Fixing Prometheus Basic Auth In Homer: A Guide

Hey guys! Ever run into a snag where your Prometheus setup in Homer just won't play nice with basic_auth? It's a classic head-scratcher, and I'm here to walk you through it. This guide dives deep into why the Prometheus service type in Homer doesn't seem to include the vital Authorization header when making API requests, even when you've painstakingly configured basic_auth. We'll explore the issue, compare it with how the Traefik service type handles things, and offer some insights into potential solutions. Buckle up, let's get into it!

The Prometheus Authorization Header Conundrum: What's the Deal?

So, the crux of the problem lies in the Prometheus service type within Homer. When you've set up basic_auth to secure your Prometheus instance, you'd expect the necessary Authorization header to tag along with every API request, right? That's how it should work to get past that login screen, but for some reason, the Prometheus type seems to be dropping the ball. This is in stark contrast to the Traefik service type, which, thankfully, does include the Authorization header as it should. This discrepancy means that while your Traefik dashboard, for instance, might be happily displaying your metrics, your Prometheus instance is locked out, throwing a frustrating 401 Unauthorized error.

Let's break down the scenario. You've got your Homer config set up something like this:

- name: "Prometheus"
  type: "Prometheus"
  url: "https://prometheus.example.com"
  basic_auth: "admin:password"

- name: "Traefik Dashboard"
  type: "Traefik"
  url: "https://traefik.example.com"
  basic_auth: "admin:password"

With this configuration, the expected behavior is that both the Prometheus and Traefik services should send an Authorization header with the request, containing your admin:password credentials in a base64 encoded format. In reality, though, what happens is:

• Traefik: Sends an OPTIONS preflight request (for CORS), then the GET request with the Authorization header, and gets a ✅ 200 OK.
• Prometheus: Sends a simple GET request, but without the Authorization header, resulting in a ❌ 401 Unauthorized error.

This discrepancy is the core issue. The Prometheus service type isn't properly including the necessary authentication information, which is a significant problem if you're trying to keep your monitoring setup secure.

This isn't a CORS preflight issue (like in PR #949); the Authorization header is simply not being sent in the first place. The server is correctly returning CORS headers on 401 responses, which suggests the issue is purely on the client-side – Homer's handling of the Prometheus service type.

This is a real pain, especially when your goal is to have a centralized and secure dashboard. Don't worry, we'll get into potential solutions and workarounds later on. Keep reading, guys!

Deep Dive: Comparing Traefik and Prometheus Service Types

Let's take a closer look at how Traefik and Prometheus services differ in Homer and why this difference matters when it comes to basic_auth. The key difference lies in how each service type handles outgoing API requests and how they manage the Authorization header. This is where the magic (or the lack thereof) happens.

The Traefik service type is built in a way that it correctly incorporates the configured basic_auth credentials. When Homer makes a request to your Traefik dashboard, it automatically includes the Authorization header, using the credentials provided in your configuration. This is usually implemented by injecting the Authorization header directly into the request headers before the request is sent. This proactive approach ensures that the credentials are sent from the start, which is a standard method to authenticate HTTP requests. This way, your Traefik dashboard can load without any authentication errors.

On the other hand, the Prometheus service type doesn't follow the same pattern. For whatever reason in the Homer codebase, the Authorization header isn't included when the request is constructed. This means that when Homer tries to fetch data from your Prometheus instance, it's essentially sending an unauthenticated request. This, of course, results in the dreaded 401 Unauthorized error, because your Prometheus server is expecting credentials that it never receives.

To see this in action, you can use your browser's developer tools (Network tab). You'll notice that the Traefik requests have an Authorization header (with a value looking something like Basic <base64-encoded credentials>), while the Prometheus requests are missing it completely. This simple check gives you a visual confirmation of the problem. You can see the OPTIONS preflight request and the subsequent GET request. The preflight check is the browser's way of checking the allowed methods and headers for cross-origin requests.

Why this difference exists is likely due to how the service types are implemented in Homer. It could be a simple oversight or a difference in how the HTTP client is configured for each type. Whatever the cause, this difference highlights the need to find a workaround or a fix to ensure that Prometheus instances are properly authenticated in Homer. The fix may involve modifying the code of the Prometheus service type to ensure the Authorization header is included with the request, the same way as the Traefik service type.

