Merge pull request #208 from benbjohnson/open-timeout

Add Open() options, flock timeout.

bolt_darwin.go

@@ -2,8 +2,6 @@ package bolt
 
 import (
 	"os"
-	"syscall"
-	"unsafe"
 )
 
 var odirect int
@@ -12,42 +10,3 @@ var odirect int
 func fdatasync(f *os.File) error {
 	return f.Sync()
 }
-
-// flock acquires an advisory lock on a file descriptor.
-func flock(f *os.File) error {
-	return syscall.Flock(int(f.Fd()), syscall.LOCK_EX)
-}
-
-// funlock releases an advisory lock on a file descriptor.
-func funlock(f *os.File) error {
-	return syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
-}
-
-// mmap memory maps a DB's data file.
-func mmap(db *DB, sz int) error {
-	b, err := syscall.Mmap(int(db.file.Fd()), 0, sz, syscall.PROT_READ, syscall.MAP_SHARED)
-	if err != nil {
-		return err
-	}
-
-	// Save the original byte slice and convert to a byte array pointer.
-	db.dataref = b
-	db.data = (*[maxMapSize]byte)(unsafe.Pointer(&b[0]))
-	db.datasz = sz
-	return nil
-}
-
-// munmap unmaps a DB's data file from memory.
-func munmap(db *DB) error {
-	// Ignore the unmap if we have no mapped data.
-	if db.dataref == nil {
-		return nil
-	}
-
-	// Unmap using the original byte slice.
-	err := syscall.Munmap(db.dataref)
-	db.dataref = nil
-	db.data = nil
-	db.datasz = 0
-	return err
-}

bolt_linux.go

@@ -3,7 +3,6 @@ package bolt
 import (
 	"os"
 	"syscall"
-	"unsafe"
 )
 
 var odirect = syscall.O_DIRECT
@@ -12,42 +11,3 @@ var odirect = syscall.O_DIRECT
 func fdatasync(f *os.File) error {
 	return syscall.Fdatasync(int(f.Fd()))
 }
-
-// flock acquires an advisory lock on a file descriptor.
-func flock(f *os.File) error {
-	return syscall.Flock(int(f.Fd()), syscall.LOCK_EX)
-}
-
-// funlock releases an advisory lock on a file descriptor.
-func funlock(f *os.File) error {
-	return syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
-}
-
-// mmap memory maps a DB's data file.
-func mmap(db *DB, sz int) error {
-	b, err := syscall.Mmap(int(db.file.Fd()), 0, sz, syscall.PROT_READ, syscall.MAP_SHARED)
-	if err != nil {
-		return err
-	}
-
-	// Save the original byte slice and convert to a byte array pointer.
-	db.dataref = b
-	db.data = (*[maxMapSize]byte)(unsafe.Pointer(&b[0]))
-	db.datasz = sz
-	return nil
-}
-
-// munmap unmaps a DB's data file from memory.
-func munmap(db *DB) error {
-	// Ignore the unmap if we have no mapped data.
-	if db.dataref == nil {
-		return nil
-	}
-
-	// Unmap using the original byte slice.
-	err := syscall.Munmap(db.dataref)
-	db.dataref = nil
-	db.data = nil
-	db.datasz = 0
-	return err
-}

bolt_unix.go

@@ -0,0 +1,69 @@
+// +build linux darwin
+
+package bolt
+
+import (
+	"os"
+	"syscall"
+	"time"
+	"unsafe"
+)
+
+// flock acquires an advisory lock on a file descriptor.
+func flock(f *os.File, timeout time.Duration) error {
+	var t time.Time
+	for {
+		// If we're beyond our timeout then return an error.
+		// This can only occur after we've attempted a flock once.
+		if t.IsZero() {
+			t = time.Now()
+		} else if timeout > 0 && time.Since(t) > timeout {
+			return ErrTimeout
+		}
+
+		// Otherwise attempt to obtain an exclusive lock.
+		err := syscall.Flock(int(f.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
+		if err == nil {
+			return nil
+		} else if err != syscall.EWOULDBLOCK {
+			return err
+		}
+
+		// Wait for a bit and try again.
+		time.Sleep(50 * time.Millisecond)
+	}
+}
+
+// funlock releases an advisory lock on a file descriptor.
+func funlock(f *os.File) error {
+	return syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
+}
+
+// mmap memory maps a DB's data file.
+func mmap(db *DB, sz int) error {
+	b, err := syscall.Mmap(int(db.file.Fd()), 0, sz, syscall.PROT_READ, syscall.MAP_SHARED)
+	if err != nil {
+		return err
+	}
+
+	// Save the original byte slice and convert to a byte array pointer.
+	db.dataref = b
+	db.data = (*[maxMapSize]byte)(unsafe.Pointer(&b[0]))
+	db.datasz = sz
+	return nil
+}
+
+// munmap unmaps a DB's data file from memory.
+func munmap(db *DB) error {
+	// Ignore the unmap if we have no mapped data.
+	if db.dataref == nil {
+		return nil
+	}
+
+	// Unmap using the original byte slice.
+	err := syscall.Munmap(db.dataref)
+	db.dataref = nil
+	db.data = nil
+	db.datasz = 0
+	return err
+}

bolt_windows.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"syscall"
+	"time"
 	"unsafe"
 )
 
