added new cache and cacheutils packages

Signed-off-by: Miguel Ángel Ortuño <ortuman@gmail.com>

cache/cache.go

@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// Provenance-includes-location: https://github.com/thanos-io/thanos/blob/main/pkg/store/cache/cache.go
+// Provenance-includes-license: Apache-2.0
+// Provenance-includes-copyright: The Thanos Authors.
+
+package cache
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/go-kit/log"
+	"github.com/pkg/errors"
+	"github.com/prometheus/client_golang/prometheus"
+
+	"github.com/grafana/dskit/cacheutil"
+)
+
+// Cache is a generic interface.
+type Cache interface {
+	// Store data into the cache.
+	//
+	// Note that individual byte buffers may be retained by the cache!
+	Store(ctx context.Context, data map[string][]byte, ttl time.Duration)
+
+	// Fetch multiple keys from cache. Returns map of input keys to data.
+	// If key isn't in the map, data for given key was not found.
+	Fetch(ctx context.Context, keys []string) map[string][]byte
+
+	Name() string
+}
+
+const (
+	BackendMemcached = "memcached"
+)
+
+type BackendConfig struct {
+	Backend   string          `yaml:"backend"`
+	Memcached MemcachedConfig `yaml:"memcached"`
+}
+
+// Validate the config.
+func (cfg *BackendConfig) Validate() error {
+	if cfg.Backend != "" && cfg.Backend != BackendMemcached {
+		return fmt.Errorf("unsupported cache backend: %s", cfg.Backend)
+	}
+
+	if cfg.Backend == BackendMemcached {
+		if err := cfg.Memcached.Validate(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func CreateClient(cacheName string, cfg BackendConfig, logger log.Logger, reg prometheus.Registerer) (Cache, error) {
+	switch cfg.Backend {
+	case "":
+		// No caching.
+		return nil, nil
+
+	case BackendMemcached:
+		client, err := cacheutil.NewMemcachedClientWithConfig(logger, cacheName, cfg.Memcached.ToMemcachedClientConfig(), reg)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to create memcached client")
+		}
+		return NewMemcachedCache(cacheName, logger, client, reg), nil
+
+	default:
+		return nil, errors.Errorf("unsupported cache type for cache %s: %s", cacheName, cfg.Backend)
+	}
+}

cache/compression.go

@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// Provenance-includes-location: https://github.com/cortexproject/cortex/blob/master/pkg/chunk/cache/snappy.go
+// Provenance-includes-license: Apache-2.0
+// Provenance-includes-copyright: The Cortex Authors.
+
+package cache
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/go-kit/log"
+	"github.com/go-kit/log/level"
+	"github.com/golang/snappy"
+
+	"github.com/grafana/dskit/util"
+)
+
+const (
+	// CompressionSnappy is the value of the snappy compression.
+	CompressionSnappy = "snappy"
+)
+
+var (
+	supportedCompressions     = []string{CompressionSnappy}
+	errUnsupportedCompression = errors.New("unsupported compression")
+)
+
+type CompressionConfig struct {
+	Compression string `yaml:"compression"`
+}
+
+// RegisterFlagsWithPrefix registers flags with provided prefix.
+func (cfg *CompressionConfig) RegisterFlagsWithPrefix(f *flag.FlagSet, prefix string) {
+	f.StringVar(&cfg.Compression, prefix+"compression", "", fmt.Sprintf("Enable cache compression, if not empty. Supported values are: %s.", strings.Join(supportedCompressions, ", ")))
+}
+
+func (cfg *CompressionConfig) Validate() error {
+	if cfg.Compression != "" && !util.StringsContain(supportedCompressions, cfg.Compression) {
+		return errUnsupportedCompression
+	}
+
+	return nil
+}
+
+func NewCompression(cfg CompressionConfig, next Cache, logger log.Logger) Cache {
+	switch cfg.Compression {
+	case CompressionSnappy:
+		return NewSnappy(next, logger)
+	default:
+		// No compression.
+		return next
+	}
+}
+
+type snappyCache struct {
+	next   Cache
+	logger log.Logger
+}
+
+// NewSnappy makes a new snappy encoding cache wrapper.
+func NewSnappy(next Cache, logger log.Logger) Cache {
+	return &snappyCache{
+		next:   next,
+		logger: logger,
+	}
+}
+
+// Store implements Cache.
+func (s *snappyCache) Store(ctx context.Context, data map[string][]byte, ttl time.Duration) {
+	encoded := make(map[string][]byte, len(data))
+	for key, value := range data {
+		encoded[key] = snappy.Encode(nil, value)
+	}
+
+	s.next.Store(ctx, encoded, ttl)
+}
+
+// Fetch implements Cache.
+func (s *snappyCache) Fetch(ctx context.Context, keys []string) map[string][]byte {
+	found := s.next.Fetch(ctx, keys)
+	decoded := make(map[string][]byte, len(found))
+
+	for key, encodedValue := range found {
+		decodedValue, err := snappy.Decode(nil, encodedValue)
+		if err != nil {
+			level.Error(s.logger).Log("msg", "failed to decode cache entry", "err", err)
+			continue
+		}
+
+		decoded[key] = decodedValue
+	}
+
+	return decoded
+}
+
+func (s *snappyCache) Name() string {
+	return s.next.Name()
+}

