Hi everyone,

I am considering using Flink in a project. The setting would be a YARN cluster 
where data is first read in from HDFS, then processed and finally written into 
an Oracle database using an upsert command. If I understand the documentation 
correctly, the DataSet API would be the natural candidate for this problem.

My first question is about the checkpointing system. Apparently (e.g. [1] and 
[2]) it does not apply to batch processing. So how does Flink handle failures 
during batch processing? For the use case described above, 'at least once' 
semantics would suffice – still, are 'exactly once' guarantees possible?
For example, how does Flink handle a failure of one taskmanager during a batch 
process? What happens in this case, if the data has already partly been written 
to the database?

Secondly, the most obvious, straight-forward approach of connecting to the 
Oracle DB would be the JDBC Output Format. In [3], it was mentioned that it 
does not have many users and might not be trusted. What is the status on this?

Best regards,
Max

[1] 
http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Flink-and-Spark-tp583p587.html
[2] 
http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Batch-Processing-as-Streaming-td1909.html
[3] 
http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/PotsgreSQL-JDBC-Sink-quot-writeRecord-failed-quot-and-quot-Batch-element-cancelled-quot-on-upsert-td623.html

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