Re: Question about DataStream serialization

Posted by rmetzger0 on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/NPE-with-Flink-Streaming-from-Kafka-tp3821p3830.html

Hi Radu,

both emails reached the mailing list :)

You can not reference to DataSets or DataStreams from inside user defined functions. Both are just abstractions for a data set or stream, so the elements are not really inside the set. 

We don't have any support for mixing the DataSet and DataStream API.

For your use case, I would recommend you to use a RichFlatMapFunction and in the open() call read the text file.

On Tue, Dec 1, 2015 at 5:03 PM, Radu Tudoran <[hidden email]> wrote:

 

Hello,

 

I am not sure if this message was received on the user list, if so I apologies for duplicate messages

 

I have the following scenario  

 

·         Reading a fixed set

DataStream<String> fixedset = env.readtextFile(…

·         Reading a continuous stream of data

DataStream<String> stream = ….

 

I would need that for each event read from the continuous stream to make some operations onit and on the fixedsettoghether

 

 

I have tried something like

 

final myObject.referenceStaticSet = fixedset;

stream.map(new MapFunction<String, String>() {

                     @Override

                     public String map(String arg0) throws Exception {

                          

                           //for example:   final string2add = arg0;

                                                                //the goal of below function would be to add the string2add to the fixedset

                           myObject.referenceStaticSet = myObject.referenceStaticSet.flatMap(new FlatMapFunction<String, String>() {

                          

                                  @Override

                                  public void flatMap(String arg0, Collector<String> arg1)

                                                                                //for example adding to the fixed set also the string2add object:   arg1.collect(string2add);

                                                                                }

…

}

 

However,  I get an exception (Exception in thread "main" org.apache.flink.api.common.InvalidProgramException: ) that object is not serializable (Object MyClass$3@a71081 not serializable )

 

Looking into this I see that the issues is that the DataStream<> is not serializable. What would be the solution to this issue?

 

As I mentioned before, I would like that for each event from the continuous stream to use the initial fixed set, add the event to it and apply an operation.

Stephan was mentioning at some point some possibility to create a DataSet and launch a batch processing while operating in stream mode– in case this is possible, can you give me a reference for it, because it might be the good solution to  use in case. I am thinking that I could keep the fixed set as a DataSet and as each new event comes, transform it into a dataset and then join with reference set and apply an operation

 

Regards,

 

 

 

 

Dr. Radu Tudoran

Research Engineer

IT R&D Division

 

HUAWEI TECHNOLOGIES Duesseldorf GmbH

European Research Center

Riesstrasse 25, 80992 München

 

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From: Vieru, Mihail [mailto:[hidden email]]
Sent: Tuesday, December 01, 2015 4:55 PM
To: [hidden email]
Subject: NPE with Flink Streaming from Kafka

 

Hi,

we get the following NullPointerException after ~50 minutes when running a streaming job with windowing and state that reads data from Kafka and writes the result to local FS.

There are around 170 million messages to be processed, Flink 0.10.1 stops at ~8 million.

Flink runs locally, started with the "start-cluster-streaming.sh" script.

12/01/2015 15:06:24    Job execution switched to status RUNNING.
12/01/2015 15:06:24    Source: Custom Source -> Map -> Map(1/1) switched to SCHEDULED
12/01/2015 15:06:24    Source: Custom Source -> Map -> Map(1/1) switched to DEPLOYING
12/01/2015 15:06:24    Fast TumblingTimeWindows(5000) of Reduce at main(ItemPriceAvgPerOrder.java:108) -> Sink: Unnamed(1/1) switched to SCHEDULED
12/01/2015 15:06:24    Fast TumblingTimeWindows(5000) of Reduce at main(ItemPriceAvgPerOrder.java:108) -> Sink: Unnamed(1/1) switched to DEPLOYING
12/01/2015 15:06:24    Source: Custom Source -> Map -> Map(1/1) switched to RUNNING
12/01/2015 15:06:24    Fast TumblingTimeWindows(5000) of Reduce at main(ItemPriceAvgPerOrder.java:108) -> Sink: Unnamed(1/1) switched to RUNNING
12/01/2015 15:56:08    Fast TumblingTimeWindows(5000) of Reduce at main(ItemPriceAvgPerOrder.java:108) -> Sink: Unnamed(1/1) switched to CANCELED
12/01/2015 15:56:08    Source: Custom Source -> Map -> Map(1/1) switched to FAILED
java.lang.Exception
    at org.apache.flink.streaming.connectors.kafka.internals.LegacyFetcher.run(LegacyFetcher.java:242)
    at org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer.run(FlinkKafkaConsumer.java:397)
    at org.apache.flink.streaming.api.operators.StreamSource.run(StreamSource.java:58)
    at org.apache.flink.streaming.runtime.tasks.SourceStreamTask.run(SourceStreamTask.java:55)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:218)
    at org.apache.flink.runtime.taskmanager.Task.run(Task.java:584)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
    at org.I0Itec.zkclient.ZkConnection.writeDataReturnStat(ZkConnection.java:115)
    at org.I0Itec.zkclient.ZkClient$10.call(ZkClient.java:817)
    at org.I0Itec.zkclient.ZkClient.retryUntilConnected(ZkClient.java:675)
    at org.I0Itec.zkclient.ZkClient.writeDataReturnStat(ZkClient.java:813)
    at org.I0Itec.zkclient.ZkClient.writeData(ZkClient.java:808)
    at org.I0Itec.zkclient.ZkClient.writeData(ZkClient.java:777)
    at kafka.utils.ZkUtils$.updatePersistentPath(ZkUtils.scala:332)
    at kafka.utils.ZkUtils.updatePersistentPath(ZkUtils.scala)
    at org.apache.flink.streaming.connectors.kafka.internals.ZookeeperOffsetHandler.setOffsetInZooKeeper(ZookeeperOffsetHandler.java:112)
    at org.apache.flink.streaming.connectors.kafka.internals.ZookeeperOffsetHandler.commit(ZookeeperOffsetHandler.java:80)
    at org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer$PeriodicOffsetCommitter.run(FlinkKafkaConsumer.java:632)

Any ideas on what could cause this behaviour?

 

Best,

Mihail