func (l *LevelDBMetricPersistence) GetRangeValues(m *model.Metric, i *model.Interval, s *metric.StalenessPolicy) (v *model.SampleSet, err error) {
begin := time.Now()
defer func() {
duration := time.Now().Sub(begin)
recordOutcome(storageOperations, storageLatency, duration, err, map[string]string{operation: getRangeValues, result: success}, map[string]string{operation: getRangeValues, result: failure})
}()
d := model.MetricToDTO(m)
f, err := model.MessageToFingerprintDTO(d)
if err != nil {
return
}
k := &dto.SampleKey{
Fingerprint: f,
Timestamp: indexable.EncodeTime(i.OldestInclusive),
}
e, err := coding.NewProtocolBufferEncoder(k).Encode()
if err != nil {
return
}
iterator, closer, err := l.metricSamples.GetIterator()
if err != nil {
return
}
defer closer.Close()
iterator.Seek(e)
predicate := keyIsOlderThan(i.NewestInclusive)
for ; iterator.Valid(); iterator.Next() {
retrievedKey := &dto.SampleKey{}
retrievedKey, err = extractSampleKey(iterator)
if err != nil {
return
}
if predicate(retrievedKey) {
break
}
if !fingerprintsEqual(retrievedKey.Fingerprint, k.Fingerprint) {
break
}
retrievedValue, err := extractSampleValue(iterator)
if err != nil {
return nil, err
}
if v == nil {
v = &model.SampleSet{}
}
v.Values = append(v.Values, model.SamplePair{
Value: model.SampleValue(*retrievedValue.Value),
Timestamp: indexable.DecodeTime(retrievedKey.Timestamp),
})
}
return
}
func (l *LevelDBMetricPersistence) GetSamplesForMetric(metric model.Metric, interval model.Interval) ([]model.Samples, error) {
metricDTO := model.MetricToDTO(&metric)
if fingerprintDTO, fingerprintDTOErr := model.MessageToFingerprintDTO(metricDTO); fingerprintDTOErr == nil {
if iterator, closer, iteratorErr := l.metricSamples.GetIterator(); iteratorErr == nil {
defer closer.Close()
start := &dto.SampleKey{
Fingerprint: fingerprintDTO,
Timestamp: indexable.EncodeTime(interval.OldestInclusive),
}
emission := make([]model.Samples, 0)
if encode, encodeErr := coding.NewProtocolBufferEncoder(start).Encode(); encodeErr == nil {
iterator.Seek(encode)
predicate := keyIsAtMostOld(interval.NewestInclusive)
for iterator = iterator; iterator.Valid(); iterator.Next() {
key := &dto.SampleKey{}
value := &dto.SampleValue{}
if keyUnmarshalErr := proto.Unmarshal(iterator.Key(), key); keyUnmarshalErr == nil {
if valueUnmarshalErr := proto.Unmarshal(iterator.Value(), value); valueUnmarshalErr == nil {
if fingerprintsEqual(fingerprintDTO, key.Fingerprint) {
// Wart
if predicate(key) {
emission = append(emission, model.Samples{
Value: model.SampleValue(*value.Value),
Timestamp: indexable.DecodeTime(key.Timestamp),
})
} else {
break
}
} else {
break
}
} else {
return nil, valueUnmarshalErr
}
} else {
return nil, keyUnmarshalErr
}
}
return emission, nil
} else {
log.Printf("Could not encode the start key: %q\n", encodeErr)
return nil, encodeErr
}
} else {
log.Printf("Could not acquire iterator: %q\n", iteratorErr)
return nil, iteratorErr
}
} else {
log.Printf("Could not create fingerprint for the metric: %q\n", fingerprintDTOErr)
return nil, fingerprintDTOErr
}
panic("unreachable")
}
func (l *LevelDBMetricPersistence) GetValueAtTime(m *model.Metric, t *time.Time, s *metric.StalenessPolicy) (sample *model.Sample, err error) {
begin := time.Now()
defer func() {
duration := time.Now().Sub(begin)
recordOutcome(storageOperations, storageLatency, duration, err, map[string]string{operation: getValueAtTime, result: success}, map[string]string{operation: getValueAtTime, result: failure})
}()
d := model.MetricToDTO(m)
f, err := model.MessageToFingerprintDTO(d)
if err != nil {
return
}
// Candidate for Refactoring
k := &dto.SampleKey{
Fingerprint: f,
Timestamp: indexable.EncodeTime(*t),
}
e, err := coding.NewProtocolBufferEncoder(k).Encode()
if err != nil {
return
}
iterator, closer, err := l.metricSamples.GetIterator()
if err != nil {
return
}
defer closer.Close()
iterator.Seek(e)
if !iterator.Valid() {
/*
* Two cases for this:
* 1.) Corruption in LevelDB.
