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https://issues.apache.org/jira/browse/PIO-102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16105493#comment-16105493
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ASF GitHub Bot commented on PIO-102:
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Github user dszeto commented on the issue:
https://github.com/apache/incubator-predictionio/pull/406
LGTM
> ESEngineInstances `getAll` results out of order (Elasticsearch 5.x)
> -------------------------------------------------------------------
>
> Key: PIO-102
> URL: https://issues.apache.org/jira/browse/PIO-102
> Project: PredictionIO
> Issue Type: Bug
> Components: Core
> Affects Versions: 0.11.0-incubating
> Reporter: Mars Hall
> Assignee: Mars Hall
>
> Using the new Elasticsearch 5.x REST storage client as the meta storage
> source (`PIO_STORAGE_REPOSITORIES_METADATA_SOURCE=ELASTICSEARCH` setup in
> conf/pio-env.sh), I found that once an engine has been trained a certain
> number of times, that the most recent engine instance is no longer retrieved.
> So, I tracked down where those Elasticsearch queries originate.
> In the original Elasticsearch 1.x storage client, [the "scroll" pagination
> responses are collected by
> *appending*|https://github.com/apache/incubator-predictionio/blob/release/0.11.0/storage/elasticsearch1/src/main/scala/org/apache/predictionio/data/storage/elasticsearch/ESUtils.scala#L44]
> them to one another.
> In the new Elasticsearch 5.x client, [the "scroll" responses are collected by
> *prepending*|https://github.com/apache/incubator-predictionio/blob/release/0.11.0/storage/elasticsearch/src/main/scala/org/apache/predictionio/data/storage/elasticsearch/ESUtils.scala#L152]
> them to one another.
> This out-of-order concatenation breaks [ESEngineInstances
> `getLatestCompleted`|https://github.com/apache/incubator-predictionio/blob/release/0.11.0/storage/elasticsearch/src/main/scala/org/apache/predictionio/data/storage/elasticsearch/ESEngineInstances.scala#L192]
> by erroneously replacing the head of the results with an older engine
> instance, when there are enough engine instances to overflow a single page of
> Elasticsearch hits.
> I've observed this buggy behavior after ten trainings, when enough engine
> instances are stored to trigger Elasticsearch's scroll feature.
> Pull request: https://github.com/apache/incubator-predictionio/pull/406
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