github.com/m3db/m3@v1.5.0/src/dbnode/storage/index/postings_list_cache.go

// Copyright (c) 2019 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package index

import (
	"errors"
	"math"
	"time"

	"github.com/m3db/m3/src/m3ninx/generated/proto/querypb"
	"github.com/m3db/m3/src/m3ninx/postings"
	"github.com/m3db/m3/src/m3ninx/search"
	"github.com/m3db/m3/src/x/instrument"

	"github.com/pborman/uuid"
	"github.com/uber-go/tally"
	"go.uber.org/zap"
)

var errInstrumentOptions = errors.New("no instrument options set")

// PatternType is an enum for the various pattern types. It allows us
// separate them logically within the cache.
type PatternType string

// Closer represents a function that will close managed resources.
type Closer func()

const (
	// PatternTypeRegexp indicates that the pattern is of type regexp.
	PatternTypeRegexp PatternType = "regexp"
	// PatternTypeTerm indicates that the pattern is of type term.
	PatternTypeTerm PatternType = "term"
	// PatternTypeField indicates that the pattern is of type field.
	PatternTypeField PatternType = "field"
	// PatternTypeSearch indicates that the pattern is of type search.
	PatternTypeSearch PatternType = "search"

	reportLoopInterval = 10 * time.Second
	emptyPattern       = ""
)

// PostingsListCacheOptions is the options struct for the query cache.
type PostingsListCacheOptions struct {
	InstrumentOptions instrument.Options
}

// Validate will return an error if the options are not valid.
func (o PostingsListCacheOptions) Validate() error {
	if o.InstrumentOptions == nil {
		return errInstrumentOptions
	}
	return nil
}

// PostingsListCache implements an LRU for caching queries and their results.
type PostingsListCache struct {
	lru *postingsListLRU

	size    int
	opts    PostingsListCacheOptions
	metrics *postingsListCacheMetrics

	logger *zap.Logger
}

// NewPostingsListCache creates a new query cache.
func NewPostingsListCache(
	size int,
	opts PostingsListCacheOptions,
) (*PostingsListCache, error) {
	err := opts.Validate()
	if err != nil {
		return nil, err
	}

	lru, err := newPostingsListLRU(postingsListLRUOptions{
		size: size,
		// Use ~1000 items per shard.
		shards: int(math.Ceil(float64(size) / 1000)),
	})
	if err != nil {
		return nil, err
	}

	plc := &PostingsListCache{
		lru:     lru,
		size:    size,
		opts:    opts,
		metrics: newPostingsListCacheMetrics(opts.InstrumentOptions.MetricsScope()),
		logger:  opts.InstrumentOptions.Logger(),
	}

	return plc, nil
}

// Start the background report loop and return a Closer to cleanup.
func (q *PostingsListCache) Start() Closer {
	return q.startReportLoop()
}

// GetRegexp returns the cached results for the provided regexp query, if any.
func (q *PostingsListCache) GetRegexp(
	segmentUUID uuid.UUID,
	field string,
	pattern string,
) (postings.List, bool) {
	return q.get(segmentUUID, field, pattern, PatternTypeRegexp)
}

// GetTerm returns the cached results for the provided term query, if any.
func (q *PostingsListCache) GetTerm(
	segmentUUID uuid.UUID,
	field string,
	pattern string,
) (postings.List, bool) {
	return q.get(segmentUUID, field, pattern, PatternTypeTerm)
}

// GetField returns the cached results for the provided field query, if any.
func (q *PostingsListCache) GetField(
	segmentUUID uuid.UUID,
	field string,
) (postings.List, bool) {
	return q.get(segmentUUID, field, emptyPattern, PatternTypeField)
}

// GetSearch returns the cached results for the provided search query, if any.
func (q *PostingsListCache) GetSearch(
	segmentUUID uuid.UUID,
	query string,
) (postings.List, bool) {
	return q.get(segmentUUID, query, emptyPattern, PatternTypeSearch)
}

func (q *PostingsListCache) get(
	segmentUUID uuid.UUID,
	field string,
	pattern string,
	patternType PatternType,
) (postings.List, bool) {
	entry, ok := q.lru.Get(segmentUUID, field, pattern, patternType)
	q.emitCacheGetMetrics(patternType, ok)
	if !ok {
		return nil, false
	}

	return entry.postings, ok
}

type cachedPostings struct {
	// key
	segmentUUID uuid.UUID
	field       string
	pattern     string
	patternType PatternType

