Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/19623#discussion_r148553358
--- Diff:
sql/core/src/main/java/org/apache/spark/sql/sources/v2/writer/DataSourceV2Writer.java
---
@@ -50,28 +53,34 @@
/**
* Creates a writer factory which will be serialized and sent to
executors.
+ *
+ * If this method fails (by throwing an exception), the action would
fail and no Spark job was
+ * submitted.
*/
DataWriterFactory<Row> createWriterFactory();
/**
* Commits this writing job with a list of commit messages. The commit
messages are collected from
- * successful data writers and are produced by {@link
DataWriter#commit()}. If this method
- * fails(throw exception), this writing job is considered to be failed,
and
- * {@link #abort(WriterCommitMessage[])} will be called. The written
data should only be visible
- * to data source readers if this method succeeds.
+ * successful data writers and are produced by {@link
DataWriter#commit()}.
+ *
+ * If this method fails (by throwing an exception), this writing job is
considered to to have been
+ * failed, and {@link #abort(WriterCommitMessage[])} would be called.
The state of the destination
+ * is undefined and @{@link #abort(WriterCommitMessage[])} may not be
able to deal with it.
*
* Note that, one partition may have multiple committed data writers
because of speculative tasks.
* Spark will pick the first successful one and get its commit message.
Implementations should be
--- End diff --
The only way to guarantee no more than one task can commit is if the
underlying storage system guarantees that. There is no way to design something
generic. It is simply not possible in a distributed system, when network
partitioning or message lost.
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