🏗️ Receive shutdown signal via RPC and terminate the gRPC server.

src/main/java/io/github/robertograham/tpp4j/DefaultGrpcController.java

@@ -0,0 +1,25 @@
+package io.github.robertograham.tpp4j;
+
+import com.hashicorp.goplugin.Empty;
+import com.hashicorp.goplugin.GRPCControllerGrpc.GRPCControllerImplBase;
+import io.grpc.stub.StreamObserver;
+
+final class DefaultGrpcController extends GRPCControllerImplBase {
+
+    final ProviderServer providerServer;
+
+    DefaultGrpcController(final ProviderServer providerServer) {
+        this.providerServer = providerServer;
+    }
+
+    @Override
+    public void shutdown(final Empty request, final StreamObserver<Empty> responseObserver) {
+        System.err.println("[INFO] Shutting down");
+
+        providerServer.stop();
+
+        responseObserver.onNext(Empty.newBuilder()
+                .build());
+        responseObserver.onCompleted();
+    }
+}

src/main/java/io/github/robertograham/tpp4j/ProviderServer.java

@@ -1,9 +1,7 @@
 package io.github.robertograham.tpp4j;
 
-import io.grpc.Attributes;
 import io.grpc.Grpc;
 import io.grpc.Server;
-import io.grpc.ServerTransportFilter;
 import io.grpc.TlsServerCredentials;
 import java.io.IOException;
 import java.io.StringWriter;
@@ -60,12 +58,7 @@ void start() throws IOException, GeneralSecurityException {
                                 .clientAuth(TlsServerCredentials.ClientAuth.REQUIRE)
                                 .build())
                         .addService(new DefaultProvider())
-                        .addTransportFilter(new ServerTransportFilter() {
-                            @Override
-                            public void transportTerminated(final Attributes attributes) {
-                                stop();
-                            }
-                        })
+                        .addService(new DefaultGrpcController(this))
                         .build()
                         .start();
             }
@@ -83,9 +76,8 @@ void blockUntilShutdown() throws InterruptedException {
         }
     }
 
-    private void stop() {
+    void stop() {
         if (server != null) {
-            System.err.println("[INFO] Shutting down provider server");
             server.shutdown();
         }
     }

src/main/proto/plugin/grpc_controller.proto

@@ -0,0 +1,16 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+syntax = "proto3";
+package plugin;
+option go_package = "./plugin";
+option java_multiple_files = true;
+option java_package = "com.hashicorp.goplugin";
+
+message Empty {
+}
+
+// The GRPCController is responsible for telling the plugin server to shutdown.
+service GRPCController {
+  rpc Shutdown(Empty) returns (Empty);
+}