cache/compression_test.go

@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package cache
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/go-kit/log"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCompressionConfig_Validate(t *testing.T) {
+	tests := map[string]struct {
+		cfg      CompressionConfig
+		expected error
+	}{
+		"should pass with default config": {
+			cfg: CompressionConfig{},
+		},
+		"should pass with snappy compression": {
+			cfg: CompressionConfig{
+				Compression: "snappy",
+			},
+		},
+		"should fail with unsupported compression": {
+			cfg: CompressionConfig{
+				Compression: "unsupported",
+			},
+			expected: errUnsupportedCompression,
+		},
+	}
+
+	for testName, testData := range tests {
+		t.Run(testName, func(t *testing.T) {
+			assert.Equal(t, testData.expected, testData.cfg.Validate())
+		})
+	}
+}
+
+func TestSnappyCache(t *testing.T) {
+	ctx := context.Background()
+	backend := NewMockCache()
+	c := NewSnappy(backend, log.NewNopLogger())
+
+	t.Run("Fetch() should return empty results if no key has been found", func(t *testing.T) {
+		assert.Empty(t, c.Fetch(ctx, []string{"a", "b", "c"}))
+	})
+
+	t.Run("Fetch() should return previously set keys", func(t *testing.T) {
+		expected := map[string][]byte{
+			"a": []byte("value-a"),
+			"b": []byte("value-b"),
+		}
+
+		c.Store(ctx, expected, time.Hour)
+		assert.Equal(t, expected, c.Fetch(ctx, []string{"a", "b", "c"}))
+	})
+
+	t.Run("Fetch() should skip entries failing to decode", func(t *testing.T) {
+		c.Store(ctx, map[string][]byte{"a": []byte("value-a")}, time.Hour)
+		backend.Store(ctx, map[string][]byte{"b": []byte("value-b")}, time.Hour)
+
+		expected := map[string][]byte{
+			"a": []byte("value-a"),
+		}
+		assert.Equal(t, expected, c.Fetch(ctx, []string{"a", "b", "c"}))
+	})
+}

cache/lru.go

@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package cache
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	lru "github.com/hashicorp/golang-lru/simplelru"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+type LRUCache struct {
+	c          Cache
+	defaultTTL time.Duration
+	name       string
+
+	mtx sync.Mutex
+	lru *lru.LRU
+
+	requests prometheus.Counter
+	hits     prometheus.Counter
+	items    prometheus.GaugeFunc
+}
+
+type Item struct {
+	Data      []byte
+	ExpiresAt time.Time
+}
+
+// WrapWithLRUCache wraps a given `Cache` c with a LRU cache. The LRU cache will always store items in both caches.
+// However it will only fetch items from the underlying cache if the LRU cache doesn't have the item.
+// Items fetched from the underlying cache will be stored in the LRU cache with a default TTL.
+// The LRU cache will also remove items from the underlying cache if they are expired.
+// The LRU cache is limited in number of items using `lruSize`. This means this cache is not tailored for large items or items that have a big
+// variation in size.
+func WrapWithLRUCache(c Cache, name string, reg prometheus.Registerer, lruSize int, defaultTTL time.Duration) (*LRUCache, error) {
+	lru, err := lru.NewLRU(lruSize, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	cache := &LRUCache{
+		c:          c,
+		lru:        lru,
+		name:       name,
+		defaultTTL: defaultTTL,
+
+		requests: promauto.With(reg).NewCounter(prometheus.CounterOpts{
+			Name:        "cortex_cache_memory_requests_total",
+			Help:        "Total number of requests to the in-memory cache.",
+			ConstLabels: map[string]string{"name": name},
+		}),
+		hits: promauto.With(reg).NewCounter(prometheus.CounterOpts{
+			Name:        "cortex_cache_memory_hits_total",
+			Help:        "Total number of requests to the in-memory cache that were a hit.",
+			ConstLabels: map[string]string{"name": name},
+		}),
+	}
+
+	cache.items = promauto.With(reg).NewGaugeFunc(prometheus.GaugeOpts{
+		Name:        "cortex_cache_memory_items_count",
+		Help:        "Total number of items currently in the in-memory cache.",
+		ConstLabels: map[string]string{"name": name},
+	}, func() float64 {
+		cache.mtx.Lock()
+		defer cache.mtx.Unlock()
+
+		return float64(cache.lru.Len())
+	})
+
+	return cache, nil
+}
+
+func (l *LRUCache) Store(ctx context.Context, data map[string][]byte, ttl time.Duration) {
+	// store the data in the shared cache.
+	l.c.Store(ctx, data, ttl)
+
+	l.mtx.Lock()
+	defer l.mtx.Unlock()
+
+	for k, v := range data {
+		l.lru.Add(k, &Item{
+			Data:      v,
+			ExpiresAt: time.Now().Add(ttl),
+		})
+	}
+}
+
+func (l *LRUCache) Fetch(ctx context.Context, keys []string) (result map[string][]byte) {
+	l.requests.Add(float64(len(keys)))
+	l.mtx.Lock()
+	defer l.mtx.Unlock()
+	var (
+		found = make(map[string][]byte, len(keys))
+		miss  = make([]string, 0, len(keys))
+		now   = time.Now()
+	)
+
+	for _, k := range keys {
+		val, ok := l.lru.Get(k)
+		if !ok {
+			miss = append(miss, k)
+			continue
+		}
+		item := val.(*Item)
+		if item.ExpiresAt.After(now) {
+			found[k] = item.Data
+			continue
+		}
+		l.lru.Remove(k)
+		miss = append(miss, k)
+
+	}
+	l.hits.Add(float64(len(found)))
+
+	if len(miss) > 0 {
+		result = l.c.Fetch(ctx, miss)
+		for k, v := range result {
+			// we don't know the ttl of the result, so we use the default one.
+			l.lru.Add(k, &Item{
+				Data:      v,
+				ExpiresAt: now.Add(l.defaultTTL),
+			})
+			found[k] = v
+		}
+	}
+
+	return found
+}
+
+func (l *LRUCache) Name() string {
+	return "in-memory-" + l.name
+}