The concept of Federation Gateway Stitching refers to the ability to combine multiple GraphQL endpoints or services into a unified API gateway. This allows clients to send queries and mutations to a single endpoint, which then routes the requests to the respective underlying services.

In this blog post, we will explore how to implement Federation Gateway Stitching in JavaScript using the popular Apollo Federation library. This approach enables seamless composition and scaling of GraphQL services.

Prerequisites

• Basic understanding of GraphQL and its concepts
• Familiarity with JavaScript and Node.js

Getting Started

To get started, we need to set up a new Node.js project and install the required dependencies.

Open your terminal and run the following commands:

mkdir federation-gateway-stitching
cd federation-gateway-stitching
npm init -y
npm install apollo-server graphql @apollo/federation graphql-tools

Setting up the Gateway

Let’s create a new file called gateway.js and add the following code:

const { ApolloGateway } = require('@apollo/gateway');

const gateway = new ApolloGateway({
  serviceList: [
    { name: 'service1', url: 'https://service1-url.com/graphql' },
    { name: 'service2', url: 'https://service2-url.com/graphql' },
    // Add more services as needed
  ],
});

(async () => {
  await gateway.load();

  const { schema, executor } = gateway;

  // Start the gateway server
  // ...
})();

In the code above, we import the ApolloGateway from the @apollo/gateway package. Then, we create a new instance of ApolloGateway with an array of services. Each service has a unique name and its corresponding GraphQL endpoint URL.

When calling gateway.load(), Apollo Gateway retrieves the schema from each service and stitches them together into a unified schema.

Starting the Gateway Server

To start the Apollo Gateway server, we need to add the following code to the end of gateway.js:

const { ApolloServer } = require('apollo-server');

const server = new ApolloServer({
  schema,
  executor,
});

server.listen().then(({ url }) => {
  console.log(`🚀 Gateway Server ready at ${url}`);
});

The code above creates a new ApolloServer instance, passing the schema and executor from the gateway object. Then, it starts the server and logs the server URL to the console.

Adding Custom Operations

To add custom operations to the gateway, we can define resolvers and additional types.

// Example resolvers
const resolvers = {
  Query: {
    customOperation: (_, args, context) => {
      // Custom logic here
    },
  },
};

const gatewayServer = new ApolloServer({
  schema,
  executor,
  resolvers,
});

The resolvers object contains resolver functions for custom operations specified in the GraphQL schema.

Conclusion

In this blog post, we learned how to implement Federation Gateway Stitching in JavaScript using the Apollo Federation library. With Federation Gateway Stitching, we can combine multiple GraphQL endpoints into a unified gateway, providing flexibility and scalability to our GraphQL services.

#javascript #graphql