CODEWITHSUNDEEP
algorithmload-balancing
Vinoth Kumar C M
Vinoth Kumar C M

Reputation: 10618

Finding the least loaded server

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 ?

Upvotes: 5

Views: 1143

Answers (2)

JRideout
JRideout

Reputation: 1635

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)

Upvotes: 5

James
James

Reputation: 8586

Basically, compute a relative cost to serve on each of the servers, and over some small fixed period, sum the total cost of the requests sent to said server. Something like:

Cost_A = 20/50
Cost_B = 20/30
Cost_C = 20/20

Running_Total_A = 0 
Running_Total_B = 0
Running_Total_c = 0

while true: 
   If One minute has passed:
     Running_Total_A = 0 
     Running_Total_B = 0
     Running_Total_c = 0

   IF (Min(Running_Total_A,Running_Total_B,Running_Total_C) == Running_Total_A):
     Running_Total_A += Cost_A
     RouteTo(A)
   ELSE IF (Min(Running_Total_A,Running_Total_B,Running_Total_C) == Running_Total_B):
     Running_Total_B += Cost_B
     RouteTo(B)
   ELSE IF (Min(Running_Total_A,Running_Total_B,Running_Total_C) == Running_Total_C):
     Running_Total_C += Cost_C
     RouteTo(C)

Upvotes: 2

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