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Keep the new map in the stack so that it is not leaked on exception. Move-construct to the heap when exchanging for the old map. Constructing the new RawPolicyMap on the stack first is both safe and efficient here. It keeps the whole update transactional: while parsing and populating the map, all temporary state remains thread-local and unpublished, so any exception simply unwinds without exposing a partially built policy map to readers. Only once the map is fully ready do we allocate the final heap object and move the finished absl::flat_hash_map into it for atomic publication. That move is efficient: for this flat_hash_map<std::string, std::shared_ptr<...>> type, Abseil’s move constructor transfers ownership of the existing backing table rather than copying or rebuilding the entries, so the extra cost at publication time is essentially just one heap allocation for the map object itself. Signed-off-by: Jarno Rajahalme <jarno@isovalent.com>
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Keep the new map in the stack so that it is not leaked on exception. Move-construct to the heap when exchanging for the old map.
Constructing the new
RawPolicyMapon the stack first is both safe and efficient here. It keeps the whole update transactional: while parsing and populating the map, all temporary state remains thread-local and unpublished, so any exception simply unwinds without exposing a partially built policy map to readers. Only once the map is fully ready do we allocate the final heap object and move the finishedabsl::flat_hash_mapinto it for atomic publication. That move is efficient: for thisflat_hash_map<std::string, std::shared_ptr<...>>type, Abseil’s move constructor transfers ownership of the existing backing table rather than copying or rebuilding the entries, so the extra cost at publication time is essentially just one heap allocation for the map object itself.