...
This Stream will implement pagination when fetching data from the FragmentRepository. (This may be implemented in a variety of ways, using Spring JpaRepository Pageable interface, or alternately Spring Data supports streaming from a repository directly, but this needs to be investigated for suitability.)
Here is a proposed end-to-end flow - a simplified example to show how greatly this can reduce memory usage:
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// In CPS core
Stream<DataNode> queryDataNodesAsStream(String dataspaceName, String anchorName, String cpsPath, FetchDescendantsOption fetchDescendantsOption) {
final var anchor = getAnchor(dataspaceName, anchorName);
return fragmentRepository.streamByAnchorAndCpsPath(anchor, cpsPath)
.map(fragment -> fetchDescendants(fragment, fetchDescendantsOption))
.map(fragment -> toDataNode(fragment));
}
// In NCMP
private YangModelCmHandle getAnyReadyCmHandleByModuleSetTag(final String moduleSetTag) {
return cmHandleQueries.queryNcmpRegistryByCpsPath("/dmi-registry/cm-handles[@module-set-tag='" + moduleSetTag + "']", DIRECT_CHILDREN_ONLY)
.map(YangDataConverter::convertCmHandleToYangModel)
.filter(cmHandle -> cmHandle.getCompositeState().getCmHandleState() == CmHandleState.READY)
.findFirst()
.orElse(null);
}
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CPS and NCMP Rest APIs
Instead of returning Collections from Rest APIs, a Stream may be returned, greatly reducing memory pressure on the server.