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https://issues.apache.org/jira/browse/PIO-106?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mars Hall resolved PIO-106.
---------------------------
Resolution: Fixed
> Elasticsearch 5.x StorageClient should reuse RestClient
> -------------------------------------------------------
>
> Key: PIO-106
> URL: https://issues.apache.org/jira/browse/PIO-106
> Project: PredictionIO
> Issue Type: Improvement
> Components: Core
> Affects Versions: 0.11.0-incubating
> Reporter: Mars Hall
> Assignee: Mars Hall
>
> When using the proposed [PIO-105 Batch
> Predictions|https://issues.apache.org/jira/browse/PIO-105] feature with an
> engine that queries Elasticsearch in {{Algorithm#predict}}, Elasticsearch's
> REST interface appears to become overloaded, ending with the Spark job being
> killed from errors like:
> {noformat}
> [ERROR] [ESChannels] Failed to access to /pio_meta/channels/_search
> [ERROR] [Utils] Aborting task
> [ERROR] [ESApps] Failed to access to /pio_meta/apps/_search
> [ERROR] [Executor] Exception in task 747.0 in stage 1.0 (TID 749)
> [ERROR] [Executor] Exception in task 735.0 in stage 1.0 (TID 737)
> [ERROR] [Common$] Invalid app name ur
> [ERROR] [Utils] Aborting task
> [ERROR] [URAlgorithm] Error when read recent events:
> java.lang.IllegalArgumentException: Invalid app name ur
> [ERROR] [Executor] Exception in task 749.0 in stage 1.0 (TID 751)
> [ERROR] [Utils] Aborting task
> [ERROR] [Executor] Exception in task 748.0 in stage 1.0 (TID 750)
> [WARN] [TaskSetManager] Lost task 749.0 in stage 1.0 (TID 751, localhost,
> executor driver): java.net.BindException: Can't assign requested address
> at sun.nio.ch.Net.connect0(Native Method)
> at sun.nio.ch.Net.connect(Net.java:454)
> at sun.nio.ch.Net.connect(Net.java:446)
> at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:648)
> at
> org.apache.http.impl.nio.reactor.DefaultConnectingIOReactor.processSessionRequests(DefaultConnectingIOReactor.java:273)
> at
> org.apache.http.impl.nio.reactor.DefaultConnectingIOReactor.processEvents(DefaultConnectingIOReactor.java:139)
> at
> org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor.execute(AbstractMultiworkerIOReactor.java:348)
> at
> org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager.execute(PoolingNHttpClientConnectionManager.java:192)
> at
> org.apache.http.impl.nio.client.CloseableHttpAsyncClientBase$1.run(CloseableHttpAsyncClientBase.java:64)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> After these errors happen & the job is killed, Elasticsearch immediately
> recovers. It responds to queries normally. I researched what could cause this
> and found an [old issue in the main Elasticsearch
> repo|https://github.com/elastic/elasticsearch/issues/3647]. With the hints
> given therein about *using keep-alive in the ES client* to avoid these
> performance issues, I investigated how PredictionIO's [Elasticsearch
> StorageClient|https://github.com/apache/incubator-predictionio/tree/develop/storage/elasticsearch/src/main/scala/org/apache/predictionio/data/storage/elasticsearch]
> manages its connections.
> I found that unlike the other StorageClients (Elasticsearch1, HBase, JDBC),
> Elasticsearch creates a new underlying connection, an Elasticsearch
> RestClient, for
> [every|https://github.com/apache/incubator-predictionio/blob/develop/storage/elasticsearch/src/main/scala/org/apache/predictionio/data/storage/elasticsearch/ESApps.scala#L80]
>
> [single|https://github.com/apache/incubator-predictionio/blob/develop/storage/elasticsearch/src/main/scala/org/apache/predictionio/data/storage/elasticsearch/ESApps.scala#L157]
>
> [query|https://github.com/apache/incubator-predictionio/blob/develop/storage/elasticsearch/src/main/scala/org/apache/predictionio/data/storage/elasticsearch/ESChannels.scala#L78]
> &
> [interaction|https://github.com/apache/incubator-predictionio/blob/develop/storage/elasticsearch/src/main/scala/org/apache/predictionio/data/storage/elasticsearch/ESEngineInstances.scala#L205]
> with its API. As a result, *there is no way Elasticsearch TCP connections
> can be reused via HTTP keep-alive*.
> High-performance workloads with Elasticsearch 5.x will suffer from these
> issues unless we refactor Elasticsearch StorageClient to share the underlying
> RestClient instead of [building a new one everytime the client is
> used|https://github.com/apache/incubator-predictionio/blob/develop/storage/elasticsearch/src/main/scala/org/apache/predictionio/data/storage/elasticsearch/StorageClient.scala#L31].
> There are certainly different approaches we could take to sharing a
> RestClient so that its keep-alive behavior may work as designed:
> * maintain a singleton RestClient that is reused throughout the ES storage
> classes
> * create a RestClient on-demand and pass it as an argument to ES storage
> methods
> * other ideas?
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