prometheus/storage/interface.go

// Copyright The Prometheus Authors
// 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 storage

import (
	"context"
	"errors"
	"fmt"

	"github.com/prometheus/prometheus/model/exemplar"
	"github.com/prometheus/prometheus/model/histogram"
	"github.com/prometheus/prometheus/model/labels"
	"github.com/prometheus/prometheus/model/metadata"
	"github.com/prometheus/prometheus/tsdb/chunkenc"
	"github.com/prometheus/prometheus/tsdb/chunks"
	"github.com/prometheus/prometheus/util/annotations"
)

// The errors exposed.
var (
	ErrNotFound = errors.New("not found")
	// ErrOutOfOrderSample is when out of order support is disabled and the sample is out of order.
	ErrOutOfOrderSample = errors.New("out of order sample")
	// ErrOutOfBounds is when out of order support is disabled and the sample is older than the min valid time for the append.
	ErrOutOfBounds = errors.New("out of bounds")
	// ErrTooOldSample is when out of order support is enabled but the sample is outside the time window allowed.
	ErrTooOldSample = errors.New("too old sample")
	// ErrDuplicateSampleForTimestamp is when the sample has same timestamp but different value.
	ErrDuplicateSampleForTimestamp = errDuplicateSampleForTimestamp{}
	ErrOutOfOrderExemplar          = errors.New("out of order exemplar")
	ErrDuplicateExemplar           = errors.New("duplicate exemplar")
	ErrExemplarLabelLength         = fmt.Errorf("label length for exemplar exceeds maximum of %d UTF-8 characters", exemplar.ExemplarMaxLabelSetLength)
	ErrExemplarsDisabled           = errors.New("exemplar storage is disabled or max exemplars is less than or equal to 0")
	ErrNativeHistogramsDisabled    = errors.New("native histograms are disabled")

	// ErrOutOfOrderST indicates failed append of ST to the storage
	// due to ST being older the then newer sample.
	// NOTE(bwplotka): This can be both an instrumentation failure or commonly expected
	// behaviour, and we currently don't have a way to determine this. As a result
	// it's recommended to ignore this error for now.
	// TODO(bwplotka): Remove with appender v1 flow; not used in v2.
	ErrOutOfOrderST      = errors.New("start timestamp out of order, ignoring")
	ErrSTNewerThanSample = errors.New("ST is newer or the same as sample's timestamp, ignoring")
)

// SeriesRef is a generic series reference. In prometheus it is either a
// HeadSeriesRef or BlockSeriesRef, though other implementations may have
// their own reference types.
type SeriesRef uint64

// Appendable allows creating Appender.
//
// WARNING: Work AppendableV2 is in progress. Appendable will be removed soon (ETA: Q2 2026).
type Appendable interface {
	// Appender returns a new appender for the storage.
	//
	// Implementations CAN choose whether to use the context e.g. for deadlines,
	// but it's not mandatory.
	Appender(ctx context.Context) Appender
}

// SampleAndChunkQueryable allows retrieving samples as well as encoded samples in form of chunks.
type SampleAndChunkQueryable interface {
	Queryable
	ChunkQueryable
}

// Storage ingests and manages samples, along with various indexes. All methods
// are goroutine-safe. Storage implements storage.Appender.
type Storage interface {
	SampleAndChunkQueryable
	Appendable

	// StartTime returns the oldest timestamp stored in the storage.
	StartTime() (int64, error)

	// Close closes the storage and all its underlying resources.
	Close() error
}

// ExemplarStorage ingests and manages exemplars, along with various indexes. All methods are
// goroutine-safe. ExemplarStorage implements storage.ExemplarAppender and storage.ExemplarQuerier.
type ExemplarStorage interface {
	ExemplarQueryable
	ExemplarAppender
}

// A Queryable handles queries against a storage.
// Use it when you need to have access to all samples without chunk encoding abstraction e.g promQL.
type Queryable interface {
	// Querier returns a new Querier on the storage.
	Querier(mint, maxt int64) (Querier, error)
}

// A MockQueryable is used for testing purposes so that a mock Querier can be used.
type MockQueryable struct {
	MockQuerier Querier
}

func (q *MockQueryable) Querier(int64, int64) (Querier, error) {
	return q.MockQuerier, nil
}

// Querier provides querying access over time series data of a fixed time range.
type Querier interface {
	LabelQuerier

