Golang bolt.Open函數代碼示例

func ExampleTx_CopyFile() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Create a bucket and a key.
	db.Update(func(tx *bolt.Tx) error {
		tx.CreateBucket([]byte("widgets"))
		tx.Bucket([]byte("widgets")).Put([]byte("foo"), []byte("bar"))
		return nil
	})

	// Copy the database to another file.
	toFile := tempfile()
	db.View(func(tx *bolt.Tx) error { return tx.CopyFile(toFile, 0666) })
	defer os.Remove(toFile)

	// Open the cloned database.
	db2, _ := bolt.Open(toFile, 0666, nil)
	defer db2.Close()

	// Ensure that the key exists in the copy.
	db2.View(func(tx *bolt.Tx) error {
		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
		fmt.Printf("The value for 'foo' in the clone is: %s\n", value)
		return nil
	})

	// Output:
	// The value for 'foo' in the clone is: bar
}

// Ensure that a re-opened database is consistent.
func TestOpen_Check(t *testing.T) {
	path := tempfile()
	defer os.Remove(path)

	db, err := bolt.Open(path, 0666, nil)
	ok(t, err)
	ok(t, db.View(func(tx *bolt.Tx) error { return <-tx.Check() }))
	db.Close()

	db, err = bolt.Open(path, 0666, nil)
	ok(t, err)
	ok(t, db.View(func(tx *bolt.Tx) error { return <-tx.Check() }))
	db.Close()
}

// Ensure that a database that is too small returns an error.
func TestDB_Open_FileTooSmall(t *testing.T) {
	path := tempfile()
	defer os.Remove(path)

	db, err := bolt.Open(path, 0666, nil)
	ok(t, err)
	db.Close()

	// corrupt the database
	ok(t, os.Truncate(path, int64(os.Getpagesize())))

	db, err = bolt.Open(path, 0666, nil)
	equals(t, errors.New("file size too small"), err)
}

// Keys retrieves a list of keys for a given bucket.
func Keys(path, name string) {
	if _, err := os.Stat(path); os.IsNotExist(err) {
		fatal(err)
		return
	}

	db, err := bolt.Open(path, 0600, nil)
	if err != nil {
		fatal(err)
		return
	}
	defer db.Close()

	err = db.View(func(tx *bolt.Tx) error {
		// Find bucket.
		b := tx.Bucket([]byte(name))
		if b == nil {
			fatalf("bucket not found: %s", name)
			return nil
		}

		// Iterate over each key.
		return b.ForEach(func(key, _ []byte) error {
			println(string(key))
			return nil
		})
	})
	if err != nil {
		fatal(err)
		return
	}
}

// Ensure that a database can be imported.
func TestImport(t *testing.T) {
	SetTestMode(true)

	// Write input file.
	input := tempfile()
	ok(t, ioutil.WriteFile(input, []byte(`[{"type":"bucket","key":"ZW1wdHk=","value":[]},{"type":"bucket","key":"d2lkZ2V0cw==","value":[{"key":"YmFy","value":""},{"key":"Zm9v","value":"MDAwMA=="}]},{"type":"bucket","key":"d29vaml0cw==","value":[{"key":"YmF6","value":"WFhYWA=="},{"type":"bucket","key":"d29vaml0cy9zdWJidWNrZXQ=","value":[{"key":"YmF0","value":"QQ=="}]}]}]`), 0600))

	// Import database.
	path := tempfile()
	output := run("import", path, "--input", input)
	equals(t, ``, output)

