In a rapidly evolving software ecosystem, it is important to have a system in place to handle versioning of your APIs. This allows you to make updates and introduce breaking changes without impacting existing consumers of your API.

In this blog post, we will discuss how to implement versioning in a JavaScript GraphQL server. We will specifically look at two popular JavaScript libraries for building GraphQL servers: Apollo Server and Express-GraphQL.

Apollo Server

Apollo Server is a powerful GraphQL server implementation for JavaScript. It provides a flexible and easy-to-use framework for building GraphQL APIs.

To implement versioning in Apollo Server, we can make use of middlewares. Middleware functions in Apollo Server are executed sequentially and can be used to transform requests, validate inputs, and handle custom logic.

To enable versioning in Apollo Server, we can create a version middleware that inspects the request and modifies it based on the requested version. Here is an example implementation:

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

const schema = require('./schema');
const resolvers = require('./resolvers');
const { parseVersion } = require('./utils');

const server = new ApolloServer({
  typeDefs: schema,
  resolvers,
  context: ({ req }) => {
    // Parse the requested version from the request headers
    const requestedVersion = parseVersion(req.headers.version);
    
    // Add the version to the context object for later use
    return {
      version: requestedVersion
    }
  },
  middleware: [
    async (resolve, parent, args, context, info) => {
      // Modify the request based on the requested version
      if (context.version === 'v1') {
        // Handle version 1 requests
        // ...
      } else if (context.version === 'v2') {
        // Handle version 2 requests
        // ...
      }
      
      // Call the next middleware in the chain
      return resolve();
    }
  ]
});

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

In this example, we parse the requested version from the request headers and add it to the context object. We then use a middleware function to inspect the requested version and modify the request accordingly.

Express-GraphQL

Express-GraphQL is a popular library for building GraphQL servers with Express.js. It provides an integration layer between Express.js and GraphQL.

To implement versioning in Express-GraphQL, we can use middlewares provided by Express.js itself. Here is an example implementation:

const express = require('express');
const { graphqlHTTP } = require('express-graphql');

const schema = require('./schema');
const resolvers = require('./resolvers');
const { parseVersion } = require('./utils');

const app = express();

app.use((req, res, next) => {
  // Parse the requested version from the request headers
  const requestedVersion = parseVersion(req.headers.version);
  
  // Add the version to the request object
  req.version = requestedVersion;
  
  next();
});

app.use('/graphql', graphqlHTTP(async (req, res, graphQLParams) => {
  // Modify the request based on the requested version
  if (req.version === 'v1') {
    // Handle version 1 requests
    // ...
  } else if (req.version === 'v2') {
    // Handle version 2 requests
    // ...
  }
  
  // Return the GraphQL middleware
  return {
    schema,
    rootValue: resolvers,
  };
}));

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

In this example, we use the Express.js middleware to parse the requested version from the request headers and add it to the request object. We then use this version information to modify the request as needed.

Conclusion

Implementing versioning in a JavaScript GraphQL server is essential for managing changes and updates to your API. By using middleware functions in Apollo Server or Express-GraphQL, you can easily handle different versions of your API and provide a seamless experience for clients.

Remember to test your API thoroughly after making changes to ensure backward compatibility and provide clear documentation to communicate the changes to your API consumers.

#graphql #javascript