Calculating memory usage of reputation writecache

writecache_sizecalc.go

package main

import (
	"sync"
	"time"
	"unsafe"

	"golang.org/x/text/language"
	"golang.org/x/text/message"
)

type NodeID [32]byte

type AuditWindow struct {
	Start       time.Time
	OnlineCount int32
	TotalCount  int32
	nul         struct{}
	unrecog     []byte
	sizecache   int32
}

type AuditHistory struct {
	Windows   []*AuditWindow
	Score     float64
	nul       struct{}
	unrecog   []byte
	sizecache int32
}

type Mutations struct {
	successes int
	failures  int
	unknowns  int
	offlines  int
	history   *AuditHistory
}

type cachedNodeReputationInfo struct {
	nodeID       NodeID
	entryLock    sync.Mutex
	info         *Info
	syncError    error
	errorRetryAt time.Time
	syncAt       time.Time
	mutations    Mutations
}

type Info struct {
	AuditSuccessCount           int64
	TotalAuditCount             int64
	VettedAt                    *time.Time
	UnknownAuditSuspended       *time.Time
	OfflineSuspended            *time.Time
	UnderReview                 *time.Time
	Disqualified                *time.Time
	DisqualificationReason      int
	OnlineScore                 float64
	AuditHistory                *AuditHistory
	AuditReputationAlpha        float64
	AuditReputationBeta         float64
	UnknownAuditReputationAlpha float64
	UnknownAuditReputationBeta  float64
}

func main() {
	const (
		// release defaults
		windowSize     = 12 * time.Hour
		flushInterval  = 2 * time.Hour
		trackingPeriod = 720 * time.Hour

		// this number is an example; adjust to the appropriate scenario
		expectedNumActiveNodes = 15000 // nodes which are holding pieces

		expectedNumWindowsInMutations = (flushInterval + windowSize - 1) / windowSize // how many windows are needed to cover a FlushInterval, rounded up
		expectedNumWindowsInInfo      = trackingPeriod / windowSize                   // this is the maximum, expected near the end of a TrackingPeriod
	)

	p := message.NewPrinter(language.English)

	auditWindowSize := unsafe.Sizeof(AuditWindow{})
	infoBaseSize := unsafe.Sizeof(Info{}) + 5*unsafe.Sizeof(time.Time{}) + unsafe.Sizeof(AuditHistory{})
	infoSize := infoBaseSize + uintptr(expectedNumWindowsInInfo)*auditWindowSize
	entryBaseSize := unsafe.Sizeof(cachedNodeReputationInfo{}) + unsafe.Sizeof(AuditHistory{})
	entrySize := entryBaseSize + infoSize + uintptr(expectedNumWindowsInMutations)*auditWindowSize

	p.Printf("%5dB (%d + %d * %d) per Info record\n", infoSize, infoBaseSize, expectedNumWindowsInInfo, auditWindowSize)
	p.Printf("%5dB (%d + %d + %d * %d) per node\n", entrySize, entryBaseSize, infoSize, expectedNumWindowsInMutations, auditWindowSize)
	p.Printf("with %d nodes, %dB total during periods of highest usage", expectedNumActiveNodes, expectedNumActiveNodes*entrySize)
}