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Andrew Kerr updated TOREE-349: ------------------------------ Attachment: avro-csv-threading.scala.ipynb Updated > ClassCastException when reading Avro from another thread (Toree master / > Spark 2.0.0) > ------------------------------------------------------------------------------------- > > Key: TOREE-349 > URL: https://issues.apache.org/jira/browse/TOREE-349 > Project: TOREE > Issue Type: Bug > Reporter: Andrew Kerr > Attachments: avro-csv-threading.scala.ipynb, > avro-csv-threading.scala.ipynb, run.sh > > > When using Toree (master branch commit > e8ecd0623c65ad104045b1797fb27f69b8dfc23f) > with `--packages=com.databricks:spark-avro_2.11:3.0.1` in `SPARK_OPTS` > and attempting to load an avro file into a dataframe *in a separate thread* > then an exception is thrown > `java.lang.ClassCastException: > com.databricks.spark.avro.DefaultSource$SerializableConfiguration cannot be > cast to com.databricks.spark.avro.DefaultSource$SerializableConfiguration` > here > https://github.com/databricks/spark-avro/blob/v3.0.1/src/main/scala/com/databricks/spark/avro/DefaultSource.scala#L156 > Will attach a Jupyter notebook that illustrates the problem and includes full > stack trace, with a script showing environment. > The class that throws the exception `DefaultSource` broadcasts Hadoop config > and returns an anonymous function that accesses that config. The exception > occurs when that function is executed and it attempts to access the config. > This looks like a class loader mismatch problem to me ("Class Identity > Crisis"). > With a bit of hacking of `spark-avro` I've seen the class loader for > `DefaultSource` when the config is broadcast to be > `scala.reflect.internal.util.ScalaClassLoader$URLClassLoader@31ac5411` > and when the config is read to be > `org.apache.spark.util.MutableURLClassLoader@3d3fcdb0` > If a fat jar including `spark-avro` is built and included with `--jars=...` > then the same problem occurs. > Interestingly the Spark's included support for CSV uses the same pattern as > Avro, broadcasting a config, but works as expected as shown in the notebook. > https://github.com/apache/spark/blob/v2.0.0/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/csv/CSVFileFormat.scala#L108 > Avro also works as expected when an application fat jar is built and passed > to > `spark-submit` without involving Toree. -- This message was sent by Atlassian JIRA (v6.3.4#6332)