forked from juicedata/juicefs
/
singleflight.go
62 lines (53 loc) · 1.27 KB
/
singleflight.go
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/*
* JuiceFS, Copyright 2020 leonatone, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package chunk
import "sync"
type request struct {
wg sync.WaitGroup
val *Page
dups int
err error
}
type Controller struct {
sync.Mutex
rs map[string]*request
}
func (con *Controller) Execute(key string, fn func() (*Page, error)) (*Page, error) {
con.Lock()
if con.rs == nil {
con.rs = make(map[string]*request)
}
if c, ok := con.rs[key]; ok {
c.dups++
con.Unlock()
c.wg.Wait()
return c.val, c.err
}
c := new(request)
c.wg.Add(1)
con.rs[key] = c
con.Unlock()
c.val, c.err = fn()
con.Lock()
for i := 0; i < c.dups; i++ {
// Acquire for the pending Execute
c.val.Acquire()
}
delete(con.rs, key)
con.Unlock()
c.wg.Done()
return c.val, c.err
}