Consolidate most memory into a LRU cache

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

Fixes gohugoio#7425
Fixes gohugoio#7437
Fixes gohugoio#7436

cache/memcache/memcache.go

@@ -0,0 +1,299 @@
+// 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 (
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/BurntSushi/locker"
+	"github.com/karlseguin/ccache"
+	"github.com/pbnjay/memory"
+)
+
+const (
+	gigabyte = 1 << 30
+)
+
+type Getter interface {
+	GetOrCreate(key string, create func() (interface{}, error)) (interface{}, error)
+	Get(key string) (interface{}, bool)
+}
+
+type ClearWhen int
+
+const (
+	ClearNever ClearWhen = iota
+	ClearOnRebuild
+	ClearPerSite
+)
+
+type getter struct {
+	c         *Cache
+	partition string
+
+	clearWhen ClearWhen
+}
+
+func (g getter) GetOrCreate(key string, create func() (interface{}, error)) (interface{}, error) {
+	return g.c.getOrCreate(g.partition, key, create)
+}
+
+func (g getter) Get(key string) (interface{}, bool) {
+	return g.c.get(g.partition, key)
+}
+
+// Cache configures a cache.
+type Cache struct {
+	mu      sync.Mutex
+	getters map[string]getter
+
+	conf  Config
+	cache *ccache.LayeredCache
+
+	ttl     time.Duration
+	nlocker *locker.Locker
+
+	stats *stats
+	stop  func()
+}
+
+func (c *Cache) GetOrCreatePartition(partition string, clearWhen ClearWhen) Getter {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if strings.Contains(strings.ToLower(partition), "todo") {
+		panic("TODO1")
+	}
+
+	g, found := c.getters[partition]
+	if found {
+		return g
+	}
+
+	g = getter{
+		partition: partition,
+		c:         c,
+		clearWhen: clearWhen,
+	}
+
+	c.getters[partition] = g
+
+	return g
+}
+
+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)),
+		getters: make(map[string]getter),
+		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
+}