	// value
	postings postings.List
	// searchQuery is only set for search queries.
	searchQuery *querypb.Query
}

// PutRegexp updates the LRU with the result of the regexp query.
func (q *PostingsListCache) PutRegexp(
	segmentUUID uuid.UUID,
	field string,
	pattern string,
	pl postings.List,
) {
	q.put(segmentUUID, field, pattern, PatternTypeRegexp, nil, pl)
}

// PutTerm updates the LRU with the result of the term query.
func (q *PostingsListCache) PutTerm(
	segmentUUID uuid.UUID,
	field string,
	pattern string,
	pl postings.List,
) {
	q.put(segmentUUID, field, pattern, PatternTypeTerm, nil, pl)
}

// PutField updates the LRU with the result of the field query.
func (q *PostingsListCache) PutField(
	segmentUUID uuid.UUID,
	field string,
	pl postings.List,
) {
	q.put(segmentUUID, field, emptyPattern, PatternTypeField, nil, pl)
}

// PutSearch updates the LRU with the result of a search query.
func (q *PostingsListCache) PutSearch(
	segmentUUID uuid.UUID,
	queryStr string,
	query search.Query,
	pl postings.List,
) {
	q.put(segmentUUID, queryStr, emptyPattern, PatternTypeSearch, query, pl)
}

func (q *PostingsListCache) put(
	segmentUUID uuid.UUID,
	field string,
	pattern string,
	patternType PatternType,
	searchQuery search.Query,
	pl postings.List,
) {
	var searchQueryProto *querypb.Query
	if searchQuery != nil {
		searchQueryProto = searchQuery.ToProto()
	}

	value := &cachedPostings{
		segmentUUID: segmentUUID,
		field:       field,
		pattern:     pattern,
		patternType: patternType,
		searchQuery: searchQueryProto,
		postings:    pl,
	}
	q.lru.Add(segmentUUID, field, pattern, patternType, value)

	q.emitCachePutMetrics(patternType)
}

// PurgeSegment removes all postings lists associated with the specified
// segment from the cache.
func (q *PostingsListCache) PurgeSegment(segmentUUID uuid.UUID) {
	q.lru.PurgeSegment(segmentUUID)
}

// startReportLoop starts a background process that will call Report()
// on a regular basis and returns a function that will end the background
// process.
func (q *PostingsListCache) startReportLoop() Closer {
	doneCh := make(chan struct{})

	go func() {
		for {
			select {
			case <-doneCh:
				return
			default:
			}

			q.Report()
			time.Sleep(reportLoopInterval)
		}
	}()

	return func() { close(doneCh) }
}

// CachedPattern defines a cached pattern.
type CachedPattern struct {
	CacheKey    PostingsListCacheKey
	SearchQuery *querypb.Query
	Postings    postings.List
}

// CachedPatternsResult defines the result of a cached pattern.
type CachedPatternsResult struct {
	InRegistry      bool
	TotalPatterns   int
	MatchedPatterns int
}

// CachedPatternForEachFn defines a function for iterating a cached pattern.
type CachedPatternForEachFn func(CachedPattern)

// CachedPatternsQuery defines a cached pattern query.
type CachedPatternsQuery struct {
	PatternType *PatternType
}

// CachedPatterns returns cached patterns for given query.
func (q *PostingsListCache) CachedPatterns(
	uuid uuid.UUID,
	query CachedPatternsQuery,
	fn CachedPatternForEachFn,
) CachedPatternsResult {
	var result CachedPatternsResult

	for _, shard := range q.lru.shards {
		shard.RLock()
		result = shardCachedPatternsWithRLock(uuid, query, fn, shard, result)
		shard.RUnlock()
	}

