Extract HighWatermarking.

Clean up the rest.

Makefile

@@ -17,7 +17,7 @@ include Makefile.INCLUDE
 
 all: binary test
 
-$(GOCC): $(BUILD_PATH)/cache/$(GOPKG) source_path
+$(GOCC): $(BUILD_PATH)/cache/$(GOPKG) $(FULL_GOPATH)
 	tar -C $(BUILD_PATH)/root -xzf $<
 	touch $@
 
@@ -58,7 +58,7 @@ format:
 model: dependencies preparation
 	$(MAKE) -C model
 
-preparation: $(GOCC) source_path
+preparation: $(GOCC) $(FULL_GOPATH)
 	$(MAKE) -C $(BUILD_PATH)
 
 race_condition_binary: build
@@ -76,9 +76,9 @@ search_index:
 server: config dependencies model preparation
 	$(MAKE) -C server
 
-# source_path is responsible for ensuring that the builder has not done anything
+# $(FULL_GOPATH) is responsible for ensuring that the builder has not done anything
 # stupid like working on Prometheus outside of ${GOPATH}.
-source_path:
+$(FULL_GOPATH):
 	-[ -d "$(FULL_GOPATH)" ] || { mkdir -vp $(FULL_GOPATH_BASE) ; ln -s "$(PWD)" "$(FULL_GOPATH)" ; }
 	[ -d "$(FULL_GOPATH)" ]
 
@@ -94,4 +94,4 @@ update:
 web: config dependencies model preparation
 	$(MAKE) -C web
 
-.PHONY: advice binary build clean config dependencies documentation format model package preparation race_condition_binary race_condition_run run search_index source_path test tools update
+.PHONY: advice binary build clean config dependencies documentation format model package preparation race_condition_binary race_condition_run run search_index test tools update

main.go

@@ -28,7 +28,6 @@ import (
 	"github.com/prometheus/prometheus/retrieval"
 	"github.com/prometheus/prometheus/rules"
 	"github.com/prometheus/prometheus/storage/metric"
-	"github.com/prometheus/prometheus/storage/raw/leveldb"
 	"github.com/prometheus/prometheus/web"
 	"github.com/prometheus/prometheus/web/api"
 )
@@ -76,7 +75,7 @@ type prometheus struct {
 	reportDatabasesTimer     *time.Ticker
 	curationMutex            sync.Mutex
 	curationState            chan metric.CurationState
-	databaseStates           chan []leveldb.DatabaseState
+	databaseStates           chan []string
 	stopBackgroundOperations chan bool
 
 	unwrittenSamples chan *extraction.Result
@@ -207,7 +206,7 @@ func main() {
 
 	unwrittenSamples := make(chan *extraction.Result, *samplesQueueCapacity)
 	curationState := make(chan metric.CurationState, 1)
-	databaseStates := make(chan []leveldb.DatabaseState, 1)
+	databaseStates := make(chan []string, 1)
 	// Coprime numbers, fool!
 	headCompactionTimer := time.NewTicker(*headCompactInterval)
 	bodyCompactionTimer := time.NewTicker(*bodyCompactInterval)

storage/metric/curator.go

@@ -92,7 +92,7 @@ type watermarkScanner struct {
 // curated.
 // curationState is the on-disk store where the curation remarks are made for
 // how much progress has been made.
-func (c *Curator) Run(ignoreYoungerThan time.Duration, instant time.Time, processor Processor, curationState, samples, watermarks *leveldb.LevelDBPersistence, status chan CurationState) (err error) {
+func (c *Curator) Run(ignoreYoungerThan time.Duration, instant time.Time, processor Processor, curationState, samples *leveldb.LevelDBPersistence, watermarks HighWatermarker, status chan CurationState) (err error) {
 	defer func(t time.Time) {
 		duration := float64(time.Since(t) / time.Millisecond)
 

storage/metric/index.go

@@ -33,6 +33,8 @@ type FingerprintMetricIndex interface {
 	IndexBatch(FingerprintMetricMapping) error
 	Lookup(*clientmodel.Fingerprint) (m clientmodel.Metric, ok bool, err error)
 	Close() error
+	State() string
+	Size() (s uint64, present bool, err error)
 }
 
 type leveldbFingerprintMetricIndex struct {
@@ -49,6 +51,15 @@ func (i *leveldbFingerprintMetricIndex) Close() error {
 	return nil
 }
 
