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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (ACCUMULO-665) large values, complex iterator stacks, and RFile readers can consume a surprising amount of memory
Date Mon, 02 Jul 2012 13:21:22 GMT

     [ https://issues.apache.org/jira/browse/ACCUMULO-665?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Josh Elser updated ACCUMULO-665:
--------------------------------

    Description: 
On a production cluster, with a complex iterator tree, a large value (~350M) was causing a
4G tserver to fail with out-of-memory.

There were several factors contributing to the problem:
# a bug: the query should not have been looking to the big data
# complex iterator tree, causing many copies of the data to be held at the same time
# RFile doubles the buffer it uses to load values, and continues to use that large buffer
for future values

This ticket is for the last point.  If we know we're not even going to look at the value,
we can read past it without storing it in memory.  It is surprising that skipping past a large
value would cause the server to run out of memory, especially since it should fit into memory
enough times to be returned to the caller.

The provided iterators inside core/org/apache/accumulo/iterators should be revisited to ensure
that they properly set the seekColumnFamilies where necessary, specifically the IntersectingIterator.

  was:
On a production cluster, with a complex iterator tree, a large value (~350M) was causing a
4G tserver to fail with out-of-memory.

There were several factors contributing to the problem:
# a bug: the query should not have been looking to the big data
# complex iterator tree, causing many copies of the data to be held at the same time
# RFile doubles the buffer it uses to load values, and continues to use that large buffer
for future values

This ticket is for the last point.  If we know we're not even going to look at the value,
we can read past it without storing it in memory.  It is surprising that skipping past a large
value would cause the server to run out of memory, especially since it should fit into memory
enough times to be returned to the caller.


    
> large values, complex iterator stacks, and RFile readers can consume a surprising amount
of memory
> --------------------------------------------------------------------------------------------------
>
>                 Key: ACCUMULO-665
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-665
>             Project: Accumulo
>          Issue Type: Bug
>          Components: tserver
>    Affects Versions: 1.5.0, 1.4.0
>         Environment: large cluster
>            Reporter: Eric Newton
>            Assignee: Eric Newton
>            Priority: Minor
>
> On a production cluster, with a complex iterator tree, a large value (~350M) was causing
a 4G tserver to fail with out-of-memory.
> There were several factors contributing to the problem:
> # a bug: the query should not have been looking to the big data
> # complex iterator tree, causing many copies of the data to be held at the same time
> # RFile doubles the buffer it uses to load values, and continues to use that large buffer
for future values
> This ticket is for the last point.  If we know we're not even going to look at the value,
we can read past it without storing it in memory.  It is surprising that skipping past a large
value would cause the server to run out of memory, especially since it should fit into memory
enough times to be returned to the caller.
> The provided iterators inside core/org/apache/accumulo/iterators should be revisited
to ensure that they properly set the seekColumnFamilies where necessary, specifically the
IntersectingIterator.

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