第十篇SparkStreaming手动维护Kafka Offset的几种方式
Spark Streaming No Receivers 方式的createDirectStream 方法不使用接收器，而是创建输入流直接从Kafka 集群节点拉取消息。输入流保证每个消息从Kafka 集群拉取以后只完全转换一次，保证语义一致性。但是当作业发生故障或重启时，要保障从当前的消费位点去处理数据(即Exactly Once语义)，单纯的依靠SparkStreaming本身的机制是不太理想的，生产环境中通常借助手动管理offset的方式来维护kafka的消费位点。本文分享将介绍如何手动管理Kafka的Offset，希望对你有所帮助。本文主要包括以下内容：
- 如何使用MySQL管理Kafka的Offset
- 如何使用Redis管理Kafka的OffSet
如何使用MySQL管理Kafka的Offset
我们可以从Spark Streaming 应用程序中编写代码来手动管理Kafka偏移量，偏移量可以从每一批流处理中生成的RDDS偏移量来获取，获取方式为：
KafkaUtils.createDirectStream(...).foreachRDD { rdd =>
// 获取偏移量
val offsetRanges = rdd.asInstanceOf[HasOffsetRanges].offsetRanges
...
}
当获取到偏移量之后，可以将将其保存到外部存储设备中(MySQL、Redis、Zookeeper、HBase等)。
使用案例代码
- MySQL中用于保存偏移量的表
CREATE TABLE `topic_par_group_offset` (
`topic` varchar(255) NOT NULL,
`partition` int(11) NOT NULL,
`groupid` varchar(255) NOT NULL,
`offset` bigint(20) DEFAULT NULL,
PRIMARY KEY (`topic`,`partition`,`groupid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 ;
- 常量配置类:ConfigConstants
object ConfigConstants {
// Kafka配置
val kafkaBrokers = "kms-2:9092,kms-3:9092,kms-4:9092"
val groupId = "group_test"
val kafkaTopics = "test"
val batchInterval = Seconds(5)
val streamingStorageLevel = StorageLevel.MEMORY_AND_DISK_SER_2
val kafkaKeySer = "org.apache.kafka.common.serialization.StringSerializer"
val kafkaValueSer = "org.apache.kafka.common.serialization.StringSerializer"
val sparkSerializer = "org.apache.spark.serializer.KryoSerializer"
val batchSize = 16384
val lingerMs = 1
val bufferMemory = 33554432
// MySQL配置
val user = "root"
val password = "123qwe"
val url = "jdbc:mysql://localhost:3306/kafka_offset"
val driver = "com.mysql.jdbc.Driver"
// 检查点配置
val checkpointDir = "file:///e:/checkpoint"
val checkpointInterval = Seconds(10)
// Redis配置
val redisAddress = "192.168.10.203"
val redisPort = 6379
val redisAuth = "123qwe"
val redisTimeout = 3000
}
- JDBC连接工具类:JDBCConnPool
object JDBCConnPool {
val log: Logger = Logger.getLogger(JDBCConnPool.getClass)
var dataSource: BasicDataSource = null
/**
* 创建数据源
*
* @return
*/
def getDataSource(): BasicDataSource = {
if (dataSource == null) {
dataSource = new BasicDataSource()
dataSource.setDriverClassName(ConfigConstants.driver)
dataSource.setUrl(ConfigConstants.url)
dataSource.setUsername(ConfigConstants.user)
dataSource.setPassword(ConfigConstants.password)
dataSource.setMaxTotal(50)
dataSource.setInitialSize(3)
dataSource.setMinIdle(3)
dataSource.setMaxIdle(10)
dataSource.setMaxWaitMillis(2 * 10000)
dataSource.setRemoveAbandonedTimeout(180)
dataSource.setRemoveAbandonedOnBorrow(true)
dataSource.setRemoveAbandonedOnMaintenance(true)
dataSource.setTestOnReturn(true)
dataSource.setTestOnBorrow(true)
}
return dataSource
}
/**
* 释放数据源
*/
def closeDataSource() = {
if (dataSource != null) {
dataSource.close()
}
}
/**
* 获取数据库连接
*
* @return
*/
def getConnection(): Connection = {
var conn: Connection = null
try {
if (dataSource != null) {
conn = dataSource.getConnection()
} else {
conn = getDataSource().getConnection()
