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一、需求背景

在有的项目中，尤其是进销存类的saas软件，一开始为了快速把产品做出来，并没有考虑缓存问题。而这类软件，有着复杂的业务逻辑。如果想在原先的代码中，添加redis缓存，改动面将非常大，还需要大量的测试工作。有些时候会有更离谱的情况，比如一些一些项目可能用JDK1.6写的，想要在这个框架下接入redis缓存，也会变得十分困难。
这时我们就会想到，能否像mysql的主从复制一样，监听mysql的binlog，对数据进行更新呢？Flink CDC就呼之欲出。

二、mysql环境搭建

需要注意的是，当前的flink-cdc，仅仅支持mysql8.0，8.4是完全不支持的。
由于我的mysql装的是8.4，为了方便起见，我们使用docker安装mysql8.0

2.1 docker-compose.yml

services:master:image: mysql:8.0.41container_name: mysql-8restart: always#mem_limit: 512Menvironment:MYSQL_ROOT_PASSWORD: study@2025TZ: Asia/Shanghaiports:- "3307:3306"volumes:- ./cfg/my.cnf:/etc/my.cnf- ./data:/var/lib/mysql- ./initdb:/docker-entrypoint-initdb.d- ./dump:/var/dump- ./log:/var/lognetworks:- mysql-cluster
networks:mysql-cluster:

2.2 初始化sql

-- 创建复制用户create role role_app;
GRANT SELECT,UPDATE,INSERT,DELETE ON *.* to role_app;
GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO role_app;CREATE USER 'app'@'%' IDENTIFIED WITH caching_sha2_password by 'study@2025' DEFAULT ROLE role_app COMMENT 'app user';FLUSH PRIVILEGES;-- 创建两个数据库，用于测试
CREATE SCHEMA `shop-center`;
FLUSH TABLES WITH READ LOCK;

2.3 注意点

首先把容器卷 - ./cfg/my.cnf:/etc/my.cnf的这一句注释掉，启动服务
而后使用下面语句，把配置文件粘出来

docker exec <id> cp /etc/my.cnf ./cfg/my.cnf

之后把注释打开，再重新启动

三、工程搭建与pom引用

3.1 主模块pom引用

flink程序不需要接入Spring框架，直接一个main就可运行。
但我们还想使用一些我们熟悉的接口，来操作redis和el。

		<dependency><groupId>org.apache.flink</groupId><artifactId>flink-core</artifactId><version>1.20.0</version></dependency><dependency><groupId>org.apache.flink</groupId><artifactId>flink-streaming-java</artifactId><version>1.20.0</version></dependency><dependency><groupId>org.apache.flink</groupId><artifactId>flink-clients</artifactId><version>1.20.0</version></dependency><dependency><groupId>org.apache.flink</groupId><artifactId>flink-runtime</artifactId><version>1.20.0</version></dependency><dependency><groupId>org.apache.flink</groupId><artifactId>flink-connector-mysql-cdc</artifactId><version>3.3.0</version></dependency>	

3.2 common-data模块

一些entity数据，为了保持各模块共通，最好独立到一个common模块。
同时，我还会把redis和el-search的操作，在这个模块接入并封装

3.2.1 pom引用

<dependencies><dependency><groupId>org.yaml</groupId><artifactId>snakeyaml</artifactId><version>2.3</version></dependency><dependency><groupId>co.elastic.clients</groupId><artifactId>elasticsearch-java</artifactId><version>8.17.0</version></dependency><dependency><groupId>org.elasticsearch</groupId><artifactId>elasticsearch-x-content</artifactId><version>8.17.0</version></dependency><dependency><groupId>cn.hutool</groupId><artifactId>hutool-core</artifactId><version>5.8.32</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional><scope>provided</scope></dependency><dependency><groupId>org.springframework.data</groupId><artifactId>spring-data-redis</artifactId><version>3.4.2</version></dependency><dependency><groupId>com.alibaba.fastjson2</groupId><artifactId>fastjson2-extension-spring6</artifactId><version>2.0.54</version></dependency><dependency><groupId>org.apache.commons</groupId><artifactId>commons-pool2</artifactId><version>2.12.1</version></dependency><dependency><groupId>com.alibaba.fastjson2</groupId><artifactId>fastjson2</artifactId><version>2.0.54</version></dependency><dependency><groupId>io.lettuce</groupId><artifactId>lettuce-core</artifactId><version>6.4.2.RELEASE</version></dependency><!-- Flink Redis Connector --><!--        <dependency>--><!--            <groupId>org.apache.bahir</groupId>--><!--            <artifactId>flink-connector-redis_2.12</artifactId>--><!--            <version>1.1.0</version>--><!--        </dependency>--></dependencies>

