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/
db.go
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/
db.go
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// Copyright 2015 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package cas
import (
"database/sql"
"fmt"
"os"
"path/filepath"
"github.com/coreos/rocket/pkg/lock"
_ "github.com/coreos/rocket/Godeps/_workspace/src/github.com/cznic/ql/driver"
)
const (
dbfilename = "ql.db"
)
type DB struct {
dbdir string
lock *lock.DirLock
sqldb *sql.DB
}
func NewDB(dbdir string) (*DB, error) {
if err := os.MkdirAll(dbdir, defaultPathPerm); err != nil {
return nil, err
}
return &DB{dbdir: dbdir}, nil
}
func (db *DB) Open() error {
// take a lock on db dir
if db.lock != nil {
panic("cas db lock already gained")
}
dl, err := lock.ExclusiveLock(db.dbdir)
if err != nil {
return err
}
db.lock = dl
sqldb, err := sql.Open("ql", filepath.Join(db.dbdir, dbfilename))
if err != nil {
dl.Close()
return err
}
db.sqldb = sqldb
return nil
}
func (db *DB) Close() error {
if db.lock == nil {
panic("cas db, Close called without lock")
}
if db.sqldb == nil {
panic("cas db, Close called without an open sqldb")
}
if err := db.sqldb.Close(); err != nil {
return fmt.Errorf("cas db close failed: %v", err)
}
db.sqldb = nil
db.lock.Close()
db.lock = nil
return nil
}
func (db *DB) Begin() (*sql.Tx, error) {
return db.sqldb.Begin()
}
type txfunc func(*sql.Tx) error
// Do Opens the db, executes DoTx and then Closes the DB
func (db *DB) Do(fns ...txfunc) error {
err := db.Open()
if err != nil {
return err
}
defer db.Close()
return db.DoTx(fns...)
}
// DoTx executes the provided txfuncs inside a unique transaction.
// If one of the functions returns an error the whole transaction is rolled back.
func (db *DB) DoTx(fns ...txfunc) error {
tx, err := db.Begin()
if err != nil {
return err
}
defer func() {
if err != nil {
tx.Rollback()
return
}
tx.Commit()
}()
for _, fn := range fns {
if err := fn(tx); err != nil {
return err
}
}
return nil
}