Epsilon-Greedy seems an odd choice for a load-balancer #2

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1. jehiah commented on May 9, 2013

   

   jehiah

   on May 9, 2013

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   Interesting. This does sounds like it might have some useful properties. I'd love to see how this works out if you get a prototype implemented.

   The Epsilon-Greedy is certainly an experiment, and it's on our to-do list to describe some of how that has worked in a few select cases at bitly. There are lots of cases where it's useless, but we've found at least one where it's very valuable.
2. dgryski commented on May 10, 2013

   

   dgryski

   on May 10, 2013

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   Since epsilon greedy already has all the time tracking, the 'easiest' way to prototype this is just to directly replace the loop that does the selection that begins "if len(possibleHosts) != 0" near epsilon_greedy.go:130 . Note this is completely untested, but it does compile :)

       switch n := len(possibleHosts); n {
       case 0:
           hostToUse = nil
       case 1:
           hostToUse = possibleHosts[0]
       default: // n > 0
   
               idx1 := rand.Intn(n)
               h1 := possibleHosts[idx1]
               // remove h1 from list of hosts -- sample without replacement
               n--
               possibleHosts[idx1] = possibleHosts[n]
               possibleHosts = possibleHosts[:n]
   
               idx2 := rand.Intn(n)
               h2 := possibleHosts[idx2]
   
               if h1.epsilonValue > h2.epsilonValue {
                   hostToUse = h1
               } else {
                   hostToUse = h2
               }
       }
   

   I'll unfortunately be unable to tes this further right now. I won't have time to play with this until closer to the end of May.
3. dgryski commented on Jul 23, 2014

   

   dgryski

   on Jul 23, 2014

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   Just realized I never came back to play with this. I still think this change makes sense. Not sure how to test this to see if it actually gives more evenly distributed load though..