE DATABASE /*!32312 IF NOT EXISTS*/`shop` /*!40100 DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci */ /*!80016 DEFAULT ENCRYPTION='N' */; USE `shop`; /*Table structure for table `brand` */ DROP TABLE IF EXISTS `brand`; CREATE TABLE `brand` ( `id` INT NOT NULL AUTO_INCREMENT COMMENT '品牌id', `name` VARCHAR(100) NOT NULL COMMENT '品牌名称', `image` VARCHAR(1000) DEFAULT '' COMMENT '品牌图片地址', `initial` VARCHAR(1) DEFAULT '' COMMENT '品牌的首字母', `sort` INT DEFAULT NULL COMMENT '排序', PRIMARY KEY (`id`) ) ENGINE=INNODB AUTO_INCREMENT=14 DEFAULT CHARSET=utf8mb3 COMMENT='品牌表'; /*Data for the table `brand` */ INSERT INTO `brand`(`id`,`name`,`image`,`initial`,`sort`) VALUES (11,'华为','https://sklll.oss-cn-beijing.aliyuncs.com/secby/eed72cc4-a9c1-4010-949a-03cef5b933d6.jpg','',NULL), (12,'中兴','https://sklll.oss-cn-beijing.aliyuncs.com/secby/4fedb361-5ab3-4ad0-a667-580c1f37dff0.jpg','',NULL), (13,'大疆','https://sklll.oss-cn-beijing.aliyuncs.com/secby/e8382c48-0487-4a9b-8fd0-a3716c3eea19.jpg','',NULL); /*!40101 SET SQL_MODE=@OLD_SQL_MODE */; /*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */; /*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */; /*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
4. 公共依赖包
<dependencies> <!--web包--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <!--MyBatis Plus--> <dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.3.2</version> </dependency> <!--MySQL--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </dependency> <!--Redis--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency> <!--Nacos--> <dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId> </dependency> <dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId> </dependency> </dependencies>
5. Redis缓存设计
这里基于Springcloud Alibaba进行设计，对应的服务名称为mall-goods
bootstrap.yaml代码如下：
server: port: 8081 spring: application: name: mall-goods datasource: driver-class-name: com.mysql.cj.jdbc.Driver url: jdbc:mysql://localhost:3306/shop?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC username: root password: 123456 cloud: nacos: config: file-extension: yaml server-addr: localhost:8848 discovery: #Nacos的注册地址 server-addr: localhost:8848 redis: host: xx //改为自己redis ip地址 port: 6379
导入RedisConfig配置
@Configuration public class RedisConfig { @Bean public RedisTemplate<String,Object> redisTemplate(RedisConnectionFactory factory){ RedisTemplate<String,Object> redisTemplate = new RedisTemplate<>(); redisTemplate.setConnectionFactory(factory); GenericJackson2JsonRedisSerializer serializer = new GenericJackson2JsonRedisSerializer(); // 值采用json序列化 redisTemplate.setValueSerializer(serializer); //使用StringRedisSerializer来序列化和反序列化redis的key值 redisTemplate.setKeySerializer(new StringRedisSerializer()); // 设置hash key 和value序列化模式 redisTemplate.setHashKeySerializer(new StringRedisSerializer()); redisTemplate.setHashValueSerializer(serializer); redisTemplate.afterPropertiesSet(); return redisTemplate; } @Bean public RedisCacheManager redisCacheManager(RedisTemplate redisTemplate) { RedisCacheWriter redisCacheWriter = RedisCacheWriter.nonLockingRedisCacheWriter(redisTemplate.getConnectionFactory()); RedisCacheConfiguration redisCacheConfiguration = RedisCacheConfiguration.defaultCacheConfig() .entryTtl(Duration.ofHours(12))//设置默认缓存时间 .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(redisTemplate.getValueSerializer())); return new RedisCacheManager(redisCacheWriter, redisCacheConfiguration); } }