	// Select returns a set of series that matches the given label matchers.
	// Results are not checked whether they match. Results that do not match
	// may cause undefined behavior.
	// Caller can specify if it requires returned series to be sorted. Prefer not requiring sorting for better performance.
	// It allows passing hints that can help in optimising select, but it's up to implementation how this is used if used at all.
	Select(ctx context.Context, sortSeries bool, hints *SelectHints, matchers ...*labels.Matcher) SeriesSet
}

// MockQuerier is used for test purposes to mock the selected series that is returned.
type MockQuerier struct {
	SelectMockFunction func(sortSeries bool, hints *SelectHints, matchers ...*labels.Matcher) SeriesSet
}

func (*MockQuerier) LabelValues(context.Context, string, *LabelHints, ...*labels.Matcher) ([]string, annotations.Annotations, error) {
	return nil, nil, nil
}

func (*MockQuerier) LabelNames(context.Context, *LabelHints, ...*labels.Matcher) ([]string, annotations.Annotations, error) {
	return nil, nil, nil
}

func (*MockQuerier) Close() error {
	return nil
}

func (q *MockQuerier) Select(_ context.Context, sortSeries bool, hints *SelectHints, matchers ...*labels.Matcher) SeriesSet {
	return q.SelectMockFunction(sortSeries, hints, matchers...)
}

// A ChunkQueryable handles queries against a storage.
// Use it when you need to have access to samples in encoded format.
type ChunkQueryable interface {
	// ChunkQuerier returns a new ChunkQuerier on the storage.
	ChunkQuerier(mint, maxt int64) (ChunkQuerier, error)
}

// ChunkQuerier provides querying access over time series data of a fixed time range.
type ChunkQuerier interface {
	LabelQuerier

	// Select returns a set of series that matches the given label matchers.
	// Results are not checked whether they match. Results that do not match
	// may cause undefined behavior.
	// Caller can specify if it requires returned series to be sorted. Prefer not requiring sorting for better performance.
	// It allows passing hints that can help in optimising select, but it's up to implementation how this is used if used at all.
	Select(ctx context.Context, sortSeries bool, hints *SelectHints, matchers ...*labels.Matcher) ChunkSeriesSet
}

// LabelQuerier provides querying access over labels.
type LabelQuerier interface {
	// LabelValues returns all potential values for a label name in sorted order.
	// It is not safe to use the strings beyond the lifetime of the querier.
	// If matchers are specified the returned result set is reduced
	// to label values of metrics matching the matchers.
	LabelValues(ctx context.Context, name string, hints *LabelHints, matchers ...*labels.Matcher) ([]string, annotations.Annotations, error)

	// LabelNames returns all the unique label names present in the block in sorted order.
	// If matchers are specified the returned result set is reduced
	// to label names of metrics matching the matchers.
	LabelNames(ctx context.Context, hints *LabelHints, matchers ...*labels.Matcher) ([]string, annotations.Annotations, error)

	// Close releases the resources of the Querier.
	Close() error
}

type ExemplarQueryable interface {
	// ExemplarQuerier returns a new ExemplarQuerier on the storage.
	ExemplarQuerier(ctx context.Context) (ExemplarQuerier, error)
}

// ExemplarQuerier provides reading access to time series data.
type ExemplarQuerier interface {
	// Select all the exemplars that match the matchers.
	// Within a single slice of matchers, it is an intersection. Between the slices, it is a union.
	Select(start, end int64, matchers ...[]*labels.Matcher) ([]exemplar.QueryResult, error)
}

// SelectHints specifies hints passed for data selections.
// This is used only as an option for implementation to use.
type SelectHints struct {
	Start int64 // Start time in milliseconds for this select.
	End   int64 // End time in milliseconds for this select.

	// Maximum number of results returned. Use a value of 0 to disable.
	Limit int

	Step int64  // Query step size in milliseconds.
	Func string // String representation of surrounding function or aggregation.

	Grouping []string // List of label names used in aggregation.
	By       bool     // Indicate whether it is without or by.
	Range    int64    // Range vector selector range in milliseconds.

