1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
|
// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.http.client.core;
import static java.lang.Math.abs;
import static java.lang.Math.max;
import static java.lang.Math.min;
/**
* Class that has a method for finding next maxInFlight.
*
* @author dybis
*/
public class ThrottlePolicy {
public static final double SMALL_DIFFERENCE_IN_SUCCESSES_RATIO = 0.15;
private static final double MINIMUM_DIFFERENCE = 0.05;
/**
* Generate nex in-flight value for throttling.
*
* @param maxPerformanceChange This value limit the dynamics of the algorithm.
* @param numOk number of success in last phase
* @param previousNumOk number of success in previous (before last) phase.
* @param previousMaxInFlight number of max-in-flight in previous (before last) phase.
* @param maxInFlightNow number of max-in-flight in last phase.
* @param messagesQueued if any messages where queued.
* @return The new value to be used for max-in-flight (should be cropped externally to fit max/min values).
*/
public int calcNewMaxInFlight(double maxPerformanceChange, int numOk, int previousNumOk, int previousMaxInFlight,
int maxInFlightNow, boolean messagesQueued) {
double difference = calculateRuleBasedDifference(maxPerformanceChange, numOk, previousNumOk, previousMaxInFlight, maxInFlightNow);
boolean previousRunWasBetter = numOk < previousNumOk;
boolean previousRunHadLessInFlight = previousMaxInFlight < maxInFlightNow;
int delta;
if (previousRunWasBetter == previousRunHadLessInFlight) {
delta = (int) (-1.1 * difference * maxInFlightNow);
} else {
delta = (int) (difference * maxInFlightNow);
}
// We don't want the same size since we need different sizes for algorithm to adjust.
if (abs(delta) < 2) {
delta = -3;
}
// We never used all permits in previous run, no reason to grow more, we should rather reduce permits.
if (!messagesQueued && delta > 0) {
delta = -2;
}
return maxInFlightNow + delta;
}
private static double calculateRuleBasedDifference(double maxPerformanceChange, double numOk, double previousNumOk,
double previousMaxInFlight, double maxInFlightNow) {
double difference = min(
maxPerformanceChange,
abs((numOk - previousNumOk) / safeDenominator(previousNumOk)));
if (abs(previousMaxInFlight - maxInFlightNow) / safeDenominator(min(previousMaxInFlight, maxInFlightNow))
< SMALL_DIFFERENCE_IN_SUCCESSES_RATIO) {
difference = min(difference, 0.2);
}
// We want some changes so we can track performance as a result of different throttling.
return max(difference, MINIMUM_DIFFERENCE);
}
private static double safeDenominator(double x) {
return x == 0.0 ? 1.0 : x;
}
}
|
