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Re: [DISCUSS] Performance of write() in file based IO


Thanks Robert

> Have you profiled to see which stages and/or operations are taking up the time?

Not yet. I'm browsing through the spark DAG produced which I've committed [1] and reading the code.

[1] https://github.com/gbif/beam-perf/tree/master/avro-to-avro 

On Wed, Aug 22, 2018 at 12:12 PM Robert Bradshaw <robertwb@xxxxxxxxxx> wrote:
I agree that this is concerning. Some of the complexity may have also
been introduced to accommodate writing files in Streaming mode, but it
seems we should be able to execute this as a single Map operation.

Have you profiled to see which stages and/or operations are taking up the time?
On Wed, Aug 22, 2018 at 11:29 AM Tim Robertson
<timrobertson100@xxxxxxxxx> wrote:
>
> Hi folks,
>
> I've recently been involved in projects rewriting Avro files and have discovered a concerning performance trait in Beam.
>
> I have observed Beam between 6-20x slower than native Spark or MapReduce code for a simple pipeline of read Avro, modify, write Avro.
>
>  - Rewriting 200TB of Avro files (big cluster): 14 hrs using Beam/Spark, 40 minutes with a map-only MR job
>  - Rewriting 1.5TB Avro file (small cluster): 2 hrs using Beam/Spark, 18 minutes using vanilla Spark code. Test code available [1]
>
> These tests were running Beam 2.6.0 on Cloudera 5.12.x clusters (Spark / YARN) on reference Dell / Cloudera hardware.
>
> I have only just started exploring but I believe the cause is rooted in the WriteFiles which is used by all our file based IO. WriteFiles is reasonably complex with reshuffles, spilling to temporary files (presumably to accommodate varying bundle sizes/avoid small files), a union, a GBK etc.
>
> Before I go too far with exploration I'd appreciate thoughts on whether we believe this is a concern (I do), if we should explore optimisations or any insight from previous work in this area.
>
> Thanks,
> Tim
>
> [1] https://github.com/gbif/beam-perf/tree/master/avro-to-avro