Overcoming 'Host Not Allowed' Error When Deploying Play Framework Application to Amazon AWS with Boxfuse

Overcoming “Host Not Allowed” Error When Deploying Play Framework Application to Amazon AWS with Boxfuse

As a data scientist or software engineer, you may come across various errors when deploying applications. One such error message is the “Host not allowed” error. This typically occurs when deploying a Play framework application to Amazon AWS with Boxfuse. This article is a step-by-step guide on how to troubleshoot and resolve this error.

What is the “Host Not Allowed” Error?

Before diving into the solution, let’s first understand what the “Host not allowed” error means.

The “Host not allowed” error is a security feature that prevents HTTP Host header attacks. When your application gets a request, the Play framework checks the Host header against the allowedHosts filter. If the Host header does not match any of the allowed hosts, it will reject the request, and you’ll receive the “Host not allowed” error.

Steps to Resolve the “Host Not Allowed” Error

Step 1: Identifying the Error

Before you can resolve the error, you need to identify it. It will usually appear as a message in your server’s console log, saying something like: play.filters.hosts.allowed: [".example.com"]. This means the application is only allowing requests from example.com.

Step 2: Modifying the Allowed Hosts

The solution to the “Host not allowed” error is to add the host of your AWS instance to the list of allowed hosts in the Play Framework’s configuration file.

In your application.conf file, you’ll find a line similar to this:

play.filters.hosts.allowed = [".example.com"]

You need to replace example.com with the URL of your AWS instance. If you have multiple instances, you can add them as a comma-separated list.

play.filters.hosts.allowed = [".aws-instance-url.com", ".another-aws-instance-url.com"]

Step 3: Deploying the Application with Boxfuse

Now that you’ve fixed the error in your application’s configuration, you can proceed to deploy it with Boxfuse. Using Boxfuse, you can create a minimal, immutable image of your application, ready for deployment on AWS.

Here’s a basic command to fuse and deploy your application:

boxfuse run myapp -env=prod

This command creates an image of myapp, and runs it on AWS in the prod environment.

Step 4: Verifying the Deployment

After deploying the application, you need to verify that the error has been resolved. You can do this by sending a request to your application and checking that you don’t receive the “Host not allowed” error.

Conclusion

The “Host not allowed” error when deploying a Play framework application to Amazon AWS with Boxfuse can be a roadblock, but it’s quite simple to resolve. By correctly configuring your application’s allowed hosts, you can ensure that your application accepts requests from your AWS instances.

Understanding the underlying cause of errors and knowing how to troubleshoot them is a vital part of being a data scientist or software engineer. Hopefully, this guide has helped you gain a better understanding of the “Host not allowed” error and how to resolve it.

Remember, the key to resolving any error is understanding what it means and knowing where to look for a solution. Stay curious, and happy coding!

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