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limiter.go
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/
limiter.go
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package main
import (
"sync"
"fmt"
"time"
)
type UnLimiter func()
type Limiter interface {
Allow(operation, user string, withTimeoutMillis int64) (bool, UnLimiter)
}
func NewLimiter() Limiter {
t := limiterImpl{}
t.inProgress = syncSet{
RWMutex:sync.RWMutex{},
elements:make(map[string]struct{}),
}
return &t
}
type limiterImpl struct {
inProgress syncSet
}
func (l *limiterImpl) Allow(operation, user string, withTimeoutMillis int64) (bool, UnLimiter) {
key := fmt.Sprintf("%s.%s", operation, user)
if l.inProgress.has(key) {
return false, nil
}
l.inProgress.put(key)
cancelled := make(chan struct{})
timeout := time.After(time.Duration(withTimeoutMillis) * time.Millisecond)
cancelFunc := func() {
cancelled <- struct{}{}
}
go func() {
select {
case <-cancelled: l.inProgress.rm(key)
case <-timeout: l.inProgress.rm(key)
}
}()
return true, cancelFunc
}
type syncSet struct {
sync.RWMutex
elements map[string]struct{}
}
func (s syncSet) put(elem string) {
s.Lock()
s.elements[elem] = struct{}{}
s.Unlock()
}
func (s syncSet) has(elem string) bool {
s.RLock()
_, ok := s.elements[elem]
s.RUnlock()
return ok
}
func (s syncSet) rm(elem string) {
s.Lock()
delete(s.elements, elem)
s.Unlock()
}