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moby--moby/pkg/discovery/memory/memory.go

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package memory
import (
"sync"
"time"
"github.com/docker/docker/pkg/discovery"
)
// Discovery implements a discovery backend that keeps
// data in memory.
type Discovery struct {
heartbeat time.Duration
values []string
mu sync.Mutex
}
func init() {
Init()
}
// Init registers the memory backend on demand.
func Init() {
discovery.Register("memory", &Discovery{})
}
// Initialize sets the heartbeat for the memory backend.
func (s *Discovery) Initialize(_ string, heartbeat time.Duration, _ time.Duration, _ map[string]string) error {
s.heartbeat = heartbeat
s.values = make([]string, 0)
return nil
}
// Watch sends periodic discovery updates to a channel.
func (s *Discovery) Watch(stopCh <-chan struct{}) (<-chan discovery.Entries, <-chan error) {
ch := make(chan discovery.Entries)
errCh := make(chan error)
ticker := time.NewTicker(s.heartbeat)
go func() {
defer close(errCh)
defer close(ch)
// Send the initial entries if available.
var currentEntries discovery.Entries
var err error
s.mu.Lock()
if len(s.values) > 0 {
currentEntries, err = discovery.CreateEntries(s.values)
}
s.mu.Unlock()
if err != nil {
errCh <- err
} else if currentEntries != nil {
ch <- currentEntries
}
// Periodically send updates.
for {
select {
case <-ticker.C:
s.mu.Lock()
newEntries, err := discovery.CreateEntries(s.values)
s.mu.Unlock()
if err != nil {
errCh <- err
continue
}
// Check if the file has really changed.
if !newEntries.Equals(currentEntries) {
ch <- newEntries
}
currentEntries = newEntries
case <-stopCh:
ticker.Stop()
return
}
}
}()
return ch, errCh
}
// Register adds a new address to the discovery.
func (s *Discovery) Register(addr string) error {
s.mu.Lock()
s.values = append(s.values, addr)
s.mu.Unlock()
return nil
}