3.2.2 一些基本的entity类

@Data
public class GenItemEntity{Long id;String name;Long price;String brand;String specification;Integer version;
}

四、 redis操作和elsearch操作的封装

4.1 redis操作的封装

在pom上，接入spring-data-redis
而后，我们可以使用我们熟悉的RedisTemplate来操作redis

public class RedisConfig {public RedisConfig(){init();}protected FastJsonConfig redisFastJson(){FastJsonConfig config = new FastJsonConfig();config.setWriterFeatures(JSONWriter.Feature.WriteNullListAsEmpty,// 写入类名JSONWriter.Feature.WriteClassName,// 将 Boolean 类型的 null 转成 falseJSONWriter.Feature.WriteNullBooleanAsFalse,JSONWriter.Feature.WriteEnumsUsingName);config.setReaderFeatures(JSONReader.Feature.SupportClassForName,// 支持autoTypeJSONReader.Feature.SupportAutoType);return config;}protected FastJsonRedisSerializer fastJsonRedisSerializer(FastJsonConfig pFastJsonConfig) {FastJsonRedisSerializer fastJsonRedisSerializer = new FastJsonRedisSerializer(Object.class);fastJsonRedisSerializer.setFastJsonConfig(pFastJsonConfig);return fastJsonRedisSerializer;}protected RedisConnectionFactory redisConnectionFactory(){// 这里最好读配置，我懒得搞了RedisStandaloneConfiguration redisConfiguration = new RedisStandaloneConfiguration("192.168.0.64",6379);redisConfiguration.setPassword("study@2025");GenericObjectPoolConfig<?> poolConfig = new GenericObjectPoolConfig<>();poolConfig.setMaxTotal(2);  // 最大连接数poolConfig.setMaxIdle(2);    // 最大空闲连接数poolConfig.setMinIdle(2);    // 最小空闲连接数poolConfig.setMaxWait(Duration.ofMillis(3000)); // 连接等待时间ClientResources clientResources = DefaultClientResources.create();LettucePoolingClientConfiguration lettucePoolingClientConfiguration = LettucePoolingClientConfiguration.builder().poolConfig(poolConfig).build();LettucePoolingClientConfiguration clientConfig = LettucePoolingClientConfiguration.builder().clientResources(clientResources).commandTimeout(Duration.ofSeconds(5)).poolConfig(poolConfig).build();LettuceConnectionFactory redisConnectionFactory = new LettuceConnectionFactory(redisConfiguration,lettucePoolingClientConfiguration);redisConnectionFactory.afterPropertiesSet(); // 初始化连接工厂return redisConnectionFactory;}protected RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory factory, FastJsonRedisSerializer pFastJsonRedisSerializer) {RedisTemplate<String, Object> redisTemplate = new RedisTemplate<String, Object>();redisTemplate.setConnectionFactory(factory);redisTemplate.setEnableTransactionSupport(true);redisTemplate.setKeySerializer(new StringRedisSerializer());redisTemplate.setValueSerializer(pFastJsonRedisSerializer);redisTemplate.setHashKeySerializer(new StringRedisSerializer());redisTemplate.setHashValueSerializer(pFastJsonRedisSerializer);return redisTemplate;}protected void init(){mFastJsonConfig = redisFastJson();mFastJsonRedisSerializer = fastJsonRedisSerializer(mFastJsonConfig);mRedisConnectionFactory = redisConnectionFactory();mRedisTemplate = redisTemplate(mRedisConnectionFactory,mFastJsonRedisSerializer);mRedisTemplate.afterPropertiesSet();}private FastJsonConfig mFastJsonConfig;private FastJsonRedisSerializer mFastJsonRedisSerializer;private RedisConnectionFactory mRedisConnectionFactory;private RedisTemplate<String, Object> mRedisTemplate;public static RedisTemplate<String, Object> redisTemplate(){return Holder.INSTANCE.mRedisTemplate;}public static <T> String serialize(T entity){return JSON.toJSONString(entity,Holder.INSTANCE.mFastJsonConfig.getWriterFeatures());}private static class Holder {private static final RedisConfig INSTANCE = new RedisConfig();}}

