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From Jan Holmberg <jan.holmb...@perigeum.fi>
Subject Re: Kafka - Kudu streaming > unpredictable write times
Date Tue, 28 Mar 2017 17:38:24 GMT
Thanks for swift response! My measurements are very informal :-)  ie. I'm looking at Spark's
'Streaming' log page that informs "processing time" directly. That value is systematically
4 sec or 0,5 sec between different program runs for all batches.

Prog is pretty simple so I do not expect that prog itself is causing the delay. I'm suspecting
two causes:

1) Kudu connection. I have not found a recent streaming example so I might have some misunderstanding
in my code. At the moment, I'm creating new KuduContext for each batch (val kuduContext =
new KuduContext("m1:7051")). Pointer to good streaming example would definitively help.

2) Kafka connection. We've seen earlier that Spark executor locations have impact on performance.


On 28 Mar 2017, at 19.16, Todd Lipcon <todd@cloudera.com<mailto:todd@cloudera.com>>

On Tue, Mar 28, 2017 at 8:24 AM, Jan Holmberg <jan.holmberg@perigeum.fi<mailto:jan.holmberg@perigeum.fi>>
I'm wondering the reason, why simple Spark prog. reading streaming data from Kafka and writing
result to Kudu, has unpredictable write times. In most cases, when running the prog, write
times are systematically 4 sec regardless of the number of messages (anything from 50 to 2000
messages per batch). But occasionally when starting the prog, it runs substantially faster
where write times are below 0,5 sec with exactly same code base, settings etc.

How are you measuring "write times" here? Are you sure the time is being spent in the Kudu
code and not in other parts of the streaming app?

Writing 2000 rows to Kudu should be on the order of a few milliseconds -- even 0.5 seconds
sounds extremely high.

Are you by chance instantiating a new KuduClient each time you write a batch, rather than
reusing an existing one?

Our environment is plain AWS cluster with 3 slaves where each slave has Kafka and Kudu tablet
server instance with CDH 5.10 & Kudu 1.2  & Spark 1.6.

Any hints what to look at?


Todd Lipcon
Software Engineer, Cloudera

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