Advanced Error Handling in GraphQL

1. Introduction

GraphQL is a powerful query language for APIs, but managing errors effectively is crucial for maintaining a robust application. This lesson covers advanced error handling techniques, custom error types, and best practices.

2. Types of Errors

In GraphQL, errors can typically be classified into two main types:

• **User Errors**: These are often related to invalid input or unauthorized access.
• **Server Errors**: These occur due to issues on the server-side, like database failures or unhandled exceptions.

3. Custom Error Handling

Custom error handling in GraphQL can be achieved by creating your own error classes. This allows you to provide more context and control over the error responses.

3.1 Defining Custom Errors

Define custom error classes extending the base error class:

class UserInputError extends Error {
    constructor(message, code) {
        super(message);
        this.code = code;
        this.name = "UserInputError";
    }
}
            

3.2 Throwing Custom Errors

Example of throwing a custom error in a resolver:

const resolvers = {
    Query: {
        getUser: async (_, { id }) => {
            const user = await findUserById(id);
            if (!user) {
                throw new UserInputError("User not found", "USER_NOT_FOUND");
            }
            return user;
        },
    },
};
            

4. Best Practices

• Always return consistent error formats.
• Log errors for debugging purposes.
• Use specific error types to allow clients to handle different errors accordingly.
• Avoid exposing sensitive information in error messages.
• Utilize middleware for centralized error handling.

5. FAQ