The dataloader seems to be working.

We need a more complex example to test.

{
  a: getBook(input: {id: "Z29vZ2xlX2V4YW1wbGVfbGlicmFyeV9ib29rX3YxX0Jvb2s6MA=="}) {
    author
  }
  b: getBook(input: {id: "Z29vZ2xlX2V4YW1wbGVfbGlicmFyeV9ib29rX3YxX0Jvb2s6MA=="}) {
    author
  }
}

INFO: stats: Statistics{loadCount=2, loadErrorCount=0, batchLoadCount=1, batchLoadExceptionCount=0, cacheHitCount=1}

examples/src/main/java/com/google/api/graphql/examples/library/graphqlserver/BookSchemaModule.java

@@ -19,21 +19,18 @@
 import com.google.api.graphql.rejoiner.RelayNode;
 import com.google.api.graphql.rejoiner.SchemaModule;
 import com.google.common.util.concurrent.ListenableFuture;
-import com.google.example.library.book.v1.Book;
-import com.google.example.library.book.v1.BookServiceGrpc;
-import com.google.example.library.book.v1.CreateBookRequest;
-import com.google.example.library.book.v1.GetBookRequest;
-import com.google.example.library.book.v1.ListBooksRequest;
-import com.google.example.library.book.v1.ListBooksResponse;
+import com.google.example.library.book.v1.*;
+import net.javacrumbs.futureconverter.java8guava.FutureConverter;
+import org.dataloader.DataLoaderRegistry;
 
 /** A GraphQL {@link SchemaModule} backed by a gRPC service. */
 final class BookSchemaModule extends SchemaModule {
 
   @Query("getBook")
   @RelayNode
-  ListenableFuture<Book> getBook(
-      GetBookRequest request, BookServiceGrpc.BookServiceFutureStub client) {
-    return client.getBook(request);
+  ListenableFuture<Book> getBook(GetBookRequest request, DataLoaderRegistry dataLoaderRegistry) {
+    return FutureConverter.toListenableFuture(
+        dataLoaderRegistry.<String, Book>getDataLoader("books").load(request.getId()));
   }
 
   @Query("listBooks")

examples/src/main/java/com/google/api/graphql/examples/library/graphqlserver/DataLoaderModule.java

@@ -41,7 +41,11 @@ DataLoaderRegistry dataLoaderRegistry(BookServiceGrpc.BookServiceFutureStub book
         keys -> {
           ListenableFuture<List<Book>> listenableFuture =
               Futures.transform(
-                  bookService.listBooks(ListBooksRequest.newBuilder().build()),
+                  bookService.listBooks(
+                      ListBooksRequest.newBuilder()
+                          .addAllIds(keys)
+                          .setPageSize(keys.size())
+                          .build()),
                   resp -> resp.getBooksList(),
                   MoreExecutors.directExecutor());
           //  ServletScopes.transferRequest(() -> ... ); ??
@@ -51,6 +55,7 @@ DataLoaderRegistry dataLoaderRegistry(BookServiceGrpc.BookServiceFutureStub book
     DataLoaderRegistry registry = new DataLoaderRegistry();
 
     registry.register("books", new DataLoader<>(bookBatchLoader));
+
     return registry;
   }
 }

examples/src/main/java/com/google/api/graphql/examples/library/graphqlserver/GraphQlServlet.java

@@ -27,10 +27,13 @@
 import graphql.GraphQL;
 import graphql.execution.instrumentation.ChainedInstrumentation;
 import graphql.execution.instrumentation.Instrumentation;
+import graphql.execution.instrumentation.dataloader.DataLoaderDispatcherInstrumentation;
 import graphql.execution.instrumentation.tracing.TracingInstrumentation;
 import graphql.schema.GraphQLSchema;
+import org.dataloader.DataLoaderRegistry;
 
 import javax.inject.Inject;
+import javax.inject.Provider;
 import javax.inject.Singleton;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
@@ -40,25 +43,28 @@
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
+import java.util.logging.Logger;
 
 @Singleton
-class GraphQlServlet extends HttpServlet {
+final class GraphQlServlet extends HttpServlet {
 
   private static final Gson GSON = new GsonBuilder().serializeNulls().create();
   private static final TypeToken<Map<String, Object>> MAP_TYPE_TOKEN =
       new TypeToken<Map<String, Object>>() {};
 
-  private static final Instrumentation instrumentation =
-      new ChainedInstrumentation(
-          Arrays.asList(
-              GuavaListenableFutureSupport.listenableFutureInstrumentation(),
-              new TracingInstrumentation()));
-
+  private static final Logger logger = Logger.getLogger(GraphQlServlet.class.getName());
   @Inject @Schema GraphQLSchema schema;
+  @Inject Provider<DataLoaderRegistry> registryProvider;
 
   @Override
   protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
 
+    Instrumentation instrumentation =
+        new ChainedInstrumentation(
+            Arrays.asList(
+                GuavaListenableFutureSupport.listenableFutureInstrumentation(),
+                new DataLoaderDispatcherInstrumentation(registryProvider.get()),
+                new TracingInstrumentation()));
     GraphQL graphql = GraphQL.newGraphQL(schema).instrumentation(instrumentation).build();
 
     Map<String, Object> json = readJson(req);
@@ -81,6 +87,7 @@ protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws I
     resp.setContentType("application/json");
     resp.setStatus(HttpServletResponse.SC_OK);
     GSON.toJson(executionResult.toSpecification(), resp.getWriter());
+    logger.info("stats: " + registryProvider.get().getStatistics());
   }
 
   private static Map<String, Object> getVariables(Object variables) {

examples/src/main/proto/library/book_service.proto

@@ -66,15 +66,18 @@ message GetBookRequest {
 }
 
 message ListBooksRequest {
+  // The ids of the book to retrieve.
+  repeated string ids = 1;
+
   // Requested page size. Server may return fewer books than requested.
   // If unspecified, server will pick an appropriate default.
-  int32 page_size = 1;
+  int32 page_size = 2;
 
   // A token identifying a page of results the server should return.
   // Typically, this is the value of
   // [ListBooksResponse.next_page_token][google.example.library.v1.ListBooksResponse.next_page_token].
   // returned from the previous call to `ListBooks` method.
-  string page_token = 2;
+  string page_token = 3;
 }
 
 message ListBooksResponse {