}
} catch {
case e: Exception =>
log.error(e.getMessage(), e)
}
conn
}
/**
* 关闭连接
*/
def closeConnection (ps:PreparedStatement , conn:Connection ) {
if (ps != null) {
try {
ps.close();
} catch {
case e:Exception =>
log.error("预编译SQL语句对象PreparedStatement关闭异常！" + e.getMessage(), e);
}
}
if (conn != null) {
try {
conn.close();
} catch {
case e:Exception =>
log.error("关闭连接对象Connection异常！" + e.getMessage(), e);
}
}
}
}
- Kafka生产者：KafkaProducerTest
object KafkaProducerTest {
def main(args: Array[String]): Unit = {
val props : Properties = new Properties()
props.put("bootstrap.servers", ConfigConstants.kafkaBrokers)
props.put("batch.size", ConfigConstants.batchSize.asInstanceOf[Integer])
props.put("linger.ms", ConfigConstants.lingerMs.asInstanceOf[Integer])
props.put("buffer.memory", ConfigConstants.bufferMemory.asInstanceOf[Integer])
props.put("key.serializer",ConfigConstants.kafkaKeySer)
props.put("value.serializer", ConfigConstants.kafkaValueSer)
val producer : Producer[String, String] = new KafkaProducer[String, String](props)
val startTime : Long = System.currentTimeMillis()
for ( i <- 1 to 100) {
producer.send(new ProducerRecord[String, String](ConfigConstants.kafkaTopics, "Spark", Integer.toString(i)))
}
println("消耗时间：" + (System.currentTimeMillis() - startTime))
producer.close()
}
}
- 读取和保存Offset：
该对象的作用是从外部设备中读取和写入Offset，包括MySQL和Redis
object OffsetReadAndSave {
/**
* 从MySQL中获取偏移量
*
* @param groupid
* @param topic
* @return
*/
def getOffsetMap(groupid: String, topic: String): mutable.Map[TopicPartition, Long] = {
val conn = JDBCConnPool.getConnection()
val selectSql = "select * from topic_par_group_offset where groupid = ? and topic = ?"
val ppst = conn.prepareStatement(selectSql)
ppst.setString(1, groupid)
ppst.setString(2, topic)
val result: ResultSet = ppst.executeQuery()
// 主题分区偏移量
val topicPartitionOffset = mutable.Map[TopicPartition, Long]()
while (result.next()) {
val topicPartition: TopicPartition = new TopicPartition(result.getString("topic"), result.getInt("partition"))
topicPartitionOffset += (topicPartition -> result.getLong("offset"))
}
JDBCConnPool.closeConnection(ppst, conn)
topicPartitionOffset
}
/**
* 从Redis中获取偏移量
*
* @param groupid
* @param topic
* @return
*/
def getOffsetFromRedis(groupid: String, topic: String): Map[TopicPartition, Long] = {
val jedis: Jedis = JedisConnPool.getConnection()
var offsets = mutable.Map[TopicPartition, Long]()
val key = s"${topic}_${groupid}"
val fields : java.util.Map[String, String] = jedis.hgetAll(key)
for (partition <- JavaConversions.mapAsScalaMap(fields)) {
offsets.put(new TopicPartition(topic, partition._1.toInt), partition._2.toLong)
}
offsets.toMap
}
/**
* 将偏移量写入MySQL
*
* @param groupid 消费者组ID
* @param offsetRange 消息偏移量范围
*/
def saveOffsetRanges(groupid: String, offsetRange: Array[OffsetRange]) = {
val conn = JDBCConnPool.getConnection()
val insertSql = "replace into topic_par_group_offset(`topic`, `partition`, `groupid`, `offset`) values(?,?,?,?)"
