rclone/fs/sync/pipe.go
Nick Craig-Wood cb7a461287 sync: add a buffer for checks, uploads and renames #379
--max-backlog controls the queue length.

Add statistics for the check/upload/rename queues.

This means that checking can complete before the uploads which will
give rclone the ability to show exactly what is outstanding.
2018-08-17 17:58:00 +01:00

100 lines
1.9 KiB
Go

package sync
import (
"context"
"sync"
"github.com/ncw/rclone/fs"
)
// pipe provides an unbounded channel like experience
//
// Note unlike channels these aren't strictly ordered.
type pipe struct {
mu sync.Mutex
c chan struct{}
queue []fs.ObjectPair
closed bool
totalSize int64
stats func(items int, totalSize int64)
}
func newPipe(stats func(items int, totalSize int64), maxBacklog int) *pipe {
return &pipe{
c: make(chan struct{}, maxBacklog),
stats: stats,
}
}
// Put an pair into the pipe
//
// It returns ok = false if the context was cancelled
//
// It will panic if you call it after Close()
func (p *pipe) Put(ctx context.Context, pair fs.ObjectPair) (ok bool) {
if ctx.Err() != nil {
return false
}
p.mu.Lock()
p.queue = append(p.queue, pair)
size := pair.Src.Size()
if size > 0 {
p.totalSize += size
}
p.stats(len(p.queue), p.totalSize)
p.mu.Unlock()
select {
case <-ctx.Done():
return false
case p.c <- struct{}{}:
}
return true
}
// Get a pair from the pipe
//
// It returns ok = false if the context was cancelled or Close() has
// been called.
func (p *pipe) Get(ctx context.Context) (pair fs.ObjectPair, ok bool) {
if ctx.Err() != nil {
return
}
select {
case <-ctx.Done():
return
case _, ok = <-p.c:
if !ok {
return
}
}
p.mu.Lock()
pair, p.queue = p.queue[0], p.queue[1:]
size := pair.Src.Size()
if size > 0 {
p.totalSize -= size
}
if p.totalSize < 0 {
p.totalSize = 0
}
p.stats(len(p.queue), p.totalSize)
p.mu.Unlock()
return pair, true
}
// Stats reads the number of items in the queue and the totalSize
func (p *pipe) Stats() (items int, totalSize int64) {
p.mu.Lock()
items, totalSize = len(p.queue), p.totalSize
p.mu.Unlock()
return items, totalSize
}
// Close the pipe
//
// Writes to a closed pipe will panic as will double closing a pipe
func (p *pipe) Close() {
p.mu.Lock()
close(p.c)
p.closed = true
p.mu.Unlock()
}