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https://issues.apache.org/jira/browse/YARN-4095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15959029#comment-15959029
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Feng Yuan commented on YARN-4095:
---------------------------------
[~zxu],thanks your patch for this issue.
Excuse me, i am not very clear the goal this patch achieve.Such as avoid the
heap memory leak like YARN-6277,
because in:
{code}
String newLocalDirs = conf.get(contextCfgItemName);
if (!newLocalDirs.equals(savedLocalDirs)) {
{code}
it create massive LocalFileSystem objects and cache them.
If your purpose is fix this heap memory leak. I guess i will understand this
issue completetly.
And i have a idea, now that the issue is caused by the configuration is
different in two place.
And i notice that ShuffleHandler use a another conf object by clone(conf)
method,how about let "SH" use the same conf?
This leads to several benefits:
1. ShuffleHandler service will timely know which disk is over-used(>95%),and
will not write data to it,avoid some map output
work to a overload disk and break by error "no space left...".
2. if we could think over the implementation model in your patch, IMHO i feel
it is not very grace just add a new name of local-dir.
Thx.
> Avoid sharing AllocatorPerContext object in LocalDirAllocator between
> ShuffleHandler and LocalDirsHandlerService.
> -----------------------------------------------------------------------------------------------------------------
>
> Key: YARN-4095
> URL: https://issues.apache.org/jira/browse/YARN-4095
> Project: Hadoop YARN
> Issue Type: Improvement
> Components: nodemanager
> Reporter: zhihai xu
> Assignee: zhihai xu
> Fix For: 2.8.0, 3.0.0-alpha1
>
> Attachments: YARN-4095.000.patch, YARN-4095.001.patch
>
>
> Currently {{ShuffleHandler}} and {{LocalDirsHandlerService}} share
> {{AllocatorPerContext}} object in {{LocalDirAllocator}} for configuration
> {{NM_LOCAL_DIRS}} because {{AllocatorPerContext}} are stored in a static
> TreeMap with configuration name as key
> {code}
> private static Map <String, AllocatorPerContext> contexts =
> new TreeMap<String, AllocatorPerContext>();
> {code}
> {{LocalDirsHandlerService}} and {{ShuffleHandler}} both create a
> {{LocalDirAllocator}} using {{NM_LOCAL_DIRS}}. Even they don't use the same
> {{Configuration}} object, but they will use the same {{AllocatorPerContext}}
> object. Also {{LocalDirsHandlerService}} may change {{NM_LOCAL_DIRS}} value
> in its {{Configuration}} object to exclude full and bad local dirs,
> {{ShuffleHandler}} always uses the original {{NM_LOCAL_DIRS}} value in its
> {{Configuration}} object. So every time {{AllocatorPerContext#confChanged}}
> is called by {{ShuffleHandler}} after {{LocalDirsHandlerService}},
> {{AllocatorPerContext}} need be reinitialized because {{NM_LOCAL_DIRS}} value
> is changed. This will cause some overhead.
> {code}
> String newLocalDirs = conf.get(contextCfgItemName);
> if (!newLocalDirs.equals(savedLocalDirs)) {
> {code}
> So it will be a good improvement to not share the same
> {{AllocatorPerContext}} instance between {{ShuffleHandler}} and
> {{LocalDirsHandlerService}}.
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