Do not return boltdb bucket not found error

While doing a boltdb operation and if the bucket is not found
we should not return a boltdb specific bucket not found error
because this causes leaky abstraction where in the user of libkv
needs to know about boltdb and import boltdb dependencies
neither of which is desirable. Replaced all the bucket not found
errors with the more generic `store.ErrKeyNotFound` error which
is more appropriate.

Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>

store/boltdb/boltdb.go

@@ -19,8 +19,6 @@ var (
 	// ErrMultipleEndpointsUnsupported is thrown when multiple endpoints specified for
 	// BoltDB. Endpoint has to be a local file path
 	ErrMultipleEndpointsUnsupported = errors.New("boltdb supports one endpoint and should be a file path")
-	// ErrBoltBucketNotFound is thrown when specified BoltBD bucket doesn't exist in the DB
-	ErrBoltBucketNotFound = errors.New("boltdb bucket doesn't exist")
 	// ErrBoltBucketOptionMissing is thrown when boltBcuket config option is missing
 	ErrBoltBucketOptionMissing = errors.New("boltBucket config option missing")
 )
@@ -141,7 +139,7 @@ func (b *BoltDB) Get(key string) (*store.KVPair, error) {
 	err = db.View(func(tx *bolt.Tx) error {
 		bucket := tx.Bucket(b.boltBucket)
 		if bucket == nil {
-			return ErrBoltBucketNotFound
+			return store.ErrKeyNotFound
 		}
 
 		v := bucket.Get([]byte(key))
@@ -217,7 +215,7 @@ func (b *BoltDB) Delete(key string) error {
 	err = db.Update(func(tx *bolt.Tx) error {
 		bucket := tx.Bucket(b.boltBucket)
 		if bucket == nil {
-			return ErrBoltBucketNotFound
+			return store.ErrKeyNotFound
 		}
 		err := bucket.Delete([]byte(key))
 		return err
@@ -243,7 +241,7 @@ func (b *BoltDB) Exists(key string) (bool, error) {
 	err = db.View(func(tx *bolt.Tx) error {
 		bucket := tx.Bucket(b.boltBucket)
 		if bucket == nil {
-			return ErrBoltBucketNotFound
+			return store.ErrKeyNotFound
 		}
 
 		val = bucket.Get([]byte(key))
@@ -276,7 +274,7 @@ func (b *BoltDB) List(keyPrefix string) ([]*store.KVPair, error) {
 	err = db.View(func(tx *bolt.Tx) error {
 		bucket := tx.Bucket(b.boltBucket)
 		if bucket == nil {
-			return ErrBoltBucketNotFound
+			return store.ErrKeyNotFound
 		}
 
 		cursor := bucket.Cursor()
@@ -326,7 +324,7 @@ func (b *BoltDB) AtomicDelete(key string, previous *store.KVPair) (bool, error)
 	err = db.Update(func(tx *bolt.Tx) error {
 		bucket := tx.Bucket(b.boltBucket)
 		if bucket == nil {
-			return ErrBoltBucketNotFound
+			return store.ErrKeyNotFound
 		}
 
 		val = bucket.Get([]byte(key))
@@ -370,7 +368,7 @@ func (b *BoltDB) AtomicPut(key string, value []byte, previous *store.KVPair, opt
 		bucket := tx.Bucket(b.boltBucket)
 		if bucket == nil {
 			if previous != nil {
-				return ErrBoltBucketNotFound
+				return store.ErrKeyNotFound
 			}
 			bucket, err = tx.CreateBucket(b.boltBucket)
 			if err != nil {
@@ -440,7 +438,7 @@ func (b *BoltDB) DeleteTree(keyPrefix string) error {
 	err = db.Update(func(tx *bolt.Tx) error {
 		bucket := tx.Bucket(b.boltBucket)
 		if bucket == nil {
-			return ErrBoltBucketNotFound
+			return store.ErrKeyNotFound
 		}
 
 		cursor := bucket.Cursor()