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Debug corner-case seeking anomaly.

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This commit is contained in:
Matt T. Proud 2013-01-07 11:23:09 +01:00
parent be9b7942c1
commit ac438e51f6
1 changed files with 39 additions and 13 deletions
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52
storage/metric/leveldb/reading.go
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@ -366,12 +366,36 @@ func (l *LevelDBMetricPersistence) GetValueAtTime(m *model.Metric, t *time.Time,
return
}
peekAhead := false
if !fingerprintsEqual(firstKey.Fingerprint, k.Fingerprint) {
return
/*
* 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) {
if t.Before(firstTime) || peekAhead {
iterator.Prev()
if !iterator.Valid() {
/*
@ -395,18 +419,20 @@ func (l *LevelDBMetricPersistence) GetValueAtTime(m *model.Metric, t *time.Time,
return
}
if fingerprintsEqual(alternativeKey.Fingerprint, k.Fingerprint) {
/*
* 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
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)