Avoid an error allocation in the server stream handler (grpc#1970)

Motivation: Existential errors unconditionally allocate. In the server stream handler a promise is failed on tear down via an API which takes an existential error. This means the handler always allocates, even if the promise has been completed. Modifications: - Statically allocate the error as an existential Result: Fewer allocations
hharng · Jul 5, 2024 · 595a416 · 595a416
1 parent b9b4711
commit 595a416
Showing 1 changed file with 8 additions and 6 deletions.
diff --git a/Sources/GRPCHTTP2Core/Server/GRPCServerStreamHandler.swift b/Sources/GRPCHTTP2Core/Server/GRPCServerStreamHandler.swift
@@ -39,6 39,13 @@ final class GRPCServerStreamHandler: ChannelDuplexHandler, RemovableChannelHandl
 
  private let methodDescriptorPromise: EventLoopPromise<MethodDescriptor>
 
  // Existential errors unconditionally allocate, avoid this per-use allocation by doing it
  // statically.
  private static let handlerRemovedBeforeDescriptorResolved: any Error = RPCError(
  code: .unavailable,
  message: "RPC stream was closed before we got any Metadata."
  )
 
  init(
  scheme: GRPCStreamStateMachineConfiguration.Scheme,
  acceptedEncodings: CompressionAlgorithmSet,
@@ -159,12 166,7 @@ extension GRPCServerStreamHandler {
 
  func handlerRemoved(context: ChannelHandlerContext) {
  self.stateMachine.tearDown()
- self.methodDescriptorPromise.fail(
- RPCError(
- code: .unavailable,
- message: "RPC stream was closed before we got any Metadata."
- )
- )
  self.methodDescriptorPromise.fail(Self.handlerRemovedBeforeDescriptorResolved)
  }
 
  func channelInactive(context: ChannelHandlerContext) {