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https://issues.apache.org/jira/browse/HDDS-6315?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Siddharth Wagle reassigned HDDS-6315:
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Assignee: Aswin Shakil Balasubramanian
> ListContainer API should use the sorted treeMaps more effectively
> -----------------------------------------------------------------
>
> Key: HDDS-6315
> URL: https://issues.apache.org/jira/browse/HDDS-6315
> Project: Apache Ozone
> Issue Type: Improvement
> Reporter: Stephen O'Donnell
> Assignee: Aswin Shakil Balasubramanian
> Priority: Major
>
> As also reported in HDDS-6314, SCMClientProtocolServer.listContainer, the
> code does not seem to use the fact that the "container lists by state" are
> already sorted and in TreeMaps, so they could perform the paging much more
> efficiently. I fear we are potentially forming some very large lists twice
> per call, only to return a small slice of the list each time.
> For example, the code looks like:
> {code:java}
> return scm.getContainerManager().getContainers(state).stream()
> .filter(info -> info.containerID().getId() >= startContainerID)
> .sorted().limit(count).collect(Collectors.toList()); {code}
> The `sorted()` call must filter and process the entire list before the limit
> can be applied, but as the list is stored in a treeMap, we should be able to
> avoid the sort.
> Better, a TreeMap allows you to obtain a sublist after a certain element
> using some combination of "floorKey" and "subMap", so we may be able to
> perform this paging much more efficiently.
> Note that the `ContainerManagerImpl.getContainers(...)` API used by this
> class is vulnerable to ConcurrentModificationException, and hence that needs
> resolved either before or as part of addressing this change.
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