val ppst = conn.prepareStatement(insertSql)
for (offset <- offsetRange) {
ppst.setString(1, offset.topic)
ppst.setInt(2, offset.partition)
ppst.setString(3, groupid)
ppst.setLong(4, offset.untilOffset)
ppst.executeUpdate()
}
JDBCConnPool.closeConnection(ppst, conn)
}
/**
* 将偏移量保存到Redis中
* @param groupid
* @param offsetRange
*/
def saveOffsetToRedis(groupid: String, offsetRange: Array[OffsetRange]) = {
val jedis :Jedis = JedisConnPool.getConnection()
for(offsetRange<-offsetRange){
val topic=offsetRange.topic
val partition=offsetRange.partition
val offset=offsetRange.untilOffset
// key为topic_groupid,field为partition，value为offset
jedis.hset(s"${topic}_${groupid}",partition.toString,offset.toString)
}
}
}
- 业务处理类
该对象是业务处理逻辑，主要是消费Kafka数据，再处理之后进行手动将偏移量保存到MySQL中。在启动程序时，会判断外部存储设备中是否存在偏移量，如果是首次启动则从最初的消费位点消费，如果存在Offset，则从当前的Offset去消费。
观察现象：当首次启动时会从头消费数据，手动停止程序，然后再次启动，会发现会从当前提交的偏移量消费数据。
object ManualCommitOffset {
def main(args: Array[String]): Unit = {
val brokers = ConfigConstants.kafkaBrokers
val groupId = ConfigConstants.groupId
val topics = ConfigConstants.kafkaTopics
val batchInterval = ConfigConstants.batchInterval
val conf = new SparkConf()
.setAppName(ManualCommitOffset.getClass.getSimpleName)
.setMaster("local[1]")
.set("spark.serializer",ConfigConstants.sparkSerializer)
val ssc = new StreamingContext(conf, batchInterval)
// 必须开启checkpoint,否则会报错
ssc.checkpoint(ConfigConstants.checkpointDir)
ssc.sparkContext.setLogLevel("OFF")
//使用broker和topic创建direct kafka stream
val topicSet = topics.split(" ").toSet
// kafka连接参数
val kafkaParams = Map[String, Object](
ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG -> brokers,
ConsumerConfig.GROUP_ID_CONFIG -> groupId,
ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG -> classOf[StringDeserializer],
ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG -> classOf[StringDeserializer],
ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG -> (false: java.lang.Boolean),
ConsumerConfig.AUTO_OFFSET_RESET_CONFIG -> "earliest"
)
// 从MySQL中读取该主题对应的消费者组的分区偏移量
val offsetMap = OffsetReadAndSave.getOffsetMap(groupId, topics)
var inputDStream: InputDStream[ConsumerRecord[String, String]] = null
//如果MySQL中已经存在了偏移量,则应该从该偏移量处开始消费
if (offsetMap.size > 0) {
println("存在偏移量，从该偏移量处进行消费！！")
inputDStream = KafkaUtils.createDirectStream[String, String](
ssc,
LocationStrategies.PreferConsistent,
ConsumerStrategies.Subscribe[String, String](topicSet, kafkaParams, offsetMap))
} else {
//如果MySQL中没有存在了偏移量，从最早开始消费
inputDStream = KafkaUtils.createDirectStream[String, String](
ssc,
LocationStrategies.PreferConsistent,
ConsumerStrategies.Subscribe[String, String](topicSet, kafkaParams))
}
// checkpoint时间间隔，必须是batchInterval的整数倍
inputDStream.checkpoint(ConfigConstants.checkpointInterval)
// 保存batch的offset
var offsetRanges = Array[OffsetRange]()
