HTTP status code

The HTTP 424 status code stands for "Failed Dependency". It is a client error response indicating that the request failed because it depends on another request that has failed. This typically occurs when multiple requests or operations are chained together, and one of them fails, causing the dependent request to also fail.

When is HTTP 424 Used?

• The 424 status code is most commonly used in systems where multiple operations are performed in sequence, and a failure in one operation causes subsequent operations to fail as well.
• It is often used in WebDAV (Web Distributed Authoring and Versioning) applications, where resources may be dependent on others, or in multi-step processes such as workflow systems, where one task must be completed before the next one can be executed.

Common Causes of HTTP 424 Errors

• Failed prerequisite operation: A prior operation required for the current request to succeed has failed. For example, trying to update a record that depends on the successful completion of another operation (e.g., creating a related resource).
• Dependency failure in workflows: In complex systems, where actions depend on each other (such as task dependencies in project management), a failure in one step can lead to the failure of all subsequent dependent steps.
• Failed resource availability: A request to modify or interact with a resource may fail if a required resource or component is missing, unavailable, or in an incorrect state.

Example Scenarios

• A transaction involves creating a new user and assigning them certain roles, but the role assignment fails. The server returns a 424 error indicating that the user creation cannot proceed because it depends on the role assignment.
• A workflow system where step 1 (data validation) fails, and step 2 (data processing) cannot proceed because of the failed validation.
• A file system operation that fails because a prerequisite file is missing or locked, causing the dependent operation to fail.

Example

Client Request (Failed Dependency)

    
        POST /users HTTP/1.1
        Host: example.com
        Content-Type: application/json

        {
          "username": "new_user",
          "role_id": "admin"
        }
    

(The client attempts to create a user and assign a role, but the role assignment fails.)

Server Response (424 Failed Dependency)

    
        HTTP/1.1 424 Failed Dependency
        Content-Type: application/json

        {
          "error": "The role assignment failed, so the user creation could not be completed."
        }
    

Best Practices for Handling HTTP 424

• Provide clear error messages: The response should clearly specify which dependent operation failed and why the current request could not be completed.
• Handle dependency failures gracefully: In systems with dependent operations, ensure that failure recovery mechanisms are in place. For example, allow for retries or provide users with instructions on how to resolve the issue that caused the dependency to fail.
• Atomic transactions: When performing operations that depend on each other, it is often a good practice to implement atomic transactions, where either all operations succeed or none of them are executed. This can help avoid situations where partial data is created or modified.
• Ensure proper sequencing: Make sure that operations are sequenced properly, so that all dependencies are met before the dependent request is made.

Summary

HTTP 424 indicates that a request failed due to a dependency failure. This happens when one operation depends on the success of another, and the prerequisite operation fails, preventing the current request from succeeding. It is often used in systems with dependent operations or multi-step processes, such as workflows, transactions, or file operations. The client should be informed about which dependency failed and what actions they can take to resolve the issue.