prometheus/storage/interface.go

// Copyright 2014 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"

	"github.com/prometheus/prometheus/pkg/labels"
	"github.com/prometheus/prometheus/tsdb/chunkenc"
	"github.com/prometheus/prometheus/tsdb/chunks"
	"github.com/prometheus/prometheus/tsdb/tombstones"
)

// The errors exposed.
var (
	ErrNotFound                    = errors.New("not found")
	ErrOutOfOrderSample            = errors.New("out of order sample")
	ErrDuplicateSampleForTimestamp = errors.New("duplicate sample for timestamp")
	ErrOutOfBounds                 = errors.New("out of bounds")
)

// Appendable allows creating appenders.
type Appendable interface {
	// Appender returns a new appender for the storage.
	Appender() Appender
}

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

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

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

// A Queryable handles queries against a storage.
type Queryable interface {
	// Querier returns a new Querier on the storage.
	Querier(ctx context.Context, mint, maxt int64) (Querier, error)
}

// Querier provides querying access over time series data of a fixed
// time range.
type Querier interface {
	// Select returns a set of series that matches the given label matchers.
	// 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(sortSeries bool, hints *SelectHints, matchers ...*labels.Matcher) (SeriesSet, Warnings, error)

	// LabelValues returns all potential values for a label name.
	// It is not safe to use the strings beyond the lifefime of the querier.
	LabelValues(name string) ([]string, Warnings, error)

	// LabelNames returns all the unique label names present in the block in sorted order.
	LabelNames() ([]string, Warnings, error)

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

	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.
}

// QueryableFunc is an adapter to allow the use of ordinary functions as
// Queryables. It follows the idea of http.HandlerFunc.
type QueryableFunc func(ctx context.Context, mint, maxt int64) (Querier, error)

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

// 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.
type Appender interface {
	// Add adds a sample pair for the given series. A reference number is
	// returned which can be used to add further samples in the same or later
	// transactions.
	// Returned reference numbers are ephemeral and may be rejected in calls
	// to AddFast() at any point. Adding the sample via Add() returns a new
	// reference number.
	// If the reference is 0 it must not be used for caching.
	Add(l labels.Labels, t int64, v float64) (uint64, error)

	// AddFast adds a sample pair for the referenced series. It is generally
	// faster than adding a sample by providing its full label set.
	AddFast(ref uint64, t int64, v float64) error

	// Commit submits the collected samples and purges the batch. If Commit
	// returns a non-nil error, it also rolls back all modifications made in
	// the appender so far, as Rollback would do. In any case, an Appender
	// must not be used anymore after Commit has been called.
	Commit() error

	// Rollback rolls back all modifications made in the appender so far.
	// Appender has to be discarded after rollback.
	Rollback() error
}

// SeriesSet contains a set of series.
type SeriesSet interface {
	Next() bool
	At() Series
	Err() error
}

var emptySeriesSet = errSeriesSet{}

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

type errSeriesSet struct {
	err error
}

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

// Series represents a single time series.
type Series interface {
	// Labels returns the complete set of labels identifying the series.
	Labels() labels.Labels

	// Iterator returns a new iterator of the data of the series.
	Iterator() chunkenc.Iterator
}

// ChunkSeriesSet exposes the chunks and intervals of a series instead of the
// actual series itself.
// TODO(bwplotka): Move it to Series like Iterator that iterates over chunks and avoiding loading all of them at once.
type ChunkSeriesSet interface {
	Next() bool
	At() (labels.Labels, []chunks.Meta, tombstones.Intervals)
	Err() error
}

type Warnings []error