* 2.) Key seek after AND outside known range.
*
* Once a LevelDB iterator goes invalid, it cannot be recovered; thusly,
* we need to create a new in order to check if the last value in the
* database is sufficient for our purposes. This is, in all reality, a
* corner case but one that could bring down the system.
*/
iterator, closer, err = l.metricSamples.GetIterator()
if err != nil {
return
}
defer closer.Close()
iterator.SeekToLast()
if !iterator.Valid() {
/*
* For whatever reason, the LevelDB cannot be recovered.
*/
return
}
}
var (
firstKey *dto.SampleKey
firstValue *dto.SampleValue
)
firstKey, err = extractSampleKey(iterator)
if err != nil {
return
}
peekAhead := false
if !fingerprintsEqual(firstKey.Fingerprint, k.Fingerprint) {
/*
* This allows us to grab values for metrics if our request time is after
* the last recorded time subject to the staleness policy due to the nuances
* of LevelDB storage:
*
* # Assumptions:
* - K0 < K1 in terms of sorting.
* - T0 < T1 in terms of sorting.
*
* # Data
*
* K0-T0
* K0-T1
* K0-T2
* K1-T0
* K1-T1
*
* # Scenario
* K0-T3, which does not exist, is requested. LevelDB will thusly seek to
* K1-T1, when K0-T2 exists as a perfectly good candidate to check subject
* to the provided staleness policy and such.
*/
peekAhead = true
}
firstTime := indexable.DecodeTime(firstKey.Timestamp)
if t.Before(firstTime) || peekAhead {
iterator.Prev()
if !iterator.Valid() {
/*
* Two cases for this:
* 1.) Corruption in LevelDB.
* 2.) Key seek before AND outside known range.
*
* This is an explicit validation to ensure that if no previous values for
* the series are found, the query aborts.
*/
return
}
var (
alternativeKey *dto.SampleKey
alternativeValue *dto.SampleValue
)
alternativeKey, err = extractSampleKey(iterator)
if err != nil {
return
}
if !fingerprintsEqual(alternativeKey.Fingerprint, k.Fingerprint) {
return
}
/*
* At this point, we found a previous value in the same series in the
* database. LevelDB originally seeked to the subsequent element given
* the key, but we need to consider this adjacency instead.
*/
alternativeTime := indexable.DecodeTime(alternativeKey.Timestamp)
firstKey = alternativeKey
firstValue = alternativeValue
firstTime = alternativeTime
}
firstDelta := firstTime.Sub(*t)
if firstDelta < 0 {
firstDelta *= -1
}
if firstDelta > s.DeltaAllowance {
return
}
firstValue, err = extractSampleValue(iterator)
if err != nil {
return
}
sample = model.SampleFromDTO(m, t, firstValue)
if firstDelta == time.Duration(0) {
return
}
iterator.Next()
if !iterator.Valid() {
/*
* Two cases for this:
* 1.) Corruption in LevelDB.
* 2.) Key seek after AND outside known range.
*
* This means that there are no more values left in the storage; and if this
* point is reached, we know that the one that has been found is within the
* allowed staleness limits.
*/
return
}
var secondKey *dto.SampleKey
secondKey, err = extractSampleKey(iterator)
if err != nil {
return
}
if !fingerprintsEqual(secondKey.Fingerprint, k.Fingerprint) {
return
} else {
/*
* At this point, current entry in the database has the same key as the
* previous. For this reason, the validation logic will expect that the
* distance between the two points shall not exceed the staleness policy
* allowed limit to reduce interpolation errors.
*
* For this reason, the sample is reset in case of other subsequent
* validation behaviors.
*/
sample = nil
}
secondTime := indexable.DecodeTime(secondKey.Timestamp)
totalDelta := secondTime.Sub(firstTime)
if totalDelta > s.DeltaAllowance {
return
}
var secondValue *dto.SampleValue
secondValue, err = extractSampleValue(iterator)
if err != nil {
return
}
interpolated := interpolate(firstTime, secondTime, *firstValue.Value, *secondValue.Value, *t)
sampleValue := &dto.SampleValue{
Value: &interpolated,
}
sample = model.SampleFromDTO(m, t, sampleValue)
return
}