feat(filelock): add filelock for dirPath so that other process will n…

…ot be able to read/write to the dir

Makefile

@@ -10,6 +10,7 @@ build:
 clean:
 	rm -rf ./nimbusdb_temp* benchmark/nimbusdb_temp*
 	rm -rf ~/nimbusdb/test_data
+	mkdir -p ~/nimbusdb/test_data
 
 test:
 	go test -v -failfast

db.go

@@ -16,6 +16,7 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/gofrs/flock"
 	"github.com/google/btree"
 	"github.com/hashicorp/golang-lru/v2/expirable"
 	utils "github.com/manosriram/nimbusdb/utils"
@@ -67,6 +68,7 @@ func NewDb(dirPath string, opts ...*Options) *Db {
 		segments: segments,
 		opts: &Options{
 			ShouldWatch: false,
+			Flock:       opts[0].Flock,
 		},
 	}
 
@@ -482,6 +484,7 @@ func (db *Db) createActiveDatafile(dirPath string) error {
 }
 
 func (db *Db) handleInterrupt() {
+	defer db.opts.Flock.Close()
 	terminateSignal := make(chan os.Signal, 1)
 	signal.Notify(terminateSignal, syscall.SIGINT, syscall.SIGKILL, syscall.SIGTERM)
 	for {
@@ -509,10 +512,27 @@ func Open(opts *Options) (*Db, error) {
 
 		dirPath = utils.JoinPaths(home, DefaultDataDir)
 	}
+
+	var builder strings.Builder
+	_, err := fmt.Fprintf(&builder, "%s.%s", dirPath, FlockSuffix)
+	if err != nil {
+		return nil, err
+	}
+
+	flock := flock.New(builder.String())
+	tryLock, err := flock.TryLock()
+	if err != nil {
+		return nil, err
+	}
+	if !tryLock {
+		return nil, ERROR_DIRPATH_ALREADY_IN_USE
+	}
+	opts.Flock = flock
+
 	db := NewDb(dirPath, opts)
 	go db.handleInterrupt()
 
-	err := os.MkdirAll(dirPath, os.ModePerm)
+	err = os.MkdirAll(dirPath, os.ModePerm)
 	if err != nil {
 		return nil, err
 	}
@@ -554,6 +574,7 @@ func Open(opts *Options) (*Db, error) {
 // Closes the database. Closes the file pointer used to read/write the activeDataFile.
 // Closes all file inactiveDataFile pointers and marks them as closed.
 func (db *Db) Close() error {
+	defer db.opts.Flock.Unlock()
 	err := db.closeActiveDataFileReader()
 	if err != nil {
 		return err

examples/db/db.go

@@ -11,8 +11,7 @@ import (
 )
 
 const (
-	// DirPath = "/Users/manosriram/nimbusdb/test_data"
-	DirPath = "./dd/"
+	DirPath = "/Users/manosriram/nimbusdb/test_data"
 )
 
 func watchKeyChange(ch chan nimbusdb.WatcherEvent) {
@@ -32,7 +31,10 @@ func watchKeyChange(ch chan nimbusdb.WatcherEvent) {
 }
 
 func main() {
-	d, _ := nimbusdb.Open(&nimbusdb.Options{Path: DirPath, WatchQueueSize: 10})
+	d, err := nimbusdb.Open(&nimbusdb.Options{Path: DirPath, WatchQueueSize: 10})
+	if err != nil {
+		log.Fatalf("error opening dirpath: %s\n", err.Error())
+	}
 	defer d.Close()
 
 	ch, _ := d.NewWatch()

go.mod

@@ -11,7 +11,9 @@ require (
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/gofrs/flock v0.8.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/segmentio/ksuid v1.0.4 // indirect
+	golang.org/x/sys v0.20.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,6 +1,8 @@
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/gofrs/flock v0.8.1 h1:+gYjHKf32LDeiEEFhQaotPbLuUXjY5ZqxKgXy7n59aw=
+github.com/gofrs/flock v0.8.1/go.mod h1:F1TvTiK9OcQqauNUHlbJvyl9Qa1QvF/gOUDKA14jxHU=
 github.com/google/btree v1.1.2 h1:xf4v41cLI2Z6FxbKm+8Bu+m8ifhj15JuZ9sa0jZCMUU=
 github.com/google/btree v1.1.2/go.mod h1:qOPhT0dTNdNzV6Z/lhRX0YXUafgPLFUh+gZMl761Gm4=
 github.com/hashicorp/golang-lru/v2 v2.0.7 h1:a+bsQ5rvGLjzHuww6tVxozPZFVghXaHOwFs4luLUK2k=
@@ -19,6 +21,8 @@ github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcU
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 golang.org/x/exp v0.0.0-20240119083558-1b970713d09a h1:Q8/wZp0KX97QFTc2ywcOE0YRjZPVIx+MXInMzdvQqcA=
 golang.org/x/exp v0.0.0-20240119083558-1b970713d09a/go.mod h1:idGWGoKP1toJGkd5/ig9ZLuPcZBC3ewk7SzmH0uou08=
+golang.org/x/sys v0.20.0 h1:Od9JTbYCk261bKm4M/mw7AklTlFYIa0bIp9BgSm1S8Y=
+golang.org/x/sys v0.20.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

types.go

@@ -7,6 +7,7 @@ import (
 	"sync"
 	"time"
 
+	flock "github.com/gofrs/flock"
 	"github.com/segmentio/ksuid"
 )
 
@@ -28,6 +29,7 @@ const (
 	TempDataFilePattern                 = "*.dfile"
 	TempInactiveDataFilePattern         = "*.idfile"
 	DefaultDataDir                      = "nimbusdb"
+	FlockSuffix                         = "flock"
 
 	DatafileThreshold = 1 * MB
 	BlockSize         = 32 * KB
@@ -67,6 +69,7 @@ var (
 	ERROR_DATA_FILE_WRITER_NOT_CLOSED = errors.New("data file writer is not closed")
 	ERROR_DATA_FILE_READER_NOT_OPEN   = errors.New("data file reader is not open")
 	ERROR_DATA_FILE_WRITER_NOT_OPEN   = errors.New("data file writer is not open")
+	ERROR_DIRPATH_ALREADY_IN_USE      = errors.New("dirpath already in use")
 )
 
 var (
@@ -95,6 +98,7 @@ type Options struct {
 	Path           string
 	ShouldWatch    bool
 	WatchQueueSize int
+	Flock          *flock.Flock
 }
 
 type KeyValuePair struct {