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package local
import "context"
type TokenBucket interface {
Take() <-chan struct{}
Put()
Do(context.Context, func() error) error
}
// StaticTokenBucket is a bucket with a fixed number of tokens,
// where the retrieval and return of tokens are manually controlled.
// In the initial state, the bucket is full.
type StaticTokenBucket struct {
bucket chan struct{}
}
func NewStaticTokenBucket(size int) StaticTokenBucket {
bucket := make(chan struct{}, size)
for range size {
bucket <- struct{}{}
}
return StaticTokenBucket{bucket: bucket}
}
func NewStaticTokenBucketWithMigration(oldBucket TokenBucket, size int) StaticTokenBucket {
if oldBucket != nil {
oldStaticBucket, ok := oldBucket.(StaticTokenBucket)
if ok {
oldSize := cap(oldStaticBucket.bucket)
migrateSize := oldSize
if size < migrateSize {
migrateSize = size
}
bucket := make(chan struct{}, size)
for range size - migrateSize {
bucket <- struct{}{}
}
if migrateSize != 0 {
go func() {
for range migrateSize {
<-oldStaticBucket.bucket
bucket <- struct{}{}
}
close(oldStaticBucket.bucket)
}()
}
return StaticTokenBucket{bucket: bucket}
}
}
return NewStaticTokenBucket(size)
}
// Take channel maybe closed when local driver is modified.
// don't call Put method after the channel is closed.
func (b StaticTokenBucket) Take() <-chan struct{} {
return b.bucket
}
func (b StaticTokenBucket) Put() {
b.bucket <- struct{}{}
}
func (b StaticTokenBucket) Do(ctx context.Context, f func() error) error {
select {
case <-ctx.Done():
return ctx.Err()
case _, ok := <-b.Take():
if ok {
defer b.Put()
}
}
return f()
}
// NopTokenBucket all function calls to this bucket will success immediately
type NopTokenBucket struct {
nop chan struct{}
}
func NewNopTokenBucket() NopTokenBucket {
nop := make(chan struct{})
close(nop)
return NopTokenBucket{nop}
}
func (b NopTokenBucket) Take() <-chan struct{} {
return b.nop
}
func (b NopTokenBucket) Put() {}
func (b NopTokenBucket) Do(_ context.Context, f func() error) error { return f() }
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