flink⼿手动维护kafka偏移量量

flink对接kafka，官方模式方式是自动维护偏移量

但并没有考虑到flink消费kafka过程中，如果出现进程中断后的事情! 如果此时，进程中段:

1:数据可能丢失

从获取了了数据，但是在执⾏行行业务逻辑过程中发⽣生中断，此时会出现丢失数据现象

2:数据可能重复处理理

flink从kafka拉去数据过程中，如果此时flink进程挂掉，那么重启flink之后，会从当前Topic的 起始偏移量量开始消费

解决flink消费kafka的弊端

上述问题，在任何公司的实际⽣生产中，都会遇到，并且⽐比较头痛的事情，主要原因是因为上述的代码 是使⽤用flink⾃自动维护kafka的偏移量量，导致⼀一些实际⽣生产问题出现。~那么为了了解决这些问题，我们就 需要⼿手动维护kafka的偏移量量，并且保证kafka的偏移量量和flink的checkpoint的数据状态保持⼀一致 (最好是⼿手动维护偏移量量的同时，和现有业务做成事务放在⼀一起)~

1）：offset和checkpoint绑定

//创建kafka数据流
val properties = new Properties() properties.setProperty("bootstrap.servers", GlobalConfigUtils.getBootstrap) properties.setProperty("zookeeper.connect", GlobalConfigUtils.getZk) properties.setProperty("group.id", GlobalConfigUtils.getConsumerGroup) properties.setProperty("enable.auto.commit" , "true")//TODO properties.setProperty("auto.commit.interval.ms" , "5000") properties.setProperty("auto.offset.reset" , "latest") properties.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer"); properties.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
val kafka09 = new FlinkKafkaConsumer09[String](
  GlobalConfigUtils.getIntputTopic,
  new SimpleStringSchema(),
  properties
)
/** *
如果checkpoint启⽤用，当checkpoint完成之后，Flink Kafka Consumer将会提交offset保存 到checkpoint State中，
这就保证了了kafka broker中的committed offset与 checkpoint stata中的offset相⼀一致。 ⽤用户可以在Consumer中调⽤用setCommitOffsetsOnCheckpoints(boolean) ⽅方法来选择启⽤用 或者禁⽤用offset committing(默认情况下是启⽤用的)
* */
kafka09.setCommitOffsetsOnCheckpoints(true)
kafka09.setStartFromLatest()//start from the latest record
kafka09.setStartFromGroupOffsets()
//添加数据源addSource(kafka09)
val data: DataStream[String] = env.addSource(kafka09)

2）：编写flink⼿手动维护kafka偏移量量

/**
* ⼿手动维护kafka的偏移量量 */
object KafkaTools {
  var offsetClient: KafkaConsumer[Array[Byte], Array[Byte]] = null
  var standardProps:Properties = null
  def init():Properties = {
    standardProps = new Properties
    standardProps.setProperty("bootstrap.servers",
GlobalConfigUtils.getBootstrap)
    standardProps.setProperty("zookeeper.connect", GlobalConfigUtils.getZk)
    standardProps.setProperty("group.id",
GlobalConfigUtils.getConsumerGroup)
    standardProps.setProperty("enable.auto.commit" , "true")//TODO
    standardProps.setProperty("auto.commit.interval.ms" , "")
    standardProps.setProperty("auto.offset.reset" , "latest")
    standardProps.put("key.deserializer",
"org.apache.kafka.common.serialization.StringDeserializer");
    standardProps.put("value.deserializer",
"org.apache.kafka.common.serialization.StringDeserializer");
    standardProps
}
  def getZkUtils():ZkUtils = {
    val zkClient = new ZkClient("hadoop01:2181")
    ZkUtils.apply(zkClient, false)
}
  def createTestTopic(topic: String, numberOfPartitions: Int,
replicationFactor: Int, topicConfig: Properties) = {
    val zkUtils = getZkUtils()
    try{
      AdminUtils.createTopic(zkUtils, topic, numberOfPartitions,
replicationFactor, topicConfig)
    }finally {
      zkUtils.close()
} }
  def offsetHandler() = {
    val props = new Properties
    props.putAll(standardProps)
    props.setProperty("key.deserializer",
"org.apache.kafka.common.serialization.ByteArrayDeserializer")

props.setProperty("value.deserializer",
"org.apache.kafka.common.serialization.ByteArrayDeserializer")
    offsetClient = new KafkaConsumer[Array[Byte], Array[Byte]](props)
  }
  def getCommittedOffset(topicName: String, partition: Int): Long = {
    init()
    offsetHandler()
    val committed = offsetClient.committed(new TopicPartition(topicName,
partition))
    println(topicName , partition , committed.offset())
    if (committed != null){
      committed.offset
    } else{
0L
} }
  def setCommittedOffset(topicName: String, partition: Int, offset: Long) {
    init()
    offsetHandler()
    var partitionAndOffset:util.Map[TopicPartition , OffsetAndMetadata] =
new util.HashMap[TopicPartition , OffsetAndMetadata]()
    partitionAndOffset.put(new TopicPartition(topicName, partition), new
OffsetAndMetadata(offset))
    offsetClient.commitSync(partitionAndOffset)
  }
  def close() {
    offsetClient.close()
}
}