// 获取当前DS的消息偏移量
val transformDS = inputDStream.transform { rdd =>
// 获取offset
offsetRanges = rdd.asInstanceOf[HasOffsetRanges].offsetRanges
rdd
}
/**
* 状态更新函数
* @param newValues:新的value值
* @param stateValue：状态值
* @return
*/
def updateFunc(newValues: Seq[Int], stateValue: Option[Int]): Option[Int] = {
var oldvalue = stateValue.getOrElse(0) // 获取状态值
// 遍历当前数据，并更新状态
for (newValue <- newValues) {
oldvalue += newValue
}
// 返回最新的状态
Option(oldvalue)
}
// 业务逻辑处理
// 该示例统计消息key的个数，用于查看是否是从已经提交的偏移量消费数据
transformDS.map(meg => ("spark", meg.value().toInt)).updateStateByKey(updateFunc).print()
// 打印偏移量和数据信息，观察输出的结果
transformDS.foreachRDD { (rdd, time) =>
// 遍历打印该RDD数据
rdd.foreach { record =>
println(s"key=${record.key()},value=${record.value()},partition=${record.partition()},offset=${record.offset()}")
}
// 打印消费偏移量信息
for (o <- offsetRanges) {
println(s"topic=${o.topic},partition=${o.partition},fromOffset=${o.fromOffset},untilOffset=${o.untilOffset},time=${time}")
}
//将偏移量保存到到MySQL中
OffsetReadAndSave.saveOffsetRanges(groupId, offsetRanges)
}
ssc.start()
ssc.awaitTermination()
}
}
如何使用Redis管理Kafka的OffSet
- Redis连接类
object JedisConnPool {
val config = new JedisPoolConfig
//最大连接数
config.setMaxTotal(60)
//最大空闲连接数
config.setMaxIdle(10)
config.setTestOnBorrow(true)
//服务器ip
val redisAddress :String = ConfigConstants.redisAddress.toString
// 端口号
val redisPort:Int = ConfigConstants.redisPort.toInt
//访问密码
val redisAuth :String = ConfigConstants.redisAuth.toString
//等待可用连接的最大时间
val redisTimeout:Int = ConfigConstants.redisTimeout.toInt
val pool = new JedisPool(config,redisAddress,redisPort,redisTimeout,redisAuth)
def getConnection():Jedis = {
pool.getResource
}
}
- 业务逻辑处理
该对象与上面的基本类似，只不过使用的是Redis来进行存储Offset，存储到Redis的数据类型是Hash，基本格式为：[key field value] -> [ topic_groupid partition offset]，即 key为topic_groupid,field为partition，value为offset。
object ManualCommitOffsetToRedis {
def main(args: Array[String]): Unit = {
val brokers = ConfigConstants.kafkaBrokers
val groupId = ConfigConstants.groupId
val topics = ConfigConstants.kafkaTopics
val batchInterval = ConfigConstants.batchInterval
val conf = new SparkConf()
.setAppName(ManualCommitOffset.getClass.getSimpleName)
.setMaster("local[1]")
.set("spark.serializer", ConfigConstants.sparkSerializer)
val ssc = new StreamingContext(conf, batchInterval)
// 必须开启checkpoint,否则会报错
ssc.checkpoint(ConfigConstants.checkpointDir)
ssc.sparkContext.setLogLevel("OFF")
//使用broker和topic创建direct kafka stream
val topicSet = topics.split(" ").toSet
// kafka连接参数
val kafkaParams = Map[String, Object](
ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG -> brokers,
ConsumerConfig.GROUP_ID_CONFIG -> groupId,
ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG -> classOf[StringDeserializer],
ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG -> classOf[StringDeserializer],
ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG -> (false: java.lang.Boolean),
ConsumerConfig.AUTO_OFFSET_RESET_CONFIG -> "earliest"
)
// 从Redis中读取该主题对应的消费者组的分区偏移量
val offsetMap = OffsetReadAndSave.getOffsetFromRedis(groupId, topics)
var inputDStream: InputDStream[ConsumerRecord[String, String]] = null
//如果Redis中已经存在了偏移量,则应该从该偏移量处开始消费
if (offsetMap.size > 0) {
println("存在偏移量，从该偏移量处进行消费！！")
inputDStream = KafkaUtils.createDirectStream[String, String](
ssc,
LocationStrategies.PreferConsistent,
ConsumerStrategies.Subscribe[String, String](topicSet, kafkaParams, offsetMap))
} else {
//如果Redis中没有存在了偏移量，从最早开始消费
inputDStream = KafkaUtils.createDirectStream[String, String](
ssc,
LocationStrategies.PreferConsistent,
ConsumerStrategies.Subscribe[String, String](topicSet, kafkaParams))
}
// checkpoint时间间隔，必须是batchInterval的整数倍
inputDStream.checkpoint(ConfigConstants.checkpointInterval)
// 保存batch的offset
var offsetRanges = Array[OffsetRange]()
// 获取当前DS的消息偏移量
val transformDS = inputDStream.transform { rdd =>
// 获取offset
offsetRanges = rdd.asInstanceOf[HasOffsetRanges].offsetRanges
rdd
}
/**
* 状态更新函数
*
* @param newValues :新的value值
* @param stateValue ：状态值
* @return
*/
def updateFunc(newValues: Seq[Int], stateValue: Option[Int]): Option[Int] = {
var oldvalue = stateValue.getOrElse(0) // 获取状态值
// 遍历当前数据，并更新状态
for (newValue <- newValues) {
oldvalue += newValue
}
// 返回最新的状态
Option(oldvalue)
}
// 业务逻辑处理
// 该示例统计消息key的个数，用于查看是否是从已经提交的偏移量消费数据
transformDS.map(meg => ("spark", meg.value().toInt)).updateStateByKey(updateFunc).print()
// 打印偏移量和数据信息，观察输出的结果
transformDS.foreachRDD { (rdd, time) =>
// 遍历打印该RDD数据
rdd.foreach { record =>
println(s"key=${record.key()},value=${record.value()},partition=${record.partition()},offset=${record.offset()}")
}
// 打印消费偏移量信息
for (o <- offsetRanges) {
println(s"topic=${o.topic},partition=${o.partition},fromOffset=${o.fromOffset},untilOffset=${o.untilOffset},time=${time}")
}
//将偏移量保存到到Redis中
OffsetReadAndSave.saveOffsetToRedis(groupId, offsetRanges)
}
ssc.start()
ssc.awaitTermination()
}
}
总结
本文介绍了如何使用外部存储设备来保存Kafka的消费位点，通过详细的代码示例说明了使用MySQL和Redis管理消费位点的方式。当然，外部存储设备很多，用户也可以使用其他的存储设备进行管理Offset，比如Zookeeper和HBase等，其基本处理思路都十分相似。
Spark Streaming No Receivers 方式的createDirectStream 方法不使用接收器，而是创建输入流直接从Kafka 集群节点拉取消息。输入流保证每个消息从Kafka 集群拉取以后只完全转换一次，保证语义一致性。但是当作业发生故障或重启时，要保障从当前的消费位点去处理数据(即Exactly Once语义)，单纯的依靠SparkStreaming本身的机制是不太理想的，生产环境中通常借助手动管理offset的方式来维护kafka的消费位点。本文分享将介绍如何手动管理Kafka的Offset，希望对你有所帮助。本文主要包括以下内容：
- 如何使用MySQL管理Kafka的Offset
- 如何使用Redis管理Kafka的OffSet
如何使用MySQL管理Kafka的Offset
我们可以从Spark Streaming 应用程序中编写代码来手动管理Kafka偏移量，偏移量可以从每一批流处理中生成的RDDS偏移量来获取，获取方式为：
KafkaUtils.createDirectStream(...).foreachRDD { rdd =>
// 获取偏移量
val offsetRanges = rdd.asInstanceOf[HasOffsetRanges].offsetRanges
...
