func newDiskFrontier(i leveldb.Iterator) (d *diskFrontier, err error) {
if !i.SeekToLast() || i.Key() == nil {
return
}
lastKey, err := extractSampleKey(i)
if err != nil {
panic(err)
}
if !i.SeekToFirst() || i.Key() == nil {
return
}
firstKey, err := extractSampleKey(i)
if i.Key() == nil {
return
}
if err != nil {
panic(err)
}
d = &diskFrontier{}
d.firstFingerprint = model.NewFingerprintFromRowKey(*firstKey.Fingerprint.Signature)
d.firstSupertime = indexable.DecodeTime(firstKey.Timestamp)
d.lastFingerprint = model.NewFingerprintFromRowKey(*lastKey.Fingerprint.Signature)
d.lastSupertime = indexable.DecodeTime(lastKey.Timestamp)
return
}
// Load deserializes this SampleKey from a DTO.
func (s *SampleKey) Load(d *dto.SampleKey) {
f := &clientmodel.Fingerprint{}
loadFingerprint(f, d.GetFingerprint())
s.Fingerprint = f
s.FirstTimestamp = indexable.DecodeTime(d.Timestamp)
s.LastTimestamp = clientmodel.TimestampFromUnix(d.GetLastTimestamp())
s.SampleCount = d.GetSampleCount()
}
func (l *LevelDBMetricPersistence) GetValueAtTime(fp model.Fingerprint, t time.Time, s StalenessPolicy) (sample *model.Sample, err error) {
begin := time.Now()
defer func() {
duration := time.Since(begin)
recordOutcome(duration, err, map[string]string{operation: getValueAtTime, result: success}, map[string]string{operation: getValueAtTime, result: failure})
}()
// TODO: memoize/cache this or change the return type to metric.SamplePair.
m, err := l.GetMetricForFingerprint(fp)
if err != nil {
return
}
// Candidate for Refactoring
k := &dto.SampleKey{
Fingerprint: fp.ToDTO(),
Timestamp: indexable.EncodeTime(t),
}
e, err := coding.NewProtocolBuffer(k).Encode()
if err != nil {
return
}
iterator := l.metricSamples.NewIterator(true)
defer iterator.Close()
if !iterator.Seek(e) {
/*
* 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 = l.metricSamples.NewIterator(true)
defer iterator.Close()
if !iterator.SeekToLast() {
/*
* For whatever reason, the LevelDB cannot be recovered.
*/
return
}
}
var (
firstKey *dto.SampleKey
firstValue *dto.SampleValueSeries
)
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 {
if !iterator.Previous() {
/*
* 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.SampleValueSeries
)
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 = extractSampleValues(iterator)
if err != nil {
return
}
sample = model.SampleFromDTO(m, &t, firstValue)
if firstDelta == time.Duration(0) {
return
}
if !iterator.Next() {
/*
* 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.SampleValueSeries
secondValue, err = extractSampleValues(iterator)
if err != nil {
return
}
fValue := *firstValue.Value[0].Value
sValue := *secondValue.Value[0].Value
interpolated := interpolate(firstTime, secondTime, fValue, sValue, t)
sampleValue := &dto.SampleValueSeries{}
sampleValue.Value = append(sampleValue.Value, &dto.SampleValueSeries_Value{Value: &interpolated})
sample = model.SampleFromDTO(m, &t, sampleValue)
return
}
func keyIsAtMostOld(t time.Time) sampleKeyPredicate {
return func(k *dto.SampleKey) bool {
return !indexable.DecodeTime(k.Timestamp).After(t)
}
}
func keyIsOlderThan(t time.Time) sampleKeyPredicate {
return func(k *dto.SampleKey) bool {
return indexable.DecodeTime(k.Timestamp).After(t)
}
}
func (l *LevelDBMetricPersistence) GetRangeValues(fp model.Fingerprint, i model.Interval) (v *model.SampleSet, err error) {
begin := time.Now()
defer func() {
duration := time.Since(begin)
recordOutcome(duration, err, map[string]string{operation: getRangeValues, result: success}, map[string]string{operation: getRangeValues, result: failure})
}()
k := &dto.SampleKey{
Fingerprint: fp.ToDTO(),
Timestamp: indexable.EncodeTime(i.OldestInclusive),
}
e, err := coding.NewProtocolBuffer(k).Encode()
if err != nil {
return
}
iterator := l.metricSamples.NewIterator(true)
defer iterator.Close()
predicate := keyIsOlderThan(i.NewestInclusive)
for valid := iterator.Seek(e); valid; 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 := extractSampleValues(iterator)
if err != nil {
return nil, err
}
if v == nil {
// TODO: memoize/cache this or change the return type to metric.SamplePair.
m, err := l.GetMetricForFingerprint(fp)
if err != nil {
return v, err
}
v = &model.SampleSet{
Metric: *m,
}
}
v.Values = append(v.Values, model.SamplePair{
Value: model.SampleValue(*retrievedValue.Value[0].Value),
Timestamp: indexable.DecodeTime(retrievedKey.Timestamp),
})
}
// XXX: We should not explicitly sort here but rather rely on the datastore.
