ADC Traffic Split Calculator

Plan a canary traffic split on the load balancer: canary load, capacity headroom, error-rate delta and whether to widen or roll back.

About ADC Traffic Split Calculator

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.

Formula

ADC Traffic Split

canary rate = total rate × weight; maximum safe weight = canary capacity ÷ total rate; error delta = canary error rate − stable error rate.

share: Fraction of traffic the load balancer sends to the new version
errorDelta: Difference in percentage points, the signal a canary exists to produce

Worked example

With the default values below, ADC Traffic Split Calculator returns Request Rate to the Canary of 400.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Total request rateaccepts 1–10,000,000 rps: 8,000 rps
Weight routed to the canaryaccepts 0–100 %: 5 %
Canary pool capacityaccepts 1–10,000,000 rps: 600 rps
Canary error rateaccepts 0–100 %: 0.8 %
Stable error rateaccepts 0–100 %: 0.2 %
Observation windowaccepts 1–10,080 minutes: 30 minutes

Results

Request Rate to the Canary: 400.0 rps
Request Rate to the Stable Pool: 7,600.0 rps
Canary Pool Utilisation: 66.7%
Maximum Weight the Canary Can Absorb: 7.5%
Error-Rate Delta vs Stable: 0.60 percentage points
Errors Observed in the Window: 5,760
Release Decision: Roll back — the canary is more than 0.5 points worse than stable

Step by step

1Values used
2ADC Traffic Split
3Request Rate to the Canary= 400.0 rps
4Request Rate to the Stable Pool= 7,600.0 rps
5Canary Pool Utilisation= 66.7
6Maximum Weight the Canary Can Absorb= 7.5
7Error-Rate Delta vs Stable= 0.60 percentage points
8Errors Observed in the Window= 5,760

Assumptions and limits

The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is ADC Traffic Split calculated?

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.

Why does ADC Traffic Split matter?

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.

What values do I need to enter?

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.