Weighted Load Distribution Calculator

Turn pool member weights into request shares, per-pool request counts and the weighted round-robin cycle length.

About Weighted Load Distribution Calculator

Weighted round robin hands out one request per unit of weight, so a member with weight 5 in a pool summing to 10 receives half the traffic. The pattern repeats once the sum of the weights has been dispensed, which is why the cycle length matters for short bursts. Weights are how you mix server generations in one pool or ramp a canary, but the cycle length means a burst shorter than the sum of the weights will not honour the ratio at all.

Formula

Weighted Load Distribution

share of member i = weight_i ÷ Σ weights; requests to member i = total requests × share; the WRR cycle repeats every Σ weights requests.

Σ weights: Sum of all pool member weights, which is also the cycle length
share: Long-run proportion of requests a member receives

Worked example

With the default values below, Weighted Load Distribution Calculator returns Weighted Round-Robin Cycle Length of 10. Change any input above and every figure here is recalculated in your browser.

Inputs used

Weight of pool member Aaccepts 0–256: 5
Weight of pool member Baccepts 0–256: 3
Weight of pool member Caccepts 0–256: 2
Requests to distributeaccepts 1–1,000,000,000 requests: 60,000 requests

Results

Weighted Round-Robin Cycle Length: 10 requests
Share to Member A: 50.00%
Share to Member B: 30.00%
Share to Member C: 20.00%
Requests to Member A: 30,000
Requests to Member B: 18,000
Requests to Member C: 12,000

Step by step

1Values used
2Weighted Load Distribution
3Weighted Round-Robin Cycle Length= 10 requests
4Share to Member A= 50.00
5Share to Member B= 30.00
6Share to Member C= 20.00
7Requests to Member A= 30,000
8Requests to Member B= 18,000

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, 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 Weighted Load Distribution calculated?

share of member i = weight_i ÷ Σ weights; requests to member i = total requests × share; the WRR cycle repeats every Σ weights requests. Weighted round robin hands out one request per unit of weight, so a member with weight 5 in a pool summing to 10 receives half the traffic. The pattern repeats once the sum of the weights has been dispensed, which is why the cycle length matters for short bursts.

Why does Weighted Load Distribution matter?

Weights are how you mix server generations in one pool or ramp a canary, but the cycle length means a burst shorter than the sum of the weights will not honour the ratio at all.

What values do I need to enter?

This calculator takes 4 inputs: Weight of pool member A, Weight of pool member B, Weight of pool member C, Requests to distribute. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.