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|
package tracker
import (
"context"
"errors"
"sync"
"time"
"gitlab.com/gitlab-org/gitaly/v15/internal/praefect/config"
)
// ErrorTracker allows tracking how many read/write errors have occurred, and whether or not it has
// exceeded a configured threshold in a configured time window
type ErrorTracker interface {
// IncrReadErr increases read errors by 1
IncrReadErr(nodeStorage string)
// IncrWriteErr increases write errors by 1
IncrWriteErr(nodeStorage string)
// ReadThresholdReached returns whether or not the read threshold was reached
ReadThresholdReached(nodeStorage string) bool
// WriteThresholdReached returns whether or not the read threshold was reached
WriteThresholdReached(nodeStorage string) bool
}
// ErrorWindowFunction is a function that is passed to `NewErrors()`. This function shall return
// `true` if the time when a specific error occurred should be considered part of the error window.
type ErrorWindowFunction func(now time.Time, errorTime time.Time) bool
// NewErrorWindowFunction derives an error window from the given configuration.
func NewErrorWindowFunction(cfg config.Failover) (ErrorWindowFunction, error) {
if cfg.ErrorThresholdWindow == 0 {
return nil, errors.New("errorWindow must be non zero")
}
errorWindow := cfg.ErrorThresholdWindow.Duration()
return func(now time.Time, errorTime time.Time) bool {
return errorTime.After(now.Add(-errorWindow))
}, nil
}
type errorTracker struct {
isInErrorWindow ErrorWindowFunction
m sync.RWMutex
writeThreshold, readThreshold int
readErrors, writeErrors map[string][]time.Time
ctx context.Context
}
func newErrors(ctx context.Context, isInErrorWindow ErrorWindowFunction, readThreshold, writeThreshold uint32) (*errorTracker, error) {
if readThreshold == 0 {
return nil, errors.New("readThreshold must be non zero")
}
if writeThreshold == 0 {
return nil, errors.New("writeThreshold must be non zero")
}
e := &errorTracker{
isInErrorWindow: isInErrorWindow,
readErrors: make(map[string][]time.Time),
writeErrors: make(map[string][]time.Time),
readThreshold: int(readThreshold),
writeThreshold: int(writeThreshold),
ctx: ctx,
}
go e.periodicallyClear()
return e, nil
}
// NewErrors creates a new Error instance given a time window in seconds, and read and write thresholds
func NewErrors(ctx context.Context, isInErrorWindow ErrorWindowFunction, readThreshold, writeThreshold uint32) (ErrorTracker, error) {
return newErrors(ctx, isInErrorWindow, readThreshold, writeThreshold)
}
// IncrReadErr increases the read errors for a node by 1
func (e *errorTracker) IncrReadErr(node string) {
e.incrReadErrTime(node, time.Now())
}
func (e *errorTracker) incrReadErrTime(node string, t time.Time) {
select {
case <-e.ctx.Done():
return
default:
e.m.Lock()
defer e.m.Unlock()
e.readErrors[node] = append(e.readErrors[node], t)
if len(e.readErrors[node]) > e.readThreshold {
e.readErrors[node] = e.readErrors[node][1:]
}
}
}
// IncrWriteErr increases the read errors for a node by 1
func (e *errorTracker) IncrWriteErr(node string) {
e.incrWriteErrTime(node, time.Now())
}
func (e *errorTracker) incrWriteErrTime(node string, t time.Time) {
select {
case <-e.ctx.Done():
return
default:
e.m.Lock()
defer e.m.Unlock()
e.writeErrors[node] = append(e.writeErrors[node], t)
if len(e.writeErrors[node]) > e.writeThreshold {
e.writeErrors[node] = e.writeErrors[node][1:]
}
}
}
// ReadThresholdReached indicates whether or not the read threshold has been reached within the time window
func (e *errorTracker) ReadThresholdReached(node string) bool {
select {
case <-e.ctx.Done():
break
default:
e.m.RLock()
defer e.m.RUnlock()
now := time.Now()
for i, errTime := range e.readErrors[node] {
if e.isInErrorWindow(now, errTime) {
if i == 0 {
return len(e.readErrors[node]) >= e.readThreshold
}
return len(e.readErrors[node][i-1:]) >= e.readThreshold
}
}
}
return false
}
// WriteThresholdReached indicates whether or not the write threshold has been reached within the time window
func (e *errorTracker) WriteThresholdReached(node string) bool {
select {
case <-e.ctx.Done():
break
default:
e.m.RLock()
defer e.m.RUnlock()
now := time.Now()
for i, errTime := range e.writeErrors[node] {
if e.isInErrorWindow(now, errTime) {
if i == 0 {
return len(e.writeErrors[node]) >= e.writeThreshold
}
return len(e.writeErrors[node][i-1:]) >= e.writeThreshold
}
}
}
return false
}
// periodicallyClear runs in an infinite loop clearing out old error entries
func (e *errorTracker) periodicallyClear() {
ticker := time.NewTicker(1 * time.Second)
for {
select {
case <-ticker.C:
e.clear()
case <-e.ctx.Done():
e.m.Lock()
defer e.m.Unlock()
e.readErrors = nil
e.writeErrors = nil
return
}
}
}
func (e *errorTracker) clear() {
e.m.Lock()
defer e.m.Unlock()
now := time.Now()
e.clearErrors(e.writeErrors, now)
e.clearErrors(e.readErrors, now)
}
func (e *errorTracker) clearErrors(errs map[string][]time.Time, now time.Time) {
for node, errors := range errs {
for i, errTime := range errors {
if e.isInErrorWindow(now, errTime) {
errs[node] = errors[i:]
break
}
if i == len(errors)-1 {
errs[node] = errs[node][:0]
}
}
}
}
|
