[jira] [Resolved] (IMPALA-11580) Memory leak in legacy catalog mode when applying incremental partition updates

["Quanlong Huang (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-11580?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Quanlong Huang resolved IMPALA-11580.
-------------------------------------
    Fix Version/s: Impala 4.2.0
       Resolution: Fixed

> Memory leak in legacy catalog mode when applying incremental partition updates
> ------------------------------------------------------------------------------
>
>                 Key: IMPALA-11580
>                 URL: https://issues.apache.org/jira/browse/IMPALA-11580
>             Project: IMPALA
>          Issue Type: Bug
>          Components: Catalog
>    Affects Versions: Impala 4.0.0, Impala 4.1.0
>            Reporter: Quanlong Huang
>            Assignee: Quanlong Huang
>            Priority: Critical
>             Fix For: Impala 4.2.0
>
>
> Since IMPALA-3127, catalogd propagates incremental metadata updates in partition level. In the legacy catalog mode, while applying the updates, impalad reuses the existing partition objects and move them to a new HdfsTable object. However, the partition objects are immutable, which means their reference to the old table object remain unchanged. JVM cannot collect the stale table objects since they still have active reference from the partitions.
> To reproduce the issue, create a partitioned table and add new partitions to it in a rate closer to the catalog update frequency (2s by default):
> {code:sql}
> impala-shell> drop table if exists my_part_tbl;
> impala-shell> create external table my_part_tbl (id int) partitioned by (p int) stored as textfile;
> {code}
> Add a partition every 2s:
> {code:bash}
> for i in `seq 1000`; do impala-shell.sh -q "alter table my_part_tbl add partition (p=$i)"; sleep 2; done
> {code}
> Then monitor the live table objects in impalad JVM:
> {code:bash}
> for p in `pidof impalad`; do echo PID=$p; jmap -histo:live $p | grep 'org.apache.impala.catalog.HdfsTable$'; done
> {code}
> You can see that only one impalad has the value unchanged. The number in the other 2 impalads keep bumping.
> {noformat}
> $ for p in `pidof impalad`; do echo PID=$p; jmap -histo:live $p | grep 'org.apache.impala.catalog.HdfsTable$'; done
> PID=27677
>  136:            14           3360  org.apache.impala.catalog.HdfsTable
> PID=27671
>  136:            14           3360  org.apache.impala.catalog.HdfsTable
> PID=27668
>  474:             1            240  org.apache.impala.catalog.HdfsTable
> $ for p in `pidof impalad`; do echo PID=$p; jmap -histo:live $p | grep 'org.apache.impala.catalog.HdfsTable$'; done
> PID=27677
>  113:            21           5040  org.apache.impala.catalog.HdfsTable
> PID=27671
>  113:            21           5040  org.apache.impala.catalog.HdfsTable
> PID=27668
>  474:             1            240  org.apache.impala.catalog.HdfsTable
> {noformat}
> This only happens in the legacy catalog mode and doesn't occur in the local-catalog mode. To workaround this, use the startup flag {{--enable_incremental_metadata_updates=false}} in catalogd to disable incremental catalog updates.



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