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https://issues.apache.org/jira/browse/SAMZA-203?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13944646#comment-13944646
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Chris Riccomini commented on SAMZA-203:
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Commenting out the Thread.sleep line, my MacBook Air SSD can restore 1 million
200 byte rows in 7 seconds.
If we leave Thread.sleep as it was before, the restoration takes many minutes
(I usually ctrl-c it).
> Bad performance in BrokerProxy when restoring changelogs
> --------------------------------------------------------
>
> Key: SAMZA-203
> URL: https://issues.apache.org/jira/browse/SAMZA-203
> Project: Samza
> Issue Type: Bug
> Components: kv
> Affects Versions: 0.6.0
> Reporter: Chris Riccomini
> Fix For: 0.7.0
>
>
> As part of SAMZA-126, we introduced a Thread.sleep call in BrokerProxy's
> fetchMessages method. The goal was to skip fetch requests on SimpleConsumer
> when the topicAndPartitionsToFetch variable was empty. Since we had no
> topic/partitions to fetch, we slowed the thread down by calling
> Thread.sleep(sleepMSWhileNoTopicPartitions), which defaults to 1000ms.
> We now see that we are only getting about 1mb/s when restoring changelogs.
> This is very slow. Upon investigation, it appears that the BrokerProxy thread
> is sleeping 90% of the time during restore, and the main SamzaContainer
> thread is polling for more messages about 60% of the time.
> The reason for the poor restore performance is that the BrokerProxy sleeps
> for 1 second every time the message queue for the restore topic is not empty.
> Effectively, the proxy starts throttling the reads. If I comment out the
> Thread.sleep line in the BrokerProxy, I get about 64mb/s network usage on my
> loopback (one broker running locally), 10mb/s disk read, and 70mb/s disk
> write on my MacBook Air SSD--the write appears to be the bottleneck (since
> we're writing all the values to the LevelDB store). This is much much faster
> than before.
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