Updater: fix stuck updater process

There are several goroutines in updateWhileRenewingLock() which were
blocking updater process because they were waiting for event which never
happened when update() function was successful.

This commit adds context which unblock other goroutines when update
pass.

updater.go

@@ -132,14 +132,16 @@ func RunUpdater(config *UpdaterConfig, datastore database.Datastore, st *stopper
 			}
 
 			if acquiredLock {
-				sleepDuration, err = updateWhileRenewingLock(datastore, whoAmI, isFirstUpdate, st)
+				err = updateWhileRenewingLock(datastore, whoAmI, isFirstUpdate, st)
 				if err != nil {
 					if err == errReceivedStopSignal {
 						log.Debug("updater received stop signal")
 						return
 					}
 					log.WithError(err).Debug("failed to acquired lock")
 					sleepDuration = timeutil.ExpBackoff(sleepDuration, config.Interval)
+				} else {
+					sleepDuration = config.Interval
 				}
 			} else {
 				sleepDuration = updaterSleepBetweenLoopsDuration
@@ -156,9 +158,13 @@ func RunUpdater(config *UpdaterConfig, datastore database.Datastore, st *stopper
 
 var errReceivedStopSignal = errors.New("stopped")
 
-func updateWhileRenewingLock(datastore database.Datastore, whoAmI string, isFirstUpdate bool, st *stopper.Stopper) (sleepDuration time.Duration, err error) {
+func updateWhileRenewingLock(datastore database.Datastore, whoAmI string, isFirstUpdate bool, st *stopper.Stopper) (err error) {
 	g, ctx := errgroup.WithContext(context.Background())
+	// done context is used when updater finishes and all other
+	// go rutines in group should finish too
+	doneCtx, done := context.WithCancel(context.Background())
 	g.Go(func() error {
+		defer done()
 		return update(ctx, datastore, isFirstUpdate)
 	})
 
@@ -175,6 +181,9 @@ func updateWhileRenewingLock(datastore database.Datastore, whoAmI string, isFirs
 			case <-ctx.Done():
 				database.ReleaseLock(datastore, updaterLockName, whoAmI)
 				return ctx.Err()
+			case <-doneCtx.Done():
+				database.ReleaseLock(datastore, updaterLockName, whoAmI)
+				return nil
 			}
 		}
 	})
@@ -185,6 +194,8 @@ func updateWhileRenewingLock(datastore database.Datastore, whoAmI string, isFirs
 			return errReceivedStopSignal
 		case <-ctx.Done():
 			return ctx.Err()
+		case <-doneCtx.Done():
+			return nil
 		}
 	})