4.2 elasticsearch操作的封装

由于el-search的连接器，需要配置apikey，以及https，我们最好使用yml配置，并且把http_ca.crt放进该模块的resouce中。
在IDEA环境下，有可能找不到子模块的资源，这时在主模块引入子模块时，只需要这样配置即可：

        <dependency><groupId>indi.zhifa.study2025</groupId><artifactId>common-data</artifactId><version>${project.version}</version><scope>compile</scope></dependency>

注意，重点是<scope>compile</scope>

public class EsClientConfig {@Setter@Getterprivate String host;@Setter@Getterprivate Integer port;@Setter@Getterprivate String apiKey;}

public class ElasticSearchClientProvider {private EsClientConfig esClientConfig;private RestClientBuilder builder;public ElasticSearchClientProvider() {try{init();}catch (Exception e){e.printStackTrace();}}public void init() throws IOException {Yaml yaml = new Yaml();try (InputStream inputStream = FileUtil.class.getClassLoader().getResourceAsStream("el-config.yml")) {if (inputStream == null) {throw new IllegalArgumentException("File not found: el-config.yml");}esClientConfig = yaml.loadAs(inputStream, EsClientConfig.class);} catch (Exception e) {throw new RuntimeException("Failed to load YAML file", e);}SSLContext sslContext;try (InputStream inputStream = FileUtil.class.getClassLoader().getResourceAsStream("http_ca.crt")){sslContext = TransportUtils.sslContextFromHttpCaCrt(inputStream);}catch (Exception e) {throw new RuntimeException("Failed to load http_ca.crt", e);}builder = RestClient.builder(new HttpHost(esClientConfig.getHost(), esClientConfig.getPort(), "https") // 替换为你的Elasticsearch地址).setDefaultHeaders(new Header[]{new BasicHeader("Authorization", "ApiKey " + esClientConfig.getApiKey())}).setFailureListener(new RestClient.FailureListener(){@Overridepublic void onFailure(Node node) {super.onFailure(node);}}).setHttpClientConfigCallback(hc->hc.setSSLContext(sslContext));}public ElasticsearchClient get(){RestClient restClient = builder.build();ElasticsearchTransport transport = new RestClientTransport(restClient, new JacksonJsonpMapper());ElasticsearchClient esClient = new ElasticsearchClient(transport);return esClient;}public static ElasticSearchClientProvider getInstance(){return Holder.INSTANCE;}private static class Holder {private static final ElasticSearchClientProvider INSTANCE = new ElasticSearchClientProvider();}}

五、 redis和elsearch的自定义sink编写

5.1 redis的sink编写

我们希望传入redis时，数据是被处理好的，redis的sink不需要处理任何逻辑，只管更新缓存和删除缓存。

5.1.1 RedisSinkCommand

public class RedisSinkCommand<T> {@Setter@Getterprotected ERedisCommand command;@Setter@Getterprotected long dua;@Setter@Getterprotected  String key;@Setter@Getterprotected  T value;public void initSet(String pKey, T pValue) {command = ERedisCommand.SET;dua = 300;key = pKey;value = pValue;}public void initDel(String pKey) {command = ERedisCommand.DEL;key = pKey;}}

