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https://issues.apache.org/jira/browse/FLINK-22190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17319910#comment-17319910
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Arvid Heise commented on FLINK-22190:
-------------------------------------
1. You get byZeroException because you are dividing by 0 in user code {{/
Random.nextInt(5)}}. That's something that you need to fix on your end.
2. Could you provide example output to show the duplicates? Where does the
fail-over happen?
Note that exactly once does not mean deduplication of records or parts thereof.
Exactly once ensures that there are no duplicates caused by fail-over/restarts.
> no guarantee on Flink exactly_once sink to Kafka
> -------------------------------------------------
>
> Key: FLINK-22190
> URL: https://issues.apache.org/jira/browse/FLINK-22190
> Project: Flink
> Issue Type: Bug
> Components: API / DataStream
> Affects Versions: 1.12.2
> Environment: *flink: 1.12.2*
> *kafka: 2.7.0*
> Reporter: Spongebob
> Priority: Major
>
> When I tried to test the function of flink exactly_once sink to kafka, I
> found it can not run as expectation. here's the pipline of the flink
> applications: raw data(flink app0)-> kafka topic1 -> flink app1 -> kafka
> topic2 -> flink app2, flink tasks may met / byZeroException in random. Below
> shows the codes:
> {code:java}
> //代码占位符
> raw data, flink app0:
> class SimpleSource1 extends SourceFunction[String] {
> var switch = true
> val students: Array[String] = Array("Tom", "Jerry", "Gory")
> override def run(sourceContext: SourceFunction.SourceContext[String]): Unit
> = {
> var i = 0
> while (switch) {
> sourceContext.collect(s"${students(Random.nextInt(students.length))},$i")
> i += 1
> Thread.sleep(5000)
> }
> }
> override def cancel(): Unit = switch = false
> }
> val streamEnv = StreamExecutionEnvironment.getExecutionEnvironment
> val dataStream = streamEnv.addSource(new SimpleSource1)
> dataStream.addSink(new FlinkKafkaProducer[String]("xfy:9092",
> "single-partition-topic-2", new SimpleStringSchema()))
> streamEnv.execute("sink kafka")
>
> flink-app1:
> val streamEnv = StreamExecutionEnvironment.getExecutionEnvironment
> streamEnv.enableCheckpointing(1000, CheckpointingMode.EXACTLY_ONCE)
> val prop = new Properties()
> prop.setProperty("bootstrap.servers", "xfy:9092")
> prop.setProperty("group.id", "test")
> val dataStream = streamEnv.addSource(new FlinkKafkaConsumer[String](
> "single-partition-topic-2",
> new SimpleStringSchema,
> prop
> ))
> val resultStream = dataStream.map(x => {
> val data = x.split(",")
> (data(0), data(1), data(1).toInt / Random.nextInt(5)).toString()
> }
> )
> resultStream.print().setParallelism(1)
> val propProducer = new Properties()
> propProducer.setProperty("bootstrap.servers", "xfy:9092")
> propProducer.setProperty("transaction.timeout.ms", s"${1000 * 60 * 5}")
> resultStream.addSink(new FlinkKafkaProducer[String](
> "single-partition-topic",
> new MyKafkaSerializationSchema("single-partition-topic"),
> propProducer,
> Semantic.EXACTLY_ONCE))
> streamEnv.execute("sink kafka")
>
> flink-app2:
> val streamEnv = StreamExecutionEnvironment.getExecutionEnvironment
> val prop = new Properties()
> prop.setProperty("bootstrap.servers", "xfy:9092")
> prop.setProperty("group.id", "test")
> prop.setProperty("isolation_level", "read_committed")
> val dataStream = streamEnv.addSource(new FlinkKafkaConsumer[String](
> "single-partition-topic",
> new SimpleStringSchema,
> prop
> ))
> dataStream.print().setParallelism(1)
> streamEnv.execute("consumer kafka"){code}
>
> flink app1 will print some duplicate numbers, and to my expectation flink
> app2 will deduplicate them but the fact shows not.
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