我正在尝试从Avro文件目录中设置结构化流。我们已经有了一些非流媒体代码来处理完全相同的数据，因此流式传输的最小努力就是重新使用该代码。
要转移到StructuredStreaming，我尝试了以下方法，它以非流方式工作（使用read代替readStream）但在流方法中给出了序列化错误。
import com.databricks.spark.avro._
import org.apache.avro._
import org.apache.spark.sql.types._
import com.databricks.spark.avro._
val schemaStr = """ {our_schema_here} """
val parser = new Schema.Parser()
val avroSchema = parser.parse(schemaStr)
val structType = SchemaConverters.toSqlType(avroSchema).dataType match {
case t: StructType => Some(t)
case _ => throw new RuntimeException(
s"""Avro schema cannot be converted to a Spark SQL StructType:
|
|${avroSchema.toString(true)}
|""".stripMargin)
}
val path = "dbfs://path/to/avro/files/*"
val avroStream = sqlContext
.readStream
.schema(structType.get)
.format("com.databricks.spark.avro")
.option("maxFilesPerTrigger", 5)
.load(path)
.writeStream
.outputMode("append")
.format("memory")
.queryName("counts")
.start()
我得到的例外情况如下所示。注意，我无法获得完整的堆栈跟踪，因为我在Databricks上并访问执行程序日志。我有点不知道究竟什么是无法序列化的对象。
org.apache.spark.SparkException: Task not serializable
at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:298)
at org.apache.spark.util.ClosureCleaner$.org$apache$spark$util$ClosureCleaner$$clean(ClosureCleaner.scala:288)
at org.apache.spark.util.ClosureCleaner$.clean(ClosureCleaner.scala:108)
at org.apache.spark.SparkContext.clean(SparkContext.scala:2326)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2099)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2125)
at org.apache.spark.rdd.RDD$$anonfun$collect$1.apply(RDD.scala:937)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
at org.apache.spark.rdd.RDD.withScope(RDD.scala:363)
at org.apache.spark.rdd.RDD.collect(RDD.scala:936)
at org.apache.spark.sql.execution.SparkPlan.executeCollect(SparkPlan.scala:299)
at org.apache.spark.sql.execution.SparkPlan.executeCollect(SparkPlan.scala:291)
at org.apache.spark.sql.Dataset.org$apache$spark$sql$Dataset$$collectFromPlan(Dataset.scala:2966)
at org.apache.spark.sql.Dataset$$anonfun$collect$1.apply(Dataset.scala:2456)
at org.apache.spark.sql.Dataset$$anonfun$collect$1.apply(Dataset.scala:2456)
at org.apache.spark.sql.Dataset$$anonfun$57.apply(Dataset.scala:2950)
at org.apache.spark.sql.execution.SQLExecution$.withCustomExecutionEnv(SQLExecution.scala:80)
at org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:99)
at org.apache.spark.sql.Dataset.withAction(Dataset.scala:2949)
at org.apache.spark.sql.Dataset.collect(Dataset.scala:2456)
at org.apache.spark.sql.execution.streaming.MemorySink.addBatch(memory.scala:217)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatch$1$$anonfun$apply$mcV$sp$1.apply$mcV$sp(StreamExecution.scala:731)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatch$1$$anonfun$apply$mcV$sp$1.apply(StreamExecution.scala:731)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatch$1$$anonfun$apply$mcV$sp$1.apply(StreamExecution.scala:731)
at org.apache.spark.sql.execution.SQLExecution$.withCustomExecutionEnv(SQLExecution.scala:80)
at org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:99)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatch$1.apply$mcV$sp(StreamExecution.scala:730)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatch$1.apply(StreamExecution.scala:730)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatch$1.apply(StreamExecution.scala:730)
at org.apache.spark.sql.execution.streaming.ProgressReporter$class.reportTimeTaken(ProgressReporter.scala:271)
at org.apache.spark.sql.execution.streaming.StreamExecution.reportTimeTaken(StreamExecution.scala:62)
at org.apache.spark.sql.execution.streaming.StreamExecution.org$apache$spark$sql$execution$streaming$StreamExecution$$runBatch(StreamExecution.scala:729)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatches$1$$anonfun$apply$mcZ$sp$1.apply$mcV$sp(StreamExecution.scala:328)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatches$1$$anonfun$apply$mcZ$sp$1.apply(StreamExecution.scala:316)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatches$1$$anonfun$apply$mcZ$sp$1.apply(StreamExecution.scala:316)
at org.apache.spark.sql.execution.streaming.ProgressReporter$class.reportTimeTaken(ProgressReporter.scala:271)
at org.apache.spark.sql.execution.streaming.StreamExecution.reportTimeTaken(StreamExecution.scala:62)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatches$1.apply$mcZ$sp(StreamExecution.scala:316)
at org.apache.spark.sql.execution.streaming.ProcessingTimeExecutor.execute(TriggerExecutor.scala:56)
at org.apache.spark.sql.execution.streaming.StreamExecution.org$apache$spark$sql$execution$streaming$StreamExecution$$runBatches(StreamExecution.scala:312)
at org.apache.spark.sql.execution.streaming.StreamExecution$$anon$1.run(StreamExecution.scala:226)
Caused by: java.io.NotSerializableException: scala.collection.immutable.MapLike$$anon$1
Serialization stack:
at org.apache.spark.serializer.SerializationDebugger$.improveException(SerializationDebugger.scala:40)
at org.apache.spark.serializer.JavaSerializationStream.writeObject(JavaSerializer.scala:46)
at org.apache.spark.serializer.JavaSerializerInstance.serialize(JavaSerializer.scala:100)
at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:295)
... 41 more