Wrap dto.SampleKey with business logic type.

The curator work can be done easier if dto.SampleKey is no longer
directly accessed but rather has a higher level type around it that
captures a certain modicum of business logic.  This doesn't look
terribly interesting today, but it will get more so.

model/samplekey.go

@@ -0,0 +1,79 @@
+// 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 model
+
+import (
+	"code.google.com/p/goprotobuf/proto"
+	"github.com/prometheus/prometheus/coding/indexable"
+	dto "github.com/prometheus/prometheus/model/generated"
+	"time"
+)
+
+// SampleKey models the business logic around the data-transfer object
+// SampleKey.
+type SampleKey struct {
+	Fingerprint    Fingerprint
+	FirstTimestamp time.Time
+	LastTimestamp  time.Time
+	SampleCount    uint32
+}
+
+// MayContain indicates whether the given SampleKey could potentially contain a
+// value at the provided time.  Even if true is emitted, that does not mean a
+// satisfactory value, in fact, exists.
+func (s SampleKey) MayContain(t time.Time) (could bool) {
+	switch {
+	case t.Before(s.FirstTimestamp):
+		return
+	case t.After(s.LastTimestamp):
+		return
+	}
+
+	return true
+}
+
+// ToDTO converts this SampleKey into a DTO for use in serialization purposes.
+func (s SampleKey) ToDTO() (out *dto.SampleKey) {
+	out = &dto.SampleKey{
+		Fingerprint:   s.Fingerprint.ToDTO(),
+		Timestamp:     indexable.EncodeTime(s.FirstTimestamp),
+		LastTimestamp: proto.Int64(s.LastTimestamp.Unix()),
+		SampleCount:   proto.Uint32(s.SampleCount),
+	}
+
+	return
+}
+
+// ToPartialDTO converts this SampleKey into a DTO that is only suitable for
+// database exploration purposes for a given (Fingerprint, First Sample Time)
+// tuple.
+func (s SampleKey) ToPartialDTO(out *dto.SampleKey) {
+	out = &dto.SampleKey{
+		Fingerprint: s.Fingerprint.ToDTO(),
+		Timestamp:   indexable.EncodeTime(s.FirstTimestamp),
+	}
+
+	return
+}
+
+// NewSampleKeyFromDTO builds a new SampleKey from a provided data-transfer
+// object.
+func NewSampleKeyFromDTO(dto *dto.SampleKey) SampleKey {
+	return SampleKey{
+		Fingerprint:    NewFingerprintFromDTO(dto.Fingerprint),
+		FirstTimestamp: indexable.DecodeTime(dto.Timestamp),
+		LastTimestamp:  time.Unix(*dto.LastTimestamp, 0),
+		SampleCount:    *dto.SampleCount,
+	}
+}

storage/metric/frontier.go

@@ -67,10 +67,10 @@ func newDiskFrontier(i leveldb.Iterator) (d *diskFrontier, err error) {
 
 	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)
+	d.firstFingerprint = firstKey.Fingerprint
+	d.firstSupertime = firstKey.FirstTimestamp
+	d.lastFingerprint = lastKey.Fingerprint
+	d.lastSupertime = lastKey.FirstTimestamp
 
 	return
 }
@@ -111,6 +111,7 @@ func newSeriesFrontier(f model.Fingerprint, d diskFrontier, i leveldb.Iterator)
 		upperSeek = indexable.EncodeTime(d.lastSupertime)
 	}
 
+	// TODO: Convert this to SampleKey.ToPartialDTO.
 	key := &dto.SampleKey{
 		Fingerprint: f.ToDTO(),
 		Timestamp:   upperSeek,
@@ -131,7 +132,7 @@ func newSeriesFrontier(f model.Fingerprint, d diskFrontier, i leveldb.Iterator)
 		panic(err)
 	}
 
-	retrievedFingerprint := model.NewFingerprintFromRowKey(*retrievedKey.Fingerprint.Signature)
+	retrievedFingerprint := retrievedKey.Fingerprint
 
 	// 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
@@ -146,7 +147,7 @@ func newSeriesFrontier(f model.Fingerprint, d diskFrontier, i leveldb.Iterator)
 		if err != nil {
 			panic(err)
 		}
-		retrievedFingerprint := model.NewFingerprintFromRowKey(*retrievedKey.Fingerprint.Signature)
+		retrievedFingerprint := retrievedKey.Fingerprint
 		// If the previous key does not match, we know that the requested
 		// fingerprint does not live in the database.
 		if !retrievedFingerprint.Equal(f) {
@@ -155,8 +156,8 @@ func newSeriesFrontier(f model.Fingerprint, d diskFrontier, i leveldb.Iterator)
 	}
 
 	s = &seriesFrontier{
-		lastSupertime: indexable.DecodeTime(retrievedKey.Timestamp),
-		lastTime:      time.Unix(*retrievedKey.LastTimestamp, 0),
+		lastSupertime: retrievedKey.FirstTimestamp,
+		lastTime:      retrievedKey.LastTimestamp,
 	}
 
 	key.Timestamp = lowerSeek
@@ -173,9 +174,9 @@ func newSeriesFrontier(f model.Fingerprint, d diskFrontier, i leveldb.Iterator)
 		panic(err)
 	}
 
-	retrievedFingerprint = model.NewFingerprintFromRowKey(*retrievedKey.Fingerprint.Signature)
+	retrievedFingerprint = retrievedKey.Fingerprint
 
