When Protocols Clash: Debugging a Broken Gateway in a Service Mesh

Intro

For enterprises relying on complex microservice architectures, misconfigurations in traffic management can disrupt operations, leading to customer dissatisfaction and loss of revenue. Our client faced just such a challenge, and resolving it swiftly was vital for their business continuity.

Problem Statement

The client, an enterprise running Tetrate Service Bridge (TSB) in a service mesh setup, reported a critical issue: traffic was not flowing through their tier1 gateway. Logs indicated repeated HTTP/1.1 400 errors with http1.codec_error, pointing to downstream HTTP protocol errors. This failure disrupted their service availability, as critical applications relying on this gateway became unreachable. The misconfiguration not only risked SLA violations but also impacted their ability to scale seamlessly within their internal and external networks. As the gateway is central to their architecture, resolving this issue was imperative to avoid further operational bottlenecks.

Solution

Initial Investigation:

Our team started by reviewing the client’s configuration and collected diagnostic data using tools like tctl collect and Kubernetes resources (kubectl get ingress and kubectl get svc). Analysis revealed that tier1 gateway logs were showing downstream protocol errors, while tier2 gateway logs were clean. This pointed to an issue localized to tier1.

Hypotheses Formulation:

• The tier1 gateway lacked TLS configuration, but the client was sending HTTPS traffic.
• A possible load balancer (LB) misconfiguration might be incorrectly terminating TLS or using an incompatible protocol.

Step-by-Step Troubleshooting:

• Protocol Alignment: We hypothesized that a load balancer (LB) between the client and tier1 gateway might be misconfigured. Specifically, it was suspected that the LB was terminating TLS but sending encrypted requests to tier1, which expected plain HTTP traffic.
• Configuration Review: We reviewed the LB configuration and confirmed that the external LB was indeed terminating TLS and forwarding encrypted traffic to tier1 on port 443. However, tier1 was configured to accept plain HTTP traffic only, causing protocol mismatches and subsequent errors.
• Verification Using Netshoot: To validate our theory, we deployed a netshoot pod within the same cluster as tier1. Running a curl command using plain HTTP traffic to tier1 verified that tier1 worked correctly when TLS was not involved.
• AWS Target Group Update: Inspection of the AWS Target Group configuration showed that the protocol was set to “TLS” instead of “TCP” for tier1. This configuration conflicted with tier1’s setup. We updated the protocol to “TCP” and retested the flow.
• Resolution Testing: After updating the protocol and ensuring consistency across LB and gateway configurations, traffic started flowing seamlessly through the tier1 gateway.

Time to Resolution:

The issue was diagnosed, a solution was implemented, and traffic was restored within a single day of collaborative troubleshooting between our team and the client.

Results

The solution resolved the issue, restoring uninterrupted traffic flow through the tier1 gateway. The client successfully met their SLA obligations, preventing operational downtime. This swift resolution saved hours of potential troubleshooting for their internal teams and ensured smooth application functionality, reinforcing their confidence in Tetrate’s support.