	// ShardCount is the total number of shards that series should be split into
	// at query time. Then, only series in the ShardIndex shard will be returned
	// by the query.
	//
	// ShardCount equal to 0 means that sharding is disabled.
	ShardCount uint64

	// ShardIndex is the series shard index to query. The index must be between 0 and ShardCount-1.
	// When ShardCount is set to a value > 0, then a query will only process series within the
	// ShardIndex's shard.
	//
	// Series are sharded by "labels stable hash" mod "ShardCount".
	ShardIndex uint64

	// DisableTrimming allows to disable trimming of matching series chunks based on query Start and End time.
	// When disabled, the result may contain samples outside the queried time range but Select() performances
	// may be improved.
	DisableTrimming bool

	// Projection hints. They are currently unused in the Prometheus promql engine but can be used by different
	// implementations of the Queryable interface and engines.
	// These hints are useful for queries like `sum by (label) (rate(metric[5m]))` - we can safely evaluate it
	// even if we only fetch the `label` label. For some storage implementations this is beneficial.

	// ProjectionLabels are the minimum amount of labels required to be fetched for this Select call
	// When honored it is required to add an __series_hash__ label containing the hash of all labels
	// of a particular series so that the engine can still perform horizontal joins.
	ProjectionLabels []string

	// ProjectionInclude defines if we have to include or exclude the labels from the ProjectLabels field.
	ProjectionInclude bool
}

// LabelHints specifies hints passed for label reads.
// This is used only as an option for implementation to use.
type LabelHints struct {
	// Maximum number of results returned. Use a value of 0 to disable.
	Limit int
}

// QueryableFunc is an adapter to allow the use of ordinary functions as
// Queryables. It follows the idea of http.HandlerFunc.
// TODO(bwplotka): Move to promql/engine_test.go?
type QueryableFunc func(mint, maxt int64) (Querier, error)

// Querier calls f() with the given parameters.
func (f QueryableFunc) Querier(mint, maxt int64) (Querier, error) {
	return f(mint, maxt)
}

// AppendOptions provides options for implementations of the Appender interface.
//
// WARNING: Work AppendableV2 is in progress. Appendable will be removed soon (ETA: Q2 2026).
type AppendOptions struct {
	// DiscardOutOfOrder tells implementation that this append should not be out
	// of order. An OOO append MUST be rejected with storage.ErrOutOfOrderSample
	// error.
	DiscardOutOfOrder bool
}

// Appender provides batched appends against a storage.
// It must be completed with a call to Commit or Rollback and must not be reused afterwards.
//
// Operations on the Appender interface are not goroutine-safe.
//
// The order of samples appended via the Appender is preserved within each series.
// I.e. timestamp order within batch is not validated, samples are not reordered per timestamp or by float/histogram
// type.
//
// WARNING: Work AppendableV2 is in progress. Appendable will be removed soon (ETA: Q2 2026).
type Appender interface {
	AppenderTransaction

	// Append adds a sample pair for the given series.
	// An optional series reference can be provided to accelerate calls.
	// A series reference number is returned which can be used to add further
	// samples to the given series in the same or later transactions.
	// Returned reference numbers are ephemeral and may be rejected in calls
	// to Append() at any point. Adding the sample via Append() returns a new
	// reference number.
	// If the reference is 0 it must not be used for caching.
	Append(ref SeriesRef, l labels.Labels, t int64, v float64) (SeriesRef, error)

	// SetOptions configures the appender with specific append options such as
	// discarding out-of-order samples even if out-of-order is enabled in the TSDB.
	SetOptions(opts *AppendOptions)

	ExemplarAppender
	HistogramAppender
	MetadataUpdater
	StartTimestampAppender
}

// GetRef is an extra interface on Appenders used by downstream projects
// (e.g. Cortex) to avoid maintaining a parallel set of references.
type GetRef interface {
	// GetRef returns a reference number that can be used to pass to AppenderV2.Append(),
	// and a set of labels that will not cause another copy when passed to AppenderV2.Append().
	// 0 means the appender does not have a reference to this series.
	// hash should be a hash of lset.
	GetRef(lset labels.Labels, hash uint64) (SeriesRef, labels.Labels)
}