	// Open database and verify contents.
	db, err := bolt.Open(path, 0600, nil)
	ok(t, err)
	db.View(func(tx *bolt.Tx) error {
		assert(t, tx.Bucket([]byte("empty")) != nil, "")

		b := tx.Bucket([]byte("widgets"))
		assert(t, b != nil, "")
		equals(t, []byte("0000"), b.Get([]byte("foo")))
		equals(t, []byte(""), b.Get([]byte("bar")))

		b = tx.Bucket([]byte("woojits"))
		assert(t, b != nil, "")
		equals(t, []byte("XXXX"), b.Get([]byte("baz")))

		b = b.Bucket([]byte("woojits/subbucket"))
		equals(t, []byte("A"), b.Get([]byte("bat")))

		return nil
	})
	db.Close()
}

// Run executes the command.
func (cmd *InfoCommand) Run(args ...string) error {
	// Parse flags.
	fs := flag.NewFlagSet("", flag.ContinueOnError)
	help := fs.Bool("h", false, "")
	if err := fs.Parse(args); err != nil {
		return err
	} else if *help {
		fmt.Fprintln(cmd.Stderr, cmd.Usage())
		return ErrUsage
	}

	// Require database path.
	path := fs.Arg(0)
	if path == "" {
		return ErrPathRequired
	} else if _, err := os.Stat(path); os.IsNotExist(err) {
		return ErrFileNotFound
	}

	// Open the database.
	db, err := bolt.Open(path, 0666, nil)
	if err != nil {
		return err
	}
	defer db.Close()

	// Print basic database info.
	info := db.Info()
	fmt.Fprintf(cmd.Stdout, "Page Size: %d\n", info.PageSize)

	return nil
}

// OpenDB opens and initialises the persistence DB, if not already open.
func (m *Manager) OpenDB() error {
	if m.dbPath == "" {
		return nil
	}
	m.dbMtx.Lock()
	defer m.dbMtx.Unlock()
	// open/initialize db
	if err := os.MkdirAll(filepath.Dir(m.dbPath), 0755); err != nil {
		return fmt.Errorf("could not mkdir for volume persistence db: %s", err)
	}
	db, err := bolt.Open(m.dbPath, 0600, &bolt.Options{Timeout: 5 * time.Second})
	if err != nil {
		return fmt.Errorf("could not open volume persistence db: %s", err)
	}
	if err := db.Update(func(tx *bolt.Tx) error {
		// idempotently create buckets.  (errors ignored because they're all compile-time impossible args checks.)
		tx.CreateBucketIfNotExists([]byte("volumes"))
		tx.CreateBucketIfNotExists([]byte("providers"))
		return nil
	}); err != nil {
		return fmt.Errorf("could not initialize volume persistence db: %s", err)
	}
	m.db = db
	if err := m.restore(); err != nil {
		return err
	}
	return m.maybeInitDefaultProvider()
}

func ExampleBucket_ForEach() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Insert data into a bucket.
	db.Update(func(tx *bolt.Tx) error {
		tx.CreateBucket([]byte("animals"))
		b := tx.Bucket([]byte("animals"))
		b.Put([]byte("dog"), []byte("fun"))
		b.Put([]byte("cat"), []byte("lame"))
		b.Put([]byte("liger"), []byte("awesome"))

		// Iterate over items in sorted key order.
		b.ForEach(func(k, v []byte) error {
			fmt.Printf("A %s is %s.\n", k, v)
			return nil
		})
		return nil
	})

	// Output:
	// A cat is lame.
	// A dog is fun.
	// A liger is awesome.
}

func ExampleBucket_Put() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Start a write transaction.
	db.Update(func(tx *bolt.Tx) error {
		// Create a bucket.
		tx.CreateBucket([]byte("widgets"))

		// Set the value "bar" for the key "foo".
		tx.Bucket([]byte("widgets")).Put([]byte("foo"), []byte("bar"))
		return nil
	})

	// Read value back in a different read-only transaction.
	db.View(func(tx *bolt.Tx) error {
		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
		fmt.Printf("The value of 'foo' is: %s\n", value)
		return nil
	})

	// Output:
	// The value of 'foo' is: bar
}

func ExampleDB_Begin_ReadOnly() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Create a bucket.
	db.Update(func(tx *bolt.Tx) error {
		_, err := tx.CreateBucket([]byte("widgets"))
		return err
	})

	// Create several keys in a transaction.
	tx, _ := db.Begin(true)
	b := tx.Bucket([]byte("widgets"))
	b.Put([]byte("john"), []byte("blue"))
	b.Put([]byte("abby"), []byte("red"))
	b.Put([]byte("zephyr"), []byte("purple"))
	tx.Commit()

