vitess.io/vitess@v0.16.2/go/vt/vttablet/tabletserver/vstreamer/packet_size_test.go (about) 1 /* 2 Copyright 2021 The Vitess Authors. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 package vstreamer 18 19 import ( 20 "math" 21 "math/rand" 22 "testing" 23 "time" 24 ) 25 26 type polynomial []float64 27 28 func (p polynomial) fit(x float64) float64 { 29 var y float64 30 for i, exp := range p { 31 y += exp * math.Pow(x, float64(i)) 32 } 33 return y 34 } 35 36 func simulate(t *testing.T, ps PacketSizer, base, mustSend int, interpolate func(float64) float64) (time.Duration, int) { 37 t.Helper() 38 39 var elapsed time.Duration 40 var sent int 41 var sentPkt int 42 packetRange := float64(base) * 10.0 43 44 packetSize := 0 45 for sent < mustSend { 46 packetSize += rand.Intn(base / 100) 47 48 if ps.ShouldSend(packetSize) { 49 x := float64(packetSize) / packetRange 50 y := interpolate(x) 51 d := time.Duration(float64(time.Microsecond) * y * float64(packetSize)) 52 ps.Record(packetSize, d) 53 54 sent += packetSize 55 elapsed += d 56 sentPkt++ 57 58 packetSize = 0 59 } 60 } 61 return elapsed, sentPkt 62 } 63 64 func TestPacketSizeSimulation(t *testing.T) { 65 cases := []struct { 66 name string 67 baseSize int 68 p polynomial 69 error time.Duration 70 }{ 71 { 72 name: "growth with tapper", 73 baseSize: 25000, 74 p: polynomial{0.767, 1.278, -12.048, 25.262, -21.270, 6.410}, 75 }, 76 { 77 name: "growth without tapper", 78 baseSize: 25000, 79 p: polynomial{0.473, 5.333, -38.663, 90.731, -87.005, 30.128}, 80 error: 5 * time.Millisecond, 81 }, 82 { 83 name: "regression", 84 baseSize: 25000, 85 p: polynomial{0.247, -0.726, 2.864, -3.022, 2.273, -0.641}, 86 error: 1 * time.Second, 87 }, 88 } 89 90 for _, tc := range cases { 91 t.Run(tc.name, func(t *testing.T) { 92 seed := time.Now().UnixNano() 93 rand.Seed(seed) 94 95 // Simulate a replication using the given polynomial and the dynamic packet sizer 96 ps1 := newDynamicPacketSizer(tc.baseSize) 97 elapsed1, sent1 := simulate(t, ps1, tc.baseSize, tc.baseSize*1000, tc.p.fit) 98 99 // Simulate the same polynomial using a fixed packet size 100 ps2 := newFixedPacketSize(tc.baseSize) 101 elapsed2, sent2 := simulate(t, ps2, tc.baseSize, tc.baseSize*1000, tc.p.fit) 102 103 // the simulation for dynamic packet sizing should always be faster then the fixed packet, 104 // and should also send fewer packets in total 105 delta := elapsed1 - elapsed2 106 if delta > tc.error { 107 t.Errorf("packet-adjusted simulation is %v slower than fixed approach, seed %d", delta, seed) 108 } 109 if sent1 > sent2 { 110 t.Errorf("packet-adjusted simulation sent more packets (%d) than fixed approach (%d), seed %d", sent1, sent2, seed) 111 } 112 // t.Logf("dynamic = (%v, %d), fixed = (%v, %d)", elapsed1, sent1, elapsed2, sent2) 113 }) 114 } 115 }