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https://issues.apache.org/jira/browse/DRILL-6762?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arina Ielchiieva updated DRILL-6762:
------------------------------------
    Reviewer: Volodymyr Vysotskyi

> Dynamic UDFs registered on one Drillbit are not visible on other Drillbits
> --------------------------------------------------------------------------
>
>                 Key: DRILL-6762
>                 URL: https://issues.apache.org/jira/browse/DRILL-6762
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Functions - Drill
>    Affects Versions: 1.13.0
>            Reporter: Kunal Khatua
>            Assignee: Arina Ielchiieva
>            Priority: Critical
>             Fix For: 1.15.0
>
>         Attachments: Dynamic UDFs issue.pdf
>
>
> Originally Reported : 
> https://stackoverflow.com/questions/52480160/dynamic-udf-in-apache-drill-cluster
> When using a 4-node Drill 1.14 cluster, UDF jars registered on one node are 
> not usable on other nodes despite the {{/registry}} and ZK showing the UDFs 
> as registered.
> This was previously working on 1.13.0
> *Root cause*
> 1. {{VersionedDelegatingStore}} was starting with version -1 and local 
> function registry with version 0. This caused issues when 
> {{LocalPersistentStore}} already existed on the file system. When adding jars 
> into remote registry its versioned was bumped to 0 and synchronization did 
> not happen since local registry had the same version.
> *Fix*: start {{VersionedDelegatingStore}} with version 0, local function 
> registry with undefined version (-2) thus first sync will always happen.
> 2. {{PersistentStoreProvider.getOrCreateVersionedStore}} was wrapping stores 
> into VersionedDelegatingStore for those store providers that did not override 
> this method. Only Zookeeper store was overriding it. But 
> {{VersionedDelegatingStore}} is only keeps versioning locally and thus can be 
> applied only for local stores, i.e. Hbase, Mongo cannot use it.
> {{CachingPersistentStoreProvider}} did not override 
> {{getOrCreateVersionedStore}} either. Mostly all stores in Drill are created 
> using {{CachingPersistentStoreProvider}}. Thus all stores where wrapped into 
> {{VersionedDelegatingStore}}, even Zookeeper one which caused function 
> registries version synchronization issues.
> *Fix*: Add {{UndefinedVersionDelegatingStore}} for those stores that do not 
> support versioning and wrap into it by default in 
> {{PersistentStoreProvider.getOrCreateVersionedStore}} if this method is not 
> overriden. {{UndefinedVersionDelegatingStore}}  will return UNDEFINED version 
> (-2). During sync between remote and local registries if remote registry has 
> UNDEFINED version sync will be done immediately, on the contrary with 
> NOT_AVAILABLE version (-1) which indicates that remote function registry is 
> not accessible.



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