Finding the least loaded server

Question

Given three servers which A , B , C in which A can handle 50% of the traffic , B can handle 30% of the traffic and C can handle 20% of the traffic come up with a formula to distribute load efficiently. The current load of the servers is also an input to the function.

I could not come up with the "formula" he is asking for. Is there any specific answer to this question ?

Answer 1

There are a few different ways to distribute load that might be applicable here.

Case 1. Random assignment biased proportionally to each servers load:

for each request
  let x = uniformly distributed random number between 0 and 1
  if x <= 0.5
    goto A
  else if x <= 0.8
    goto B
  else
    goto C

Case 2. Round-Robin biased proportionally to each servers load:

let x = new list
push A on x 5 times
push B on x 3 times
push C on x 2 times

for each request
  y = pop x
  goto y
  push y to back of x

Case 3. Forget about the supposed capacity and poll for current load

let La = A, load of A
let Lb = B, load of B
let Lc = C, load of C

goto argmin (La,Lb,Lc)