etcd: add namespace support to separate key spaces

This commit extends etcd db with namespaces without additional storage
space requirements. This is simply done by instead of using an all zero
root bucket id, we use the sha256 hash of the name space as our root
bucket id.

channeldb/kvdb/etcd/bucket.go

@@ -16,12 +16,6 @@ var (
 	sequencePrefix = []byte("$")
 )
 
-// rootBucketId returns a zero filled 32 byte array
-func rootBucketID() []byte {
-	var rootID [bucketIDLength]byte
-	return rootID[:]
-}
-
 // makeBucketID returns a deterministic key for the passed byte slice.
 // Currently it returns the sha256 hash of the slice.
 func makeBucketID(key []byte) [bucketIDLength]byte {

channeldb/kvdb/etcd/bucket_test.go

@@ -7,7 +7,8 @@ package etcd
 func bkey(buckets ...string) string {
 	var bucketKey []byte
 
-	parent := rootBucketID()
+	rootID := makeBucketID([]byte(""))
+	parent := rootID[:]
 
 	for _, bucketName := range buckets {
 		bucketKey = makeBucketKey(parent, []byte(bucketName))
@@ -28,7 +29,8 @@ func bval(buckets ...string) string {
 // vkey is a helper function used in tests to create a value key from the
 // passed key and bucket list.
 func vkey(key string, buckets ...string) string {
-	bucket := rootBucketID()
+	rootID := makeBucketID([]byte(""))
+	bucket := rootID[:]
 
 	for _, bucketName := range buckets {
 		bucketKey := makeBucketKey(bucket, []byte(bucketName))

channeldb/kvdb/etcd/db.go

@@ -143,6 +143,11 @@ type BackendConfig struct {
 	// skip TLS verification.
 	InsecureSkipVerify bool
 
+	// Prefix the hash of the prefix will be used as the root
+	// bucket id. This enables key space separation similar to
+	// name spaces.
+	Prefix string
+
 	// CollectCommitStats indicates wheter to commit commit stats.
 	CollectCommitStats bool
 }
@@ -203,7 +208,7 @@ func (db *db) getSTMOptions() []STMOptionFunc {
 // occur).
 func (db *db) View(f func(tx walletdb.ReadTx) error) error {
 	apply := func(stm STM) error {
-		return f(newReadWriteTx(stm))
+		return f(newReadWriteTx(stm, db.config.Prefix))
 	}
 
 	return RunSTM(db.cli, apply, db.getSTMOptions()...)
@@ -217,7 +222,7 @@ func (db *db) View(f func(tx walletdb.ReadTx) error) error {
 // returned.
 func (db *db) Update(f func(tx walletdb.ReadWriteTx) error) error {
 	apply := func(stm STM) error {
-		return f(newReadWriteTx(stm))
+		return f(newReadWriteTx(stm, db.config.Prefix))
 	}
 
 	return RunSTM(db.cli, apply, db.getSTMOptions()...)
@@ -234,12 +239,18 @@ func (db *db) PrintStats() string {
 
 // BeginReadTx opens a database read transaction.
 func (db *db) BeginReadWriteTx() (walletdb.ReadWriteTx, error) {
-	return newReadWriteTx(NewSTM(db.cli, db.getSTMOptions()...)), nil
+	return newReadWriteTx(
+		NewSTM(db.cli, db.getSTMOptions()...),
+		db.config.Prefix,
+	), nil
 }
 
 // BeginReadWriteTx opens a database read+write transaction.
 func (db *db) BeginReadTx() (walletdb.ReadTx, error) {
-	return newReadWriteTx(NewSTM(db.cli, db.getSTMOptions()...)), nil
+	return newReadWriteTx(
+		NewSTM(db.cli, db.getSTMOptions()...),
+		db.config.Prefix,
+	), nil
 }
 
 // Copy writes a copy of the database to the provided writer.  This call will

channeldb/kvdb/etcd/readwrite_bucket.go

@@ -24,7 +24,7 @@ type readWriteBucket struct {
 // newReadWriteBucket creates a new rw bucket with the passed transaction
 // and bucket id.
 func newReadWriteBucket(tx *readWriteTx, key, id []byte) *readWriteBucket {
-	if !bytes.Equal(id, rootBucketID()) {
+	if !bytes.Equal(id, tx.rootBucketID[:]) {
 		// Add the bucket key/value to the lock set.
 		tx.lock(string(key), string(id))
 	}

channeldb/kvdb/etcd/readwrite_tx.go

@@ -11,6 +11,10 @@ type readWriteTx struct {
 	// stm is the reference to the parent STM.
 	stm STM
 
