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Better examples of using per request data loaders (#758)
* Better examples of using per request data loaders * Typo
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‎docs/batching.rst‎

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@@ -124,3 +124,40 @@ One thing to note is the above only works if you use `DataLoaderDispatcherInstru
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is called. If this was not in place, then all the promises to data will never be dispatched ot the batch loader function
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and hence nothing would ever resolve.
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Per Request Data Loaders
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^^^^^^^^^^^^^^^^^^^^^^^^
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If you are serving web requests then the data can be specific to the user requesting it. If you have user specific data then you will not want to
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cache data meant for user A to then later give it user B in a subsequent request.
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The scope of your DataLoader instances is important. You might want to create them per web request to
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ensure data is only cached within that web request and no more.
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If your data can be shared across web requests then you might want to scope your data loaders so they survive
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longer than the web request say.
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But if you are doing per request data loaders then creating a new set of ``GraphQL`` and ``DataLoader`` objects per
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request is super cheap. Its the ``GraphQLSchema`` creation that can be expensive, especially if you are using graphql IDL parsing.
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Structure your code so that the schema is statically held, perhaps in a static variable or in a singleton IoC component but
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build out a new ``GraphQL`` set of objects on each request.
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.. code-block:: java
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GraphQLSchema staticSchema = staticSchema_Or_MayBeFrom_IoC_Injection();
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DataLoaderRegistry registry = new DataLoaderRegistry();
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registry.register("character", getCharacterDataLoader());
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DataLoaderDispatcherInstrumentation dispatcherInstrumentation
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= new DataLoaderDispatcherInstrumentation(registry);
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GraphQL graphQL = GraphQL.newGraphQL(staticSchema)
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.instrumentation(dispatcherInstrumentation)
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.build();
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graphQL.execute("{ helloworld }");
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// you can now throw away the GraphQL and hence DataLoaderDispatcherInstrumentation
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// and DataLoaderRegistry objects since they are really cheap to build per request

‎src/main/java/graphql/GraphQL.java‎

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@@ -140,7 +140,7 @@ public static Builder newGraphQL(GraphQLSchema graphQLSchema) {
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* This helps you transform the current GraphQL object into another one by starting a builder with all
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* the current values and allows you to transform it how you want.
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*
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* @param builderConsumer the consumer code that will be given a builder to changee
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* @param builderConsumer the consumer code that will be given a builder to transform
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*
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* @return a new GraphQL object based on calling build on that builder
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*/

‎src/main/java/graphql/schema/GraphQLSchema.java‎

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import java.util.List;
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import java.util.Map;
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import java.util.Set;
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import java.util.function.Consumer;
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import static graphql.Assert.assertNotNull;
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import static graphql.schema.visibility.DefaultGraphqlFieldVisibility.DEFAULT_FIELD_VISIBILITY;
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return subscriptionType != null;
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}
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/**
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* This helps you transform the current GraphQLSchema object into another one by starting a builder with all
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* the current values and allows you to transform it how you want.
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*
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* @param builderConsumer the consumer code that will be given a builder to transform
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*
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* @return a new GraphQLSchema object based on calling build on that builder
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*/
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public GraphQLSchema transform(Consumer<Builder> builderConsumer) {
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Builder builder = newSchema(this);
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builderConsumer.accept(builder);
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return builder.build();
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}
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/**
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* @return a new schema builder
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*/

‎src/test/groovy/graphql/schema/GraphQLSchemaTest.groovy‎

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def existingSchema = TestUtil.schema(idl, runtimeWiring)
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GraphQLSchema schema = GraphQLSchema.newSchema(existingSchema).build()
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GraphQLSchema schema = existingSchema.transform({})
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expect:
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assert 0 == runQuery(existingSchema).getErrors().size()

‎src/test/groovy/readme/BatchingExamples.java‎

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@@ -71,7 +71,7 @@ public Object get(DataFetchingEnvironment environment) {
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// as each level fo the graphql query is executed and hence make batched objects
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// available to the query and the associated DataFetchers
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//
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DataLoaderDispatcherInstrumentation dispatcherInstrumentation
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DataLoaderDispatcherInstrumentation dispatcherInstrumentation
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= new DataLoaderDispatcherInstrumentation(registry);
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//
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}
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private void perRequestGraphQl() {
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GraphQLSchema staticSchema = staticSchema_Or_MayBeFrom_IoC_Injection();
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DataLoaderRegistry registry = new DataLoaderRegistry();
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registry.register("character", getCharacterDataLoader());
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DataLoaderDispatcherInstrumentation dispatcherInstrumentation
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= new DataLoaderDispatcherInstrumentation(registry);
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GraphQL graphQL = GraphQL.newGraphQL(staticSchema)
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.instrumentation(dispatcherInstrumentation)
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.build();
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graphQL.execute("{ helloworld }");
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// you can now throw away the GraphQL and hence DataLoaderDispatcherInstrumentation
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// and DataLoaderRegistry objects since they are really cheap to build per request
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}
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private GraphQLSchema staticSchema_Or_MayBeFrom_IoC_Injection() {
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return null;
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}
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private DataLoader<?, ?> getCharacterDataLoader() {
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return null;
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}
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private GraphQLSchema buildSchema() {
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return null;
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}

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