// ExemplarAppender provides an interface for adding samples to exemplar storage, which
// within Prometheus is in-memory only.
//
// WARNING: Work AppendableV2 is in progress. Appendable will be removed soon (ETA: Q2 2026).
type ExemplarAppender interface {
	// AppendExemplar adds an exemplar for the given series labels.
	// An optional reference number can be provided to accelerate calls.
	// A reference number is returned which can be used to add further
	// exemplars in the same or later transactions.
	// Returned reference numbers are ephemeral and may be rejected in calls
	// to Append() at any point. Adding the sample via Append() returns a new
	// reference number.
	// If the reference is 0 it must not be used for caching.
	// Note that in our current implementation of Prometheus' exemplar storage
	// calls to Append should generate the reference numbers, AppendExemplar
	// generating a new reference number should be considered possible erroneous behaviour and be logged.
	AppendExemplar(ref SeriesRef, l labels.Labels, e exemplar.Exemplar) (SeriesRef, error)
}

// HistogramAppender provides an interface for appending histograms to the storage.
//
// WARNING: Work AppendableV2 is in progress. Appendable will be removed soon (ETA: Q2 2026).
type HistogramAppender interface {
	// AppendHistogram adds a histogram for the given series labels. An
	// optional reference number can be provided to accelerate calls. A
	// reference number is returned which can be used to add further
	// histograms in the same or later transactions. Returned reference
	// numbers are ephemeral and may be rejected in calls to Append() at any
	// point. Adding the sample via Append() returns a new reference number.
	// If the reference is 0, it must not be used for caching.
	//
	// For efficiency reasons, the histogram is passed as a
	// pointer. AppendHistogram won't mutate the histogram, but in turn
	// depends on the caller to not mutate it either.
	AppendHistogram(ref SeriesRef, l labels.Labels, t int64, h *histogram.Histogram, fh *histogram.FloatHistogram) (SeriesRef, error)
	// AppendHistogramSTZeroSample adds synthetic zero sample for the given st timestamp,
	// which will be associated with given series, labels and the incoming
	// sample's t (timestamp). AppendHistogramSTZeroSample returns error if zero sample can't be
	// appended, for example when st is too old, or when it would collide with
	// incoming sample (sample has priority).
	//
	// AppendHistogramSTZeroSample has to be called before the corresponding histogram AppendHistogram.
	// A series reference number is returned which can be used to modify the
	// ST for the given series in the same or later transactions.
	// Returned reference numbers are ephemeral and may be rejected in calls
	// to AppendHistogramSTZeroSample() at any point.
	//
	// If the reference is 0 it must not be used for caching.
	AppendHistogramSTZeroSample(ref SeriesRef, l labels.Labels, t, st int64, h *histogram.Histogram, fh *histogram.FloatHistogram) (SeriesRef, error)
}

// MetadataUpdater provides an interface for associating metadata to stored series.
//
// WARNING: Work AppendableV2 is in progress. Appendable will be removed soon (ETA: Q2 2026).
type MetadataUpdater interface {
	// UpdateMetadata updates a metadata entry for the given series and labels.
	// A series reference number is returned which can be used to modify the
	// metadata of the given series in the same or later transactions.
	// Returned reference numbers are ephemeral and may be rejected in calls
	// to UpdateMetadata() at any point. If the series does not exist,
	// UpdateMetadata returns an error.
	// If the reference is 0 it must not be used for caching.
	UpdateMetadata(ref SeriesRef, l labels.Labels, m metadata.Metadata) (SeriesRef, error)
}

// StartTimestampAppender provides an interface for appending ST to storage.
//
// WARNING: Work AppendableV2 is in progress. Appendable will be removed soon (ETA: Q2 2026).
type StartTimestampAppender interface {
	// AppendSTZeroSample adds synthetic zero sample for the given st timestamp,
	// which will be associated with given series, labels and the incoming
	// sample's t (timestamp). AppendSTZeroSample returns error if zero sample can't be
	// appended, for example when st is too old, or when it would collide with
	// incoming sample (sample has priority).
	//
	// AppendSTZeroSample has to be called before the corresponding sample Append.
	// A series reference number is returned which can be used to modify the
	// ST for the given series in the same or later transactions.
	// Returned reference numbers are ephemeral and may be rejected in calls
	// to AppendSTZeroSample() at any point.
	//
	// If the reference is 0 it must not be used for caching.
	AppendSTZeroSample(ref SeriesRef, l labels.Labels, t, st int64) (SeriesRef, error)
}

