added a check preventing a second dispatch instrumentation when one p…

src/main/java/graphql/servlet/GraphQLQueryInvoker.java

@@ -63,17 +63,27 @@ protected Instrumentation getInstrumentation(Object context) {
         if (context instanceof GraphQLContext) {
             return ((GraphQLContext) context).getDataLoaderRegistry()
                     .map(registry -> {
-                        List<Instrumentation> instrumentations = new ArrayList<>();
-                        instrumentations.add(getInstrumentation.get());
-                        instrumentations.add(new DataLoaderDispatcherInstrumentation(dataLoaderDispatcherInstrumentationOptionsSupplier.get()));
-                        return new ChainedInstrumentation(instrumentations);
+                        Instrumentation instrumentation = getInstrumentation.get();
+                        if (!containsDispatchInstrumentation(instrumentation)) {
+                            List<Instrumentation> instrumentations = new ArrayList<>();
+                            instrumentations.add(instrumentation);
+                            instrumentations.add(new DataLoaderDispatcherInstrumentation(dataLoaderDispatcherInstrumentationOptionsSupplier.get()));
+                            instrumentation = new ChainedInstrumentation(instrumentations);
+                        }
+                        return instrumentation;
                     })
-                    .map(Instrumentation.class::cast)
                     .orElse(getInstrumentation.get());
         }
         return getInstrumentation.get();
     }
 
+    private boolean containsDispatchInstrumentation(Instrumentation instrumentation) {
+        if (instrumentation instanceof ChainedInstrumentation) {
+            return ((ChainedInstrumentation)instrumentation).getInstrumentations().stream().anyMatch(this::containsDispatchInstrumentation);
+        }
+        return instrumentation instanceof DataLoaderDispatcherInstrumentation;
+    }
+
     private ExecutionResult query(GraphQLInvocationInput invocationInput, ExecutionInput executionInput) {
         if (Subject.getSubject(AccessController.getContext()) == null && invocationInput.getSubject().isPresent()) {
             return Subject.doAs(invocationInput.getSubject().get(), (PrivilegedAction<ExecutionResult>) () -> {

src/test/groovy/graphql/servlet/AbstractGraphQLHttpServletSpec.groovy

@@ -5,6 +5,7 @@ import graphql.Scalars
 import graphql.execution.ExecutionStepInfo
 import graphql.execution.instrumentation.ChainedInstrumentation
 import graphql.execution.instrumentation.Instrumentation
+import graphql.execution.instrumentation.dataloader.DataLoaderDispatcherInstrumentation
 import graphql.schema.DataFetcher
 import graphql.execution.reactive.SingleSubscriberPublisher
 import graphql.schema.GraphQLNonNull
@@ -1214,4 +1215,23 @@ class AbstractGraphQLHttpServletSpec extends Specification {
         actualInstrumentation instanceof ChainedInstrumentation
         actualInstrumentation != servletInstrumentation
     }
+
+    def "getInstrumentation does not add dataloader dispatch instrumentation if one is provided"() {
+        setup:
+        Instrumentation servletInstrumentation = Mock()
+        DataLoaderDispatcherInstrumentation mockDispatchInstrumentation = Mock()
+        ChainedInstrumentation chainedInstrumentation = new ChainedInstrumentation(Arrays.asList(servletInstrumentation,
+                mockDispatchInstrumentation))
+        GraphQLContext context = new GraphQLContext(request, response, null, null, null)
+        DataLoaderRegistry dlr = Mock()
+        context.setDataLoaderRegistry(dlr)
+        SimpleGraphQLHttpServlet simpleGraphQLServlet = SimpleGraphQLHttpServlet
+                .newBuilder(TestUtils.createGraphQlSchema())
+                .withQueryInvoker(GraphQLQueryInvoker.newBuilder().withInstrumentation(chainedInstrumentation).build())
+                .build();
+        when:
+        Instrumentation actualInstrumentation = simpleGraphQLServlet.getQueryInvoker().getInstrumentation(context)
+        then:
+        actualInstrumentation == chainedInstrumentation
+    }
 }