	// Iterate over the values in sorted key order.
	tx, _ = db.Begin(false)
	c := tx.Bucket([]byte("widgets")).Cursor()
	for k, v := c.First(); k != nil; k, v = c.Next() {
		fmt.Printf("%s likes %s\n", k, v)
	}
	tx.Rollback()

	// Output:
	// abby likes red
	// john likes blue
	// zephyr likes purple
}

// NewTestDB returns a new instance of TestDB.
func NewTestDB() *TestDB {
	db, err := bolt.Open(tempfile(), 0666, nil)
	if err != nil {
		panic("cannot open db: " + err.Error())
	}
	return &TestDB{db}
}

func ExampleDB_View() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Insert data into a bucket.
	db.Update(func(tx *bolt.Tx) error {
		tx.CreateBucket([]byte("people"))
		b := tx.Bucket([]byte("people"))
		b.Put([]byte("john"), []byte("doe"))
		b.Put([]byte("susy"), []byte("que"))
		return nil
	})

	// Access data from within a read-only transactional block.
	db.View(func(tx *bolt.Tx) error {
		v := tx.Bucket([]byte("people")).Get([]byte("john"))
		fmt.Printf("John's last name is %s.\n", v)
		return nil
	})

	// Output:
	// John's last name is doe.
}

func ExampleDB_Update() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Execute several commands within a write transaction.
	err := db.Update(func(tx *bolt.Tx) error {
		b, err := tx.CreateBucket([]byte("widgets"))
		if err != nil {
			return err
		}
		if err := b.Put([]byte("foo"), []byte("bar")); err != nil {
			return err
		}
		return nil
	})

	// If our transactional block didn't return an error then our data is saved.
	if err == nil {
		db.View(func(tx *bolt.Tx) error {
			value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
			fmt.Printf("The value of 'foo' is: %s\n", value)
			return nil
		})
	}

	// Output:
	// The value of 'foo' is: bar
}

// OpenDB opens and initialises the persistence DB, if not already open.
func (s *State) OpenDB() error {
	s.dbCond.L.Lock()
	defer s.dbCond.L.Unlock()

	if s.stateDB != nil {
		return nil
	}

	// open/initialize db
	if err := os.MkdirAll(filepath.Dir(s.stateFilePath), 0755); err != nil {
		return fmt.Errorf("could not not mkdir for db: %s", err)
	}
	stateDB, err := bolt.Open(s.stateFilePath, 0600, &bolt.Options{Timeout: 5 * time.Second})
	if err != nil {
		return fmt.Errorf("could not open db: %s", err)
	}
	s.stateDB = stateDB
	if err := s.stateDB.Update(func(tx *bolt.Tx) error {
		// idempotently create buckets.  (errors ignored because they're all compile-time impossible args checks.)
		tx.CreateBucketIfNotExists([]byte("jobs"))
		tx.CreateBucketIfNotExists([]byte("backend-jobs"))
		tx.CreateBucketIfNotExists([]byte("backend-global"))
		tx.CreateBucketIfNotExists([]byte("persistent-jobs"))
		return nil
	}); err != nil {
		return fmt.Errorf("could not initialize host persistence db: %s", err)
	}
	return nil
}

func ExampleTx_Rollback() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Create a bucket.
	db.Update(func(tx *bolt.Tx) error {
		_, err := tx.CreateBucket([]byte("widgets"))
		return err
	})

	// Set a value for a key.
	db.Update(func(tx *bolt.Tx) error {
		return tx.Bucket([]byte("widgets")).Put([]byte("foo"), []byte("bar"))
	})

	// Update the key but rollback the transaction so it never saves.
	tx, _ := db.Begin(true)
	b := tx.Bucket([]byte("widgets"))
	b.Put([]byte("foo"), []byte("baz"))
	tx.Rollback()

	// Ensure that our original value is still set.
	db.View(func(tx *bolt.Tx) error {
		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
		fmt.Printf("The value for 'foo' is still: %s\n", value)
		return nil
	})

	// Output:
	// The value for 'foo' is still: bar
}