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https://issues.apache.org/jira/browse/HDDS-1080?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Elek, Marton updated HDDS-1080:
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Attachment: HDDS-1080.001.patch
> Ozonefs Isolated class loader should support FsStorageStatistics
> ----------------------------------------------------------------
>
> Key: HDDS-1080
> URL: https://issues.apache.org/jira/browse/HDDS-1080
> Project: Hadoop Distributed Data Store
> Issue Type: Improvement
> Components: Ozone Filesystem
> Reporter: Elek, Marton
> Assignee: Elek, Marton
> Priority: Major
> Attachments: HDDS-1080.001.patch
>
>
> HDDS-1033 introduced the storage statistics for ozonefs. Unfortunately the
> isolated classloader (HDDS-922) doesn't work any more after this change.
> To explain the problem, let's use the specific expression
> _classname[classloader]_ for a class (named by classname) which is loaded by
> the classloader.
> We have two classloaders the _main_ which is the standard classloader of the
> application and the _isolated_ classloader which is created by the
> OzoneClientAdapterFactory.java.
> By default java classloaders delegate the loading to the parent class loader,
> and they load all the classes from the parent first (if possible). The
> isolated class loader does the oposit, loads all the classes from a specific
> location of the jar files. With this approach we can use hadoop3.2+ozone
> classes together with older hadoop versions.
> But back to the problem:
> OzoneFilesystem[main] is loaded by the application. In this class an
> OzoneFSStorageStatistics[main] is created and with the help of
> OzoneClientAdapterFactory[main] a new OzoneClientAdapterImpl[isolated!!] is
> instantiated which implements the OzoneClientAdapter[main] and will do all
> the main work[isolated].
> OzoneClientAdapterImp[isolated] has a new constructor which requires
> (String[system], String[system], OzoneFSStorageStatistics[isolated]).
> And this is the problem, it requires OzoneFSStorageStatistics[isolated] but
> we have a OzoneFSStorageStatistics[main].
> The fix is very straightforward. In the FilteredClassLoader.java we ha a list
> for the classes which should be shared by the two classloaders. For these
> classes the isolated classloader will delegate the loading to the parent
> ([main]) classloader and we will have one (and only one)
> OzoneFSStorageStatistics[main] everywhere.
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