session: move all Bolt DB code to kvdb_store.go

Keep all KVDB logic contained within the same file.

Author: ellemouton

session/db.go

@@ -2,8 +2,11 @@ package session
 
 import (
 	"bytes"
+	"encoding/binary"
 	"errors"
 	"fmt"
+	"os"
+	"path/filepath"
 	"time"
 
 	"github.com/btcsuite/btcd/btcec/v2"
@@ -53,8 +56,122 @@ var (
 	// ErrDBInitErr is returned when a bucket that we expect to have been
 	// set up during DB initialisation is not found.
 	ErrDBInitErr = errors.New("db did not initialise properly")
+
+	// byteOrder is the default byte order we'll use for serialization
+	// within the database.
+	byteOrder = binary.BigEndian
+)
+
+const (
+	// DBFilename is the default filename of the session database.
+	DBFilename = "session.db"
+
+	// dbFilePermission is the default permission the session database file
+	// is created with.
+	dbFilePermission = 0600
+
+	// DefaultSessionDBTimeout is the default maximum time we wait for the
+	// session bbolt database to be opened. If the database is already
+	// opened by another process, the unique lock cannot be obtained. With
+	// the timeout we error out after the given time instead of just
+	// blocking for forever.
+	DefaultSessionDBTimeout = 5 * time.Second
 )
 
+// DB is a bolt-backed persistent store.
+type DB struct {
+	*bbolt.DB
+}
+
+// A compile-time check to ensure that DB implements the Store interface.
+var _ Store = (*DB)(nil)
+
+// NewDB creates a new bolt database that can be found at the given directory.
+func NewDB(dir, fileName string) (*DB, error) {
+	firstInit := false
+	path := filepath.Join(dir, fileName)
+
+	// If the database file does not exist yet, create its directory.
+	if !fileExists(path) {
+		if err := os.MkdirAll(dir, 0700); err != nil {
+			return nil, err
+		}
+		firstInit = true
+	}
+
+	db, err := initDB(path, firstInit)
+	if err != nil {
+		return nil, err
+	}
+
+	// Attempt to sync the database's current version with the latest known
+	// version available.
+	if err := syncVersions(db); err != nil {
+		return nil, err
+	}
+
+	return &DB{DB: db}, nil
+}
+
+// fileExists reports whether the named file or directory exists.
+func fileExists(path string) bool {
+	if _, err := os.Stat(path); err != nil {
+		if os.IsNotExist(err) {
+			return false
+		}
+	}
+	return true
+}
+
+// initDB initializes all the required top-level buckets for the database.
+func initDB(filepath string, firstInit bool) (*bbolt.DB, error) {
+	db, err := bbolt.Open(filepath, dbFilePermission, &bbolt.Options{
+		Timeout: DefaultSessionDBTimeout,
+	})
+	if err == bbolt.ErrTimeout {
+		return nil, fmt.Errorf("error while trying to open %s: timed "+
+			"out after %v when trying to obtain exclusive lock",
+			filepath, DefaultSessionDBTimeout)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	err = db.Update(func(tx *bbolt.Tx) error {
+		if firstInit {
+			metadataBucket, err := tx.CreateBucketIfNotExists(
+				metadataBucketKey,
+			)
+			if err != nil {
+				return err
+			}
+			err = setDBVersion(metadataBucket, latestDBVersion)
+			if err != nil {
+				return err
+			}
+		}
+
+		sessionBkt, err := tx.CreateBucketIfNotExists(sessionBucketKey)
+		if err != nil {
+			return err
+		}
+
+		_, err = sessionBkt.CreateBucketIfNotExists(idIndexKey)
+		if err != nil {
+			return err
+		}
+
+		_, err = sessionBkt.CreateBucketIfNotExists(groupIDIndexKey)
+
+		return err
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return db, nil
+}
+
 // getSessionKey returns the key for a session.
 func getSessionKey(session *Session) []byte {
 	return session.LocalPublicKey.SerializeCompressed()