/
subscriber.go
101 lines (88 loc) · 2.13 KB
/
subscriber.go
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package postgres
import (
"log"
"strings"
"time"
"github.com/akornatskyy/scheduler/domain"
"github.com/lib/pq"
)
const (
chTableUpdate = "table_update"
)
type sqlSubscriber struct {
callback domain.UpdateEventCallback
listener *pq.Listener
done chan struct{}
}
func NewSubscriber(dsn string) domain.Subscriber {
minReconn := 5 * time.Second
maxReconn := time.Minute
s := &sqlSubscriber{
done: make(chan struct{}, 1),
}
s.listener = pq.NewListener(dsn, minReconn, maxReconn, s.onListenerEvent)
return s
}
func (s *sqlSubscriber) SetCallback(callback domain.UpdateEventCallback) {
s.callback = callback
}
func (s *sqlSubscriber) Start() {
go s.waitForEvents()
if err := s.listener.Listen(chTableUpdate); err != nil {
panic(err)
}
}
func (s *sqlSubscriber) Stop() {
s.done <- struct{}{}
}
func (s *sqlSubscriber) onListenerEvent(ev pq.ListenerEventType, err error) {
switch ev {
case pq.ListenerEventConnected:
if err := s.callback(domain.Connected); err != nil {
log.Printf("subscriber connected: %s", err)
}
case pq.ListenerEventDisconnected:
if err := s.callback(domain.Disconnected); err != nil {
log.Printf("subscriber disconnected: %s", err)
}
case pq.ListenerEventReconnected:
if err := s.callback(domain.Reconnected); err != nil {
log.Printf("subscriber reconnected: %s", err)
}
case pq.ListenerEventConnectionAttemptFailed:
log.Printf("subscriber connection attempt failed, %s", err)
}
}
func (s *sqlSubscriber) waitForEvents() {
log.Printf("subscriber started")
var e domain.UpdateEvent
loop:
for {
select {
case n := <-s.listener.Notify:
if n == nil {
continue
}
switch n.Channel {
case chTableUpdate:
fields := strings.Fields(n.Extra)
e.Operation = fields[0]
e.ObjectType = fields[1]
e.ObjectID = fields[2]
if err := s.callback(&e); err != nil {
log.Printf("subscriber waiting for events: %s", err)
}
}
case <-time.After(1 * time.Minute):
s.listener.Ping()
case <-s.done:
break loop
}
}
s.close()
log.Printf("subscriber stopped")
}
func (s *sqlSubscriber) close() error {
s.listener.UnlistenAll()
return s.listener.Close()
}