etcd: implement temporary db support

- temporary db support is implemented with a unique key prefix
- prevent closing etcd connection when closing temporary db

database/etcddb/database.go

@@ -32,7 +32,7 @@ func NewDB(url string) (database.Storage, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &EtcDStorage{url, cli}, nil
+	return &EtcDStorage{url, cli, ""}, nil
 }
 
 func NewOpenDB(url string) (database.Storage, error) {

database/etcddb/storage.go

@@ -2,21 +2,38 @@ package etcddb
 
 import (
 	"github.com/aptly-dev/aptly/database"
+	"github.com/pborman/uuid"
 	clientv3 "go.etcd.io/etcd/client/v3"
+
+	"fmt"
 )
 
 type EtcDStorage struct {
-	url string
-	db  *clientv3.Client
+	url       string
+	db        *clientv3.Client
+	tmpPrefix string // prefix for temporary DBs
 }
 
 // CreateTemporary creates new DB of the same type in temp dir
 func (s *EtcDStorage) CreateTemporary() (database.Storage, error) {
-	return s, nil
+	tmp := uuid.NewRandom().String()
+	return &EtcDStorage{
+		url:       s.url,
+		db:        s.db,
+		tmpPrefix: tmp,
+	}, nil
+}
+
+func (s *EtcDStorage) applyPrefix(key []byte) []byte {
+	if len(s.tmpPrefix) != 0 {
+		return append([]byte(s.tmpPrefix+"/"), key...)
+	}
+	return key
 }
 
 // Get key value from etcd
 func (s *EtcDStorage) Get(key []byte) (value []byte, err error) {
+	key = s.applyPrefix(key)
 	getResp, err := s.db.Get(Ctx, string(key))
 	if err != nil {
 		return
@@ -33,6 +50,7 @@ func (s *EtcDStorage) Get(key []byte) (value []byte, err error) {
 
 // Put saves key to etcd, if key has the same value in DB already, it is not saved
 func (s *EtcDStorage) Put(key []byte, value []byte) (err error) {
+	key = s.applyPrefix(key)
 	_, err = s.db.Put(Ctx, string(key), string(value))
 	if err != nil {
 		return
@@ -42,6 +60,7 @@ func (s *EtcDStorage) Put(key []byte, value []byte) (err error) {
 
 // Delete removes key from etcd
 func (s *EtcDStorage) Delete(key []byte) (err error) {
+	key = s.applyPrefix(key)
 	_, err = s.db.Delete(Ctx, string(key))
 	if err != nil {
 		return
@@ -51,6 +70,7 @@ func (s *EtcDStorage) Delete(key []byte) (err error) {
 
 // KeysByPrefix returns all keys that start with prefix
 func (s *EtcDStorage) KeysByPrefix(prefix []byte) [][]byte {
+	prefix = s.applyPrefix(prefix)
 	result := make([][]byte, 0, 20)
 	getResp, err := s.db.Get(Ctx, string(prefix), clientv3.WithPrefix())
 	if err != nil {
@@ -67,6 +87,7 @@ func (s *EtcDStorage) KeysByPrefix(prefix []byte) [][]byte {
 
 // FetchByPrefix returns all values with keys that start with prefix
 func (s *EtcDStorage) FetchByPrefix(prefix []byte) [][]byte {
+	prefix = s.applyPrefix(prefix)
 	result := make([][]byte, 0, 20)
 	getResp, err := s.db.Get(Ctx, string(prefix), clientv3.WithPrefix())
 	if err != nil {
@@ -83,6 +104,7 @@ func (s *EtcDStorage) FetchByPrefix(prefix []byte) [][]byte {
 
 // HasPrefix checks whether it can find any key with given prefix and returns true if one exists
 func (s *EtcDStorage) HasPrefix(prefix []byte) bool {
+	prefix = s.applyPrefix(prefix)
 	getResp, err := s.db.Get(Ctx, string(prefix), clientv3.WithPrefix())
 	if err != nil {
 		return false
@@ -96,6 +118,7 @@ func (s *EtcDStorage) HasPrefix(prefix []byte) bool {
 // ProcessByPrefix iterates through all entries where key starts with prefix and calls
 // StorageProcessor on key value pair
 func (s *EtcDStorage) ProcessByPrefix(prefix []byte, proc database.StorageProcessor) error {
+	prefix = s.applyPrefix(prefix)
 	getResp, err := s.db.Get(Ctx, string(prefix), clientv3.WithPrefix())
 	if err != nil {
 		return err
@@ -112,6 +135,10 @@ func (s *EtcDStorage) ProcessByPrefix(prefix []byte, proc database.StorageProces
 
 // Close finishes etcd connect
 func (s *EtcDStorage) Close() error {
+	// do not close temporary db
+	if len(s.tmpPrefix) != 0 {
+		return nil
+	}
 	if s.db == nil {
 		return nil
 	}
@@ -132,6 +159,9 @@ func (s *EtcDStorage) Open() error {
 
 // CreateBatch creates a Batch object
 func (s *EtcDStorage) CreateBatch() database.Batch {
+	if s.db == nil {
+		return nil
+	}
 	return &EtcDBatch{
 		db: s.db,
 	}
@@ -147,13 +177,25 @@ func (s *EtcDStorage) OpenTransaction() (database.Transaction, error) {
 	return &transaction{t: kvc}, nil
 }
 
-// CompactDB compacts database by merging layers
+// CompactDB does nothing for etcd
 func (s *EtcDStorage) CompactDB() error {
 	return nil
 }
 
-// Drop removes all the etcd files (DANGEROUS!)
+// Drop removes only temporary DBs with etcd (i.e. remove all prefixed keys)
 func (s *EtcDStorage) Drop() error {
+	if len(s.tmpPrefix) != 0 {
+		getResp, err := s.db.Get(Ctx, s.tmpPrefix, clientv3.WithPrefix())
+		if err != nil {
+			return nil
+		}
+		for _, kv := range getResp.Kvs {
+			_, err = s.db.Delete(Ctx, string(kv.Key))
+			if err != nil {
+				return fmt.Errorf("cannot delete tempdb entry: %s", kv.Key)
+			}
+		}
+	}
 	return nil
 }