SeaweedFS: S3 To Filer HTTP Communication

Hey there! Let's dive into a common SeaweedFS configuration snag: getting your S3 endpoint to talk to your Filer endpoint exclusively over HTTP, especially when you've got mTLS (mutual TLS) enabled. This scenario pops up more often than you'd think, and it's super important to understand how to troubleshoot it. In this guide, we'll break down the issue, explore the root cause, and offer a practical solution. I will share with you the details of the problem I faced when setting up S3 in SeaweedFS to communicate with the filer exclusively using HTTP.

The mTLS Challenge: When S3 Tries HTTP to HTTPS

So, you've gone the extra mile and enabled mTLS in your SeaweedFS setup. This is fantastic for security, as it ensures all your components—Master, Volume servers, Filer, and S3—can authenticate each other before exchanging data. All components running in separate Docker containers. But here's where the plot thickens: your S3 endpoint, when it tries to talk to the Filer, insists on using HTTP. When using the default configuration, the S3 server attempts to communicate with the Filer using HTTP, but the Filer is set up with HTTPS. This mismatch is what triggers the infamous “client sent an HTTP request to an HTTPS server” error. It's like trying to speak English to someone who only understands French. It simply won't work.

Symptoms of the Issue

When you attempt to upload a file through the S3 endpoint, the operation fails. The logs provide clear clues:

• S3 Logs: You'll typically find an error message indicating a problem during the communication with the Filer. The error often pinpoints the origin of the issue. The S3 logs are the first place to look. They'll tell you which component is having trouble, and that helps narrow down the problem.

• Filer Logs: These logs are often where you'll see the HTTP to HTTPS mismatch clearly. The Filer will log errors related to TLS handshake failures, confirming that it's expecting a secure connection.

• The Root Cause: The S3 endpoint is configured to send HTTP requests to the Filer, even when mTLS is enabled. This configuration is fine until mTLS is enforced on the Filer side. This is because, by default, SeaweedFS's S3 API constructs the destination URL for the Filer using http://. This is true irrespective of whether mTLS is enabled. The S3 server, by default, is set to use HTTP to communicate with the filer. When mTLS is enabled, the filer rejects the HTTP requests from the S3 server, triggering a TLS handshake error.

Unpacking the Error: putToFiler and toFilerUrl

To understand the solution, let's look at the source code of the issue, we can understand why the S3 server is using HTTP to talk to the Filer.

Diving into the Code

The problem stems from how the S3 endpoint constructs the URL to communicate with the Filer. Specifically, the function toFilerUrl is where the destination URL is created. This function puts the destination URL into the Filer server.

destUrl := fmt.Sprintf("http://%s%s/%s%s",s3a.option.Filer.ToHttpAddress(), s3a.option.BucketsPath, bucket, object)

As you can see, the URL is built using the format http://. The ToHttpAddress function provides the address to be used, but the crucial part is that it forces HTTP, regardless of whether TLS is enabled or disabled. This is where the configuration needs adjustment to support either HTTP or HTTPS, depending on your setup.

The Solution: Configuring HTTP Communication

Given the mTLS setup, there are two primary approaches to tackle this issue:

1. Configure S3 to use HTTPS: The simplest solution. Configure the S3 endpoint to use HTTPS when communicating with the Filer. This requires the proper certificate setup. In the configuration for the S3 server, specify HTTPS protocol and point to the Filer's HTTPS address and port. Ensure that S3 and the Filer both trust the same Certificate Authority (CA) if you are not using a public CA. Update the S3 configuration to point to the Filer's HTTPS address. The S3 server will then be able to communicate with the Filer.

2. Ensure HTTP Communication: Configure the S3 endpoint and the Filer to use HTTP. Make sure the Filer accepts HTTP connections.

Modifying the toFilerUrl function (If Needed)

In some situations, you might need to modify the toFilerUrl function. This would involve ensuring the URL protocol (HTTP or HTTPS) is determined dynamically based on your configuration. This is necessary if you need to be able to switch between HTTP and HTTPS without changing the code every time.

For example:

1. Configuration Parameter: Add a configuration option to specify whether to use HTTP or HTTPS. This might be a simple boolean value, such as UseHTTPS. The configuration option allows you to select whether to use HTTP or HTTPS. This adds flexibility.

2. Conditional URL Construction: Modify the toFilerUrl function to check this configuration parameter. Then, construct the URL with either http:// or https:// accordingly. The function will generate an HTTP or HTTPS URL according to the configuration.

var destUrl string
if s3a.option.UseHTTPS {
    destUrl = fmt.Sprintf("https://%s%s/%s%s", s3a.option.Filer.ToHttpAddress(), s3a.option.BucketsPath, bucket, object)
} else {
    destUrl = fmt.Sprintf("http://%s%s/%s%s", s3a.option.Filer.ToHttpAddress(), s3a.option.BucketsPath, bucket, object)
}

Key Steps to Resolution

• Configuration: Verify your SeaweedFS configuration files for both the S3 endpoint and the Filer. Confirm that the S3 endpoint's configuration correctly specifies the Filer's address and port. Be sure that ToHttpAddress is returning the correct protocol.

• mTLS Setup: Ensure that your mTLS setup is correctly configured, including the generation and distribution of certificates and keys for all components. If you are using mTLS, make sure the S3 endpoint's configuration is also updated to use HTTPS.

• Restart and Test: After making any configuration changes, restart your SeaweedFS containers. Test your file upload through the S3 endpoint to confirm that the issue is resolved.

Further considerations

• Security Implications: If you choose HTTP communication between the S3 endpoint and the Filer, be aware of the security implications. Data transmitted over HTTP is not encrypted and is vulnerable to eavesdropping. Ensure that your network is secure and that you understand the risks.

• Load Balancing and Reverse Proxies: If you are using load balancing or reverse proxies in your SeaweedFS setup, ensure that they are correctly configured to handle HTTP or HTTPS traffic, depending on your chosen solution.

Conclusion

Resolving the HTTP to HTTPS mismatch between your SeaweedFS S3 endpoint and Filer is essential for a smooth operation. By understanding the root cause and implementing the appropriate configuration changes, you can ensure your data uploads work correctly and your system functions as intended. Always prioritize security, and consider the implications of your configuration choices. I hope this guide helps you in setting up your SeaweedFS.

For additional support and more in-depth discussions on SeaweedFS, feel free to visit the SeaweedFS documentation. This is a great resource to get more information and troubleshooting guides.

If you are still struggling with this configuration, please visit the SeaweedFS GitHub repository for more support. You might find a solution or be able to discuss with the SeaweedFS developers.