azureblob: implement memory pooling to control memory use

This commit implements memory pooling to control excessive memory use
as was implemented in the s3 backend.

backend/azureblob/azureblob.go

@@ -35,6 +35,7 @@ import (
 	"github.com/rclone/rclone/lib/bucket"
 	"github.com/rclone/rclone/lib/encoder"
 	"github.com/rclone/rclone/lib/pacer"
+	"github.com/rclone/rclone/lib/pool"
 )
 
 const (
@@ -59,6 +60,8 @@ const (
 	emulatorAccount      = "devstoreaccount1"
 	emulatorAccountKey   = "Eby8vdM02xNOcqFlqUwJPLlmEtlCDXJ1OUzFT50uSRZ6IFsuFq2UVErCz4I6tq/K1SZFPTOtr/KBHBeksoGMGw=="
 	emulatorBlobEndpoint = "http://127.0.0.1:10000/devstoreaccount1"
+	memoryPoolFlushTime  = fs.Duration(time.Minute) // flush the cached buffers after this long
+	memoryPoolUseMmap    = false
 )
 
 // Register with Fs
@@ -135,6 +138,18 @@ for data integrity checking but can cause long delays for large files
 to start uploading.`,
 			Default:  false,
 			Advanced: true,
+		}, {
+			Name:     "memory_pool_flush_time",
+			Default:  memoryPoolFlushTime,
+			Advanced: true,
+			Help: `How often internal memory buffer pools will be flushed.
+Uploads which requires additional buffers (f.e multipart) will use memory pool for allocations.
+This option controls how often unused buffers will be removed from the pool.`,
+		}, {
+			Name:     "memory_pool_use_mmap",
+			Default:  memoryPoolUseMmap,
+			Advanced: true,
+			Help:     `Whether to use mmap buffers in internal memory pool.`,
 		}, {
 			Name:     config.ConfigEncoding,
 			Help:     config.ConfigEncodingHelp,
@@ -151,17 +166,19 @@ to start uploading.`,
 
 // Options defines the configuration for this backend
 type Options struct {
-	Account         string               `config:"account"`
-	Key             string               `config:"key"`
-	Endpoint        string               `config:"endpoint"`
-	SASURL          string               `config:"sas_url"`
-	UploadCutoff    fs.SizeSuffix        `config:"upload_cutoff"`
-	ChunkSize       fs.SizeSuffix        `config:"chunk_size"`
-	ListChunkSize   uint                 `config:"list_chunk"`
-	AccessTier      string               `config:"access_tier"`
-	UseEmulator     bool                 `config:"use_emulator"`
-	DisableCheckSum bool                 `config:"disable_checksum"`
-	Enc             encoder.MultiEncoder `config:"encoding"`
+	Account             string               `config:"account"`
+	Key                 string               `config:"key"`
+	Endpoint            string               `config:"endpoint"`
+	SASURL              string               `config:"sas_url"`
+	UploadCutoff        fs.SizeSuffix        `config:"upload_cutoff"`
+	ChunkSize           fs.SizeSuffix        `config:"chunk_size"`
+	ListChunkSize       uint                 `config:"list_chunk"`
+	AccessTier          string               `config:"access_tier"`
+	UseEmulator         bool                 `config:"use_emulator"`
+	DisableCheckSum     bool                 `config:"disable_checksum"`
+	MemoryPoolFlushTime fs.Duration          `config:"memory_pool_flush_time"`
+	MemoryPoolUseMmap   bool                 `config:"memory_pool_use_mmap"`
+	Enc                 encoder.MultiEncoder `config:"encoding"`
 }
 
 // Fs represents a remote azure server
@@ -180,6 +197,7 @@ type Fs struct {
 	cache         *bucket.Cache                   // cache for container creation status
 	pacer         *fs.Pacer                       // To pace and retry the API calls
 	uploadToken   *pacer.TokenDispenser           // control concurrency
+	pool          *pool.Pool                      // memory pool
 }
 
 // Object describes a azure object
@@ -399,6 +417,12 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 		client:      fshttp.NewClient(fs.Config),
 		cache:       bucket.NewCache(),
 		cntURLcache: make(map[string]*azblob.ContainerURL, 1),
+		pool: pool.New(
+			time.Duration(opt.MemoryPoolFlushTime),
+			int(opt.ChunkSize),
+			fs.Config.Transfers,
+			opt.MemoryPoolUseMmap,
+		),
 	}
 	f.setRoot(root)
 	f.features = (&fs.Features{
@@ -995,6 +1019,19 @@ func (f *Fs) Copy(ctx context.Context, src fs.Object, remote string) (fs.Object,
 	return f.NewObject(ctx, remote)
 }
 
+func (f *Fs) getMemoryPool(size int64) *pool.Pool {
+	if size == int64(f.opt.ChunkSize) {
+		return f.pool
+	}
+
+	return pool.New(
+		time.Duration(f.opt.MemoryPoolFlushTime),
+		int(size),
+		fs.Config.Transfers,
+		f.opt.MemoryPoolUseMmap,
+	)
+}
+
 // ------------------------------------------------------------
 
 // Fs returns the parent Fs
@@ -1303,6 +1340,7 @@ func (o *Object) uploadMultipart(in io.Reader, size int64, blob *azblob.BlobURL,
 	position := int64(0)
 	errs := make(chan error, 1)
 	var wg sync.WaitGroup
+	memPool := o.fs.getMemoryPool(chunkSize)
 outer:
 	for part := 0; part < int(totalParts); part++ {
 		// Check any errors
@@ -1317,23 +1355,27 @@ outer:
 			reqSize = chunkSize
 		}
 
-		// Make a block of memory
-		buf := make([]byte, reqSize)
+		// Get a block of memory from the pool and a token which limits concurrency
+		o.fs.uploadToken.Get()
+		buf := memPool.Get()
+		buf = buf[:reqSize]
 
 		// Read the chunk
 		_, err = io.ReadFull(in, buf)
 		if err != nil {
 			err = errors.Wrap(err, "multipart upload failed to read source")
+			memPool.Put(buf)       // return the buf
+			o.fs.uploadToken.Put() // return the token
 			break outer
 		}
 
 		// Transfer the chunk
 		nextID()
 		wg.Add(1)
-		o.fs.uploadToken.Get()
 		go func(part int, position int64, blockID string) {
 			defer wg.Done()
 			defer o.fs.uploadToken.Put()
+			defer memPool.Put(buf)
 			fs.Debugf(o, "Uploading part %d/%d offset %v/%v part size %v", part+1, totalParts, fs.SizeSuffix(position), fs.SizeSuffix(size), fs.SizeSuffix(chunkSize))
 
 			// Upload the block, with MD5 for check