}
当获取到偏移量之后，可以将将其保存到外部存储设备中(MySQL、Redis、Zookeeper、HBase等)。
使用案例代码
- MySQL中用于保存偏移量的表
CREATE TABLE `topic_par_group_offset` (
`topic` varchar(255) NOT NULL,
`partition` int(11) NOT NULL,
`groupid` varchar(255) NOT NULL,
`offset` bigint(20) DEFAULT NULL,
PRIMARY KEY (`topic`,`partition`,`groupid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 ;
- 常量配置类:ConfigConstants
object ConfigConstants {
// Kafka配置
val kafkaBrokers = "kms-2:9092,kms-3:9092,kms-4:9092"
val groupId = "group_test"
val kafkaTopics = "test"
val batchInterval = Seconds(5)
val streamingStorageLevel = StorageLevel.MEMORY_AND_DISK_SER_2
val kafkaKeySer = "org.apache.kafka.common.serialization.StringSerializer"
val kafkaValueSer = "org.apache.kafka.common.serialization.StringSerializer"
val sparkSerializer = "org.apache.spark.serializer.KryoSerializer"
val batchSize = 16384
val lingerMs = 1
val bufferMemory = 33554432
// MySQL配置
val user = "root"
val password = "123qwe"
val url = "jdbc:mysql://localhost:3306/kafka_offset"
val driver = "com.mysql.jdbc.Driver"
// 检查点配置
val checkpointDir = "file:///e:/checkpoint"
val checkpointInterval = Seconds(10)
// Redis配置
val redisAddress = "192.168.10.203"
val redisPort = 6379
val redisAuth = "123qwe"
val redisTimeout = 3000
}
- JDBC连接工具类:JDBCConnPool
object JDBCConnPool {
val log: Logger = Logger.getLogger(JDBCConnPool.getClass)
var dataSource: BasicDataSource = null
/**
* 创建数据源
*
* @return
*/
def getDataSource(): BasicDataSource = {
if (dataSource == null) {
dataSource = new BasicDataSource()
dataSource.setDriverClassName(ConfigConstants.driver)
dataSource.setUrl(ConfigConstants.url)
dataSource.setUsername(ConfigConstants.user)
dataSource.setPassword(ConfigConstants.password)
dataSource.setMaxTotal(50)
dataSource.setInitialSize(3)
dataSource.setMinIdle(3)
dataSource.setMaxIdle(10)
dataSource.setMaxWaitMillis(2 * 10000)
dataSource.setRemoveAbandonedTimeout(180)
dataSource.setRemoveAbandonedOnBorrow(true)
dataSource.setRemoveAbandonedOnMaintenance(true)
dataSource.setTestOnReturn(true)
dataSource.setTestOnBorrow(true)
}
return dataSource
}
/**
* 释放数据源
*/
def closeDataSource() = {
if (dataSource != null) {
dataSource.close()
}
}
/**
* 获取数据库连接
*
* @return
*/
def getConnection(): Connection = {
var conn: Connection = null
try {
if (dataSource != null) {
conn = dataSource.getConnection()
} else {
conn = getDataSource().getConnection()
}
} catch {
case e: Exception =>
log.error(e.getMessage(), e)
}
conn
}
/**
* 关闭连接
*/
def closeConnection (ps:PreparedStatement , conn:Connection ) {
if (ps != null) {
try {
ps.close();
} catch {
case e:Exception =>
log.error("预编译SQL语句对象PreparedStatement关闭异常！" + e.getMessage(), e);
}
}
if (conn != null) {
try {
conn.close();
} catch {
case e:Exception =>
log.error("关闭连接对象Connection异常！" + e.getMessage(), e);
}
}
}
}
- Kafka生产者：KafkaProducerTest
object KafkaProducerTest {
def main(args: Array[String]): Unit = {
val props : Properties = new Properties()
props.put("bootstrap.servers", ConfigConstants.kafkaBrokers)
props.put("batch.size", ConfigConstants.batchSize.asInstanceOf[Integer])
props.put("linger.ms", ConfigConstants.lingerMs.asInstanceOf[Integer])
props.put("buffer.memory", ConfigConstants.bufferMemory.asInstanceOf[Integer])
props.put("key.serializer",ConfigConstants.kafkaKeySer)
props.put("value.serializer", ConfigConstants.kafkaValueSer)
val producer : Producer[String, String] = new KafkaProducer[String, String](props)
val startTime : Long = System.currentTimeMillis()
for ( i <- 1 to 100) {
producer.send(new ProducerRecord[String, String](ConfigConstants.kafkaTopics, "Spark", Integer.toString(i)))
}
println("消耗时间：" + (System.currentTimeMillis() - startTime))
producer.close()
}
}
- 读取和保存Offset：
该对象的作用是从外部设备中读取和写入Offset，包括MySQL和Redis
object OffsetReadAndSave {
/**
* 从MySQL中获取偏移量
*
* @param groupid
* @param topic
* @return
*/
def getOffsetMap(groupid: String, topic: String): mutable.Map[TopicPartition, Long] = {
val conn = JDBCConnPool.getConnection()
val selectSql = "select * from topic_par_group_offset where groupid = ? and topic = ?"
val ppst = conn.prepareStatement(selectSql)
ppst.setString(1, groupid)
ppst.setString(2, topic)
val result: ResultSet = ppst.executeQuery()
// 主题分区偏移量
val topicPartitionOffset = mutable.Map[TopicPartition, Long]()
while (result.next()) {
val topicPartition: TopicPartition = new TopicPartition(result.getString("topic"), result.getInt("partition"))
topicPartitionOffset += (topicPartition -> result.getLong("offset"))
}
JDBCConnPool.closeConnection(ppst, conn)
topicPartitionOffset
}
/**
* 从Redis中获取偏移量
*
* @param groupid
* @param topic
* @return
*/
def getOffsetFromRedis(groupid: String, topic: String): Map[TopicPartition, Long] = {
val jedis: Jedis = JedisConnPool.getConnection()
var offsets = mutable.Map[TopicPartition, Long]()
val key = s"${topic}_${groupid}"
val fields : java.util.Map[String, String] = jedis.hgetAll(key)
for (partition <- JavaConversions.mapAsScalaMap(fields)) {
offsets.put(new TopicPartition(topic, partition._1.toInt), partition._2.toLong)
}
offsets.toMap
}
/**
* 将偏移量写入MySQL
*
* @param groupid 消费者组ID
* @param offsetRange 消息偏移量范围
*/
def saveOffsetRanges(groupid: String, offsetRange: Array[OffsetRange]) = {
val conn = JDBCConnPool.getConnection()
val insertSql = "replace into topic_par_group_offset(`topic`, `partition`, `groupid`, `offset`) values(?,?,?,?)"
