Consolidate most memory into a LRU cache

This commit also consolidates all (or the most important) memory caches in Hugo.

Fixes gohugoio#7425

cache/memcache/memcache.go

@@ -0,0 +1,241 @@
+// Copyright 2020 The Hugo Authors. All rights reserved.
+//
+// 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 memcache provides the core memory cache used in Hugo.
+package memcache
+
+import (
+	"fmt"
+	"runtime"
+	"sync/atomic"
+	"time"
+
+	"github.com/BurntSushi/locker"
+	"github.com/gohugoio/hugo/helpers"
+	"github.com/karlseguin/ccache"
+	"github.com/pbnjay/memory"
+)
+
+const (
+	gigabyte = 1 << 30
+)
+
+// Cache configures a cache.
+type Cache struct {
+	conf  Config
+	cache *ccache.LayeredCache
+
+	ttl     time.Duration
+	nlocker *locker.Locker
+
+	stats *stats
+	stop  func()
+}
+
+type stats struct {
+	memstatsStart   runtime.MemStats
+	memstatsCurrent runtime.MemStats
+	maxSize         int64
+
+	// This is an estimated/best guess value. TODO1 env factor.
+	availableMemory uint64
+
+	numItems uint64
+}
+
+func (s *stats) isLowOnMemory() bool {
+	return s.memstatsCurrent.Alloc > s.availableMemory
+}
+
+func (s *stats) newMaxSize() int64 {
+	s.maxSize = s.maxSize / 2
+	if s.maxSize < 20 {
+		s.maxSize = 20
+	}
+	return s.maxSize
+}
+
+func (s *stats) incr(i int) {
+	atomic.AddUint64(&s.numItems, uint64(i))
+}
+
+func (s *stats) decr(i int) {
+	atomic.AddUint64(&s.numItems, ^uint64(i-1))
+}
+
+type cacheEntry struct {
+	size  int64
+	value interface{}
+	err   error
+}
+
+func (c cacheEntry) Size() int64 {
+	return c.size
+}
+
+type Config struct {
+	CheckInterval time.Duration
+	MaxSize       int64
+	ItemsToPrune  uint32
+	TTL           time.Duration
+}
+
+// New creates a new cache.
+func New(conf Config) *Cache {
+	if conf.TTL == 0 {
+		conf.TTL = time.Second * 33
+	}
+	if conf.CheckInterval == 0 {
+		conf.CheckInterval = time.Second * 2
+	}
+	if conf.MaxSize == 0 {
+		conf.MaxSize = 1000
+	}
+	if conf.ItemsToPrune == 0 {
+		conf.ItemsToPrune = 200
+	}
+
+	var m runtime.MemStats
+	runtime.ReadMemStats(&m)
+
+	var availableMemory uint64
+
+	// The total memory does not exclude memory used by other processes.
+	// For now, let's say that Hugo can use a fraction of it.
+	total := memory.TotalMemory()
+	if total != 0 {
+		availableMemory = total / 4
+	} else {
+		availableMemory = 2 * gigabyte
+	}
+
+	stats := &stats{
+		memstatsStart:   m,
+		maxSize:         conf.MaxSize,
+		availableMemory: availableMemory,
+	}
+
+	if stats.isLowOnMemory() {
+		conf.MaxSize = stats.newMaxSize()
+	}
+
+	c := &Cache{
+		conf:    conf,
+		cache:   ccache.Layered(ccache.Configure().MaxSize(conf.MaxSize).ItemsToPrune(conf.ItemsToPrune)),
+		ttl:     conf.TTL,
+		stats:   stats,
+		nlocker: locker.NewLocker(),
+	}
+
+	c.stop = c.start()
+
+	return c
+}
+
+func (c *Cache) start() func() {
+	ticker := time.NewTicker(c.conf.CheckInterval)
+	quit := make(chan struct{})
+
+	checkAndAdjustMaxSize := func() {
+		var m runtime.MemStats
+		cacheDropped := c.GetDropped()
+		c.stats.decr(cacheDropped)
+
+		runtime.ReadMemStats(&m)
+		c.stats.memstatsCurrent = m
+		if c.stats.isLowOnMemory() {
+			c.cache.SetMaxSize(c.stats.newMaxSize())
+		}
+
+		fmt.Printf("\n\nAlloc = %v\nTotalAlloc = %v\nSys = %v\nNumGC = %v\nMemCacheDropped = %d\n\n", helpers.FormatByteCount(m.Alloc), helpers.FormatByteCount(m.TotalAlloc), helpers.FormatByteCount(m.Sys), m.NumGC, cacheDropped)
+
+	}
+	go func() {
+		for {
+			select {
+			case <-ticker.C:
+				checkAndAdjustMaxSize()
+			case <-quit:
+				ticker.Stop()
+				return
+			}
+		}
+	}()
+
+	return func() {
+		close(quit)
+	}
+}
+
+// Clear clears the cache state.
+// This method is not thread safe.
+func (c *Cache) Clear() {
+	c.nlocker = locker.NewLocker()
+	c.cache.Clear()
+}
+
+func (c *Cache) Has(primary, secondary string) bool {
+	return c.cache.Get(primary, secondary) != nil
+}
+
+func (c *Cache) Get(primary, secondary string) (interface{}, bool) {
+	v := c.cache.Get(primary, secondary)
+	if v == nil {
+		return nil, false
+	}
+	return v.Value(), true
+}
+
+func (c *Cache) DeleteAll(primary string) bool {
+	return c.cache.DeleteAll(primary)
+}
+
+func (c *Cache) Stop() {
+	c.stop()
+	c.cache.Stop()
+}
+
+func (c *Cache) GetDropped() int {
+	return c.cache.GetDropped()
+}
+
+// GetOrCreate tries to get the value with the given cache keys, if not found
+// create will be called and cached.
+// This method is thread safe.
+func (c *Cache) GetOrCreate(primary, secondary string, create func() (interface{}, error)) (interface{}, error) {
+	if v := c.cache.Get(primary, secondary); v != nil {
+		entry := v.Value().(cacheEntry)
+		return entry.value, entry.err
+	}
+
+	// The provided create function may be a relatively time consuming operation,
+	// and there will in the commmon case be concurrent requests for the same key'd
+	// resource, so make sure we pause these until the result is ready.
+	key := primary + secondary
+	c.nlocker.Lock(key)
+	defer c.nlocker.Unlock(key)
+
+	// Try again.
+	if v := c.cache.Get(primary, secondary); v != nil {
+		entry := v.Value().(cacheEntry)
+		return entry.value, entry.err
+	}
+
+	// Create it and store it in cache.
+	value, err := create()
+
+	c.cache.Set(primary, secondary, cacheEntry{value: value, err: err, size: 1}, c.ttl)
+	c.stats.incr(1)
+
+	return value, err
+}

