perf(grpc-js): lazily allocate Metadata opaqueData map - #3095
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Every Metadata instance previously allocated a Map for opaqueData in its constructor, even though opaqueData is only used in specific scenarios like caching parsed ORCA load reports on trailers. On high-throughput RPC paths where multiple Metadata instances are created per call, this eager allocation resulted in unnecessary heap allocation and GC pressure. Changes: - Make Metadata.prototype.opaqueData optional and lazily instantiate the Map on the first setOpaque() call. - Use optional chaining in getOpaque() when reading from opaqueData. - Preserve existing clone() and constructor behavior to maintain exact compatibility. - Add unit tests covering lazy allocation, key updates, value types, and cloned instance behavior.
murgatroid99
approved these changes
Sep 25, 2026
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Every Metadata instance previously allocated a Map for opaqueData in its constructor, even though opaqueData is only used in specific scenarios like caching parsed ORCA load reports on trailers.
On high-throughput RPC paths where multiple Metadata instances are created per call, this eager allocation resulted in unnecessary heap allocation and GC pressure.
Changes: