Federation example (ExpediaGroup#315)

* Start a federation example

Requires an update from graphql-java first graphql-java/graphql-java#1644

* fix federation example

* exclude federation example from code coverage

* Move to top-level examples folder

Author: smyrick

README.md

@@ -11,7 +11,8 @@ GraphQL Kotlin consists of number of libraries that aim to simplify GraphQL inte
 
 * [graphql-kotlin-federation](/graphql-kotlin-federation) - Schema generator extension to build federated GraphQL schemas
 * [graphql-kotlin-schema-generator](/graphql-kotlin-schema-generator) - Code only GraphQL schema generation for Kotlin
-* [graphql-kotlin-spring-example](/graphql-kotlin-spring-example) - Example SpringBoot app that uses GraphQL Kotlin schema generator
+* [examples/spring](/examples/spring) - Example SpringBoot app that uses GraphQL Kotlin schema generator
+* [examples/federation](/examples/federation) - Example Federation module with multiple SpringBoot apps that use GraphQL Kotlin federation generator
 
 ## Documentation
 

codecov.yml

@@ -5,4 +5,4 @@
 
 # Ingore the example app from coverage reports
 ignore:
-  - "graphql-kotlin-spring-example/**/*"
+  - "examples/**/*"

examples/federation/README.md

@@ -0,0 +1,31 @@
+# Federation Example
+
+This example is two Spring applications `base-app` and `extend-app` that use `graphql-kotlin-federation` to generate the schema.
+These apps run on different ports (`8080`, `8081`) so they can run simultaniously
+
+Then the `gateway` is a Node.js app running Apollo Gateway on port `4000` and connects to the two spring apps.
+You can make queries against the spring apps directly or combined queries from the gateway.
+
+## Running Locally
+
+
+### Spring Apps
+Build the spring applications by running the following commands in the `/federation` directory
+
+```shell script
+mvn clean install
+``` 
+
+Start the servers:
+
+* Run each `Application.kt` directly from your IDE
+* Alternatively you can also use the spring boot maven plugin by running `mvn spring-boot:run` from the command line.
+
+
+Once the app has started you can explore the example schema by opening Playground endpoint
+* `base-app` http://localhost:8080/playground
+* `extend-app` http://localhost:8081/playground
+
+### Gateway
+
+See the instructions in the [README](/gateway/README.md) for this folder

graphql-kotlin-spring-example/README.md renamed to examples/federation/base-app/README.md

@@ -0,0 +1,112 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>com.expedia</groupId>
+        <artifactId>graphql-kotlin</artifactId>
+        <version>1.0.0-RC6-SNAPSHOT</version>
+        <relativePath>..</relativePath>
+    </parent>
+
+    <artifactId>base-app</artifactId>
+    <description>Example SpringBoot app using graphql-kotlin</description>
+    <url>https://github.com/ExpediaDotCom/graphql-kotlin</url>
+    <packaging>jar</packaging>
+
+    <properties>
+        <spring-boot.version>2.1.2.RELEASE</spring-boot.version>
+
+        <!-- skip release plugins -->
+        <maven.source.skip>true</maven.source.skip>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.expedia</groupId>
+            <artifactId>graphql-kotlin-schema-generator</artifactId>
+            <version>${project.parent.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.expedia</groupId>
+            <artifactId>graphql-kotlin-federation</artifactId>
+            <version>${project.parent.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-webflux</artifactId>
+            <version>${spring-boot.version}</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
+        <testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+                <version>${spring-boot.version}</version>
+            </plugin>
+
+            <plugin>
+                <artifactId>kotlin-maven-plugin</artifactId>
+                <groupId>org.jetbrains.kotlin</groupId>
+                <executions>
+                    <execution>
+                        <id>compile</id>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>test-compile</id>
+                        <phase>test-compile</phase>
+                        <goals>
+                            <goal>test-compile</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <compilerPlugins>
+                        <plugin>spring</plugin>
+                    </compilerPlugins>
+                    <jvmTarget>${java.version}</jvmTarget>
+                </configuration>
+                <dependencies>
+                    <dependency>
+                        <groupId>org.jetbrains.kotlin</groupId>
+                        <artifactId>kotlin-maven-allopen</artifactId>
+                        <version>${kotlin.version}</version>
+                    </dependency>
+                </dependencies>
+            </plugin>
+            <!-- TODO enable detekt/ktlint -->
+<!--            <plugin>-->
+<!--                <groupId>org.apache.maven.plugins</groupId>-->
+<!--                <artifactId>maven-antrun-plugin</artifactId>-->
+<!--            </plugin>-->
+            <plugin>
+                <groupId>org.jetbrains.dokka</groupId>
+                <artifactId>dokka-maven-plugin</artifactId>
+                <version>${dokka-maven-plugin.version}</version>
+                <configuration>
+                    <!-- don't generate javadocs as there is no artifact-->
+                    <skip>true</skip>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.sonatype.plugins</groupId>
+                <artifactId>nexus-staging-maven-plugin</artifactId>
+                <version>1.6.8</version>
+                <extensions>true</extensions>
+                <executions>
+                    <execution>
+                        <id>default-deploy</id>
+                        <phase>none</phase>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

