[toc]
一、背景
业务背景: MySQL增量数据实时更新同步到Kafka中供下游使用
查看了一下Flink CDC的官方文档,其中Features的描述中提到了SQL和DataStream API不同的支持程度。
Features
1. Supports reading database snapshot and continues to read binlogs with exactly-once processing even failures happen.
2. CDC connectors for DataStream API, users can consume changes on multiple databases and tables in a single job without Debezium and Kafka deployed.
3. CDC connectors for Table/SQL API, users can use SQL DDL to create a CDC source to monitor changes on a single table.
虽然SQL API使用很丝滑,也很简单。但是由于业务表较多,若是使用一个表的监听就开启一个Flink Job,会对资源消耗和运维操作带来很大的麻烦,所以笔者决定使用DataStream API实现单任务监听库级的MySQL CDC并根据表名将数据发往不同的Kafka Topic中。
二、代码实现
1. 关键maven依赖
com.alibaba.ververica
flink-connector-mysql-cdc
1.1.1
org.apache.flink
flink-connector-kafka_2.11
org.apache.kafka
kafka-clients
org.apache.kafka
kafka-clients
2.4.0
2. 自定义CDC数据反序列化器
Flink CDC定义了com.alibaba.ververica.cdc.debezium.DebeziumDeserializationSchema
接口用以对CDC数据进行反序列化。默认实现类com.alibaba.ververica.cdc.debezium.table.RowDataDebeziumDeserializeSchema
和com.alibaba.ververica.cdc.debezium.StringDebeziumDeserializationSchema
,由于我们需要自定义Schema,所以我们不采用这两周默认的实现类,自己实现该接口定义我们需要的Schema.
定义JsonDebeziumDeserializeSchema
实现DebeziumDeserializationSchema
接口方法
class JsonDebeziumDeserializeSchema extends DebeziumDeserializationSchema[String] {
private final val log: Logger = LoggerFactory.getLogger(classOf[JsonDebeziumDeserializeSchema])
override def deserialize(sourceRecord: SourceRecord, collector: Collector[String]): Unit = {
val op = Envelope.operationFor(sourceRecord)
val source = sourceRecord.topic()
val value = sourceRecord.value().asInstanceOf[Struct]
val valueSchema: Schema = sourceRecord.valueSchema()
if (op != Operation.CREATE && op != Operation.READ) {
if (op == Operation.DELETE) {
val data = extractBeforeData(value, valueSchema)
val record = new JSONObject()
.fluentPut("source", source)
.fluentPut("data", data)
.fluentPut("op", RowKind.DELETE.shortString())
.toJSONString
collector.collect(record)
} else {
val beforeData = extractBeforeData(value, valueSchema)
val beforeRecord = new JSONObject()
.fluentPut("source", source)
.fluentPut("data", beforeData)
.fluentPut("op", RowKind.UPDATE_BEFORE.shortString())
.toJSONString
collector.collect(beforeRecord)
val afterData = extractAfterData(value, valueSchema)
val afterRecord = new JSONObject()
.fluentPut("source", source)
.fluentPut("data", afterData)
.fluentPut("op", RowKind.UPDATE_AFTER.shortString())
.toJSONString
collector.collect(afterRecord)
}
} else {
val data = extractAfterData(value, valueSchema)
val record = new JSONObject()
.fluentPut("source", source)
.fluentPut("data", data)
.fluentPut("op", RowKind.INSERT.shortString())
.toJSONString
collector.collect(record)
}
}
override def getProducedType: TypeInformation[String] = BasicTypeInfo.STRING_TYPE_INFO
...
