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From Gourav Sengupta <gourav.sengu...@gmail.com>
Subject Re: CSV write to S3 failing silently with partial completion
Date Mon, 11 Sep 2017 13:31:05 GMT
Hi,

Can you please let me know the following:
1. Why are you using JAVA?
2. The way you are creating the SPARK cluster
3. The way you are initiating SPARK session or context
4. Are you able to query the data that is written to S3 using a SPARK
dataframe and validate that the number of rows in the source are same as
the ones written to target?
5. how are you loading the data to Redshift (cluster size, version,
command, compression, command, manifest file)
6. using Redshift JDBC (https://github.com/databricks/spark-redshift) you
will have to play around with it a bit to understand how it works (be
careful that it does not drop the table at target Redshift database)

Regards,
Gourav

On Thu, Sep 7, 2017 at 7:02 AM, abbim <abbim@amazon.com> wrote:

> Hi all,
> My team has been experiencing a recurring unpredictable bug where only a
> partial write to CSV in S3 on one partition of our Dataset is performed.
> For
> example, in a Dataset of 10 partitions written to CSV in S3, we might see 9
> of the partitions as 2.8 GB in size, but one of them as 1.6 GB. However,
> the
> job does not exit with an error code.
>
> This becomes problematic in the following ways:
> 1. When we copy the data to Redshift, we get a bad decrypt error on the
> partial file, suggesting that the failure occurred at a weird byte in the
> file.
> 2. We lose data - sometimes as much as 10%.
>
> We don't see this problem with parquet format, which we also use, but
> moving
> all of our data to parquet is not currently feasible. We're using the Java
> API with Spark 2.2 and Amazon EMR 5.8, code is a simple as this:
> df.write().csv("s3://some-bucket/some_location"). We're experiencing the
> issue 1-3x/week on a daily job and are unable to reliably reproduce the
> problem.
>
> Any thoughts on why we might be seeing this and how to resolve?
> Thanks in advance.
>
>
>
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