val ppst = conn.prepareStatement(insertSql)
for (offset <- offsetRange) {
ppst.setString(1, offset.topic)
ppst.setInt(2, offset.partition)
ppst.setString(3, groupid)
ppst.setLong(4, offset.untilOffset)
ppst.executeUpdate()
}
JDBCConnPool.closeConnection(ppst, conn)
}
/**
* 将偏移量保存到Redis中
* @param groupid
* @param offsetRange
*/
def saveOffsetToRedis(groupid: String, offsetRange: Array[OffsetRange]) = {
val jedis :Jedis = JedisConnPool.getConnection()
for(offsetRange<-offsetRange){
val topic=offsetRange.topic
val partition=offsetRange.partition
val offset=offsetRange.untilOffset
// key为topic_groupid,field为partition，value为offset
jedis.hset(s"${topic}_${groupid}",partition.toString,offset.toString)
}
}
}
- 业务处理类
该对象是业务处理逻辑，主要是消费Kafka数据，再处理之后进行手动将偏移量保存到MySQL中。在启动程序时，会判断外部存储设备中是否存在偏移量，如果是首次启动则从最初的消费位点消费，如果存在Offset，则从当前的Offset去消费。
观察现象：当首次启动时会从头消费数据，手动停止程序，然后再次启动，会发现会从当前提交的偏移量消费数据。
object ManualCommitOffset {
def main(args: Array[String]): Unit = {
val brokers = ConfigConstants.kafkaBrokers
val groupId = ConfigConstants.groupId
val topics = ConfigConstants.kafkaTopics
val batchInterval = ConfigConstants.batchInterval
val conf = new SparkConf()
.setAppName(ManualCommitOffset.getClass.getSimpleName)
.setMaster("local[1]")
.set("spark.serializer",ConfigConstants.sparkSerializer)
val ssc = new StreamingContext(conf, batchInterval)
// 必须开启checkpoint,否则会报错
ssc.checkpoint(ConfigConstants.checkpointDir)
ssc.sparkContext.setLogLevel("OFF")
//使用broker和topic创建direct kafka stream
val topicSet = topics.split(" ").toSet
// kafka连接参数
val kafkaParams = Map[String, Object](
ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG -> brokers,
ConsumerConfig.GROUP_ID_CONFIG -> groupId,
ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG -> classOf[StringDeserializer],
ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG -> classOf[StringDeserializer],
ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG -> (false: java.lang.Boolean),
ConsumerConfig.AUTO_OFFSET_RESET_CONFIG -> "earliest"
)
// 从MySQL中读取该主题对应的消费者组的分区偏移量
val offsetMap = OffsetReadAndSave.getOffsetMap(groupId, topics)
var inputDStream: InputDStream[ConsumerRecord[String, String]] = null
//如果MySQL中已经存在了偏移量,则应该从该偏移量处开始消费
if (offsetMap.size > 0) {
println("存在偏移量，从该偏移量处进行消费！！")
inputDStream = KafkaUtils.createDirectStream[String, String](
ssc,
LocationStrategies.PreferConsistent,
ConsumerStrategies.Subscribe[String, String](topicSet, kafkaParams, offsetMap))
} else {
//如果MySQL中没有存在了偏移量，从最早开始消费
inputDStream = KafkaUtils.createDirectStream[String, String](
ssc,
LocationStrategies.PreferConsistent,
ConsumerStrategies.Subscribe[String, String](topicSet, kafkaParams))
}
// checkpoint时间间隔，必须是batchInterval的整数倍
inputDStream.checkpoint(ConfigConstants.checkpointInterval)
// 保存batch的offset
var offsetRanges = Array[OffsetRange]()
// 获取当前DS的消息偏移量
val transformDS = inputDStream.transform { rdd =>
// 获取offset
offsetRanges = rdd.asInstanceOf[HasOffsetRanges].offsetRanges
rdd
}
/**
* 状态更新函数
* @param newValues:新的value值
* @param stateValue：状态值
* @return
*/
def updateFunc(newValues: Seq[Int], stateValue: Option[Int]): Option[Int] = {
var oldvalue = stateValue.getOrElse(0) // 获取状态值
// 遍历当前数据，并更新状态
for (newValue <- newValues) {
oldvalue += newValue
}
// 返回最新的状态
Option(oldvalue)
}
// 业务逻辑处理
// 该示例统计消息key的个数，用于查看是否是从已经提交的偏移量消费数据
transformDS.map(meg => ("spark", meg.value().toInt)).updateStateByKey(updateFunc).print()
// 打印偏移量和数据信息，观察输出的结果
transformDS.foreachRDD { (rdd, time) =>
// 遍历打印该RDD数据
rdd.foreach { record =>
println(s"key=${record.key()},value=${record.value()},partition=${record.partition()},offset=${record.offset()}")
}
// 打印消费偏移量信息
for (o <- offsetRanges) {
println(s"topic=${o.topic},partition=${o.partition},fromOffset=${o.fromOffset},untilOffset=${o.untilOffset},time=${time}")
}
//将偏移量保存到到MySQL中
OffsetReadAndSave.saveOffsetRanges(groupId, offsetRanges)
}
ssc.start()
ssc.awaitTermination()
}
}
如何使用Redis管理Kafka的OffSet
- Redis连接类