+	// rootBucketID holds the sha256 hash of the root bucket id, which is used
+	// for key space spearation.
+	rootBucketID [bucketIDLength]byte
+
 	// active is true if the transaction hasn't been committed yet.
 	active bool
 
@@ -24,18 +28,19 @@ type readWriteTx struct {
 }
 
 // newReadWriteTx creates an rw transaction with the passed STM.
-func newReadWriteTx(stm STM) *readWriteTx {
+func newReadWriteTx(stm STM, prefix string) *readWriteTx {
 	return &readWriteTx{
 		stm:          stm,
 		active:       true,
+		rootBucketID: makeBucketID([]byte(prefix)),
 		lset:         make(map[string]string),
 	}
 }
 
 // rooBucket is a helper function to return the always present
-// root bucket.
+// pseudo root bucket.
 func rootBucket(tx *readWriteTx) *readWriteBucket {
-	return newReadWriteBucket(tx, rootBucketID(), rootBucketID())
+	return newReadWriteBucket(tx, tx.rootBucketID[:], tx.rootBucketID[:])
 }
 
 // lock adds a key value to the lock set.

channeldb/kvdb/kvdb_etcd.go

@@ -12,7 +12,7 @@ const TestBackend = EtcdBackendName
 
 // GetEtcdBackend returns an etcd backend configured according to the
 // passed etcdConfig.
-func GetEtcdBackend(etcdConfig *EtcdConfig) (Backend, error) {
+func GetEtcdBackend(prefix string, etcdConfig *EtcdConfig) (Backend, error) {
 	// Config translation is needed here in order to keep the
 	// etcd package fully independent from the rest of the source tree.
 	backendConfig := etcd.BackendConfig{
@@ -22,6 +22,7 @@ func GetEtcdBackend(etcdConfig *EtcdConfig) (Backend, error) {
 		CertFile:           etcdConfig.CertFile,
 		KeyFile:            etcdConfig.KeyFile,
 		InsecureSkipVerify: etcdConfig.InsecureSkipVerify,
+		Prefix:             prefix,
 		CollectCommitStats: etcdConfig.CollectStats,
 	}
 

channeldb/kvdb/kvdb_no_etcd.go

@@ -13,7 +13,7 @@ const TestBackend = BoltBackendName
 var errEtcdNotAvailable = fmt.Errorf("etcd backend not available")
 
 // GetEtcdBackend is a stub returning nil and errEtcdNotAvailable error.
-func GetEtcdBackend(etcdConfig *EtcdConfig) (Backend, error) {
+func GetEtcdBackend(prefix string, etcdConfig *EtcdConfig) (Backend, error) {
 	return nil, errEtcdNotAvailable
 }
 

lncfg/db.go

@@ -2,6 +2,7 @@ package lncfg
 
 import (
 	"fmt"
+	"path"
 
 	"github.com/lightningnetwork/lnd/channeldb/kvdb"
 )
@@ -50,12 +51,14 @@ func (db *DB) Validate() error {
 }
 
 // GetBackend returns a kvdb.Backend as set in the DB config.
-func (db *DB) GetBackend(path string) (kvdb.Backend, error) {
+func (db *DB) GetBackend(dbPath string) (kvdb.Backend, error) {
 	if db.Backend == etcdBackend {
-		return kvdb.GetEtcdBackend(db.Etcd)
+		// Prefix will separate key/values in the db.
+		prefix := path.Join(dbPath, dbName)
+		return kvdb.GetEtcdBackend(prefix, db.Etcd)
 	}
 
-	return kvdb.GetBoltBackend(path, dbName, db.Bolt.NoFreeListSync)
+	return kvdb.GetBoltBackend(dbPath, dbName, db.Bolt.NoFreeListSync)
 }
 
 // Compile-time constraint to ensure Workers implements the Validator interface.