+func (i *leveldbFingerprintMetricIndex) State() string {
+	return i.p.State()
+}
+
+func (i *leveldbFingerprintMetricIndex) Size() (uint64, bool, error) {
+	s, err := i.p.ApproximateSize()
+	return s, true, err
+}
+
 func (i *leveldbFingerprintMetricIndex) IndexBatch(mapping FingerprintMetricMapping) error {
 	b := leveldb.NewBatch()
 	defer b.Close()
@@ -102,6 +113,8 @@ type LabelNameFingerprintIndex interface {
 	Lookup(clientmodel.LabelName) (fps clientmodel.Fingerprints, ok bool, err error)
 	Has(clientmodel.LabelName) (ok bool, err error)
 	Close() error
+	State() string
+	Size() (s uint64, present bool, err error)
 }
 
 type leveldbLabelNameFingerprintIndex struct {
@@ -164,6 +177,15 @@ func (i *leveldbLabelNameFingerprintIndex) Close() error {
 	return nil
 }
 
+func (i *leveldbLabelNameFingerprintIndex) Size() (uint64, bool, error) {
+	s, err := i.p.ApproximateSize()
+	return s, true, err
+}
+
+func (i *leveldbLabelNameFingerprintIndex) State() string {
+	return i.p.State()
+}
+
 type LevelDBLabelNameFingerprintIndexOptions struct {
 	leveldb.LevelDBOptions
 }
@@ -188,6 +210,8 @@ type LabelSetFingerprintIndex interface {
 	Lookup(*LabelPair) (m clientmodel.Fingerprints, ok bool, err error)
 	Has(*LabelPair) (ok bool, err error)
 	Close() error
+	State() string
+	Size() (s uint64, present bool, err error)
 }
 
 type leveldbLabelSetFingerprintIndex struct {
@@ -265,6 +289,15 @@ func (i *leveldbLabelSetFingerprintIndex) Close() error {
 	return nil
 }
 
+func (i *leveldbLabelSetFingerprintIndex) Size() (uint64, bool, error) {
+	s, err := i.p.ApproximateSize()
+	return s, true, err
+}
+
+func (i *leveldbLabelSetFingerprintIndex) State() string {
+	return i.p.State()
+}
+
 func NewLevelDBLabelSetFingerprintIndex(o *LevelDBLabelSetFingerprintIndexOptions) (LabelSetFingerprintIndex, error) {
 	s, err := leveldb.NewLevelDBPersistence(&o.LevelDBOptions)
 	if err != nil {
@@ -280,6 +313,8 @@ type MetricMembershipIndex interface {
 	IndexBatch([]clientmodel.Metric) error
 	Has(clientmodel.Metric) (ok bool, err error)
 	Close() error
+	State() string
+	Size() (s uint64, present bool, err error)
 }
 
 type leveldbMetricMembershipIndex struct {
@@ -314,6 +349,15 @@ func (i *leveldbMetricMembershipIndex) Close() error {
 	return nil
 }
 
+func (i *leveldbMetricMembershipIndex) Size() (uint64, bool, error) {
+	s, err := i.p.ApproximateSize()
+	return s, true, err
+}
+
+func (i *leveldbMetricMembershipIndex) State() string {
+	return i.p.State()
+}
+
 type LevelDBMetricMembershipIndexOptions struct {
 	leveldb.LevelDBOptions
 }

