org.apache.spark.sql.sources.v2.writer

Interface DataSourceWriter

All Known Subinterfaces:

StreamWriter

@InterfaceStability.Evolving
public interface DataSourceWriter

A data source writer that is returned by WriteSupport.createWriter(String, StructType, SaveMode, DataSourceOptions)/ StreamWriteSupport.createStreamWriter( String, StructType, OutputMode, DataSourceOptions). It can mix in various writing optimization interfaces to speed up the data saving. The actual writing logic is delegated to DataWriter. If an exception was throw when applying any of these writing optimizations, the action will fail and no Spark job will be submitted. The writing procedure is: 1. Create a writer factory by createWriterFactory(), serialize and send it to all the partitions of the input data(RDD). 2. For each partition, create the data writer, and write the data of the partition with this writer. If all the data are written successfully, call DataWriter.commit(). If exception happens during the writing, call DataWriter.abort(). 3. If all writers are successfully committed, call commit(WriterCommitMessage[]). If some writers are aborted, or the job failed with an unknown reason, call abort(WriterCommitMessage[]). While Spark will retry failed writing tasks, Spark won't retry failed writing jobs. Users should do it manually in their Spark applications if they want to retry. Please refer to the documentation of commit/abort methods for detailed specifications.

Method Summary

Modifier and Type	Method and Description
void	abort(WriterCommitMessage[] messages) Aborts this writing job because some data writers are failed and keep failing when retry, or the Spark job fails with some unknown reasons, or onDataWriterCommit(WriterCommitMessage) fails, or commit(WriterCommitMessage[]) fails.
void	commit(WriterCommitMessage[] messages) Commits this writing job with a list of commit messages.
DataWriterFactory<org.apache.spark.sql.catalyst.InternalRow>	createWriterFactory() Creates a writer factory which will be serialized and sent to executors.
default void	onDataWriterCommit(WriterCommitMessage message) Handles a commit message on receiving from a successful data writer.
default boolean	useCommitCoordinator() Returns whether Spark should use the commit coordinator to ensure that at most one task for each partition commits.

Method Detail

createWriterFactory

DataWriterFactory<org.apache.spark.sql.catalyst.InternalRow> createWriterFactory()

Creates a writer factory which will be serialized and sent to executors. If this method fails (by throwing an exception), the action will fail and no Spark job will be submitted.

useCommitCoordinator

default boolean useCommitCoordinator()

Returns whether Spark should use the commit coordinator to ensure that at most one task for each partition commits.

Returns:

true if commit coordinator should be used, false otherwise.

onDataWriterCommit

default void onDataWriterCommit(WriterCommitMessage message)

Handles a commit message on receiving from a successful data writer. If this method fails (by throwing an exception), this writing job is considered to to have been failed, and abort(WriterCommitMessage[]) would be called.

commit

void commit(WriterCommitMessage[] messages)

Commits this writing job with a list of commit messages. The commit messages are collected from successful data writers and are produced by DataWriter.commit(). If this method fails (by throwing an exception), this writing job is considered to to have been failed, and abort(WriterCommitMessage[]) would be called. The state of the destination is undefined and @abort(WriterCommitMessage[]) may not be able to deal with it. Note that speculative execution may cause multiple tasks to run for a partition. By default, Spark uses the commit coordinator to allow at most one task to commit. Implementations can disable this behavior by overriding useCommitCoordinator(). If disabled, multiple tasks may have committed successfully and one successful commit message per task will be passed to this commit method. The remaining commit messages are ignored by Spark.

abort

void abort(WriterCommitMessage[] messages)

Aborts this writing job because some data writers are failed and keep failing when retry, or the Spark job fails with some unknown reasons, or onDataWriterCommit(WriterCommitMessage) fails, or commit(WriterCommitMessage[]) fails. If this method fails (by throwing an exception), the underlying data source may require manual cleanup. Unless the abort is triggered by the failure of commit, the given messages should have some null slots as there maybe only a few data writers that are committed before the abort happens, or some data writers were committed but their commit messages haven't reached the driver when the abort is triggered. So this is just a "best effort" for data sources to clean up the data left by data writers.