Add central LRU cache that adjusts to available memory

Hugo has always been a active user of in-memory caches, but before this commit we did nothing to control the memory usage.

One failing example would be loading lots of big JSON data files and unmarshal them via `transform.Unmarshal`.

This commit consolidates all these caches into one single LRU cache with an eviction strategy that also considers used vs. available memory.

Hugo will try to limit its memory usage to 1/4 or total system memory, but this can be controlled with the `HUGO_MEMORYLIMIT` environment variable (a float value representing Gigabytes).

A natural next step after this would be to use this cache for `.Content`.

Fixes #7425
Fixes #7437
Fixes #7436
Updates #7544

cache/memcache/memcache_test.go

@@ -0,0 +1,169 @@
+// 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
+
+import (
+	"fmt"
+	"path/filepath"
+	"sync"
+	"testing"
+	"time"
+
+	qt "github.com/frankban/quicktest"
+)
+
+func TestCache(t *testing.T) {
+	t.Parallel()
+	c := qt.New(t)
+
+	cache := New(Config{})
+
+	counter := 0
+	create := func() Entry {
+		counter++
+		return Entry{Value: counter}
+	}
+
+	for i := 0; i < 5; i++ {
+		v1, err := cache.getOrCreate("a", "a1", create)
+		c.Assert(err, qt.IsNil)
+		c.Assert(v1, qt.Equals, 1)
+		v2, err := cache.getOrCreate("a", "a2", create)
+		c.Assert(err, qt.IsNil)
+		c.Assert(v2, qt.Equals, 2)
+	}
+
+	cache.Clear()
+
+	v3, err := cache.getOrCreate("a", "a2", create)
+	c.Assert(err, qt.IsNil)
+	c.Assert(v3, qt.Equals, 3)
+}
+
+func TestCacheConcurrent(t *testing.T) {
+	t.Parallel()
+
+	c := qt.New(t)
+
+	var wg sync.WaitGroup
+
+	cache := New(Config{})
+
+	create := func(i int) func() Entry {
+		return func() Entry {
+			return Entry{Value: i}
+		}
+	}
+
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for j := 0; j < 100; j++ {
+				id := fmt.Sprintf("id%d", 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() Entry {
+		counter++
+		return Entry{Value: counter}
+	}
+
+	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)
+}
+
+func TestSplitBasePathAndExt(t *testing.T) {
+	t.Parallel()
+	c := qt.New(t)
+
+	tests := []struct {
+		path string
+		a    string
+		b    string
+	}{
+		{"a/b.json", "a", "json"},
+		{"a/b/c/d.json", "a", "json"},
+	}
+	for i, this := range tests {
+		msg := qt.Commentf("test %d", i)
+		a, b := splitBasePathAndExt(this.path)
+
+		c.Assert(a, qt.Equals, this.a, msg)
+		c.Assert(b, qt.Equals, this.b, msg)
+	}
+
+}
+
+func TestCleanKey(t *testing.T) {
+	c := qt.New(t)
+
+	c.Assert(CleanKey(filepath.FromSlash("a/b/c.js")), qt.Equals, "a/b/c.js")
+	c.Assert(CleanKey("a//b////c.js"), qt.Equals, "a/b/c.js")
+	c.Assert(CleanKey("a.js"), qt.Equals, "_root/a.js")
+	c.Assert(CleanKey("b/a"), qt.Equals, "b/a.unkn")
+
+}
+
+func TestKeyValid(t *testing.T) {
+	c := qt.New(t)
+
+	c.Assert(keyValid("a/b.j"), qt.Equals, true)
+	c.Assert(keyValid("a/b."), qt.Equals, false)
+	c.Assert(keyValid("a/b"), qt.Equals, false)
+	c.Assert(keyValid("/a/b.txt"), qt.Equals, false)
+	c.Assert(keyValid("a\\b.js"), qt.Equals, false)
+
+}
+
+func TestInsertKeyPathElement(t *testing.T) {
+	c := qt.New(t)
+
+	c.Assert(InsertKeyPathElements("a/b.j", "en"), qt.Equals, "a/en/b.j")
+	c.Assert(InsertKeyPathElements("a/b.j", "en", "foo"), qt.Equals, "a/en/foo/b.j")
+	c.Assert(InsertKeyPathElements("a/b.j", "", "foo"), qt.Equals, "a/foo/b.j")
+
+}

commands/hugo.go

@@ -433,8 +433,14 @@ func (c *commandeer) initMemTicker() func() {
 	quit := make(chan struct{})
 	printMem := func() {
 		var m runtime.MemStats
+		var cacheDropped int
+		h := c.hugo()
+		if h != nil && h.MemCache != nil {
+			cacheDropped = h.MemCache.GetDropped()
+		}
+
 		runtime.ReadMemStats(&m)
-		fmt.Printf("\n\nAlloc = %v\nTotalAlloc = %v\nSys = %v\nNumGC = %v\n\n", formatByteCount(m.Alloc), formatByteCount(m.TotalAlloc), formatByteCount(m.Sys), m.NumGC)
+		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)
 
 	}
 
@@ -1215,17 +1221,3 @@ func pickOneWriteOrCreatePath(events []fsnotify.Event) string {
 
 	return name
 }
-
-func formatByteCount(b uint64) string {
-	const unit = 1000
-	if b < unit {
-		return fmt.Sprintf("%d B", b)
-	}
-	div, exp := int64(unit), 0
-	for n := b / unit; n >= unit; n /= unit {
-		div *= unit
-		exp++
-	}
-	return fmt.Sprintf("%.1f %cB",
-		float64(b)/float64(div), "kMGTPE"[exp])
-}