cache/namedmemcache/named_cache_test.go → cache/memcache/memcache_test.go

@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2020 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -11,21 +11,22 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package namedmemcache
+package memcache
 
 import (
 	"fmt"
 	"sync"
 	"testing"
+	"time"
 
 	qt "github.com/frankban/quicktest"
 )
 
-func TestNamedCache(t *testing.T) {
+func TesCache(t *testing.T) {
 	t.Parallel()
 	c := qt.New(t)
 
-	cache := New()
+	cache := New(Config{})
 
 	counter := 0
 	create := func() (interface{}, error) {
@@ -34,29 +35,29 @@ func TestNamedCache(t *testing.T) {
 	}
 
 	for i := 0; i < 5; i++ {
-		v1, err := cache.GetOrCreate("a1", create)
+		v1, err := cache.GetOrCreate("a", "a1", create)
 		c.Assert(err, qt.IsNil)
 		c.Assert(v1, qt.Equals, 1)
-		v2, err := cache.GetOrCreate("a2", create)
+		v2, err := cache.GetOrCreate("a", "a2", create)
 		c.Assert(err, qt.IsNil)
 		c.Assert(v2, qt.Equals, 2)
 	}
 
 	cache.Clear()
 
-	v3, err := cache.GetOrCreate("a2", create)
+	v3, err := cache.GetOrCreate("a", "a2", create)
 	c.Assert(err, qt.IsNil)
 	c.Assert(v3, qt.Equals, 3)
 }
 
-func TestNamedCacheConcurrent(t *testing.T) {
+func TestCacheConcurrent(t *testing.T) {
 	t.Parallel()
 
 	c := qt.New(t)
 
 	var wg sync.WaitGroup
 
-	cache := New()
+	cache := New(Config{})
 
 	create := func(i int) func() (interface{}, error) {
 		return func() (interface{}, error) {
@@ -70,11 +71,46 @@ func TestNamedCacheConcurrent(t *testing.T) {
 			defer wg.Done()
 			for j := 0; j < 100; j++ {
 				id := fmt.Sprintf("id%d", j)
-				v, err := cache.GetOrCreate(id, create(j))
+				v, err := cache.GetOrCreate("a", id, create(j))
 				c.Assert(err, qt.IsNil)
 				c.Assert(v, qt.Equals, j)
 			}
 		}()
 	}
 	wg.Wait()
 }
+
+func TestCacheMemStats(t *testing.T) {
+	t.Parallel()
+	c := qt.New(t)
+
+	cache := New(Config{
+		ItemsToPrune:  10,
+		CheckInterval: 500 * time.Millisecond,
+	})
+
+	s := cache.stats
+
+	c.Assert(s.memstatsStart.Alloc > 0, qt.Equals, true)
+	c.Assert(s.memstatsCurrent.Alloc, qt.Equals, uint64(0))
+	c.Assert(s.availableMemory > 0, qt.Equals, true)
+	c.Assert(s.numItems, qt.Equals, uint64(0))
+
+	counter := 0
+	create := func() (interface{}, error) {
+		counter++
+		return counter, nil
+	}
+
+	for i := 1; i <= 20; i++ {
+		_, err := cache.GetOrCreate("a", fmt.Sprintf("b%d", i), create)
+		c.Assert(err, qt.IsNil)
+	}
+
+	c.Assert(s.numItems, qt.Equals, uint64(20))
+	cache.cache.SetMaxSize(10)
+	time.Sleep(time.Millisecond * 600)
+	c.Assert(int(s.numItems), qt.Equals, 10)
+
+	c.Assert(s.memstatsCurrent.Alloc > 0, qt.Equals, true)
+}