对于Brand进行redis缓存设计
在主启动类上添加@EnableCaching开启缓存。
@Cacheable 注解可以标记一个方法需要被缓存。在注解中，可以指定缓存的名称和缓存的键。当方法被执行时，Spring Boot 会先查找缓存，如果缓存中存在相应的数据，则直接从缓存中读取，否则执行方法并将结果缓存到缓存中。
@CachePut 注解可以标记一个方法需要更新缓存。在注解中，可以指定缓存的名称和缓存的键。当方法被执行时，Spring Boot 会更新缓存中的数据。
@CacheEvict 注解可以标记一个方法需要删除缓存。在注解中，可以指定缓存的名称和缓存的键。当方法被执行时，Spring Boot 会删除缓存中对应的数据。
代码如下：
@RestController @RequestMapping("/brand") public class BrandController { @Autowired BrandService brandService; @GetMapping("/{id}") @Cacheable(value = "brand",key = "#id") public Brand search(@PathVariable(value = "id")Integer id){ return brandService.getById(id); } /**** * 添加缓存 */ @PostMapping @CachePut(value = "brand",key = "#brand.id") public Brand add(@RequestBody Brand brand){ return brand; } /**** * 修改缓存 */ @PutMapping @CachePut(value = "brand",key = "#brand.id") public Brand update(@RequestBody Brand brand){ return brand; } /**** * 删除缓存 */ @DeleteMapping("/{id}") @CacheEvict(value = "brand",key = "#id") public void delete(@PathVariable(value = "id")Integer id){ } }
6. mall-canal-service
这里微服务名称为mall-canal-service，监控Mysql数据库数据变化进行实时的更新缓存。
除公共依赖外导入依赖
<dependency> <groupId>top.javatool</groupId> <artifactId>canal-spring-boot-starter</artifactId> <version>1.2.1-RELEASE</version> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-openfeign</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-loadbalancer</artifactId> </dependency>
bootstrap.yaml设计如下：
server: port: 8083 spring: application: name: mall-canal cloud: nacos: config: file-extension: yaml server-addr: localhost:8848 discovery: #Nacos的注册地址 server-addr: localhost:8848 #Canal配置 canal: server: localhost:11111 destination: example
设计Feign接口
@FeignClient(value = "mall-goods",contextId = "brand")//服务名字 public interface BrandFeign { @GetMapping("/brand/{id}") Brand search(@PathVariable(value = "id")Integer id); @PostMapping("/brand") Brand add(@RequestBody Brand brand); /**** * 修改方法 */ @PutMapping("/brand") Brand update(@RequestBody Brand brand); /**** * 删除方法 */ @DeleteMapping("/brand/{id}") void delete(@PathVariable(value = "id")Integer id); }
Canal实时监控Mysql数据库变化，代码设计如下：
@Component @CanalTable(value = "brand") public class BrandHandler implements EntryHandler<Brand> { @Autowired BrandFeign brandFeign; @Override public void insert(Brand brand) { System.out.println(brand); brandFeign.add(brand); } @Override public void update(Brand before, Brand after) { System.out.println(after); brandFeign.update(after); } @Override public void delete(Brand brand) { System.out.println(brand); brandFeign.delete(brand.getId()); } }
在MallCanalApplication主启动类上添加@EnableFeignClients(basePackages = {"org.example.feign"})，包名为feign接口路径。
注意：本人在使用canal时，数据库有非varchar类型的null值，在运行时会抛异常错误。
at top.javatool.canal.client.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:52) ~[canal-client-1.2.1-RELEASE.jar:na] at top.javatool.canal.client.handler.impl.AsyncMessageHandlerImpl.lambda$handleMessage$0(AsyncMessageHandlerImpl.java:30) ~[canal-client-1.2.1-RELEASE.jar:na] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_281] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_281] at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_281] Caused by: java.lang.NumberFormatException: For input string: "" at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) ~[na:1.8.0_281]
代码运行后，经过测试成功。