storage/metric/leveldb.go

@@ -39,7 +39,7 @@ type LevelDBMetricPersistence struct {
 	fingerprintToMetrics    FingerprintMetricIndex
 	labelNameToFingerprints LabelNameFingerprintIndex
 	labelSetToFingerprints  LabelSetFingerprintIndex
-	MetricHighWatermarks    *leveldb.LevelDBPersistence
+	MetricHighWatermarks    HighWatermarker
 	metricMembershipIndex   MetricMembershipIndex
 	MetricSamples           *leveldb.LevelDBPersistence
 }
@@ -114,6 +114,8 @@ func NewLevelDBMetricPersistence(baseDirectory string) (*LevelDBMetricPersistenc
 				var err error
 				emission.fingerprintToMetrics, err = NewLevelDBFingerprintMetricIndex(&LevelDBFingerprintMetricIndexOptions{
 					LevelDBOptions: leveldb.LevelDBOptions{
+						Name:           "Metrics by Fingerprint",
+						Purpose:        "Index",
 						Path:           baseDirectory + "/label_name_and_value_pairs_by_fingerprint",
 						CacheSizeBytes: *fingerprintsToLabelPairCacheSize,
 					},
@@ -126,6 +128,8 @@ func NewLevelDBMetricPersistence(baseDirectory string) (*LevelDBMetricPersistenc
 			func() {
 				var err error
 				o := &leveldb.LevelDBOptions{
+					Name:           "Samples",
+					Purpose:        "Timeseries",
 					Path:           baseDirectory + "/samples_by_fingerprint",
 					CacheSizeBytes: *fingerprintsToLabelPairCacheSize,
 				}
@@ -137,11 +141,13 @@ func NewLevelDBMetricPersistence(baseDirectory string) (*LevelDBMetricPersistenc
 			"High Watermarks by Fingerprint",
 			func() {
 				var err error
-				o := &leveldb.LevelDBOptions{
-					Path:           baseDirectory + "/high_watermarks_by_fingerprint",
-					CacheSizeBytes: *highWatermarkCacheSize,
-				}
-				emission.MetricHighWatermarks, err = leveldb.NewLevelDBPersistence(o)
+				emission.MetricHighWatermarks, err = NewLevelDBHighWatermarker(&LevelDBHighWatermarkerOptions{
+					LevelDBOptions: leveldb.LevelDBOptions{
+						Name:           "High Watermarks",
+						Purpose:        "The youngest sample in the database per metric.",
+						Path:           baseDirectory + "/high_watermarks_by_fingerprint",
+						CacheSizeBytes: *highWatermarkCacheSize,
+					}})
 				workers.MayFail(err)
 			},
 		},
@@ -151,6 +157,8 @@ func NewLevelDBMetricPersistence(baseDirectory string) (*LevelDBMetricPersistenc
 				var err error
 				emission.labelNameToFingerprints, err = NewLevelLabelNameFingerprintIndex(&LevelDBLabelNameFingerprintIndexOptions{
 					LevelDBOptions: leveldb.LevelDBOptions{
+						Name:           "Fingerprints by Label Name",
+						Purpose:        "Index",
 						Path:           baseDirectory + "/fingerprints_by_label_name",
 						CacheSizeBytes: *labelNameToFingerprintsCacheSize,
 					},
@@ -164,6 +172,8 @@ func NewLevelDBMetricPersistence(baseDirectory string) (*LevelDBMetricPersistenc
 				var err error
 				emission.labelSetToFingerprints, err = NewLevelDBLabelSetFingerprintIndex(&LevelDBLabelSetFingerprintIndexOptions{
 					LevelDBOptions: leveldb.LevelDBOptions{
+						Name:           "Fingerprints by Label Pair",
+						Purpose:        "Index",
 						Path:           baseDirectory + "/fingerprints_by_label_name_and_value_pair",
 						CacheSizeBytes: *labelPairToFingerprintsCacheSize,
 					},
@@ -178,6 +188,8 @@ func NewLevelDBMetricPersistence(baseDirectory string) (*LevelDBMetricPersistenc
 				emission.metricMembershipIndex, err = NewLevelDBMetricMembershipIndex(
 					&LevelDBMetricMembershipIndexOptions{
 						LevelDBOptions: leveldb.LevelDBOptions{
+							Name:           "Metric Membership",
+							Purpose:        "Index",
 							Path:           baseDirectory + "/metric_membership_index",
 							CacheSizeBytes: *metricMembershipIndexCacheSize,
 						},
@@ -190,6 +202,8 @@ func NewLevelDBMetricPersistence(baseDirectory string) (*LevelDBMetricPersistenc
 			func() {
 				var err error
 				o := &leveldb.LevelDBOptions{
+					Name:           "Sample Curation Remarks",
+					Purpose:        "Ledger of Progress for Various Curators",
 					Path:           baseDirectory + "/curation_remarks",
 					CacheSizeBytes: *curationRemarksCacheSize,
 				}
@@ -459,41 +473,16 @@ func (l *LevelDBMetricPersistence) refreshHighWatermarks(groups map[clientmodel.
 		recordOutcome(duration, err, map[string]string{operation: refreshHighWatermarks, result: success}, map[string]string{operation: refreshHighWatermarks, result: failure})
 	}(time.Now())
 
