Why Does the Spark Streaming Application Fail to Be Started from the Checkpoint When the Input Stream Has No Output Logic?

Question

One input stream was created for the Spark Streaming application, but the input stream had no output logic. The application failed to be started from the checkpoint. The error information is as follows:

17/04/24 10:13:57 ERROR Utils: Exception encountered
java.lang.NullPointerException
at org.apache.spark.streaming.dstream.DStreamCheckpointData$$anonfun$writeObject$1.apply$mcV$sp(DStreamCheckpointData.scala:125)
at org.apache.spark.streaming.dstream.DStreamCheckpointData$$anonfun$writeObject$1.apply(DStreamCheckpointData.scala:123)
at org.apache.spark.streaming.dstream.DStreamCheckpointData$$anonfun$writeObject$1.apply(DStreamCheckpointData.scala:123)
at org.apache.spark.util.Utils$.tryOrIOException(Utils.scala:1195)
at org.apache.spark.streaming.dstream.DStreamCheckpointData.writeObject(DStreamCheckpointData.scala:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1028)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:441)
at org.apache.spark.streaming.dstream.DStream$$anonfun$writeObject$1.apply$mcV$sp(DStream.scala:515)
at org.apache.spark.streaming.dstream.DStream$$anonfun$writeObject$1.apply(DStream.scala:510)
at org.apache.spark.streaming.dstream.DStream$$anonfun$writeObject$1.apply(DStream.scala:510)
at org.apache.spark.util.Utils$.tryOrIOException(Utils.scala:1195)
at org.apache.spark.streaming.dstream.DStream.writeObject(DStream.scala:510)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1028)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1378)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:441)
at org.apache.spark.streaming.DStreamGraph$$anonfun$writeObject$1.apply$mcV$sp(DStreamGraph.scala:191)
at org.apache.spark.streaming.DStreamGraph$$anonfun$writeObject$1.apply(DStreamGraph.scala:186)
at org.apache.spark.streaming.DStreamGraph$$anonfun$writeObject$1.apply(DStreamGraph.scala:186)
at org.apache.spark.util.Utils$.tryOrIOException(Utils.scala:1195)
at org.apache.spark.streaming.DStreamGraph.writeObject(DStreamGraph.scala:186)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1028)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
at org.apache.spark.streaming.Checkpoint$$anonfun$serialize$1.apply$mcV$sp(Checkpoint.scala:142)
at org.apache.spark.streaming.Checkpoint$$anonfun$serialize$1.apply(Checkpoint.scala:142)
at org.apache.spark.streaming.Checkpoint$$anonfun$serialize$1.apply(Checkpoint.scala:142)
at org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1230)
at org.apache.spark.streaming.Checkpoint$.serialize(Checkpoint.scala:143)
at org.apache.spark.streaming.StreamingContext.validate(StreamingContext.scala:566)
at org.apache.spark.streaming.StreamingContext.liftedTree1$1(StreamingContext.scala:612)
at org.apache.spark.streaming.StreamingContext.start(StreamingContext.scala:611)
at com.spark.test.kafka08LifoTwoInkfk$.main(kafka08LifoTwoInkfk.scala:21)
at com.spark.test.kafka08LifoTwoInkfk.main(kafka08LifoTwoInkfk.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:772)
at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:183)
at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:208)
at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:123)
at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)

Answer

When Streaming Context is started, if a checkpoint is set for an application, the DStream checkpoint object in the application needs to be serialized. dstream.context is used during serialization.

dstream.context is used to reversely search for dependent DStreams from output Streams when Streaming Context is started, and to set context one by one. If an input stream is created for a Spark Streaming application but the input stream has no output logic, no context is set for the input stream. As a result, NullPointerException is reported during serialization.

Solution: If the input stream of the output logic does not exist in the application, delete the input stream from the code or add the output logic of the input stream.