examples/federation/base-app/pom.xml

@@ -0,0 +1,80 @@
+package com.expedia.graphql.sample
+
+import com.expedia.graphql.TopLevelObject
+import com.expedia.graphql.execution.KotlinDataFetcherFactoryProvider
+import com.expedia.graphql.extensions.print
+import com.expedia.graphql.federation.FederatedSchemaGeneratorConfig
+import com.expedia.graphql.federation.FederatedSchemaGeneratorHooks
+import com.expedia.graphql.federation.execution.FederatedTypeRegistry
+import com.expedia.graphql.federation.toFederatedSchema
+import com.expedia.graphql.hooks.SchemaGeneratorHooks
+import com.expedia.graphql.sample.datafetchers.CustomDataFetcherFactoryProvider
+import com.expedia.graphql.sample.datafetchers.SpringDataFetcherFactory
+import com.expedia.graphql.sample.exceptions.CustomDataFetcherExceptionHandler
+import com.expedia.graphql.sample.query.Query
+import graphql.GraphQL
+import graphql.execution.AsyncExecutionStrategy
+import graphql.execution.AsyncSerialExecutionStrategy
+import graphql.execution.DataFetcherExceptionHandler
+import graphql.execution.SubscriptionExecutionStrategy
+import graphql.schema.GraphQLSchema
+import org.slf4j.LoggerFactory
+import org.springframework.boot.autoconfigure.SpringBootApplication
+import org.springframework.boot.runApplication
+import org.springframework.context.annotation.Bean
+
+@SpringBootApplication
+class Application {
+
+    private val logger = LoggerFactory.getLogger(Application::class.java)
+
+    @Bean
+    fun hooks() = FederatedSchemaGeneratorHooks(FederatedTypeRegistry(emptyMap()))
+
+    @Bean
+    fun dataFetcherFactoryProvider(springDataFetcherFactory: SpringDataFetcherFactory, hooks: SchemaGeneratorHooks) =
+        CustomDataFetcherFactoryProvider(springDataFetcherFactory, hooks)
+
+    @Bean
+    fun schemaConfig(hooks: FederatedSchemaGeneratorHooks, dataFetcherFactoryProvider: KotlinDataFetcherFactoryProvider) = FederatedSchemaGeneratorConfig(
+        supportedPackages = listOf("com.expedia"),
+        hooks = hooks,
+        dataFetcherFactoryProvider = dataFetcherFactoryProvider
+    )
+
+    @Bean
+    fun schema(
+        queries: List<Query>,
+        schemaConfig: FederatedSchemaGeneratorConfig
+    ): GraphQLSchema {
+        fun List<Any>.toTopLevelObjects() = this.map {
+            TopLevelObject(it)
+        }
+
+        val schema = toFederatedSchema(
+            config = schemaConfig,
+            queries = queries.toTopLevelObjects()
+        )
+
+        logger.info(schema.print())
+
+        return schema
+    }
+
+    @Bean
+    fun dataFetcherExceptionHandler(): DataFetcherExceptionHandler = CustomDataFetcherExceptionHandler()
+
+    @Bean
+    fun graphQL(
+        schema: GraphQLSchema,
+        dataFetcherExceptionHandler: DataFetcherExceptionHandler
+    ): GraphQL = GraphQL.newGraphQL(schema)
+        .queryExecutionStrategy(AsyncExecutionStrategy(dataFetcherExceptionHandler))
+        .mutationExecutionStrategy(AsyncSerialExecutionStrategy(dataFetcherExceptionHandler))
+        .subscriptionExecutionStrategy(SubscriptionExecutionStrategy(dataFetcherExceptionHandler))
+        .build()
+}
+
+fun main(args: Array<String>) {
+    runApplication<Application>(*args)
+}

examples/federation/base-app/src/main/kotlin/com/expedia/graphql/sample/Application.kt

@@ -13,6 +13,6 @@ fun GraphQLRequest.toExecutionInput(graphQLContext: MyGraphQLContext? = null): E
     ExecutionInput.newExecutionInput()
         .query(this.query)
         .operationName(this.operationName)
-        .variables(this.variables)
+        .variables(this.variables ?: emptyMap())
         .context(graphQLContext)
         .build()

graphql-kotlin-spring-example/src/main/kotlin/com/expedia/graphql/sample/GraphQLRequest.kt renamed to examples/federation/base-app/src/main/kotlin/com/expedia/graphql/sample/GraphQLRequest.kt

