database: add FindLock dbutil

database/dbutil.go

@@ -15,6 +15,7 @@
 package database
 
 import (
+	"errors"
 	"time"
 
 	"github.com/deckarep/golang-set"
@@ -350,3 +351,24 @@ func ReleaseLock(datastore Datastore, name, owner string) {
 		return
 	}
 }
+
+// ErrLockNotFound is returned when FindLock succeeds, but cannot find a lock.
+var ErrLockNotFound = errors.New("no lock was found")
+
+// FindLock determines if a global lock with the provided name already exists.
+func FindLock(datastore Datastore, updaterLockName string) (owner string, expiration time.Time, err error) {
+	var tx Session
+	tx, err = datastore.Begin()
+	if err != nil {
+		return
+	}
+	defer tx.Rollback()
+
+	var found bool
+	owner, expiration, found, err = tx.FindLock(updaterLockName)
+	if err != nil && !found {
+		err = ErrLockNotFound
+	}
+
+	return
+}

updater.go

@@ -142,9 +142,9 @@ func RunUpdater(config *UpdaterConfig, datastore database.Datastore, st *stopper
 				}
 				continue
 			} else {
-				lockOwner, lockExpiration, ok, err := findLock(datastore, updaterLockName)
-				if !ok || err != nil {
-					log.Debug("update lock is already taken")
+				lockOwner, lockExpiration, err := database.FindLock(datastore, updaterLockName)
+				if err != nil {
+					log.WithError(err).Warn("failed to find update lock")
 					nextUpdate = hasLockUntil
 				} else {
 					log.WithFields(log.Fields{"lock owner": lockOwner, "lock expiration": lockExpiration}).Debug("update lock is already taken")
@@ -464,15 +464,6 @@ func doVulnerabilitiesNamespacing(vulnerabilities []database.VulnerabilityWithAf
 	return response
 }
 
-func findLock(datastore database.Datastore, updaterLockName string) (string, time.Time, bool, error) {
-	tx, err := datastore.Begin()
-	if err != nil {
-		log.WithError(err).Error()
-	}
-	defer tx.Rollback()
-	return tx.FindLock(updaterLockName)
-}
-
 // updateUpdaterFlags updates the flags specified by updaters, every transaction
 // is independent of each other.
 func updateUpdaterFlags(datastore database.Datastore, flags map[string]string) error {