Grafana V11.6.4 TLS Timeout: Troubleshooting Valid Certificates

by Rajiv Sharma 64 views

Hey everyone, ever run into a TLS handshake timeout issue with Grafana, especially when you're using valid CA-signed certificates? It's a head-scratcher, right? This article dives into a peculiar problem reported with Grafana v11.6.4 where connections to Prometheus data sources fail despite having perfectly valid SSL certificates. We’ll break down the issue, explore potential causes, and discuss how to troubleshoot it. Let’s get started!

Understanding the TLS Handshake Timeout Issue

The core problem? Grafana v11.6.4 throws a net/http: TLS handshake timeout error when trying to connect to Prometheus endpoints that are secured with valid CA-signed SSL certificates. Now, you might think, "Okay, maybe it's a certificate issue." But here’s the twist: this happens even when the “Skip TLS Verification” option is enabled in the data source configuration. It’s like Grafana is stubbornly refusing to trust these certificates, despite being told it’s okay to ignore verification.

What makes this even weirder is that the same Grafana instance can happily connect to endpoints with self-signed or invalid certificates – you know, the ones that make your browser scream “Not Secure!” It's paradoxical! The endpoints themselves are properly exposed via Kubernetes Ingress with valid TLS certificates and work perfectly fine with other tools. So, the certificates are valid and working.

Why Valid Certificates Matter

Before we dive deeper, let’s quickly touch on why valid certificates are crucial. Certificates issued by trusted Certificate Authorities (CAs) provide a level of assurance that the server you're connecting to is who it claims to be. This is essential for secure communication over HTTPS. When Grafana (or any client) can't establish trust, you get errors like the TLS handshake timeout.

The Unexpected Behavior

So, to recap, we've got Grafana failing to connect to validly secured endpoints while happily connecting to insecure ones. This is the opposite of what we’d expect and points to a potential bug or misconfiguration within Grafana itself.

Expected Behavior vs. Reality

Ideally, Grafana should smoothly establish connections to Prometheus endpoints that use valid CA-signed SSL certificates. This is the standard behavior we expect from any application dealing with HTTPS connections. If, for some reason, there were certificate issues, the “Skip TLS Verification” option should bypass those checks, allowing the connection to proceed (though, of course, with reduced security).

The Regression: A Step Backwards

Here’s another crucial piece of the puzzle: this issue wasn’t always present. Users have reported that everything worked flawlessly in Grafana v7 with the same endpoints and identical CA-signed SSL certificates. This strongly suggests that the problem was introduced somewhere between v7 and v11.6.4. Such regressions are frustrating because they break previously working setups and can be tricky to diagnose.

Reproducing the Issue: A Step-by-Step Guide

To really nail down a problem, it’s essential to be able to reproduce it consistently. Here’s how you can recreate this TLS handshake timeout issue:

  1. Set up a Prometheus Endpoint: First, you’ll need a Prometheus instance secured with a valid CA-signed SSL certificate. A common setup involves using Kubernetes Ingress with proper TLS configuration. This means your Ingress controller (like Nginx or Traefik) handles the SSL termination, presenting a valid certificate to clients.
  2. Configure Grafana: In Grafana v11.6.4, navigate to Configuration > Data Sources in the sidebar.
  3. Add a New Prometheus Data Source: Click the “Add data source” button and select “Prometheus”.
  4. Specify the URL: Enter the HTTPS endpoint of your Prometheus instance (e.g., https://prometheus.example.com).
  5. Test with and without TLS Verification:
    • Try connecting with “Skip TLS Verification” enabled.
    • Then, try again with it disabled.
  6. Save & Test: Click the “Save & Test” button at the bottom of the page.
  7. Observe the Error: If you’re encountering the issue, you should see the dreaded net/http: TLS handshake timeout error message.

The Key Observation

Remember, the crucial part is that these steps work perfectly fine with endpoints that use self-signed or invalid certificates. This highlights the specific problem with valid CA-signed certificates.

Environment Details: The Crime Scene Investigation

To effectively debug any issue, it’s essential to gather as much information about the environment as possible. Here are the key details relevant to this TLS handshake timeout problem:

  • Grafana Version: v11.6.4 (This is the version where the issue is confirmed.)
  • Data Source: Prometheus (The specific data source experiencing the problem.)
  • Deployment: Kubernetes with Ingress TLS termination (The infrastructure setup.)
  • Certificate Type: Valid CA-signed SSL certificates (The type of certificates causing the issue.)
  • Previous Working Version: Grafana v7 (This helps pinpoint when the issue was introduced.)

Additional Environmental Factors

While the above details are the primary ones, other factors might also play a role. These could include:

  • Operating System: The OS Grafana is running on (e.g., Linux, Windows, macOS).
  • Containerization: Whether Grafana is running in a container (e.g., Docker) and the container runtime used.
  • Networking: Any network proxies or firewalls that might be interfering with the connection.
  • Certificate Authority: The specific CA that issued the certificates (e.g., Let's Encrypt, DigiCert).