@@ -15,7 +16,7 @@ func fdatasync(f *os.File) error {
 }
 
 // flock acquires an advisory lock on a file descriptor.
-func flock(f *os.File) error {
+func flock(f *os.File, _ time.Duration) error {
 	return nil
 }
 

bucket_test.go

@@ -1003,7 +1003,7 @@ func TestBucket_Delete_Quick(t *testing.T) {
 
 func ExampleBucket_Put() {
 	// Open the database.
-	db, _ := Open(tempfile(), 0666)
+	db, _ := Open(tempfile(), 0666, nil)
 	defer os.Remove(db.Path())
 	defer db.Close()
 
@@ -1030,7 +1030,7 @@ func ExampleBucket_Put() {
 
 func ExampleBucket_Delete() {
 	// Open the database.
-	db, _ := Open(tempfile(), 0666)
+	db, _ := Open(tempfile(), 0666, nil)
 	defer os.Remove(db.Path())
 	defer db.Close()
 
@@ -1070,7 +1070,7 @@ func ExampleBucket_Delete() {
 
 func ExampleBucket_ForEach() {
 	// Open the database.
-	db, _ := Open(tempfile(), 0666)
+	db, _ := Open(tempfile(), 0666, nil)
 	defer os.Remove(db.Path())
 	defer db.Close()
 

cmd/bolt/bench.go

@@ -41,7 +41,7 @@ func Bench(options *BenchOptions) {
 	}
 
 	// Create database.
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		fatal(err)
 		return

cmd/bolt/buckets.go

@@ -13,7 +13,7 @@ func Buckets(path string) {
 		return
 	}
 
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		fatal(err)
 		return

cmd/bolt/check.go

@@ -13,7 +13,7 @@ func Check(path string) {
 		return
 	}
 
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		fatal(err)
 		return

cmd/bolt/export.go

@@ -16,7 +16,7 @@ func Export(path string) {
 	}
 
 	// Open the database.
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		fatal(err)
 		return

cmd/bolt/get.go

@@ -13,7 +13,7 @@ func Get(path, name, key string) {
 		return
 	}
 
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		fatal(err)
 		return

cmd/bolt/import.go

@@ -29,7 +29,7 @@ func Import(path string, input string) {
 
 func importBuckets(path string, root []*rawMessage) {
 	// Open the database.
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		fatal(err)
 		return

cmd/bolt/import_test.go

@@ -23,7 +23,7 @@ func TestImport(t *testing.T) {
 	assert.Equal(t, ``, output)
 
 	// Open database and verify contents.
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	assert.NoError(t, err)
 	db.View(func(tx *bolt.Tx) error {
 		assert.NotNil(t, tx.Bucket([]byte("empty")))

cmd/bolt/info.go

@@ -13,7 +13,7 @@ func Info(path string) {
 		return
 	}
 
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		fatal(err)
 		return

cmd/bolt/keys.go

@@ -13,7 +13,7 @@ func Keys(path, name string) {
 		return
 	}
 
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		fatal(err)
 		return

cmd/bolt/main_test.go

@@ -14,7 +14,7 @@ func open(fn func(*bolt.DB, string)) {
 	path := tempfile()
 	defer os.RemoveAll(path)
 
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		panic("db open error: " + err.Error())
 	}

cmd/bolt/pages.go

@@ -14,7 +14,7 @@ func Pages(path string) {
 		return
 	}
 
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		fatal(err)
 		return

cmd/bolt/stats.go

@@ -14,7 +14,7 @@ func Stats(path, prefix string) {
 		return
 	}
 
-	db, err := bolt.Open(path, 0600)
+	db, err := bolt.Open(path, 0600, nil)
 	if err != nil {
 		fatal(err)
 		return

db.go

@@ -8,6 +8,7 @@ import (
 	"runtime/debug"
 	"strings"
 	"sync"
+	"time"
 	"unsafe"
 )
 
@@ -50,6 +51,10 @@ var (
 
 	// ErrChecksum is returned when either meta page checksum does not match.
 	ErrChecksum = errors.New("checksum error")
+
+	// ErrTimeout is returned when a database cannot obtain an exclusive lock
+	// on the data file after the timeout passed to Open().
+	ErrTimeout = errors.New("timeout")
 )
 
 // DB represents a collection of buckets persisted to a file on disk.
@@ -108,9 +113,15 @@ func (db *DB) String() string {
 
 // Open creates and opens a database at the given path.
 // If the file does not exist then it will be created automatically.
-func Open(path string, mode os.FileMode) (*DB, error) {
+// Passing in nil options will cause Bolt to open the database with the default options.
+func Open(path string, mode os.FileMode, options *Options) (*DB, error) {
 	var db = &DB{opened: true, FillPercent: DefaultFillPercent}
 
+	// Set default options.
+	if options == nil {
+		options = &Options{}
+	}
+
 	// Open data file and separate sync handler for metadata writes.
 	db.path = path
 
@@ -123,7 +134,7 @@ func Open(path string, mode os.FileMode) (*DB, error) {
 	// Lock file so that other processes using Bolt cannot use the database
 	// at the same time. This would cause corruption since the two processes
 	// would write meta pages and free pages separately.
-	if err := flock(db.file); err != nil {
+	if err := flock(db.file, options.Timeout); err != nil {
 		_ = db.close()
 		return nil, err
 	}
@@ -556,6 +567,14 @@ func (db *DB) allocate(count int) (*page, error) {
 	return p, nil
 }
 
+// Options represents the options that can be set when opening a database.
+type Options struct {
+	// Timeout is the amount of time to wait to obtain a file lock.
+	// When set to zero it will wait indefinitely. This option is only
+	// available on Darwin and Linux.
+	Timeout time.Duration
+}
+
 // Stats represents statistics about the database.
 type Stats struct {
 	// Freelist stats