@@ -0,0 +1,25 @@
+package com.expedia.graphql.sample
+
+import com.expedia.graphql.sample.context.MyGraphQLContext
+import com.expedia.graphql.sample.exceptions.SimpleKotlinGraphQLError
+import graphql.ErrorType
+import graphql.GraphQL
+import org.springframework.stereotype.Component
+import reactor.core.publisher.Mono
+
+@Component
+class QueryHandler(private val graphql: GraphQL) {
+
+    fun executeQuery(request: GraphQLRequest): Mono<GraphQLResponse> = Mono.subscriberContext()
+        .flatMap { ctx ->
+            val graphQLContext: MyGraphQLContext = ctx.get("graphQLContext")
+            val input = request.toExecutionInput(graphQLContext)
+
+            Mono.fromFuture(graphql.executeAsync(input))
+                .map { executionResult -> executionResult.toGraphQLResponse() }
+        }.onErrorResume {
+            val graphQLError = SimpleKotlinGraphQLError(it, ErrorType.DataFetchingException)
+
+            Mono.just(GraphQLResponse(errors = listOf(graphQLError)))
+        }
+}

graphql-kotlin-spring-example/src/main/kotlin/com/expedia/graphql/sample/GraphQLResponse.kt renamed to examples/federation/base-app/src/main/kotlin/com/expedia/graphql/sample/GraphQLResponse.kt

@@ -0,0 +1,25 @@
+package com.expedia.graphql.sample.exceptions
+
+import graphql.ErrorClassification
+import graphql.ErrorType
+import graphql.GraphQLError
+import graphql.language.SourceLocation
+
+open class SimpleKotlinGraphQLError(
+    private val exception: Throwable,
+    private val errorType: ErrorType
+    ) : GraphQLError {
+    override fun getErrorType(): ErrorClassification = errorType
+
+    override fun getLocations(): List<SourceLocation> = emptyList()
+
+    override fun getMessage(): String = "Exception while running code outside of data handler: ${exception.message}"
+
+    override fun getExtensions(): Map<String, Any> {
+        val newExtensions = mutableMapOf<String, Any>()
+        if (exception is GraphQLError && exception.extensions != null) {
+            newExtensions.putAll(exception.extensions)
+        }
+        return newExtensions
+    }
+}

examples/federation/base-app/src/main/kotlin/com/expedia/graphql/sample/QueryHandler.kt

@@ -0,0 +1,17 @@
+package com.expedia.graphql.sample.model
+
+import com.expedia.graphql.annotations.GraphQLDescription
+import com.expedia.graphql.federation.directives.FieldSet
+import com.expedia.graphql.federation.directives.KeyDirective
+
+@KeyDirective(fields = FieldSet("id"))
+@GraphQLDescription("A useful widget")
+data class Widget(
+    val id: Int,
+    @GraphQLDescription("The widget's value that can be null")
+    val value: Int? = null
+) {
+
+    @GraphQLDescription("returns original value multiplied by target OR null if original value was null")
+    fun multiplyValueBy(multiplier: Int) = value?.times(multiplier)
+}

graphql-kotlin-spring-example/src/main/kotlin/com/expedia/graphql/sample/RoutesConfiguration.kt renamed to examples/federation/base-app/src/main/kotlin/com/expedia/graphql/sample/RoutesConfiguration.kt

@@ -0,0 +1,8 @@
+package com.expedia.graphql.sample.query
+
+import org.springframework.stereotype.Component
+
+@Component
+class SimpleQuery : Query {
+    fun dataFromBaseApp() = "hello from base app"
+}

graphql-kotlin-spring-example/src/main/kotlin/com/expedia/graphql/sample/context/MyGraphQLContext.kt renamed to examples/federation/base-app/src/main/kotlin/com/expedia/graphql/sample/context/MyGraphQLContext.kt

@@ -0,0 +1,5 @@
+spring:
+  application:
+    name: base-app
+server:
+  port: 8080

graphql-kotlin-spring-example/src/main/kotlin/com/expedia/graphql/sample/context/MyGraphQLContextWebFilter.kt renamed to examples/federation/base-app/src/main/kotlin/com/expedia/graphql/sample/context/MyGraphQLContextWebFilter.kt

@@ -0,0 +1,18 @@
+# GraphQL Kotlin Spring Example
+
+One way to run a GraphQL server is with [Spring Boot](https://github.com/spring-projects/spring-boot). This example app uses [Spring Webflux](https://docs.spring.io/spring/docs/current/spring-framework-reference/web-reactive.html) together with `graphql-kotlin` and [graphql-playground](https://github.com/prisma/graphql-playground).
+
+### Running locally
+Build the application
+
+```bash
+mvn clean install
+```
+
+Start the server:
+
+* Run `Application.kt` directly from your IDE
+* Alternatively you can also use the spring boot maven plugin by running `mvn spring-boot:run` from the command line.
+
+
+Once the app has started you can explore the example schema by opening Playground endpoint at http://localhost:8080/playground.