-	batch := leveldb.NewBatch()
-	defer batch.Close()
-
-	value := &dto.MetricHighWatermark{}
-	for fingerprint, samples := range groups {
-		value.Reset()
-		f := new(dto.Fingerprint)
-		dumpFingerprint(f, &fingerprint)
-		present, err := l.MetricHighWatermarks.Get(f, value)
-		if err != nil {
-			return err
-		}
-
-		newestSampleTimestamp := samples[len(samples)-1].Timestamp
-
-		if !present {
-			value.Timestamp = proto.Int64(newestSampleTimestamp.Unix())
-			batch.Put(f, value)
-
+	b := FingerprintHighWatermarkMapping{}
+	for fp, ss := range groups {
+		if len(ss) == 0 {
 			continue
 		}
 
-		// BUG(matt): Repace this with watermark management.
-		if newestSampleTimestamp.After(time.Unix(value.GetTimestamp(), 0)) {
-			value.Timestamp = proto.Int64(newestSampleTimestamp.Unix())
-			batch.Put(f, value)
-		}
-	}
-
-	err = l.MetricHighWatermarks.Commit(batch)
-	if err != nil {
-		return err
+		b[fp] = ss[len(ss)-1].Timestamp
 	}
 
-	return nil
+	return l.MetricHighWatermarks.UpdateBatch(b)
 }
 
 func (l *LevelDBMetricPersistence) AppendSamples(samples clientmodel.Samples) (err error) {
@@ -783,7 +772,7 @@ func (l *LevelDBMetricPersistence) CompactKeyspaces() {
 	// l.fingerprintToMetrics.CompactKeyspace()
 	//	l.labelNameToFingerprints.CompactKeyspace()
 	//	l.labelSetToFingerprints.CompactKeyspace()
-	l.MetricHighWatermarks.CompactKeyspace()
+	//	l.MetricHighWatermarks.CompactKeyspace()
 	// 	l.metricMembershipIndex.CompactKeyspace()
 	l.MetricSamples.CompactKeyspace()
 }
@@ -796,30 +785,30 @@ func (l *LevelDBMetricPersistence) ApproximateSizes() (total uint64, err error)
 	}
 	total += size
 
-	// if size, err = l.fingerprintToMetrics.ApproximateSize(); err != nil {
-	// 	return 0, err
-	// }
-	// total += size
+	if size, _, err = l.fingerprintToMetrics.Size(); err != nil {
+		return 0, err
+	}
+	total += size
 
-	// if size, err = l.labelNameToFingerprints.ApproximateSize(); err != nil {
-	// 	return 0, err
-	// }
-	// total += size
+	if size, _, err = l.labelNameToFingerprints.Size(); err != nil {
+		return 0, err
+	}
+	total += size
 
-	// if size, err = l.labelSetToFingerprints.ApproximateSize(); err != nil {
-	// 	return 0, err
-	// }
-	// total += size
+	if size, _, err = l.labelSetToFingerprints.Size(); err != nil {
+		return 0, err
+	}
+	total += size
 
