架构师训练营第五周 - 作业

(def m (math/expt 2 32))

(defn consistent-hash [x number-of-nodes]
  (math/ceil (/ (mod x m) (int (/ m number-of-nodes)))))

(ns consistent-hash.core
  (:require [clojure.math.numeric-tower :as math]
            )
  )

(def m (math/expt 2 32))

(defn consistent-hash [x number-of-nodes]
  (math/ceil (/ (mod x m) (int (/ m number-of-nodes)))))

(defn average [num-seq]
  (/ (apply + num-seq) (count num-seq)))

(defn standard-deviation [num-seq]
  (let [avg (average num-seq)]
    (->> (map (fn [x]
                (let [n (math/abs (- x avg))]
                  (* n n)
                  )
                ) num-seq)
         average
         math/sqrt
         )
    )
  )

(defn -main [& args]
  (dotimes [n 10]
    (let [number-of-nodes 10
          times 1000000
          hash-values  (repeatedly times (fn [] (consistent-hash (long (rand m)) number-of-nodes)))
          loads (sort (reduce (fn [ret node] (update ret node inc)) (zipmap (range 1 (inc number-of-nodes)) (repeat 0)) hash-values))
          ]
      (println "Test" (inc n))
      (println "Server load: " loads)
      (println "Standard deviation: " (standard-deviation (map second loads)))
      )
    )
  )


consistent-hash on  master [!]
➜ lein run
Test 1
Server load:  ([1 99935] [2 99672] [3 100057] [4 100364] [5 100368] [6 99835] [7 99740] [8 99855] [9 100260] [10 99914])
Standard deviation:  239.5462377078797
Test 2
Server load:  ([1 100346] [2 99479] [3 99432] [4 99978] [5 100362] [6 99822] [7 100190] [8 100146] [9 99852] [10 100393])
Standard deviation:  333.28096255261863
Test 3
Server load:  ([1 99890] [2 99895] [3 99926] [4 99823] [5 99989] [6 99659] [7 100480] [8 100141] [9 99821] [10 100376])
Standard deviation:  244.95509792613012
Test 4
Server load:  ([1 100170] [2 100411] [3 99720] [4 100021] [5 99680] [6 100136] [7 99722] [8 99967] [9 100201] [10 99972])
Standard deviation:  227.40184695819863
Test 5
Server load:  ([1 100093] [2 99987] [3 99735] [4 100110] [5 100498] [6 99870] [7 99784] [8 99398] [9 100470] [10 100055])
Standard deviation:  314.48879153318006
Test 6
Server load:  ([1 99654] [2 99906] [3 100346] [4 99983] [5 100660] [6 99370] [7 99595] [8 100176] [9 100805] [10 99505])
Standard deviation:  465.7368355627457
Test 7
Server load:  ([1 100073] [2 99934] [3 100243] [4 99690] [5 99684] [6 100088] [7 99906] [8 100358] [9 99759] [10 100265])
Standard deviation:  231.89221634198935
Test 8
Server load:  ([1 99933] [2 99388] [3 100096] [4 99626] [5 99927] [6 100204] [7 100054] [8 100202] [9 100186] [10 100384])
Standard deviation:  282.99151930755806
Test 9
Server load:  ([1 100429] [2 100245] [3 100177] [4 100295] [5 99943] [6 99687] [7 99213] [8 100452] [9 99910] [10 99649])
Standard deviation:  376.6446601241016
Test 10
Server load:  ([1 100118] [2 100691] [3 100076] [4 99777] [5 99853] [6 99581] [7 100174] [8 100247] [9 99562] [10 99921])
Standard deviation:  321.47317150891456

consistent-hash on  master [!] took 16s
➜ lein run
Test 1
Standard deviation:  95.42861206158246
Test 2
Standard deviation:  96.88663478519625
Test 3
Standard deviation:  104.64052752160607
Test 4
Standard deviation:  106.48258073506672
Test 5
Standard deviation:  99.03191404794718
Test 6
Standard deviation:  106.48333202900818
Test 7
Standard deviation:  106.9067818241668
Test 8
Standard deviation:  104.08102612868495
Test 9
Standard deviation:  107.8383976142079
Test 10
Standard deviation:  95.76659125185567