public enum ERedisCommand {SET,DEL
}

5.1.2 SpringDataRedisSink

@Slf4j
public class SpringDataRedisSink<T> implements Sink<RedisSinkCommand<T>> {@Overridepublic SinkWriter<RedisSinkCommand<T>> createWriter(InitContext context) throws IOException {return null;}@Overridepublic SinkWriter<RedisSinkCommand<T>> createWriter(WriterInitContext context){return new LettuceRedisSinkWriter();}class LettuceRedisSinkWriter implements SinkWriter<RedisSinkCommand<T>> {@Overridepublic void write(RedisSinkCommand<T> pCmd, Context context) throws IOException, InterruptedException {RedisTemplate<String, Object> redisTemplate = RedisConfig.redisTemplate();switch (pCmd.getCommand()){case SET-> {redisTemplate.opsForValue().set(pCmd.getKey(),pCmd.getValue(),pCmd.getDua());}case DEL -> {redisTemplate.delete(pCmd.getKey());}}}@Overridepublic void flush(boolean endOfInput) throws IOException, InterruptedException {}@Overridepublic void close() throws Exception {}}}

5.2 elasticsearch的sink编写

elasticsearch的sink与redis的要求一致，在sink中不关心业务逻辑

5.2.1 ElCommand

@Data
public class ElCommand<T> {protected EElCommand command;protected String index;protected T entity;protected String id;
}

public enum EElCommand {CREATE,UPDATE,DELETE
}

5.2.2 ElSearchSink

public class ElSearchSink<T> implements Sink<ElCommand<T>> {@Overridepublic SinkWriter<ElCommand<T>> createWriter(InitContext context) throws IOException {return null;}@Overridepublic SinkWriter<ElCommand<T>> createWriter(WriterInitContext context){return new ElSearchSink.ElSearchSinkWriter();}class ElSearchSinkWriter implements SinkWriter<ElCommand<T>> {@Overridepublic void write(ElCommand<T> pCmd, Context context) throws IOException, InterruptedException {ElasticSearchClientProvider elasticSearchClientProvider = ElasticSearchClientProvider.getInstance();ElasticsearchClient elClient =  elasticSearchClientProvider.get();String index = pCmd.getIndex();String id = pCmd.getId();T entity = pCmd.getEntity();switch (pCmd.getCommand()){case CREATE,UPDATE -> {elClient.index(i->i.index(index).id(id).document(entity));}case DELETE -> {elClient.delete(d->d.index(index).id(id));}}}@Overridepublic void flush(boolean endOfInput) throws IOException, InterruptedException {}@Overridepublic void close() throws Exception {}}
}