Troubleshooting and Potential Solutions for Prometheus Basic Auth

Alright, so you're staring at that 401 error, and you want to fix it, right? Let's get into some ways you can potentially address the Prometheus basic_auth issue within Homer. Keep in mind, these are workarounds, not perfect solutions, until the underlying issue is fixed. There is no easy fix.

1. Manual Authorization Header in Reverse Proxy: If you're running a reverse proxy in front of your Prometheus instance (like Nginx or Traefik), you could configure the proxy to handle the authentication. This means you'd configure the proxy to add the Authorization header before forwarding the request to your Prometheus server. This shifts the authentication burden to the proxy, which is a common practice. You would configure the proxy to handle the authorization header and forward the request to the Prometheus instance. The proxy will then handle the basic_auth for you, so your Homer configuration remains unchanged. This will give you the chance to see the Prometheus metrics.

   • Pros: Relatively straightforward if you're already using a reverse proxy; doesn't require changes to Homer code.
   • Cons: Adds complexity to your proxy configuration; requires an additional layer of setup.

2. Feature Request or Code Contribution: The best solution is to fix the Prometheus service type directly within Homer. You could consider creating a feature request on the Homer GitHub repository or, even better, contribute a code change yourself. This would involve modifying the code to include the Authorization header when making requests to Prometheus. This is probably the most effective, but also the most involved, as it requires understanding the Homer codebase and submitting a pull request.

   • Pros: Addresses the root cause of the issue; improves Homer functionality for everyone.
   • Cons: Requires coding skills and familiarity with the project's contribution guidelines.

3. Using API Keys (If Applicable): Some Prometheus setups support authentication via API keys. If your setup allows it, consider using an API key instead of basic_auth. This might be a simpler workaround, as you could potentially include the API key in the URL or request headers (depending on how your Prometheus instance is configured). Check to see if your Prometheus instance supports an API key, then configure it in your Homer configuration.

   • Pros: Potentially easier to implement than a reverse proxy; might be supported out-of-the-box by Homer.
   • Cons: Requires support for API keys in your Prometheus instance; might not be as secure as basic_auth.

4. Community Forums: Engage with the Homer community. The maintainers and other users might have come across similar issues and already have a solution. Check their forums, GitHub Discussions, or other community channels. Ask questions, and share your findings. You can use their forums to learn if there's someone else having the same issue.

   • Pros: Helps you find new solutions; connect with other users that have the same issue.
   • Cons: Requires time spent going through forums.

Each of these solutions has its trade-offs. The best approach depends on your specific setup, technical skills, and preferences. Until a proper fix is implemented in Homer, these are your options to get that Prometheus data flowing into your dashboard!

Conclusion and Next Steps for Basic Auth

So, there you have it, guys. We've dug deep into the Prometheus and basic_auth conundrum within Homer. We've pinpointed the issue – the missing Authorization header – and contrasted it with the working Traefik implementation. We've also explored several potential workarounds, including reverse proxies, API keys, and the option to contribute to the Homer project itself. Remember, the ultimate goal is to get your Prometheus metrics displayed securely and reliably in your Homer dashboard.

What should you do next? Well, depending on your comfort level and technical skills, here are a few suggestions:

• Evaluate your current setup: Start by assessing your current infrastructure. Do you have a reverse proxy? Does your Prometheus instance support API keys? This will help you decide which workaround is best for you.
• Test and experiment: Try out the different solutions. Experiment with setting up a reverse proxy or configuring API keys. See which one works best in your environment. Test, test, test.
• Contribute to Homer: Consider contributing to the Homer project. If you have the skills, submit a pull request with a fix for the Prometheus service type. This is the best way to ensure the issue is resolved for everyone.
• Stay informed: Keep an eye on the Homer GitHub repository and community forums. The issue might get addressed in a future update. Stay updated on the latest developments.

I hope this guide has been helpful, guys. Don't let this minor setback keep you from enjoying your fully functional, secure Homer dashboard! With a little bit of effort, you can overcome this challenge and get those Prometheus metrics looking amazing. Happy monitoring! Good luck! Remember, we are here to help.