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subscription.go
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subscription.go
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package subscriptions
import (
"errors"
"fmt"
"sync"
"time"
)
type SubscriptionID string
type Subscription struct {
mu sync.RWMutex
id SubscriptionID
signal *filterSignal
quit chan struct{}
filter filter
started bool
}
func NewSubscription(namespace string, filter filter) *Subscription {
subscriptionID := NewSubscriptionID(namespace, filter.getID())
return &Subscription{
id: subscriptionID,
signal: newFilterSignal(string(subscriptionID)),
filter: filter,
}
}
func (s *Subscription) Start(checkPeriod time.Duration) error {
s.mu.Lock()
if s.started {
s.mu.Unlock()
return errors.New("subscription already started or used")
}
s.started = true
s.quit = make(chan struct{})
quit := s.quit
s.mu.Unlock()
ticker := time.NewTicker(checkPeriod)
defer ticker.Stop()
for {
select {
case <-ticker.C:
filterData, err := s.filter.getChanges()
if err != nil {
s.signal.SendError(err)
} else if len(filterData) > 0 {
s.signal.SendData(filterData)
}
case <-quit:
return nil
}
}
}
func (s *Subscription) Stop(uninstall bool) error {
s.mu.Lock()
defer s.mu.Unlock()
if !s.started {
return nil
}
select {
case _, ok := <-s.quit:
// handle a case of a closed channel
if !ok {
return nil
}
default:
close(s.quit)
}
if !uninstall {
return nil
}
return s.filter.uninstall()
}
func NewSubscriptionID(namespace, filterID string) SubscriptionID {
return SubscriptionID(fmt.Sprintf("%s-%s", namespace, filterID))
}