fs/cache: factor Fs caching from fs/rc into its own package

fs/cache/cache.go

@@ -0,0 +1,92 @@
+// Package cache implements the Fs cache
+package cache
+
+import (
+	"sync"
+	"time"
+
+	"github.com/ncw/rclone/fs"
+)
+
+var (
+	fsCacheMu           sync.Mutex
+	fsCache             = map[string]*cacheEntry{}
+	fsNewFs             = fs.NewFs // for tests
+	expireRunning       = false
+	cacheExpireDuration = 300 * time.Second // expire the cache entry when it is older than this
+	cacheExpireInterval = 60 * time.Second  // interval to run the cache expire
+)
+
+type cacheEntry struct {
+	f        fs.Fs     // cached f
+	err      error     // nil or fs.ErrorIsFile
+	fsString string    // remote string
+	lastUsed time.Time // time used for expiry
+}
+
+// Get gets a fs.Fs named fsString either from the cache or creates it afresh
+func Get(fsString string) (f fs.Fs, err error) {
+	fsCacheMu.Lock()
+	defer fsCacheMu.Unlock()
+	entry, ok := fsCache[fsString]
+	if !ok {
+		f, err = fsNewFs(fsString)
+		if err != nil && err != fs.ErrorIsFile {
+			return f, err
+		}
+		entry = &cacheEntry{
+			f:        f,
+			fsString: fsString,
+			err:      err,
+		}
+		fsCache[fsString] = entry
+	}
+	entry.lastUsed = time.Now()
+	if !expireRunning {
+		time.AfterFunc(cacheExpireInterval, cacheExpire)
+		expireRunning = true
+	}
+	return entry.f, entry.err
+}
+
+// Put puts an fs.Fs named fsString into the cache
+func Put(fsString string, f fs.Fs) {
+	fsCacheMu.Lock()
+	defer fsCacheMu.Unlock()
+	fsCache[fsString] = &cacheEntry{
+		f:        f,
+		fsString: fsString,
+		lastUsed: time.Now(),
+	}
+	if !expireRunning {
+		time.AfterFunc(cacheExpireInterval, cacheExpire)
+		expireRunning = true
+	}
+}
+
+// cacheExpire expires any entries that haven't been used recently
+func cacheExpire() {
+	fsCacheMu.Lock()
+	defer fsCacheMu.Unlock()
+	now := time.Now()
+	for fsString, entry := range fsCache {
+		if now.Sub(entry.lastUsed) > cacheExpireDuration {
+			delete(fsCache, fsString)
+		}
+	}
+	if len(fsCache) != 0 {
+		time.AfterFunc(cacheExpireInterval, cacheExpire)
+		expireRunning = true
+	} else {
+		expireRunning = false
+	}
+}
+
+// Clear removes everything from the cahce
+func Clear() {
+	fsCacheMu.Lock()
+	for k := range fsCache {
+		delete(fsCache, k)
+	}
+	fsCacheMu.Unlock()
+}

fs/cache/cache_test.go

@@ -0,0 +1,147 @@
+package cache
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/ncw/rclone/fs"
+	"github.com/ncw/rclone/fstest/mockfs"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+var (
+	called      = 0
+	errSentinel = errors.New("an error")
+)
+
+func mockNewFs(t *testing.T) func() {
+	called = 0
+	oldFsNewFs := fsNewFs
+	fsNewFs = func(path string) (fs.Fs, error) {
+		assert.Equal(t, 0, called)
+		called++
+		switch path {
+		case "/":
+			return mockfs.NewFs("mock", "mock"), nil
+		case "/file.txt":
+			return mockfs.NewFs("mock", "mock"), fs.ErrorIsFile
+		case "/error":
+			return nil, errSentinel
+		}
+		panic(fmt.Sprintf("Unknown path %q", path))
+	}
+	return func() {
+		fsNewFs = oldFsNewFs
+		fsCacheMu.Lock()
+		fsCache = map[string]*cacheEntry{}
+		expireRunning = false
+		fsCacheMu.Unlock()
+	}
+}
+
+func TestGet(t *testing.T) {
+	defer mockNewFs(t)()
+
+	assert.Equal(t, 0, len(fsCache))
+
+	f, err := Get("/")
+	require.NoError(t, err)
+
+	assert.Equal(t, 1, len(fsCache))
+
+	f2, err := Get("/")
+	require.NoError(t, err)
+
+	assert.Equal(t, f, f2)
+}
+
+func TestGetFile(t *testing.T) {
+	defer mockNewFs(t)()
+
+	assert.Equal(t, 0, len(fsCache))
+
+	f, err := Get("/file.txt")
+	require.Equal(t, fs.ErrorIsFile, err)
+
+	assert.Equal(t, 1, len(fsCache))
+
+	f2, err := Get("/file.txt")
+	require.Equal(t, fs.ErrorIsFile, err)
+
+	assert.Equal(t, f, f2)
+}
+
+func TestGetError(t *testing.T) {
+	defer mockNewFs(t)()
+
+	assert.Equal(t, 0, len(fsCache))
+
+	f, err := Get("/error")
+	require.Equal(t, errSentinel, err)
+	require.Equal(t, nil, f)
+
+	assert.Equal(t, 0, len(fsCache))
+}
+
+func TestPut(t *testing.T) {
+	defer mockNewFs(t)()
+
+	f := mockfs.NewFs("mock", "mock")
+
+	assert.Equal(t, 0, len(fsCache))
+
+	Put("/alien", f)
+
+	assert.Equal(t, 1, len(fsCache))
+
+	fNew, err := Get("/alien")
+	require.NoError(t, err)
+	require.Equal(t, f, fNew)
+
+	assert.Equal(t, 1, len(fsCache))
+}
+
+func TestCacheExpire(t *testing.T) {
+	defer mockNewFs(t)()
+
+	cacheExpireInterval = time.Millisecond
+	assert.Equal(t, false, expireRunning)
+
+	_, err := Get("/")
+	require.NoError(t, err)
+
+	fsCacheMu.Lock()
+	entry := fsCache["/"]
+
+	assert.Equal(t, 1, len(fsCache))
+	fsCacheMu.Unlock()
+	cacheExpire()
+	fsCacheMu.Lock()
+	assert.Equal(t, 1, len(fsCache))
+	entry.lastUsed = time.Now().Add(-cacheExpireDuration - 60*time.Second)
+	assert.Equal(t, true, expireRunning)
+	fsCacheMu.Unlock()
+	time.Sleep(10 * time.Millisecond)
+	fsCacheMu.Lock()
+	assert.Equal(t, false, expireRunning)
+	assert.Equal(t, 0, len(fsCache))
+	fsCacheMu.Unlock()
+}
+
+func TestClear(t *testing.T) {
+	defer mockNewFs(t)()
+
+	assert.Equal(t, 0, len(fsCache))
+
+	_, err := Get("/")
+	require.NoError(t, err)
+
+	assert.Equal(t, 1, len(fsCache))
+
+	Clear()
+
+	assert.Equal(t, 0, len(fsCache))
+}