// This adds appreciable overhead.
if v != nil {
sort.Sort(v.Values)
}
return
}
// newSeriesFrontier furnishes a populated diskFrontier for a given
// fingerprint. A nil diskFrontier will be returned if the series cannot
// be found in the store.
func newSeriesFrontier(f model.Fingerprint, d diskFrontier, i leveldb.Iterator) (s *seriesFrontier, err error) {
var (
lowerSeek = firstSupertime
upperSeek = lastSupertime
)
// If the diskFrontier for this iterator says that the candidate fingerprint
// is outside of its seeking domain, there is no way that a seriesFrontier
// could be materialized. Simply bail.
if !d.ContainsFingerprint(f) {
return
}
// If we are either the first or the last key in the database, we need to use
// pessimistic boundary frontiers.
if f.Equal(d.firstFingerprint) {
lowerSeek = indexable.EncodeTime(d.firstSupertime)
}
if f.Equal(d.lastFingerprint) {
upperSeek = indexable.EncodeTime(d.lastSupertime)
}
key := &dto.SampleKey{
Fingerprint: f.ToDTO(),
Timestamp: upperSeek,
}
raw, err := coding.NewProtocolBuffer(key).Encode()
if err != nil {
panic(err)
}
i.Seek(raw)
if i.Key() == nil {
return
}
retrievedKey, err := extractSampleKey(i)
if err != nil {
panic(err)
}
retrievedFingerprint := model.NewFingerprintFromRowKey(*retrievedKey.Fingerprint.Signature)
// The returned fingerprint may not match if the original seek key lives
// outside of a metric's frontier. This is probable, for we are seeking to
// to the maximum allowed time, which could advance us to the next
// fingerprint.
//
//
if !retrievedFingerprint.Equal(f) {
i.Previous()
retrievedKey, err = extractSampleKey(i)
if err != nil {
panic(err)
}
retrievedFingerprint := model.NewFingerprintFromRowKey(*retrievedKey.Fingerprint.Signature)
// If the previous key does not match, we know that the requested
// fingerprint does not live in the database.
if !retrievedFingerprint.Equal(f) {
return
}
}
s = &seriesFrontier{
lastSupertime: indexable.DecodeTime(retrievedKey.Timestamp),
lastTime: time.Unix(*retrievedKey.LastTimestamp, 0),
}
key.Timestamp = lowerSeek
raw, err = coding.NewProtocolBuffer(key).Encode()
if err != nil {
panic(err)
}
i.Seek(raw)
retrievedKey, err = extractSampleKey(i)
if err != nil {
panic(err)
}
retrievedFingerprint = model.NewFingerprintFromRowKey(*retrievedKey.Fingerprint.Signature)
s.firstSupertime = indexable.DecodeTime(retrievedKey.Timestamp)
return
}
func (t *tieredStorage) loadChunkAroundTime(iterator leveldb.Iterator, frontier *seriesFrontier, fingerprint model.Fingerprint, ts time.Time) (chunk []model.SamplePair) {
var (
targetKey = &dto.SampleKey{
Fingerprint: fingerprint.ToDTO(),
}
foundKey = &dto.SampleKey{}
foundValue *dto.SampleValueSeries
)
// Limit the target key to be within the series' keyspace.
if ts.After(frontier.lastSupertime) {
targetKey.Timestamp = indexable.EncodeTime(frontier.lastSupertime)
} else {
targetKey.Timestamp = indexable.EncodeTime(ts)
}
// Try seeking to target key.
rawKey, _ := coding.NewProtocolBuffer(targetKey).Encode()
iterator.Seek(rawKey)
foundKey, err := extractSampleKey(iterator)
if err != nil {
panic(err)
}
// Figure out if we need to rewind by one block.
// Imagine the following supertime blocks with time ranges:
//
// Block 1: ft 1000 - lt 1009 <data>
// Block 1: ft 1010 - lt 1019 <data>
//
// If we are aiming to find time 1005, we would first seek to the block with
// supertime 1010, then need to rewind by one block by virtue of LevelDB
// iterator seek behavior.
//
// Only do the rewind if there is another chunk before this one.
rewound := false
firstTime := indexable.DecodeTime(foundKey.Timestamp)
if ts.Before(firstTime) && !frontier.firstSupertime.After(ts) {
iterator.Previous()
rewound = true
}
foundValue, err = extractSampleValues(iterator)
if err != nil {
panic(err)
}
// If we rewound, but the target time is still past the current block, return
// the last value of the current (rewound) block and the entire next block.
if rewound {
foundKey, err = extractSampleKey(iterator)
if err != nil {
panic(err)
}
currentChunkLastTime := time.Unix(*foundKey.LastTimestamp, 0)
if ts.After(currentChunkLastTime) {
sampleCount := len(foundValue.Value)
chunk = append(chunk, model.SamplePair{
Timestamp: time.Unix(*foundValue.Value[sampleCount-1].Timestamp, 0),
Value: model.SampleValue(*foundValue.Value[sampleCount-1].Value),
})
// We know there's a next block since we have rewound from it.
iterator.Next()
foundValue, err = extractSampleValues(iterator)
if err != nil {
panic(err)
}
}
}
// Now append all the samples of the currently seeked block to the output.
for _, sample := range foundValue.Value {
chunk = append(chunk, model.SamplePair{
Timestamp: time.Unix(*sample.Timestamp, 0),
Value: model.SampleValue(*sample.Value),
})
}
return
}