The "gRPC Server" section of the Micronaut gRPC docs says, in part:
…by default the server will be setup to use Micronaut’s I/O executor service.
That suggests to me that it should be possible to configure the server to use a non-default executor service. I'm specifically interested in getting it to use the VIRTUAL executor service.
The configuration reference for Micronaut gRPC identifies grpc.server.executor as a configurable property of GrpcServerConfiguration, but with a type of java.util.concurrent.Executor. Looking at the source code for GrpcServerConfiguration, it's not at all clear to me that the server executor can actually be changed, though.
The constructor accepts an executor, but calls out TaskExecutors.IO specifically, and I don't see any hooks to override that. GrpcServerConfiguration only calls NettyServerBuilder#executor from its constructor, and there are no public (or private) methods for changing it after construction.
I think I have to be missing something; is there some other way to configure Micronaut gRPC to use virtual threads (or any executor other than TaskExecutors.IO) for the gRPC server executor?
EDIT: to be clear, I have tried the obvious thing of setting grpc.server.executor to BLOCKING/VIRTUAL (even though there's no real reason to believe that would have any effect), and gRPC calls continue to get sent to the IO executor.
As discussed in https://github.com/micronaut-projects/micronaut-grpc/issues/1097, this is, in fact, a bug in micronaut-grpc; there is not (yet!) a way to configure the server executor via the Micronaut configuration layer.
Please see the linked issue for additional discussion and workarounds.