Potential Causes and Troubleshooting Steps

Now that we have a clear understanding of the issue and the environment, let’s explore some potential causes and how to troubleshoot them.

  1. TLS Protocol Mismatch:

    • The Problem: Grafana might be trying to negotiate a TLS protocol version that the Prometheus endpoint doesn’t support (or vice-versa). For example, Grafana might be configured to use TLS 1.3, while the endpoint only supports TLS 1.2.
    • Troubleshooting:
      • Check TLS Versions: Examine the TLS configuration of both Grafana and your Prometheus endpoint. Look for any explicit settings that might be enforcing a specific TLS version.
      • Grafana Configuration: You can try setting the GF_SERVER_TLS_MIN_VERSION and GF_SERVER_TLS_MAX_VERSION environment variables in Grafana to control the TLS versions it uses. For example, setting both to TLS1.2 might resolve the issue if there’s a problem with TLS 1.3 negotiation.
      • Prometheus Configuration: Review the Prometheus server’s command-line flags or configuration file for TLS settings.

  2. Cipher Suite Mismatch:

    • The Problem: Similar to TLS protocol versions, Grafana and the Prometheus endpoint need to agree on a cipher suite – the encryption algorithms used for the TLS connection. If there’s no overlap in supported cipher suites, the handshake will fail.
    • Troubleshooting:
      • Inspect Cipher Suites: Use tools like openssl to inspect the cipher suites supported by both Grafana and the Prometheus endpoint.
      • Grafana Configuration: Grafana doesn’t directly expose cipher suite configuration. However, the underlying Go TLS library it uses has default cipher suites. If necessary, you might need to investigate custom builds or patches to modify these defaults (which is generally not recommended unless you’re an expert).
      • Prometheus Configuration: Prometheus might allow you to specify a list of preferred cipher suites.

  3. Intermediate Certificate Issues:

    • The Problem: A valid CA-signed certificate relies on a chain of trust, which includes intermediate certificates. If these intermediate certificates aren’t properly configured on the server (Prometheus endpoint), clients like Grafana might not be able to verify the certificate.
    • Troubleshooting:
      • Certificate Chain Verification: Use online tools or the openssl command to verify the certificate chain of your Prometheus endpoint. Ensure that all intermediate certificates are present and valid.
      • Server Configuration: Make sure your web server (e.g., Nginx, Apache) is configured to serve the complete certificate chain, including the intermediate certificates.

  4. Network Issues:

    • The Problem: While less likely given the specific behavior (working with self-signed certificates), network issues like firewalls or proxies could still be interfering with the TLS handshake.
    • Troubleshooting:
      • Firewall Rules: Check firewall rules between Grafana and the Prometheus endpoint to ensure that traffic on port 443 (or the port you’re using for HTTPS) is allowed.
      • Proxy Configuration: If you’re using a proxy, ensure that Grafana is configured to use it correctly and that the proxy is not interfering with TLS connections.

  5. Grafana Bug:

    • The Problem: Given that the issue appeared between v7 and v11.6.4, there’s a strong possibility that a bug in Grafana’s TLS handling is the root cause. The fact that “Skip TLS Verification” doesn’t seem to be working as expected further supports this theory.
    • Troubleshooting:
      • Check Grafana Issues: Search the Grafana GitHub repository for existing issues related to TLS handshake timeouts or certificate problems. Someone else might have already reported the same issue.
      • Report a New Issue: If you can’t find an existing issue, create a new one, providing as much detail as possible (including the steps to reproduce, environment details, and any troubleshooting steps you’ve already taken).
      • Downgrade Grafana: As a temporary workaround, you could consider downgrading to a previous version of Grafana (e.g., v7) where the issue wasn’t present.

Workarounds and Temporary Solutions

While we aim for a permanent fix, sometimes temporary solutions are necessary to keep things running. Here are a few workarounds you might consider:

  • Downgrade Grafana: If possible, downgrading to a previous version (like v7) where the issue didn’t exist can be a quick way to restore functionality. However, keep in mind that you’ll be missing out on any new features or security patches in the newer versions.
  • Use Self-Signed Certificates (Not Recommended for Production): As a temporary measure, you could switch to using self-signed certificates on your Prometheus endpoint. Grafana seems to be connecting to these without issues. However, this is not recommended for production environments as self-signed certificates don’t provide the same level of security as CA-signed certificates.
  • Investigate Reverse Proxy Configuration: If you're using a reverse proxy in front of Grafana, double-check its configuration. Ensure it's not stripping or altering the TLS connection in a way that causes Grafana to misinterpret the certificate.

Conclusion: Hunting Down the Timeout

The net/http: TLS handshake timeout error in Grafana v11.6.4 with valid CA-signed certificates is a tricky issue, but by systematically investigating potential causes – from TLS protocol mismatches to Grafana bugs – we can work towards a solution. Remember to gather detailed environment information, try the reproduction steps, and check for existing issues or report new ones. Let’s keep the Grafana dashboards shining brightly!

Have you encountered this issue? Share your experiences and troubleshooting tips in the comments below!