Awesome

Lilo

Lilo and Stitch

Lilo is a super-fast GraphQL stitching library. The project is heavily inspired by Atlassian Braid. Lilo focuses on simplicity and easy to use. You can find plenty of samples in the codebase and we aim to add more and more in every release. Please do not forget to check /samples directory.

We are planning to add additional frameworks supports. For now SpringBoot is supported. If you will use Lilo with SpringBoot. Please check Lilo Spring Documentation.

Installation

Just add a single Lilo dependency to your pom.xml file.

<dependencies>
  ...
  <dependency>
    <groupId>io.fria</groupId>
    <artifactId>lilo</artifactId>
    <version>24.5.0</version>
  </dependency>
  ...
</dependencies>

If you're using gradle add the dependency to your build.gradle file.

implementation 'io.fria:lilo:24.5.0'

Basic Usage

Here is the story, Alice has 2 GraphQL microservices and she wants to make her gateway to dispatch the GraphQL requests to their respective microservices. Microservice A provides a GraphQL query for user listing, and Microservice B provides a GraphQL mutation for user creation. So Alice can use both query and mutation via just sending requests to the Gateway directly. Lilo stitches the GraphQL schemas and provides a combined schema.

  +----------------+
  |                |
  | Microservice A | <---------+
  |                |           |            +----------------+
  +----------------+           |            |                |        o~
                               +----------- |    Gateway     | <---- /|\
  +----------------+           |            |                |       / \
  |                |           |            +----------------+
  | Microservice B | <---------+
  |                |
  +----------------+

A very basic working example for that scenario would be:

final Lilo lilo = Lilo.builder()
    .addSource(RemoteSchemaSource.create("SERVER_1", "https://server1/graphql"))
    .addSource(RemoteSchemaSource.create("SERVER_2", "https://server2/graphql"))
    .build();

But for a complete working example you need to serve the stitching logic from a GraphQL endpoint. (Probably /graphql) Please examine the 01-spring-boot-hello-world example in lilo-samples folder.

In most cases, we need an authentication or some sort of header manipulation. In that case, creating custom introspection and query retrievers might help us to modify outgoing requests or incoming responses. The following example shows a very basic example for custom retrievers.

    .addSource(
        RemoteSchemaSource.create(
            "SERVER_1",
            new MyIntrospectionRetriever("https://server1/graphql"),
            new MyQueryRetriever("https://server1/graphql")
        )
    )
    .addSource(
        RemoteSchemaSource.create(
            "SERVER_2",
            new MyIntrospectionRetriever("https://server2/graphql"),
            new MyQueryRetriever("https://server2/graphql")
        )
    )

For further details, you can examine the 02-spring-boot-basic-stitching example in lilo-samples folder.

If Gateway distributes the messages to Microservice A and also contains an embedded schema then the architecture might be something like this:


  +----------------+                       +----------------+
  |                |                       |                |        o~
  | Microservice A |---------------------- |    Gateway     | <---- /|\
  |                |                       |                |       / \
  +----------------+                       +----------------+
                                                  A    |
                                                  |    |
                                                  +<---+

final Lilo lilo = Lilo.builder()
    .addSource(
        RemoteSchemaSource.create(
            "SERVER_1",
            new MyIntrospectionRetriever("https://server1/graphql"),
            new MyQueryRetriever("https://server1/graphql")
        )
    )
    .addSource(
        DefinedSchemaSource.create(
            "SCHEMA_2",
            stringQueryDefinition,
            typeWiring
        )
    )
    .build();

We need to provide an IntrospectionRetriever and QueryRetriever. Those can fetch the query result from a remote source and/or local source.

After source definitions are properly set you can run your implementation similar to this:

final Map<String, Object> resultMap = lilo.stitch("{greeting1}").toSpecification();

Or more advanced GraphQL request which includes querym operation name and variables:


final GraphQLRequest graphQLRequest = GraphQLRequest.builder()
    .query(incomingGraphQlQuery)
    .operationName(incomingGraphQlOperationName)
    .variables(incomingGraphQlVariables)
    .build();

final Map<String, Object> resultMap = lilo.stitch(graphQLRequest.toExecutionInput()).toSpecification();

Parameter passing

Sometimes an HTTP header or a JWT token must be passed to the retrievers. You can pass a local context object inside the execution input.

final ExecutionInput executionInput = ExecutionInput.newExecutionInput()
    .localContext("aLocalContextObject")
    .query("{add(a: 1, b: 2)}")
    .build();

The localContext object is now accessible from your IntrospectionRetriever and QueryRetriever.

Subscription

GraphQL provides a subscription methodology for providing continuous data. It's a well-known pub/sub pattern for applications. If your application needs a continuous stream of real-time events, notifications, sensor data. Subscription might be wise choice for you.

Use Lilo framework library

Subscription usage needs a few configuration class definition and handlers definition. Lilo core library is framework-agnostic. If you are using a framework like SpringBoot. Please check the lilo documentation for that specific framework. Currently, SpringBoot is supported. Please check Lilo Spring Documentation.

Subscription Usage

If you're going to use Subscription stitching. You need to define an additional retriever other than QueryRetriever and IntrospectionRetriever. As you might guess, it's a SubscriptionRetriever. Besides retrievers, we need to define handlers:

SubscriptionGatewayHandler is responsible for handling web socket sessions coming from GraphQL clients to Lilo Stitching Gateway.
SubscriptionSourceHandler is responsible for handling websocket sessions going from gateway to remote GraphQL servers.

Since those handler classes are framework-agnostic. A binding should be implemented between framework and handlers.

Additional Resources

You can watch Tame Your Spring Microservices With GraphQL Stitching Using Lilo presentation.