Plan a canary traffic split on the load balancer: canary load, capacity headroom, error-rate delta and whether to widen or roll back.
The split is a weighted distribution, so the canary receives the weight times the total rate and must have the capacity to serve it. Comparing the canary's error rate to the stable pool over a fixed window turns the split into a pass/fail signal, with the sample size shown so you can judge whether the difference is meaningful. Most canary rollbacks are triggered by a canary pool that was simply too small for its weight, so separating a capacity problem from a code problem is the whole point of checking utilisation alongside the error delta.
ADC Traffic Split
canary rate = total rate × weight; maximum safe weight = canary capacity ÷ total rate; error delta = canary error rate − stable error rate.
canary rate = total rate × weight; maximum safe weight = canary capacity ÷ total rate; error delta = canary error rate − stable error rate. The split is a weighted distribution, so the canary receives the weight times the total rate and must have the capacity to serve it. Comparing the canary's error rate to the stable pool over a fixed window turns the split into a pass/fail signal, with the sample size shown so you can judge whether the difference is meaningful.
Most canary rollbacks are triggered by a canary pool that was simply too small for its weight, so separating a capacity problem from a code problem is the whole point of checking utilisation alongside the error delta.
This calculator takes 6 inputs: Total request rate, Weight routed to the canary, Canary pool capacity, Canary error rate, Stable error rate, Observation window. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.