-	s.firstSupertime = indexable.DecodeTime(retrievedKey.Timestamp)
+	s.firstSupertime = retrievedKey.FirstTimestamp
 
 	return
 }

storage/metric/leveldb.go

@@ -17,7 +17,6 @@ import (
 	"code.google.com/p/goprotobuf/proto"
 	"flag"
 	"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"
@@ -608,12 +607,12 @@ func (l *LevelDBMetricPersistence) AppendSamples(samples model.Samples) (err err
 			chunk := group[0:take]
 			group = group[take:lengthOfGroup]
 
-			key := &dto.SampleKey{
-				Fingerprint:   fingerprint.ToDTO(),
-				Timestamp:     indexable.EncodeTime(chunk[0].Timestamp),
-				LastTimestamp: proto.Int64(chunk[take-1].Timestamp.Unix()),
-				SampleCount:   proto.Uint32(uint32(take)),
-			}
+			key := model.SampleKey{
+				Fingerprint:    fingerprint,
+				FirstTimestamp: chunk[0].Timestamp,
+				LastTimestamp:  chunk[take-1].Timestamp,
+				SampleCount:    uint32(take),
+			}.ToDTO()
 
 			value := &dto.SampleValueSeries{}
 			for _, sample := range chunk {
@@ -645,26 +644,19 @@ func (l *LevelDBMetricPersistence) AppendSamples(samples model.Samples) (err err
 	return
 }
 
-func extractSampleKey(i leveldb.Iterator) (k *dto.SampleKey, err error) {
-	if i == nil {
-		panic("nil iterator")
+func extractSampleKey(i leveldb.Iterator) (key model.SampleKey, err error) {
+	k := &dto.SampleKey{}
+	err = proto.Unmarshal(i.Key(), k)
+	if err != nil {
+		return
 	}
 
-	k = &dto.SampleKey{}
-	rawKey := i.Key()
-	if rawKey == nil {
-		panic("illegal condition; got nil key...")
-	}
-	err = proto.Unmarshal(rawKey, k)
+	key = model.NewSampleKeyFromDTO(k)
 
 	return
 }
 
 func extractSampleValues(i leveldb.Iterator) (v *dto.SampleValueSeries, err error) {
-	if i == nil {
-		panic("nil iterator")
-	}
-
 	v = &dto.SampleValueSeries{}
 	err = proto.Unmarshal(i.Value(), v)
 
@@ -691,20 +683,6 @@ func fingerprintsEqual(l *dto.Fingerprint, r *dto.Fingerprint) bool {
 	return false
 }
 
-type sampleKeyPredicate func(k *dto.SampleKey) bool
-
-func keyIsOlderThan(t time.Time) sampleKeyPredicate {
-	return func(k *dto.SampleKey) bool {
-		return indexable.DecodeTime(k.Timestamp).After(t)
-	}
-}
-
-func keyIsAtMostOld(t time.Time) sampleKeyPredicate {
-	return func(k *dto.SampleKey) bool {
-		return !indexable.DecodeTime(k.Timestamp).After(t)
-	}
-}
-
 func (l *LevelDBMetricPersistence) hasIndexMetric(dto *dto.Metric) (value bool, err error) {
 	begin := time.Now()
 

storage/metric/stochastic_test.go

@@ -189,14 +189,6 @@ func AppendSampleAsPureSingleEntityAppendTests(p MetricPersistence, t test.Teste
 }
 
 func levelDBGetRangeValues(l *LevelDBMetricPersistence, fp model.Fingerprint, i model.Interval) (samples model.Values, 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),
@@ -210,21 +202,17 @@ func levelDBGetRangeValues(l *LevelDBMetricPersistence, fp model.Fingerprint, i
 	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)
+		retrievedKey, err := extractSampleKey(iterator)
 		if err != nil {
-			return
+			return samples, err
 		}
 
-		if predicate(retrievedKey) {
+		if retrievedKey.FirstTimestamp.After(i.NewestInclusive) {
 			break
 		}
 
-		if !fingerprintsEqual(retrievedKey.Fingerprint, k.Fingerprint) {
+		if !retrievedKey.Fingerprint.Equal(fp) {
 			break
 		}
 

storage/metric/tiered.go

@@ -472,7 +472,7 @@ func (t *tieredStorage) loadChunkAroundTime(iterator leveldb.Iterator, frontier
 		targetKey = &dto.SampleKey{
 			Fingerprint: fingerprint.ToDTO(),
 		}
-		foundKey   = &dto.SampleKey{}
+		foundKey   model.SampleKey
 		foundValue *dto.SampleValueSeries
 	)
 
@@ -504,7 +504,7 @@ func (t *tieredStorage) loadChunkAroundTime(iterator leveldb.Iterator, frontier
 	//
 	// Only do the rewind if there is another chunk before this one.
 	rewound := false
-	firstTime := indexable.DecodeTime(foundKey.Timestamp)
+	firstTime := foundKey.FirstTimestamp
 	if ts.Before(firstTime) && !frontier.firstSupertime.After(ts) {
 		iterator.Previous()
 		rewound = true
@@ -522,7 +522,7 @@ func (t *tieredStorage) loadChunkAroundTime(iterator leveldb.Iterator, frontier
 		if err != nil {
 			panic(err)
 		}
-		currentChunkLastTime := time.Unix(*foundKey.LastTimestamp, 0)
+		currentChunkLastTime := foundKey.LastTimestamp
 
 		if ts.After(currentChunkLastTime) {
 			sampleCount := len(foundValue.Value)