rclone/backend/dropbox/batcher.go

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// This file contains the implementation of the sync batcher for uploads
//
// Dropbox rules say you can start as many batches as you want, but
// you may only have one batch being committed and must wait for the
// batch to be finished before committing another.
package dropbox
import (
"context"
"errors"
"fmt"
"sync"
"time"
2021-10-16 12:29:52 +08:00
"github.com/dropbox/dropbox-sdk-go-unofficial/v6/dropbox/async"
"github.com/dropbox/dropbox-sdk-go-unofficial/v6/dropbox/files"
"github.com/rclone/rclone/fs"
"github.com/rclone/rclone/fs/fserrors"
"github.com/rclone/rclone/lib/atexit"
)
const (
maxBatchSize = 1000 // max size the batch can be
defaultTimeoutSync = 500 * time.Millisecond // kick off the batch if nothing added for this long (sync)
defaultTimeoutAsync = 10 * time.Second // kick off the batch if nothing added for this long (ssync)
defaultBatchSizeAsync = 100 // default batch size if async
)
// batcher holds info about the current items waiting for upload
type batcher struct {
f *Fs // Fs this batch is part of
mode string // configured batch mode
size int // maximum size for batch
timeout time.Duration // idle timeout for batch
async bool // whether we are using async batching
in chan batcherRequest // incoming items to batch
closed chan struct{} // close to indicate batcher shut down
atexit atexit.FnHandle // atexit handle
shutOnce sync.Once // make sure we shutdown once only
wg sync.WaitGroup // wait for shutdown
}
// batcherRequest holds an incoming request with a place for a reply
type batcherRequest struct {
commitInfo *files.UploadSessionFinishArg
result chan<- batcherResponse
}
// Return true if batcherRequest is the quit request
func (br *batcherRequest) isQuit() bool {
return br.commitInfo == nil
}
// Send this to get the engine to quit
var quitRequest = batcherRequest{}
// batcherResponse holds a response to be delivered to clients waiting
// for a batch to complete.
type batcherResponse struct {
err error
entry *files.FileMetadata
}
// newBatcher creates a new batcher structure
func newBatcher(ctx context.Context, f *Fs, mode string, size int, timeout time.Duration) (*batcher, error) {
// fs.Debugf(f, "Creating batcher with mode %q, size %d, timeout %v", mode, size, timeout)
if size > maxBatchSize || size < 0 {
return nil, fmt.Errorf("dropbox: batch size must be < %d and >= 0 - it is currently %d", maxBatchSize, size)
}
async := false
switch mode {
case "sync":
if size <= 0 {
ci := fs.GetConfig(ctx)
size = ci.Transfers
}
if timeout <= 0 {
timeout = defaultTimeoutSync
}
case "async":
if size <= 0 {
size = defaultBatchSizeAsync
}
if timeout <= 0 {
timeout = defaultTimeoutAsync
}
async = true
case "off":
size = 0
default:
return nil, fmt.Errorf("dropbox: batch mode must be sync|async|off not %q", mode)
}
b := &batcher{
f: f,
mode: mode,
size: size,
timeout: timeout,
async: async,
in: make(chan batcherRequest, size),
closed: make(chan struct{}),
}
if b.Batching() {
b.atexit = atexit.Register(b.Shutdown)
b.wg.Add(1)
go b.commitLoop(context.Background())
}
return b, nil
}
// Batching returns true if batching is active
func (b *batcher) Batching() bool {
return b.size > 0
}
// finishBatch commits the batch, returning a batch status to poll or maybe complete
func (b *batcher) finishBatch(ctx context.Context, items []*files.UploadSessionFinishArg) (batchStatus *files.UploadSessionFinishBatchLaunch, err error) {
var arg = &files.UploadSessionFinishBatchArg{
Entries: items,
}
err = b.f.pacer.Call(func() (bool, error) {
batchStatus, err = b.f.srv.UploadSessionFinishBatch(arg)
// If error is insufficient space then don't retry
if e, ok := err.(files.UploadSessionFinishAPIError); ok {
if e.EndpointError != nil && e.EndpointError.Path != nil && e.EndpointError.Path.Tag == files.WriteErrorInsufficientSpace {
err = fserrors.NoRetryError(err)
return false, err
}
}
// after the first chunk is uploaded, we retry everything
return err != nil, err
})
if err != nil {
return nil, fmt.Errorf("batch commit failed: %w", err)
}
return batchStatus, nil
}
// finishBatchJobStatus waits for the batch to complete returning completed entries
func (b *batcher) finishBatchJobStatus(ctx context.Context, launchBatchStatus *files.UploadSessionFinishBatchLaunch) (complete *files.UploadSessionFinishBatchResult, err error) {
if launchBatchStatus.AsyncJobId == "" {
return nil, errors.New("wait for batch completion: empty job ID")
}
var batchStatus *files.UploadSessionFinishBatchJobStatus
sleepTime := 100 * time.Millisecond
const maxSleepTime = 1 * time.Second
startTime := time.Now()
try := 1
for {
remaining := time.Duration(b.f.opt.BatchCommitTimeout) - time.Since(startTime)
if remaining < 0 {
break
}
err = b.f.pacer.Call(func() (bool, error) {
batchStatus, err = b.f.srv.UploadSessionFinishBatchCheck(&async.PollArg{
AsyncJobId: launchBatchStatus.AsyncJobId,
})
return shouldRetry(ctx, err)
})
if err != nil {