}
定义MySqlSource监听MySQL库数据变化:
val properties = new Properties()
properties.setProperty("snapshotMode", snapshotMode)
val mysqlCdcSource = MySQLSource.builder[String]()
.hostname(hostname)
.port(port)
.databaseList(database)
.tableList(tableName)
.username(username)
.password(password)
.deserializer(new JsonDebeziumDeserializeSchema)
.debeziumProperties(properties)
.serverId(serverId)
.build()
3. 数据动态发往Kafka不同的Topic
由上面自定义的Schema我们可以知道,source字段的构成为mysql_binlog_source
.库名
.表名
。此时我们可以自定义KafkaSerializationSchema
来实现将不同的数据发往不同的topic,即OverridingTopicSchema
:
abstract class OverridingTopicSchema extends KafkaSerializationSchema[String] {
val topicPrefix: String
val topicSuffix: String
val topicKey: String
override def serialize(element: String, timestamp: lang.Long): ProducerRecord[Array[Byte], Array[Byte]] = {
val topic = if (element != null && element.contains(topicKey)) {
val topicStr = JSON.parseObject(element).getString(topicKey).replaceAll("\\.", "_")
topicPrefix.concat(topicStr).concat(topicSuffix)
} else null
new ProducerRecord[Array[Byte], Array[Byte]](topic, element.getBytes(StandardCharsets.UTF_8))
}
}
同时定义创建将数据动态发往不同topic的kafka生产者的方法
/**
* 创建将数据动态发往不同topic的kafka生产者
*
* @param boostrapServers kafka集群地址
* @param kafkaSerializationSchema kafka序列器
* @return
*/
def createDynamicFlinkProducer(boostrapServers: String, kafkaSerializationSchema: KafkaSerializationSchema[String]): FlinkKafkaProducer[String] = {
if (StringUtils.isEmpty(boostrapServers))
throw new IllegalArgumentException("boostrapServers is necessary")
val properties = initDefaultKafkaProducerConfig(boostrapServers)
properties.put(ACKS_CONFIG, "all")
new FlinkKafkaProducer[String](DEFAULT_TOPIC, kafkaSerializationSchema,
properties, FlinkKafkaProducer.Semantic.EXACTLY_ONCE)
}
4. 主类完整实现
object Cdc2KafkaByStream {
def main(args: Array[String]): Unit = {
val parameterTool = ParameterTool.fromArgs(args)
//cdc config
val hostname = parameterTool.get("hostname")
val port = parameterTool.getInt("port", 3306)
val username = parameterTool.get("username")
val password = parameterTool.get("password")
val database = parameterTool.get("database")
val tableName = parameterTool.get("tableName")
val serverId = parameterTool.getInt("serverId")
val snapshotMode = parameterTool.get("snapshotMode", "initial")
//kafka config
val kafkaBrokers = parameterTool.get("kafkaBrokers")
val kafkaTopicPrefix = parameterTool.get("kafkaTopicPrefix", "topic_")
val kafkaTopicSuffix = parameterTool.get("kafkaTopicSuffix", "")
val kafkaTopicKey = parameterTool.get("kafkaTopicKey", "source")
val env = StreamExecutionEnvironment.getExecutionEnvironment
ExecutionEnvUtils.configStreamExecutionEnv(env, parameterTool)
ExecutionEnvUtils.parameterPrint(parameterTool)
val properties = new Properties()
properties.setProperty("snapshotMode", snapshotMode)
val mysqlCdcSource = MySQLSource.builder[String]()
.hostname(hostname)
.port(port)
.databaseList(database)
.tableList(tableName)
.username(username)
.password(password)
.deserializer(new JsonDebeziumDeserializeSchema)
.debeziumProperties(properties)
.serverId(serverId)
.build()
val kafkaSink = KafkaUtils.createDynamicFlinkProducer(kafkaBrokers, new OverridingTopicSchema() {
override val topicPrefix: String = kafkaTopicPrefix
override val topicSuffix: String = kafkaTopicSuffix
override val topicKey: String = kafkaTopicKey
})
env.addSource(mysqlCdcSource).addSink(kafkaSink).setParallelism(1)
env.execute()
}
}
启动任务后可以看到kakfa中根据表名创建了不同的topic,并保存了不同表里的数据。
至此,实现了使用DataStream API单任务监听库级的MySQL CDC并根据表名将数据发往不同的Kafka Topic的功能。
三、小结
本文主要介绍了通过Flink CDC DataStream API实现监听MySQL库数据发往kafka不同Topic的功能,其中运用到自定义DebeziumDeserializationSchema
实现CDC Schema自定义反序列化解析以及自定义KafkaSerializationSchema
实现根据数据内容将消息发送到不同的topic等功能。