	return result
}

func shardCachedPatternsWithRLock(
	uuid uuid.UUID,
	query CachedPatternsQuery,
	fn CachedPatternForEachFn,
	shard *postingsListLRUShard,
	result CachedPatternsResult,
) CachedPatternsResult {
	segmentPostings, ok := shard.items[uuid.Array()]
	if !ok {
		return result
	}

	result.InRegistry = true
	result.TotalPatterns += len(segmentPostings)
	for key, value := range segmentPostings {
		if v := query.PatternType; v != nil && *v != key.PatternType {
			continue
		}

		fn(CachedPattern{
			CacheKey:    key,
			SearchQuery: value.Value.(*entry).cachedPostings.searchQuery,
			Postings:    value.Value.(*entry).cachedPostings.postings,
		})
		result.MatchedPatterns++
	}

	return result
}

// Report will emit metrics about the status of the cache.
func (q *PostingsListCache) Report() {
	q.metrics.capacity.Update(float64(q.size))
}

func (q *PostingsListCache) emitCacheGetMetrics(patternType PatternType, hit bool) {
	var method *postingsListCacheMethodMetrics
	switch patternType {
	case PatternTypeRegexp:
		method = q.metrics.regexp
	case PatternTypeTerm:
		method = q.metrics.term
	case PatternTypeField:
		method = q.metrics.field
	case PatternTypeSearch:
		method = q.metrics.search
	default:
		method = q.metrics.unknown // should never happen
	}
	if hit {
		method.hits.Inc(1)
	} else {
		method.misses.Inc(1)
	}
}

func (q *PostingsListCache) emitCachePutMetrics(patternType PatternType) {
	switch patternType {
	case PatternTypeRegexp:
		q.metrics.regexp.puts.Inc(1)
	case PatternTypeTerm:
		q.metrics.term.puts.Inc(1)
	case PatternTypeField:
		q.metrics.field.puts.Inc(1)
	case PatternTypeSearch:
		q.metrics.search.puts.Inc(1)
	default:
		q.metrics.unknown.puts.Inc(1) // should never happen
	}
}

type postingsListCacheMetrics struct {
	regexp  *postingsListCacheMethodMetrics
	term    *postingsListCacheMethodMetrics
	field   *postingsListCacheMethodMetrics
	search  *postingsListCacheMethodMetrics
	unknown *postingsListCacheMethodMetrics

	size     tally.Gauge
	capacity tally.Gauge

	pooledGet              tally.Counter
	pooledGetErrAddIter    tally.Counter
	pooledPut              tally.Counter
	pooledPutErrNotMutable tally.Counter
}

func newPostingsListCacheMetrics(scope tally.Scope) *postingsListCacheMetrics {
	return &postingsListCacheMetrics{
		regexp: newPostingsListCacheMethodMetrics(scope.Tagged(map[string]string{
			"query_type": "regexp",
		})),
		term: newPostingsListCacheMethodMetrics(scope.Tagged(map[string]string{
			"query_type": "term",
		})),
		field: newPostingsListCacheMethodMetrics(scope.Tagged(map[string]string{
			"query_type": "field",
		})),
		search: newPostingsListCacheMethodMetrics(scope.Tagged(map[string]string{
			"query_type": "search",
		})),
		unknown: newPostingsListCacheMethodMetrics(scope.Tagged(map[string]string{
			"query_type": "unknown",
		})),
		size:      scope.Gauge("size"),
		capacity:  scope.Gauge("capacity"),
		pooledGet: scope.Counter("pooled_get"),
		pooledGetErrAddIter: scope.Tagged(map[string]string{
			"error_type": "add_iter",
		}).Counter("pooled_get_error"),
		pooledPut: scope.Counter("pooled_put"),
		pooledPutErrNotMutable: scope.Tagged(map[string]string{
			"error_type": "not_mutable",
		}).Counter("pooled_put_error"),
	}
}

type postingsListCacheMethodMetrics struct {
	hits   tally.Counter
	misses tally.Counter
	puts   tally.Counter
}

func newPostingsListCacheMethodMetrics(scope tally.Scope) *postingsListCacheMethodMetrics {
	return &postingsListCacheMethodMetrics{
		hits:   scope.Counter("hits"),
		misses: scope.Counter("misses"),
		puts:   scope.Counter("puts"),
	}
}