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//go:build js || wasip1
// +build js wasip1
/*
* SPDX-FileCopyrightText: © Hypermode Inc. <hello@hypermode.com>
* SPDX-License-Identifier: Apache-2.0
*/
package badger
import (
"fmt"
"os"
"path/filepath"
"github.com/dgraph-io/badger/v4/y"
)
// directoryLockGuard holds a lock on a directory and a pid file inside. The pid file isn't part
// of the locking mechanism, it's just advisory.
type directoryLockGuard struct {
// File handle on the directory, which we've flocked.
f *os.File
// The absolute path to our pid file.
path string
// Was this a shared lock for a read-only database?
readOnly bool
}
// acquireDirectoryLock gets a lock on the directory (using flock). If
// this is not read-only, it will also write our pid to
// dirPath/pidFileName for convenience.
func acquireDirectoryLock(dirPath string, pidFileName string, readOnly bool) (
*directoryLockGuard, error) {
// Convert to absolute path so that Release still works even if we do an unbalanced
// chdir in the meantime.
absPidFilePath, err := filepath.Abs(filepath.Join(dirPath, pidFileName))
if err != nil {
return nil, y.Wrapf(err, "cannot get absolute path for pid lock file")
}
f, err := os.Open(dirPath)
if err != nil {
return nil, y.Wrapf(err, "cannot open directory %q", dirPath)
}
// NOTE: Here is where we would normally call flock.
// This is not supported in js / wasm, so skip it.
if !readOnly {
// Yes, we happily overwrite a pre-existing pid file. We're the
// only read-write badger process using this directory.
err = os.WriteFile(absPidFilePath, []byte(fmt.Sprintf("%d\n", os.Getpid())), 0666)
if err != nil {
f.Close()
return nil, y.Wrapf(err,
"Cannot write pid file %q", absPidFilePath)
}
}
return &directoryLockGuard{f, absPidFilePath, readOnly}, nil
}
// Release deletes the pid file and releases our lock on the directory.
func (guard *directoryLockGuard) release() error {
var err error
if !guard.readOnly {
// It's important that we remove the pid file first.
err = os.Remove(guard.path)
}
if closeErr := guard.f.Close(); err == nil {
err = closeErr
}
guard.path = ""
guard.f = nil
return err
}
// openDir opens a directory for syncing.
func openDir(path string) (*os.File, error) { return os.Open(path) }
// When you create or delete a file, you have to ensure the directory entry for the file is synced
// in order to guarantee the file is visible (if the system crashes). (See the man page for fsync,
// or see https://github.com/coreos/etcd/issues/6368 for an example.)
func syncDir(dir string) error {
f, err := openDir(dir)
if err != nil {
return y.Wrapf(err, "While opening directory: %s.", dir)
}
err = f.Sync()
closeErr := f.Close()
if err != nil {
return y.Wrapf(err, "While syncing directory: %s.", dir)
}
return y.Wrapf(closeErr, "While closing directory: %s.", dir)
}
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