object JedisConnPool {
val config = new JedisPoolConfig
//最大连接数
config.setMaxTotal(60)
//最大空闲连接数
config.setMaxIdle(10)
config.setTestOnBorrow(true)
//服务器ip
val redisAddress :String = ConfigConstants.redisAddress.toString
// 端口号
val redisPort:Int = ConfigConstants.redisPort.toInt
//访问密码
val redisAuth :String = ConfigConstants.redisAuth.toString
//等待可用连接的最大时间
val redisTimeout:Int = ConfigConstants.redisTimeout.toInt
val pool = new JedisPool(config,redisAddress,redisPort,redisTimeout,redisAuth)
def getConnection():Jedis = {
pool.getResource
}
}
- 业务逻辑处理
该对象与上面的基本类似，只不过使用的是Redis来进行存储Offset，存储到Redis的数据类型是Hash，基本格式为：[key field value] -> [ topic_groupid partition offset]，即 key为topic_groupid,field为partition，value为offset。
object ManualCommitOffsetToRedis {
def main(args: Array[String]): Unit = {
val brokers = ConfigConstants.kafkaBrokers
val groupId = ConfigConstants.groupId
val topics = ConfigConstants.kafkaTopics
val batchInterval = ConfigConstants.batchInterval
val conf = new SparkConf()
.setAppName(ManualCommitOffset.getClass.getSimpleName)
.setMaster("local[1]")
.set("spark.serializer", ConfigConstants.sparkSerializer)
val ssc = new StreamingContext(conf, batchInterval)
// 必须开启checkpoint,否则会报错
ssc.checkpoint(ConfigConstants.checkpointDir)
ssc.sparkContext.setLogLevel("OFF")
//使用broker和topic创建direct kafka stream
val topicSet = topics.split(" ").toSet
// kafka连接参数
val kafkaParams = Map[String, Object](
ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG -> brokers,
ConsumerConfig.GROUP_ID_CONFIG -> groupId,
ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG -> classOf[StringDeserializer],
ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG -> classOf[StringDeserializer],
ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG -> (false: java.lang.Boolean),
ConsumerConfig.AUTO_OFFSET_RESET_CONFIG -> "earliest"
)
// 从Redis中读取该主题对应的消费者组的分区偏移量
val offsetMap = OffsetReadAndSave.getOffsetFromRedis(groupId, topics)
var inputDStream: InputDStream[ConsumerRecord[String, String]] = null
//如果Redis中已经存在了偏移量,则应该从该偏移量处开始消费
if (offsetMap.size > 0) {
println("存在偏移量，从该偏移量处进行消费！！")
inputDStream = KafkaUtils.createDirectStream[String, String](
ssc,
LocationStrategies.PreferConsistent,
ConsumerStrategies.Subscribe[String, String](topicSet, kafkaParams, offsetMap))
} else {
//如果Redis中没有存在了偏移量，从最早开始消费
inputDStream = KafkaUtils.createDirectStream[String, String](
ssc,
LocationStrategies.PreferConsistent,
ConsumerStrategies.Subscribe[String, String](topicSet, kafkaParams))
}
// checkpoint时间间隔，必须是batchInterval的整数倍
inputDStream.checkpoint(ConfigConstants.checkpointInterval)
// 保存batch的offset
var offsetRanges = Array[OffsetRange]()
// 获取当前DS的消息偏移量
val transformDS = inputDStream.transform { rdd =>
// 获取offset
offsetRanges = rdd.asInstanceOf[HasOffsetRanges].offsetRanges
rdd
}
/**
* 状态更新函数
*
* @param newValues :新的value值
* @param stateValue ：状态值
* @return
*/
def updateFunc(newValues: Seq[Int], stateValue: Option[Int]): Option[Int] = {
var oldvalue = stateValue.getOrElse(0) // 获取状态值
// 遍历当前数据，并更新状态
for (newValue <- newValues) {
oldvalue += newValue
}
// 返回最新的状态
Option(oldvalue)
}
// 业务逻辑处理
// 该示例统计消息key的个数，用于查看是否是从已经提交的偏移量消费数据
transformDS.map(meg => ("spark", meg.value().toInt)).updateStateByKey(updateFunc).print()
// 打印偏移量和数据信息，观察输出的结果
transformDS.foreachRDD { (rdd, time) =>
// 遍历打印该RDD数据
rdd.foreach { record =>
println(s"key=${record.key()},value=${record.value()},partition=${record.partition()},offset=${record.offset()}")
}
// 打印消费偏移量信息
for (o <- offsetRanges) {
println(s"topic=${o.topic},partition=${o.partition},fromOffset=${o.fromOffset},untilOffset=${o.untilOffset},time=${time}")
}
//将偏移量保存到到Redis中
OffsetReadAndSave.saveOffsetToRedis(groupId, offsetRanges)
}
ssc.start()
ssc.awaitTermination()
}
}
总结
本文介绍了如何使用外部存储设备来保存Kafka的消费位点，通过详细的代码示例说明了使用MySQL和Redis管理消费位点的方式。当然，外部存储设备很多，用户也可以使用其他的存储设备进行管理Offset，比如Zookeeper和HBase等，其基本处理思路都十分相似。
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