prometheus/storage/metric/frontier.go

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// Copyright 2013 Prometheus Team
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package metric
import (
"fmt"
"github.com/prometheus/prometheus/coding"
"github.com/prometheus/prometheus/coding/indexable"
"github.com/prometheus/prometheus/model"
dto "github.com/prometheus/prometheus/model/generated"
"github.com/prometheus/prometheus/storage/raw/leveldb"
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"time"
)
// diskFrontier describes an on-disk store of series to provide a
// representation of the known keyspace and time series values available.
//
// This is used to reduce the burden associated with LevelDB iterator
// management.
type diskFrontier struct {
firstFingerprint model.Fingerprint
firstSupertime time.Time
lastFingerprint model.Fingerprint
lastSupertime time.Time
}
func (f diskFrontier) String() string {
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return fmt.Sprintf("diskFrontier from %s at %s to %s at %s", f.firstFingerprint.ToRowKey(), f.firstSupertime, f.lastFingerprint.ToRowKey(), f.lastSupertime)
}
func (f diskFrontier) ContainsFingerprint(fingerprint model.Fingerprint) bool {
return !(fingerprint.Less(f.firstFingerprint) || f.lastFingerprint.Less(fingerprint))
}
func newDiskFrontier(i leveldb.Iterator) (d *diskFrontier, err error) {
if !i.SeekToLast() || i.Key() == nil {
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return
}
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lastKey, err := extractSampleKey(i)
if err != nil {
panic(fmt.Sprintln(err, i.Key(), i.Value()))
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}
if !i.SeekToFirst() || i.Key() == nil {
return
}
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firstKey, err := extractSampleKey(i)
if i.Key() == nil {
return
}
if err != nil {
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panic(err)
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}
d = &diskFrontier{}
d.firstFingerprint = firstKey.Fingerprint
d.firstSupertime = firstKey.FirstTimestamp
d.lastFingerprint = lastKey.Fingerprint
d.lastSupertime = lastKey.FirstTimestamp
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return
}
// seriesFrontier represents the valid seek frontier for a given series.
type seriesFrontier struct {
firstSupertime time.Time
lastSupertime time.Time
lastTime time.Time
}
func (f seriesFrontier) String() string {
return fmt.Sprintf("seriesFrontier from %s to %s at %s", f.firstSupertime, f.lastSupertime, f.lastTime)
}
// 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) {
lowerSeek := firstSupertime
upperSeek := lastSupertime
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// 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
}
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// 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)
}
// TODO: Convert this to SampleKey.ToPartialDTO.
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key := &dto.SampleKey{
Fingerprint: f.ToDTO(),
Timestamp: upperSeek,
}
raw, err := coding.NewProtocolBuffer(key).Encode()
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if err != nil {
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panic(err)
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}
i.Seek(raw)
if i.Key() == nil {
return
}
retrievedKey, err := extractSampleKey(i)
if err != nil {
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panic(err)
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}
retrievedFingerprint := retrievedKey.Fingerprint
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// 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()
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retrievedKey, err = extractSampleKey(i)
if err != nil {
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panic(err)
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}
retrievedFingerprint := retrievedKey.Fingerprint
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// 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: retrievedKey.FirstTimestamp,
lastTime: retrievedKey.LastTimestamp,
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}
key.Timestamp = lowerSeek
raw, err = coding.NewProtocolBuffer(key).Encode()
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if err != nil {
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panic(err)
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}
i.Seek(raw)
retrievedKey, err = extractSampleKey(i)
if err != nil {
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panic(err)
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}
retrievedFingerprint = retrievedKey.Fingerprint
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s.firstSupertime = retrievedKey.FirstTimestamp
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return
}
// Contains indicates whether a given time value is within the recorded
// interval.
func (s seriesFrontier) Contains(t time.Time) bool {
return !(t.Before(s.firstSupertime) || t.After(s.lastTime))
}
// InSafeSeekRange indicates whether the time is within the recorded time range
// and is safely seekable such that a seek does not result in an iterator point
// after the last value of the series or outside of the entire store.
func (s seriesFrontier) InSafeSeekRange(t time.Time) (safe bool) {
if !s.Contains(t) {
return
}
if s.lastSupertime.Before(t) {
return
}
return true
}
func (s seriesFrontier) After(t time.Time) bool {
return s.firstSupertime.After(t)
}
// optimalStartTime indicates what the best start time for a curation operation
// should be given the curation remark.
func (s seriesFrontier) optimalStartTime(remark *model.CurationRemark) (t time.Time) {
switch {
case remark == nil:
t = s.firstSupertime
case s.After(remark.LastCompletionTimestamp):
t = s.firstSupertime
case !s.InSafeSeekRange(remark.LastCompletionTimestamp):
t = s.lastSupertime
default:
t = remark.LastCompletionTimestamp
}
return
}