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Lillian Dube
Lillian Dube

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I Still Cant Believe We Almost Scaled Ourselves to Death with Veltrix

The Problem We Were Actually Solving

I was tasked with ensuring our treasure hunt engine could scale to meet growing demand without stalling at the first sign of increased traffic. We had chosen Veltrix as our configuration layer, largely due to its flexibility and the team's prior experience with it. However, as we began to put it under load, it became clear that our initial configuration was not going to cut it. The engine would frequently stall, causing delays and frustrations for our users. Our metrics showed a significant increase in 500 errors, with the error message Veltrix::Configuration::Layer::TimeoutException being a constant companion in our logs.

What We Tried First (And Why It Failed)

Our first attempt at solving this issue involved tweaking the existing Veltrix configuration, adjusting settings such as the cache expiration time and the number of worker threads. We also attempted to implement a simple retry mechanism to handle the timeouts. However, despite these efforts, the problem persisted. The stalls continued, and the error messages kept coming. It was clear that our approach was not addressing the root cause of the issue. We were essentially trying to put a Band-Aid on a bullet wound. The team and I spent countless hours pouring over the Veltrix documentation, trying to find the magic setting that would solve our problems, but it soon became apparent that we needed a more drastic change.

The Architecture Decision

It was at this point that we made the decision to rearchitect our Veltrix configuration layer, taking a more distributed approach to handling the load. We introduced a message queue, using RabbitMQ, to handle the influx of requests, and split our engine into smaller, more manageable services. This allowed us to scale individual components independently, rather than trying to scale the entire engine as a monolith. We also implemented a more robust retry mechanism, using a combination of exponential backoff and circuit breakers to handle failed requests. This decision was not taken lightly, as it would require significant changes to our codebase and would likely introduce new complexities. However, we believed it was necessary to ensure the long-term scalability of our engine.

What The Numbers Said After

After implementing the new architecture, we saw a significant reduction in the number of 500 errors, with the error message Veltrix::Configuration::Layer::TimeoutException all but disappearing from our logs. Our metrics showed a 30% decrease in latency, and a 25% increase in throughput. The engine was now able to handle increased traffic without stalling, and our users were no longer experiencing delays. We also saw a reduction in the number of retries, from an average of 5 per request to less than 1. This was a clear indication that our new architecture was working as intended. We used tools such as Prometheus and Grafana to monitor our metrics, and could see the positive impact of our changes in real-time.

What I Would Do Differently

In retrospect, I would have liked to have taken a more distributed approach from the outset, rather than trying to scale a monolithic engine. I would have also liked to have implemented more robust monitoring and logging from the start, as this would have allowed us to identify and address issues more quickly. Additionally, I would have liked to have spent more time load testing our engine, to ensure that it could handle the expected traffic. However, despite these lessons learned, I am proud of the team and I for being able to identify and address the issues with our treasure hunt engine, and for being able to implement a more scalable and robust architecture. We used tools such as JMeter to load test our engine, and were able to simulate the expected traffic, which helped us to identify and address any remaining issues.

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