feat: Add etcd database support

improve concurrent access and high availability of aptly with the help of the characteristics of etcd

database/etcddb/storage.go

@@ -0,0 +1,163 @@
+package etcddb
+
+import (
+	"github.com/aptly-dev/aptly/database"
+	clientv3 "go.etcd.io/etcd/client/v3"
+)
+
+type EtcDStorage struct {
+	url string
+	db  *clientv3.Client
+}
+
+// CreateTemporary creates new DB of the same type in temp dir
+func (s *EtcDStorage) CreateTemporary() (database.Storage, error) {
+	return s, nil
+}
+
+// Get key value from etcd
+func (s *EtcDStorage) Get(key []byte) (value []byte, err error) {
+	getResp, err := s.db.Get(Ctx, string(key))
+	if err != nil {
+		return
+	}
+	for _, kv := range getResp.Kvs {
+		value = kv.Value
+	}
+	if len(value) == 0 {
+		err = database.ErrNotFound
+		return
+	}
+	return
+}
+
+// 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) {
+	_, err = s.db.Put(Ctx, string(key), string(value))
+	if err != nil {
+		return
+	}
+	return
+}
+
+// Delete removes key from etcd
+func (s *EtcDStorage) Delete(key []byte) (err error) {
+	_, err = s.db.Delete(Ctx, string(key))
+	if err != nil {
+		return
+	}
+	return
+}
+
+// KeysByPrefix returns all keys that start with prefix
+func (s *EtcDStorage) KeysByPrefix(prefix []byte) [][]byte {
+	result := make([][]byte, 0, 20)
+	getResp, err := s.db.Get(Ctx, string(prefix), clientv3.WithPrefix())
+	if err != nil {
+		return nil
+	}
+	for _, ev := range getResp.Kvs {
+		key := ev.Key
+		keyc := make([]byte, len(key))
+		copy(keyc, key)
+		result = append(result, key)
+	}
+	return result
+}
+
+// FetchByPrefix returns all values with keys that start with prefix
+func (s *EtcDStorage) FetchByPrefix(prefix []byte) [][]byte {
+	result := make([][]byte, 0, 20)
+	getResp, err := s.db.Get(Ctx, string(prefix), clientv3.WithPrefix())
+	if err != nil {
+		return nil
+	}
+	for _, kv := range getResp.Kvs {
+		valc := make([]byte, len(kv.Value))
+		copy(valc, kv.Value)
+		result = append(result, kv.Value)
+	}
+
+	return result
+}
+
+// HasPrefix checks whether it can find any key with given prefix and returns true if one exists
+func (s *EtcDStorage) HasPrefix(prefix []byte) bool {
+	getResp, err := s.db.Get(Ctx, string(prefix), clientv3.WithPrefix())
+	if err != nil {
+		return false
+	}
+	if getResp.Count != 0 {
+		return true
+	}
+	return false
+}
+
+// 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 {
+	getResp, err := s.db.Get(Ctx, string(prefix), clientv3.WithPrefix())
+	if err != nil {
+		return err
+	}
+
+	for _, kv := range getResp.Kvs {
+		err := proc(kv.Key, kv.Value)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Close finishes etcd connect
+func (s *EtcDStorage) Close() error {
+	if s.db == nil {
+		return nil
+	}
+	err := s.db.Close()
+	s.db = nil
+	return err
+}
+
+// Reopen tries to open (re-open) the database
+func (s *EtcDStorage) Open() error {
+	if s.db != nil {
+		return nil
+	}
+	var err error
+	s.db, err = internalOpen(s.url)
+	return err
+}
+
+// CreateBatch creates a Batch object
+func (s *EtcDStorage) CreateBatch() database.Batch {
+	return &EtcDBatch{
+		db: s.db,
+	}
+}
+
+// OpenTransaction creates new transaction.
+func (s *EtcDStorage) OpenTransaction() (database.Transaction, error) {
+	cli, err := internalOpen(s.url)
+	if err != nil {
+		return nil, err
+	}
+	kvc := clientv3.NewKV(cli)
+	return &transaction{t: kvc}, nil
+}
+
+// CompactDB compacts database by merging layers
+func (s *EtcDStorage) CompactDB() error {
+	return nil
+}
+
+// Drop removes all the etcd files (DANGEROUS!)
+func (s *EtcDStorage) Drop() error {
+	return nil
+}
+
+// Check interface
+var (
+	_ database.Storage = &EtcDStorage{}
+)