Delayed Horizontal Pod Scaling During Peak Load

HPA scaled too slowly during a traffic surge, leading to application unavailability.

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What Happened

During a peak load event, HPA failed to scale pods quickly enough to meet the demand, causing slow response times and eventual application downtime.

Diagnosis Steps

1Checked HPA metrics and found that it was using average CPU utilization as the scaling trigger, which was too slow to respond to spikes.
2Analyzed the scaling history and observed that scaling events were delayed by over 5 minutes.

Root Cause

Insufficiently responsive HPA trigger settings and outdated scaling thresholds.

Fix/Workaround

• Adjusted HPA trigger to use both CPU and memory metrics for scaling.
• Reduced the scaling thresholds to trigger scaling actions more rapidly.

Lessons Learned

Scaling based on a single metric can be inadequate during peak loads, especially if there is a delay in detecting resource spikes.

How to Avoid

1Use multiple metrics to trigger HPA scaling, such as CPU, memory, and custom application metrics.
2Set more aggressive scaling thresholds for high-traffic scenarios.