// SeriesSet contains a set of series.
type SeriesSet interface {
	Next() bool
	// At returns full series. Returned series should be iterable even after Next is called.
	At() Series
	// Err returns the error that iteration has failed with.
	// When an error occurs, set cannot continue to iterate.
	Err() error
	// Warnings returns a collection of warnings for the whole set.
	// Warnings could be return even iteration has not failed with error.
	Warnings() annotations.Annotations
}

var emptySeriesSet = errSeriesSet{}

// EmptySeriesSet returns a series set that's always empty.
func EmptySeriesSet() SeriesSet {
	return emptySeriesSet
}

type testSeriesSet struct {
	series Series
}

func (testSeriesSet) Next() bool                        { return true }
func (s testSeriesSet) At() Series                      { return s.series }
func (testSeriesSet) Err() error                        { return nil }
func (testSeriesSet) Warnings() annotations.Annotations { return nil }

// TestSeriesSet returns a mock series set.
func TestSeriesSet(series Series) SeriesSet {
	return testSeriesSet{series: series}
}

type errSeriesSet struct {
	err error
}

func (errSeriesSet) Next() bool                        { return false }
func (errSeriesSet) At() Series                        { return nil }
func (s errSeriesSet) Err() error                      { return s.err }
func (errSeriesSet) Warnings() annotations.Annotations { return nil }

// ErrSeriesSet returns a series set that wraps an error.
func ErrSeriesSet(err error) SeriesSet {
	return errSeriesSet{err: err}
}

var emptyChunkSeriesSet = errChunkSeriesSet{}

// EmptyChunkSeriesSet returns a chunk series set that's always empty.
func EmptyChunkSeriesSet() ChunkSeriesSet {
	return emptyChunkSeriesSet
}

type errChunkSeriesSet struct {
	err error
}

func (errChunkSeriesSet) Next() bool                        { return false }
func (errChunkSeriesSet) At() ChunkSeries                   { return nil }
func (s errChunkSeriesSet) Err() error                      { return s.err }
func (errChunkSeriesSet) Warnings() annotations.Annotations { return nil }

// ErrChunkSeriesSet returns a chunk series set that wraps an error.
func ErrChunkSeriesSet(err error) ChunkSeriesSet {
	return errChunkSeriesSet{err: err}
}

// Series exposes a single time series and allows iterating over samples.
type Series interface {
	Labels
	SampleIterable
}

type mockSeries struct {
	startTimestamps []int64
	timestamps      []int64
	values          []float64
	labelSet        []string
}

func (s mockSeries) Labels() labels.Labels {
	return labels.FromStrings(s.labelSet...)
}

func (s mockSeries) Iterator(chunkenc.Iterator) chunkenc.Iterator {
	return chunkenc.MockSeriesIterator(s.startTimestamps, s.timestamps, s.values)
}

// MockSeries returns a series with custom start timestamp, timestamps, values,
// and labelSet.
// Start timestamps is optional, pass nil or empty slice to indicate no start
// timestamps.
func MockSeries(startTimestamps, timestamps []int64, values []float64, labelSet []string) Series {
	return mockSeries{
		startTimestamps: startTimestamps,
		timestamps:      timestamps,
		values:          values,
		labelSet:        labelSet,
	}
}

// ChunkSeriesSet contains a set of chunked series.
type ChunkSeriesSet interface {
	Next() bool
	// At returns full chunk series. Returned series should be iterable even after Next is called.
	At() ChunkSeries
	// The error that iteration has failed with.
	// When an error occurs, set cannot continue to iterate.
	Err() error
	// A collection of warnings for the whole set.
	// Warnings could be return even iteration has not failed with error.
	Warnings() annotations.Annotations
}

// ChunkSeries exposes a single time series and allows iterating over chunks.
type ChunkSeries interface {
	Labels
	ChunkIterable
}

// Labels represents an item that has labels e.g. time series.
type Labels interface {
	// Labels returns the complete set of labels. For series it means all labels identifying the series.
	Labels() labels.Labels
}

type SampleIterable interface {
	// Iterator returns an iterator of the data of the series.
	// The iterator passed as argument is for re-use, if not nil.
	// Depending on implementation, the iterator can
	// be re-used or a new iterator can be allocated.
	Iterator(chunkenc.Iterator) chunkenc.Iterator
}

type ChunkIterable interface {
	// Iterator returns an iterator that iterates over potentially overlapping
	// chunks of the series, sorted by min time.
	Iterator(chunks.Iterator) chunks.Iterator
}