六、主函数编写

public class FlinkMain {public static void main(String[] args) throws Exception {MySqlSource<String> mySqlSource = MySqlSource.<String>builder().hostname("192.168.0.64").port(3307).databaseList("shop-center") // set captured database.tableList("shop-center.item") // set captured table.username("app").password("study@2025").serverTimeZone("Asia/Shanghai").deserializer(new JsonDebeziumDeserializationSchema()) // converts SourceRecord to JSON String.startupOptions(StartupOptions.latest()).includeSchemaChanges(true).build();//        FlinkJedisPoolConfig jedisConfig = new FlinkJedisPoolConfig.Builder()
//                .setHost("192.168.0.64") // 替换为 Redis 主机
//                .setPort(6379) // Redis 端口
//                .setPassword("ilv0404@1314") // 如果有密码，设置密码
//                .build();StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();env.setParallelism(1);//        DataStream<BinlogInfo> mysqlStream = env.fromSource(mySqlSource, WatermarkStrategy.noWatermarks(),"Mysql source")
//                .map(str->{
//                    BinlogInfo res =JSONObject.parseObject(str, BinlogInfo.class);
//                    return res;
//                    }
//                 ).filter(bi->bi.getOp().equals("c")||bi.getOp().equals("u")||bi.getOp().equals("d"));
//
//        mysqlStream.addSink(new RedisSink(jedisConfig,new RedisItemMapper()));DataStream<RedisSinkCommand<GenItemEntity>> newMysqlStream = env.fromSource(mySqlSource, WatermarkStrategy.noWatermarks(),"Mysql source to redis").map(str->JSONObject.parseObject(str, new TypeReference<BinlogInfo<GenItemEntity>>() {}), TypeInformation.of(new TypeHint<BinlogInfo<GenItemEntity>>() {})).filter(bi->bi.getSource().getTable().equals("item") &&  (bi.getOp().equals("c")||bi.getOp().equals("u")||bi.getOp().equals("d"))).map(bi->{String op = bi.getOp();GenItemEntity itemEntity = bi.getAfter();String key = "item:"+itemEntity.getId();switch (op){case "c","u"->{RedisSinkCommand<GenItemEntity> redisSinkCommand = new RedisSinkCommand();redisSinkCommand.initSet(key,itemEntity);return redisSinkCommand;}case "d" ->{RedisSinkCommand<GenItemEntity> redisSinkCommand = new RedisSinkCommand();redisSinkCommand.initDel(key);return redisSinkCommand;}default -> {RedisSinkCommand<GenItemEntity> redisSinkCommand = new RedisSinkCommand();redisSinkCommand.initDel(key);return redisSinkCommand;}}},TypeInformation.of(new TypeHint<RedisSinkCommand<GenItemEntity>>() {}));newMysqlStream.sinkTo(new SpringDataRedisSink<GenItemEntity>());DataStream<ElCommand<GenItemEntity>> mySqlToElStream = env.fromSource(mySqlSource, WatermarkStrategy.noWatermarks(),"Mysql source to el").map(str->JSONObject.parseObject(str, new TypeReference<BinlogInfo<GenItemEntity>>() {}), TypeInformation.of(new TypeHint<BinlogInfo<GenItemEntity>>() {})).filter(bi->bi.getSource().getTable().equals("item") &&  (bi.getOp().equals("c")||bi.getOp().equals("u")||bi.getOp().equals("d"))).map(bi->{ElCommand elCommand = new ElCommand();GenItemEntity itemEntity = bi.getAfter();elCommand.setId(itemEntity.getId().toString());elCommand.setEntity(itemEntity);elCommand.setIndex("item_npc");String op = bi.getOp();switch (op){case "c"->elCommand.setCommand(EElCommand.CREATE);case "u"->elCommand.setCommand(EElCommand.UPDATE);case "d"->elCommand.setCommand(EElCommand.DELETE);}return elCommand;},TypeInformation.of(new TypeHint<ElCommand<GenItemEntity>>() {}));mySqlToElStream.sinkTo(new ElSearchSink());env.execute();}
}

七、代码展示

请道友移步码云

八、相关实践的思考

8.1 redis相关

我这里的代码，仅仅是学习用的。在真实项目中，redis缓存的更新，通常源于查询时，如果发现缓存中没有数据，则查mysql，并把缓存数据加入redis。如果监听到表数据的更改或删除，则直接删除相应缓存，等待查询时重新加入缓存。当然，这样做在同一数据并发访问时，会有重复设置缓存的可能性，我们把这种现象叫缓存穿透。可以在更新缓存前，用redisson加个锁，防止重复读取mysql并更新redis。

public class CacheService {@Autowiredprivate RedissonClient redissonClient;@Autowiredprivate RedisTemplate<String, Object> redisTemplate;@Autowiredprivate DataRepository dataRepository;public Object getData(String key) {// 第一次检查缓存Object value = redisTemplate.opsForValue().get(key);if (value != null) {return value;}RLock lock = redissonClient.getLock(key + ":LOCK");try {// 尝试加锁，设置锁超时时间防止死锁if (lock.tryLock(5, 30, TimeUnit.SECONDS)) {try {// 双重检查缓存value = redisTemplate.opsForValue().get(key);if (value != null) {return value;}// 查询数据库Object dbData = dataRepository.findById(key);// 更新缓存，设置合理过期时间redisTemplate.opsForValue().set(key, dbData, 1, TimeUnit.HOURS);return dbData;} finally {lock.unlock();}} else {// 未获取到锁，短暂等待后重试Thread.sleep(100);return redisTemplate.opsForValue().get(key);}} catch (InterruptedException e) {Thread.currentThread().interrupt();throw new RuntimeException("获取锁失败", e);}}
}

8.2 es相关

对于es，其实更新数据不建议采用这种方式。因为es中需要反范式设计，不可能用1张表的数据做es查询数据的。
对于电商系统的商品查询，我们可以在商品上架的时候更新es。并且商品商家状态下，不允许修改商品。商品下架时，删除es的数据。想要修改商品数据，可以先下架，再修改，而后上架。