-	if size, err = l.MetricHighWatermarks.ApproximateSize(); err != nil {
+	if size, _, err = l.MetricHighWatermarks.Size(); err != nil {
 		return 0, err
 	}
 	total += size
 
-	// if size, err = l.metricMembershipIndex.ApproximateSize(); err != nil {
-	// 	return 0, err
-	// }
-	// total += size
+	if size, _, err = l.metricMembershipIndex.Size(); err != nil {
+		return 0, err
+	}
+	total += size
 
 	if size, err = l.MetricSamples.ApproximateSize(); err != nil {
 		return 0, err
@@ -829,43 +818,14 @@ func (l *LevelDBMetricPersistence) ApproximateSizes() (total uint64, err error)
 	return total, nil
 }
 
-func (l *LevelDBMetricPersistence) States() []leveldb.DatabaseState {
-	states := []leveldb.DatabaseState{}
-
-	state := l.CurationRemarks.State()
-	state.Name = "Curation Remarks"
-	state.Type = "Watermark"
-	states = append(states, state)
-
-	// state = l.fingerprintToMetrics.State()
-	// state.Name = "Fingerprints to Metrics"
-	// state.Type = "Index"
-	// states = append(states, state)
-
-	// state = l.labelNameToFingerprints.State()
-	// state.Name = "Label Name to Fingerprints"
-	// state.Type = "Inverted Index"
-	// states = append(states, state)
-
-	// state = l.labelSetToFingerprints.State()
-	// state.Name = "Label Pair to Fingerprints"
-	// state.Type = "Inverted Index"
-	// states = append(states, state)
-
-	state = l.MetricHighWatermarks.State()
-	state.Name = "Metric Last Write"
-	state.Type = "Watermark"
-	states = append(states, state)
-
-	// state = l.metricMembershipIndex.State()
-	// state.Name = "Metric Membership"
-	// state.Type = "Index"
-	// states = append(states, state)
-
-	state = l.MetricSamples.State()
-	state.Name = "Samples"
-	state.Type = "Time Series"
-	states = append(states, state)
-
-	return states
+func (l *LevelDBMetricPersistence) States() []string {
+	return []string{
+		l.CurationRemarks.State(),
+		l.fingerprintToMetrics.State(),
+		l.labelNameToFingerprints.State(),
+		l.labelSetToFingerprints.State(),
+		l.MetricHighWatermarks.State(),
+		l.metricMembershipIndex.State(),
+		l.MetricSamples.State(),
+	}
 }

storage/metric/processor_test.go

@@ -854,10 +854,11 @@ func TestCuratorCompactionProcessor(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		defer curatorStates.Close()
 
-		watermarkStates, err := leveldb.NewLevelDBPersistence(&leveldb.LevelDBOptions{
-			Path: watermarkDirectory.Path(),
+		watermarkStates, err := NewLevelDBHighWatermarker(&LevelDBHighWatermarkerOptions{
+			LevelDBOptions: leveldb.LevelDBOptions{
+				Path: watermarkDirectory.Path(),
+			},
 		})
 		if err != nil {
 			t.Fatal(err)
@@ -1380,8 +1381,11 @@ func TestCuratorDeletionProcessor(t *testing.T) {
 		}
 		defer curatorStates.Close()
 
-		watermarkStates, err := leveldb.NewLevelDBPersistence(&leveldb.LevelDBOptions{
-			Path: watermarkDirectory.Path()})
+		watermarkStates, err := NewLevelDBHighWatermarker(&LevelDBHighWatermarkerOptions{
+			LevelDBOptions: leveldb.LevelDBOptions{
+				Path: watermarkDirectory.Path(),
+			},
+		})
 		if err != nil {
 			t.Fatal(err)
 		}

