feat(server): stop when the host asks

[devgianlu]

@coderabbitai ignore

Two commits:

• the server stops when its go-plugin host asks it to;
• CI and the preset build vcpkg's dependencies release-only.

Stop when the host asks

A go-plugin host stops a plugin in three steps:

1. it calls GRPCController.Shutdown;
2. it waits a grace period (two seconds in go-plugin) for the process to exit;
3. it kills the process if it has not.

This library did not serve GRPCController, so a C++ plugin answered Unimplemented and kept running. It was always killed, so nothing after Wait() in its main ever ran, and neither did the teardown there.

PluginServer now serves the controller.

• Registered without generated code. Its one method, /plugin.GRPCController/Shutdown, takes and returns plugin.Empty, which is zero bytes on the wire. So it is registered over raw grpc::ByteBuffers, the way generated code registers a method. That needs no .proto and no code generation, so a consumer's build, a vcpkg port for instance, needs no protoc as an extra build tool.
• Handed to the watchdog thread. The request arrives on a gRPC thread, which cannot wait for its own server to shut down. It sets a flag and wakes the parent-death watchdog thread, which calls Shutdown() as it already does when the host dies. Wait() then returns and main unwinds.

Build vcpkg's dependencies release-only

CI and the vcpkg preset built every dependency for x64-linux, vcpkg's default, which builds each dependency twice: debug and release. The host tools (protoc, grpc_cpp_plugin) share that triplet, because target and host are the same machine. CI builds Release, so nothing links the debug copies.

x64-linux-release, vcpkg's release-only triplet, is now both the target and the host triplet. Switching only the host would add a second build here rather than remove one, since the target triplet was not release-only. The example's go:generate follows protoc to the new install path.

Tested

• All 30 tests pass.

• New Server.StopsWhenTheHostAsks test: it calls /plugin.GRPCController/Shutdown the way go-plugin does, and expects Wait() to return with nothing else calling Shutdown().

  • It fails without the change: the call gets Unimplemented and Wait() never returns.
  • It passed 30 repeated runs of the server tests.

• CI steps replayed from a clean vcpkg install on the new triplet, in 6 min 44 s:

  • configure;
  • build;
  • ctest;
  • the Go example's go generate and build.

  Only an x64-linux-release tree was installed.

🤖 Generated with Claude Code