spark streaming讀取kafka資料令丟失(二)
阿新 • • 發佈:2019-02-01
方式二:
方法二就是每次streaming 消費了kafka的資料後,將消費的kafka offsets更新到zookeeper。當你的程式掛掉或者升級的時候,就可以接著上次的讀取,實現資料的令丟失和 at most once。而且使用checkpoint的方式可能會導致資料重複消費,spark streaming維護的offset和zookeeper維護的偏移量不同步導致資料丟失或者重複消費等。那麼我們可以在dstream 出發action的時候 特別是在output的時候出發offset更新,這樣子就能確保已消費的資料能夠將offsets更新到zookeeper。好了不多說,直接上程式碼。
def start(ssc:StreamingContext,
brokerList:String,
zkConnect:String,
groupId:String,
topic: String): InputDStream[(String, String)] ={
val zkClient = new ZkClient(zkConnect, 60000, 60000, new ZkSerializer {
override def serialize(data: Object ): Array[Byte] = {
try {
return data.toString().getBytes("UTF-8")
} catch {
case _: ZkMarshallingError => return null
}
}
override def deserialize(bytes: Array[Byte]): Object = {
try {
return new String(bytes, "UTF-8")
} catch {
case _: ZkMarshallingError => return null
}
}
})
val kafkaParams = Map("metadata.broker.list" -> brokerList, "group.id" -> groupId,
"zookeeper.connect"->zkConnect,
"auto.offset.reset" -> kafka.api.OffsetRequest.SmallestTimeString)
val topics = topic.split(",").toSet
val broker = brokerList.split(",")(0).split(":")(0)
val topicDirs = new ZKGroupTopicDirs(groupId, topic)
val zkTopicPath = s"${topicDirs.consumerOffsetDir}"
val children = zkClient.countChildren(s"${topicDirs.consumerOffsetDir}")
var kafkaStream: InputDStream[(String, String)] = null
var fromOffsets: Map[TopicAndPartition, Long] = Map()
if (children > 0) {
val topicList = List(topic)
val req = new TopicMetadataRequest(topicList,0)
val getLeaderConsumer = new SimpleConsumer(broker,9092,10000,10000,"OffsetLookup")
val res = getLeaderConsumer.send(req)
val topicMetaOption = res.topicsMetadata.headOption
val partitions = topicMetaOption match{
case Some(tm) =>
tm.partitionsMetadata.map(pm=>(pm.partitionId,pm.leader.get.host)).toMap[Int,String]
case None =>
Map[Int,String]()
}
for (i <- 0 until children) {
val partitionOffset = zkClient.readData[String](s"$zkTopicPath/${i}")
val tp = TopicAndPartition(topic, i)
val requestMin = OffsetRequest(Map(tp -> PartitionOffsetRequestInfo(OffsetRequest.EarliestTime,1)))
val consumerMin = new SimpleConsumer(partitions(i),9092,10000,10000,"getMinOffset")
val curOffsets = consumerMin.getOffsetsBefore(requestMin).partitionErrorAndOffsets(tp).offsets
var nextOffset = partitionOffset.toLong
if(curOffsets.nonEmpty && nextOffset < curOffsets.head){
nextOffset = curOffsets.head
}
fromOffsets += (tp -> nextOffset)
fromOffsets += (tp -> partitionOffset.toLong)
logger.info(tp.topic+":"+tp.partition +";partitionOffset:"+partitionOffset+"**********"+"nextOffset:"+nextOffset)
}
val messageHandler = (mmd: MessageAndMetadata[String, String]) => (mmd.topic, mmd.message())
kafkaStream = KafkaUtils.createDirectStream[String, String, StringDecoder, StringDecoder, (String, String)](
ssc, kafkaParams, fromOffsets, messageHandler)
} else {
kafkaStream = KafkaUtils.createDirectStream[String, String, StringDecoder, StringDecoder](ssc, kafkaParams, topics)
}
var offsetRanges = Array[OffsetRange]()
kafkaStream.transform { rdd =>
offsetRanges = rdd.asInstanceOf[HasOffsetRanges].offsetRanges
rdd
}.foreachRDD {
rdd =>
{
for (o <- offsetRanges) {
ZkUtils.updatePersistentPath(zkClient, s"${topicDirs.consumerOffsetDir}/${o.partition}", ````````
.fromOffset.toString)
}
}
}
kafkaStream
}