storage/metric/tiered.go

@@ -331,7 +331,7 @@ func (t *TieredStorage) seriesTooOld(f *clientmodel.Fingerprint, i time.Time) (b
 		value := &dto.MetricHighWatermark{}
 		k := &dto.Fingerprint{}
 		dumpFingerprint(k, f)
-		diskHit, err := t.DiskStorage.MetricHighWatermarks.Get(k, value)
+		_, diskHit, err := t.DiskStorage.MetricHighWatermarks.Get(f)
 		if err != nil {
 			return false, err
 		}

storage/metric/watermark.go

@@ -23,6 +23,10 @@ import (
 	clientmodel "github.com/prometheus/client_golang/model"
 
 	dto "github.com/prometheus/prometheus/model/generated"
+
+	"github.com/prometheus/prometheus/storage"
+	"github.com/prometheus/prometheus/storage/raw"
+	"github.com/prometheus/prometheus/storage/raw/leveldb"
 )
 
 // unsafe.Sizeof(watermarks{})
@@ -162,3 +166,97 @@ func (lru *WatermarkCache) checkCapacity() {
 		lru.size -= elementSize
 	}
 }
+
+type FingerprintHighWatermarkMapping map[clientmodel.Fingerprint]time.Time
+
+type HighWatermarker interface {
+	raw.ForEacher
+
+	UpdateBatch(FingerprintHighWatermarkMapping) error
+	Get(*clientmodel.Fingerprint) (t time.Time, ok bool, err error)
+	Close() error
+	State() string
+	Size() (uint64, bool, error)
+}
+
+type leveldbHighWatermarker struct {
+	p *leveldb.LevelDBPersistence
+}
+
+func (w *leveldbHighWatermarker) Get(f *clientmodel.Fingerprint) (t time.Time, ok bool, err error) {
+	k := new(dto.Fingerprint)
+	dumpFingerprint(k, f)
+	v := new(dto.MetricHighWatermark)
+	ok, err = w.p.Get(k, v)
+	if err != nil {
+		return t, ok, err
+	}
+	if !ok {
+		return t, ok, err
+	}
+	t = time.Unix(v.GetTimestamp(), 0)
+	return t, true, nil
+}
+
+func (w *leveldbHighWatermarker) UpdateBatch(m FingerprintHighWatermarkMapping) error {
+	batch := leveldb.NewBatch()
+	defer batch.Close()
+
+	for fp, t := range m {
+		existing, present, err := w.Get(&fp)
+		if err != nil {
+			return err
+		}
+		k := new(dto.Fingerprint)
+		dumpFingerprint(k, &fp)
+		v := new(dto.MetricHighWatermark)
+		if !present {
+			v.Timestamp = proto.Int64(t.Unix())
+			batch.Put(k, v)
+
+			continue
+		}
+
+		// BUG(matt): Repace this with watermark management.
+		if t.After(existing) {
+			v.Timestamp = proto.Int64(t.Unix())
+			batch.Put(k, v)
+		}
+	}
+
+	return w.p.Commit(batch)
+}
+
+func (i *leveldbHighWatermarker) ForEach(d storage.RecordDecoder, f storage.RecordFilter, o storage.RecordOperator) (bool, error) {
+	return i.p.ForEach(d, f, o)
+}
+
+func (i *leveldbHighWatermarker) Close() error {
+	i.p.Close()
+
+	return nil
+}
+
+func (i *leveldbHighWatermarker) State() string {
+	return i.p.State()
+}
+
+func (i *leveldbHighWatermarker) Size() (uint64, bool, error) {
+	s, err := i.p.ApproximateSize()
+	return s, true, err
+}
+
+type LevelDBHighWatermarkerOptions struct {
+	leveldb.LevelDBOptions
+}
+
+func NewLevelDBHighWatermarker(o *LevelDBHighWatermarkerOptions) (HighWatermarker, error) {
+	s, err := leveldb.NewLevelDBPersistence(&o.LevelDBOptions)
+	if err != nil {
+		return nil, err
+	}
+
+	return &leveldbHighWatermarker{
+		p: s,
+	}, nil
+}

storage/raw/index/leveldb/leveldb.go

@@ -75,6 +75,6 @@ func (l *LevelDBMembershipIndex) ApproximateSize() (uint64, error) {
 	return l.persistence.ApproximateSize()
 }
 
