apache flink：如何从cassandra读取数据流/数据集？

de90aj5v  于 2021-06-24  发布在  Flink
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我试图将cassandra视为flink中的数据源，以下链接提供了相关信息：
从cassandra读取数据，以便在flink中进行处理
https://www.javatips.net/api/flink-master/flink-examples/flink-examples-streaming/src/main/java/org/apache/flink/streaming/examples/async/asyncioexample.java
我拿到钱了 AsyncWaitOperator 运行任务时出现异常。根据第一个链接，此异常是由于网络问题引起的。然而，奇怪的是，我在本地vm上运行cassandra，目标表中只有10行数据。
@jicaar在第一个链接中也提到了 RichAsyncFunction 至 RichMapFunction 可以避免 AsyncWaitOperator 例外，有类似经验的人能分享一下如何做吗 RichMapFunction ? AsyncWaitOperator 异常跟踪-->

02:21:00.164 [AsyncIO-Emitter-Thread (Source: Custom Source -> async wait operator -> (Flat Map, Sink: Unnamed) (1/1))] INFO  org.apache.flink.runtime.taskmanager.Task  - Source: Custom Source -> async wait operator -> (Flat Map, Sink: Unnamed) (1/1) (2809cef511194e612b2cc65510f78c64) switched from RUNNING to FAILED.
java.lang.Exception: An async function call terminated with an exception. Failing the AsyncWaitOperator.
  at org.apache.flink.streaming.api.operators.async.Emitter.output(Emitter.java:137) [flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  at org.apache.flink.streaming.api.operators.async.Emitter.run(Emitter.java:85) [flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  at java.lang.Thread.run(Thread.java:745) [na:1.8.0_60]
Caused by: org.apache.flink.streaming.runtime.tasks.ExceptionInChainedOperatorException: Could not forward element to next operator
  at org.apache.flink.streaming.runtime.tasks.OperatorChain$CopyingChainingOutput.pushToOperator(OperatorChain.java:566) ~[flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  at org.apache.flink.streaming.runtime.tasks.OperatorChain$CopyingChainingOutput.collect(OperatorChain.java:524) ~[flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  at org.apache.flink.streaming.runtime.tasks.OperatorChain$CopyingChainingOutput.collect(OperatorChain.java:504) ~[flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  at org.apache.flink.streaming.runtime.tasks.OperatorChain$BroadcastingOutputCollector.collect(OperatorChain.java:611) ~[flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  at org.apache.flink.streaming.runtime.tasks.OperatorChain$BroadcastingOutputCollector.collect(OperatorChain.java:572) ~[flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  at org.apache.flink.streaming.api.operators.AbstractStreamOperator$CountingOutput.collect(AbstractStreamOperator.java:830) ~[flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  at org.apache.flink.streaming.api.operators.AbstractStreamOperator$CountingOutput.collect(AbstractStreamOperator.java:808) ~[flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  at org.apache.flink.streaming.api.operators.TimestampedCollector.collect(TimestampedCollector.java:51) ~[flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  at org.apache.flink.streaming.api.operators.async.Emitter.output(Emitter.java:133) [flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  ... 2 common frames omitted
Caused by: com.esotericsoftware.kryo.KryoException: java.util.ConcurrentModificationException
Serialization trace:
classes (sun.misc.Launcher$AppClassLoader)
classloader (java.security.ProtectionDomain)
context (java.security.AccessControlContext)
acc (org.apache.flink.runtime.execution.librarycache.FlinkUserCodeClassLoaders$ChildFirstClassLoader)
contextClassLoader (java.lang.Thread)
threads (java.lang.ThreadGroup)
groups (java.lang.ThreadGroup)
threadGroup (io.netty.util.concurrent.DefaultThreadFactory)
val$backingThreadFactory (com.google.common.util.concurrent.ThreadFactoryBuilder$1)
threadFactory (java.util.concurrent.ThreadPoolExecutor)
delegate (com.google.common.util.concurrent.MoreExecutors$ListeningDecorator)
blockingExecutor (com.datastax.driver.core.Cluster$Manager)
manager (com.datastax.driver.core.Host)
triedHosts (com.datastax.driver.core.ExecutionInfo)
info (com.datastax.driver.core.ArrayBackedResultSet$SinglePage)
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:82) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeClassAndObject(Kryo.java:599) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.DefaultArraySerializers$ObjectArraySerializer.write(DefaultArraySerializers.java:348) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.DefaultArraySerializers$ObjectArraySerializer.write(DefaultArraySerializers.java:289) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObjectOrNull(Kryo.java:577) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:68) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeClassAndObject(Kryo.java:599) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.DefaultArraySerializers$ObjectArraySerializer.write(DefaultArraySerializers.java:348) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.DefaultArraySerializers$ObjectArraySerializer.write(DefaultArraySerializers.java:289) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeClassAndObject(Kryo.java:599) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.DefaultArraySerializers$ObjectArraySerializer.write(DefaultArraySerializers.java:348) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.DefaultArraySerializers$ObjectArraySerializer.write(DefaultArraySerializers.java:289) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeClassAndObject(Kryo.java:599) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.CollectionSerializer.write(CollectionSerializer.java:82) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.CollectionSerializer.write(CollectionSerializer.java:22) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.FieldSerializer.write(FieldSerializer.java:495) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:505) ~[kryo-2.24.0.jar:na]
  at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.copy(KryoSerializer.java:182) ~[flink-core-1.4.2.jar:1.4.2]
  at org.apache.flink.streaming.runtime.tasks.OperatorChain$CopyingChainingOutput.pushToOperator(OperatorChain.java:547) ~[flink-streaming-java_2.11-1.4.2.jar:1.4.2]
  ... 10 common frames omitted
Caused by: java.util.ConcurrentModificationException: null
  at java.util.Vector$Itr.checkForComodification(Vector.java:1184) ~[na:1.8.0_60]
  at java.util.Vector$Itr.next(Vector.java:1137) ~[na:1.8.0_60]
  at com.esotericsoftware.kryo.serializers.CollectionSerializer.write(CollectionSerializer.java:74) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.CollectionSerializer.write(CollectionSerializer.java:22) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.Kryo.writeObject(Kryo.java:523) ~[kryo-2.24.0.jar:na]
  at com.esotericsoftware.kryo.serializers.ObjectField.write(ObjectField.java:61) ~[kryo-2.24.0.jar:na]
  ... 68 common frames omitted
cassandraapache-flink

1条答案

按热度按时间
wyyhbhjk

wyyhbhjk1#

下面的代码应该可以从cassandra中读取，以便在flink中进行批处理。

final ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

ClusterBuilder clusterBuilder = new ClusterBuilder() {

        @Override
        public Cluster buildCluster(Cluster.Builder builder) {

            return builder.addContactPoint(<cassandraHost>))
                  .withPort(9042)
                  .withCredentials(<cassandraUserName>,<cassandraPassword>)
                  .build();
        } 
    };  

DataSet<Tuple3<String,String,String>> inputRecords = env
            .createInput    
            (new CassandraInputFormat<Tuple3<String,String,String>>(<select query>,clusterBuilder)          
            ,TupleTypeInfo.of(new TypeHint<Tuple3<String,String,String>>() {}));

数据集的数据类型（示例中的tuple3由三个字符串组成）将根据select查询返回的字段的类型和数量而变化。

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