fs.Debugf(b.f, "Wait for batch: sleeping for %v after error: %v: try %d remaining %v", sleepTime, err, try, remaining)
} else {
if batchStatus.Tag == "complete" {
fs.Debugf(b.f, "Upload batch completed in %v", time.Since(startTime))
return batchStatus.Complete, nil
}
fs.Debugf(b.f, "Wait for batch: sleeping for %v after status: %q: try %d remaining %v", sleepTime, batchStatus.Tag, try, remaining)
}
time.Sleep(sleepTime)
sleepTime *= 2
if sleepTime > maxSleepTime {
sleepTime = maxSleepTime
}
try++
}
if err == nil {
err = errors.New("batch didn't complete")
}
return nil, fmt.Errorf("wait for batch failed after %d tries in %v: %w", try, time.Since(startTime), err)
}
// commit a batch
func (b *batcher) commitBatch(ctx context.Context, items []*files.UploadSessionFinishArg, results []chan<- batcherResponse) (err error) {
// If commit fails then signal clients if sync
var signalled = b.async
defer func() {
if err != nil && signalled {
// Signal to clients that there was an error
for _, result := range results {
result <- batcherResponse{err: err}
}
}
}()
desc := fmt.Sprintf("%s batch length %d starting with: %s", b.mode, len(items), items[0].Commit.Path)
fs.Debugf(b.f, "Committing %s", desc)
// finalise the batch getting either a result or a job id to poll
batchStatus, err := b.finishBatch(ctx, items)
if err != nil {
return err
}
// check whether batch is complete
var complete *files.UploadSessionFinishBatchResult
switch batchStatus.Tag {
case "async_job_id":
// wait for batch to complete
complete, err = b.finishBatchJobStatus(ctx, batchStatus)
if err != nil {
return err
}
case "complete":
complete = batchStatus.Complete
default:
return fmt.Errorf("batch returned unknown status %q", batchStatus.Tag)
}
// Check we got the right number of entries
entries := complete.Entries
if len(entries) != len(results) {
return fmt.Errorf("expecting %d items in batch but got %d", len(results), len(entries))
}
// Report results to clients
var (
errorTag = ""
errorCount = 0
)
for i := range results {
item := entries[i]
resp := batcherResponse{}
if item.Tag == "success" {
resp.entry = item.Success
} else {
errorCount++
errorTag = item.Tag
if item.Failure != nil {
errorTag = item.Failure.Tag
if item.Failure.LookupFailed != nil {
errorTag += "/" + item.Failure.LookupFailed.Tag
}
if item.Failure.Path != nil {
errorTag += "/" + item.Failure.Path.Tag
}
if item.Failure.PropertiesError != nil {
errorTag += "/" + item.Failure.PropertiesError.Tag
}
}
resp.err = fmt.Errorf("batch upload failed: %s", errorTag)
}
if !b.async {
results[i] <- resp
}
}
// Show signalled so no need to report error to clients from now on
signalled = true
// Report an error if any failed in the batch
if errorTag != "" {
return fmt.Errorf("batch had %d errors: last error: %s", errorCount, errorTag)
}
fs.Debugf(b.f, "Committed %s", desc)
return nil
}
// commitLoop runs the commit engine in the background
func (b *batcher) commitLoop(ctx context.Context) {
var (
items []*files.UploadSessionFinishArg // current batch of uncommitted files
results []chan<- batcherResponse // current batch of clients awaiting results
idleTimer = time.NewTimer(b.timeout)
commit = func() {
err := b.commitBatch(ctx, items, results)
if err != nil {
fs.Errorf(b.f, "%s batch commit: failed to commit batch length %d: %v", b.mode, len(items), err)
}
items, results = nil, nil
}
)
defer b.wg.Done()
defer idleTimer.Stop()
idleTimer.Stop()
outer:
for {
select {
case req := <-b.in:
if req.isQuit() {
break outer
}
items = append(items, req.commitInfo)
results = append(results, req.result)
idleTimer.Stop()
if len(items) >= b.size {
commit()
} else {
idleTimer.Reset(b.timeout)
}
case <-idleTimer.C:
if len(items) > 0 {
fs.Debugf(b.f, "Batch idle for %v so committing", b.timeout)
commit()
}
}
}
// commit any remaining items
if len(items) > 0 {
commit()
}
}
// Shutdown finishes any pending batches then shuts everything down
//
// Can be called from atexit handler
func (b *batcher) Shutdown() {
b.shutOnce.Do(func() {
atexit.Unregister(b.atexit)
fs.Infof(b.f, "Commiting uploads - please wait...")
// show that batcher is shutting down
close(b.closed)
// quit the commitLoop by sending a quitRequest message
//
// Note that we don't close b.in because that will
// cause write to closed channel in Commit when we are
// exiting due to a signal.
b.in <- quitRequest
b.wg.Wait()
})
}
// Commit commits the file using a batch call, first adding it to the
// batch and then waiting for the batch to complete in a synchronous
// way if async is not set.
func (b *batcher) Commit(ctx context.Context, commitInfo *files.UploadSessionFinishArg) (entry *files.FileMetadata, err error) {
select {
case <-b.closed:
return nil, fserrors.FatalError(errors.New("batcher is shutting down"))
default:
}
fs.Debugf(b.f, "Adding %q to batch", commitInfo.Commit.Path)
resp := make(chan batcherResponse, 1)
b.in <- batcherRequest{
commitInfo: commitInfo,
result: resp,
}
// If running async then don't wait for the result
if b.async {
return nil, nil
}
result := <-resp
return result.entry, result.err
}