-func (l *LevelDBMembershipIndex) State() leveldb.DatabaseState {
+func (l *LevelDBMembershipIndex) State() string {
 	return l.persistence.State()
 }

storage/raw/leveldb/leveldb.go

@@ -27,7 +27,9 @@ import (
 
 // LevelDBPersistence is a disk-backed sorted key-value store.
 type LevelDBPersistence struct {
-	path string
+	path    string
+	name    string
+	purpose string
 
 	cache        *levigo.Cache
 	filterPolicy *levigo.FilterPolicy
@@ -162,7 +164,9 @@ func (i levigoIterator) GetError() (err error) {
 }
 
 type LevelDBOptions struct {
-	Path string
+	Path    string
+	Name    string
+	Purpose string
 
 	CacheSizeBytes    int
 	OpenFileAllowance int
@@ -202,7 +206,9 @@ func NewLevelDBPersistence(o *LevelDBOptions) (*LevelDBPersistence, error) {
 	writeOptions.SetSync(o.FlushOnMutate)
 
 	return &LevelDBPersistence{
-		path: o.Path,
+		path:    o.Path,
+		name:    o.Name,
+		purpose: o.Purpose,
 
 		cache:        cache,
 		filterPolicy: filterPolicy,

storage/raw/leveldb/state.go

@@ -14,8 +14,10 @@
 package leveldb
 
 import (
+	"bytes"
+	"fmt"
+
 	"github.com/prometheus/prometheus/utility"
-	"time"
 )
 
 const (
@@ -26,9 +28,8 @@ const (
 // DatabaseState models a bundle of metadata about a LevelDB database used in
 // template format string interpolation.
 type DatabaseState struct {
-	LastRefreshed   time.Time
-	Type            string
 	Name            string
+	Purpose         string
 	Path            string
 	LowLevelStatus  string
 	SSTablesStatus  string
@@ -36,10 +37,25 @@ type DatabaseState struct {
 	Error           error
 }
 
-func (l *LevelDBPersistence) State() DatabaseState {
+func (s DatabaseState) String() string {
+	b := new(bytes.Buffer)
+
+	fmt.Fprintln(b, "Name:", s.Name)
+	fmt.Fprintln(b, "Path:", s.Path)
+	fmt.Fprintln(b, "Purpose:", s.Purpose)
+	fmt.Fprintln(b, "Low Level Diagnostics:", s.LowLevelStatus)
+	fmt.Fprintln(b, "SSTable Statistics:", s.SSTablesStatus)
+	fmt.Fprintln(b, "Approximate Size:", s.ApproximateSize)
+	fmt.Fprintln(b, "Error:", s.Error)
+
+	return b.String()
+}
+
+func (l *LevelDBPersistence) LowLevelState() DatabaseState {
 	databaseState := DatabaseState{
-		LastRefreshed:  time.Now(),
 		Path:           l.path,
+		Name:           l.name,
+		Purpose:        l.purpose,
 		LowLevelStatus: l.storage.PropertyValue(statsKey),
 		SSTablesStatus: l.storage.PropertyValue(sstablesKey),
 	}
@@ -52,3 +68,7 @@ func (l *LevelDBPersistence) State() DatabaseState {
 
 	return databaseState
 }
+
+func (l *LevelDBPersistence) State() string {
+	return l.LowLevelState().String()
+}

web/databases.go

@@ -14,15 +14,14 @@
 package web
 
 import (
-	"github.com/prometheus/prometheus/storage/raw/leveldb"
 	"net/http"
 	"sync"
 )
 
 type DatabasesHandler struct {
-	States []leveldb.DatabaseState
+	States []string
 
-	Incoming chan []leveldb.DatabaseState
+	Incoming chan []string
 
 	mutex sync.RWMutex
 }