diff options
| -rw-r--r-- | README.md | 7 | ||||
| -rw-r--r-- | bolt_linux.go | 2 | ||||
| -rw-r--r-- | bolt_openbsd.go | 2 | ||||
| -rw-r--r-- | bolt_windows.go | 2 | ||||
| -rw-r--r-- | boltsync_unix.go | 2 | ||||
| -rw-r--r-- | tx.go | 22 |
6 files changed, 18 insertions, 19 deletions
@@ -426,8 +426,11 @@ func (*Bucket) DeleteBucket(key []byte) error Bolt is a single file so it's easy to backup. You can use the `Tx.WriteTo()` function to write a consistent view of the database to a writer. If you call this from a read-only transaction, it will perform a hot backup and not block -your other database reads and writes. It will also use `O_DIRECT` when available -to prevent page cache trashing. +your other database reads and writes. + +By default, it will use a regular file handle which will utilize the operating +system's page cache. See the [`Tx`](https://godoc.org/github.com/boltdb/bolt#Tx) +documentation for information about optimizing for larger-than-RAM datasets. One common use case is to backup over HTTP so you can use tools like `cURL` to do database backups: diff --git a/bolt_linux.go b/bolt_linux.go index e9d1c90..2b67666 100644 --- a/bolt_linux.go +++ b/bolt_linux.go @@ -4,8 +4,6 @@ import ( "syscall" ) -var odirect = syscall.O_DIRECT - // fdatasync flushes written data to a file descriptor. func fdatasync(db *DB) error { return syscall.Fdatasync(int(db.file.Fd())) diff --git a/bolt_openbsd.go b/bolt_openbsd.go index 7c1bef1..7058c3d 100644 --- a/bolt_openbsd.go +++ b/bolt_openbsd.go @@ -11,8 +11,6 @@ const ( msInvalidate // invalidate cached data ) -var odirect int - func msync(db *DB) error { _, _, errno := syscall.Syscall(syscall.SYS_MSYNC, uintptr(unsafe.Pointer(db.data)), uintptr(db.datasz), msInvalidate) if errno != 0 { diff --git a/bolt_windows.go b/bolt_windows.go index f048365..91c4968 100644 --- a/bolt_windows.go +++ b/bolt_windows.go @@ -40,8 +40,6 @@ func unlockFileEx(h syscall.Handle, reserved, locklow, lockhigh uint32, ol *sysc return nil } -var odirect int - // fdatasync flushes written data to a file descriptor. func fdatasync(db *DB) error { return db.file.Sync() diff --git a/boltsync_unix.go b/boltsync_unix.go index 8db8977..f504425 100644 --- a/boltsync_unix.go +++ b/boltsync_unix.go @@ -2,8 +2,6 @@ package bolt -var odirect int - // fdatasync flushes written data to a file descriptor. func fdatasync(db *DB) error { return db.file.Sync() @@ -29,6 +29,14 @@ type Tx struct { pages map[pgid]*page stats TxStats commitHandlers []func() + + // WriteFlag specifies the flag for write-related methods like WriteTo(). + // Tx opens the database file with the specified flag to copy the data. + // + // By default, the flag is unset, which works well for mostly in-memory + // workloads. For databases that are much larger than available RAM, + // set the flag to syscall.O_DIRECT to avoid trashing the page cache. + WriteFlag int } // init initializes the transaction. @@ -272,21 +280,18 @@ func (tx *Tx) Copy(w io.Writer) error { // WriteTo writes the entire database to a writer. // If err == nil then exactly tx.Size() bytes will be written into the writer. func (tx *Tx) WriteTo(w io.Writer) (n int64, err error) { - // Attempt to open reader directly. - var f *os.File - if f, err = os.OpenFile(tx.db.path, os.O_RDONLY|odirect, 0); err != nil { - // Fallback to a regular open if that doesn't work. - if f, err = os.OpenFile(tx.db.path, os.O_RDONLY, 0); err != nil { - return 0, err - } + // Attempt to open reader with WriteFlag + f, err := os.OpenFile(tx.db.path, os.O_RDONLY|tx.WriteFlag, 0) + if err != nil { + return 0, err } + defer f.Close() // Copy the meta pages. tx.db.metalock.Lock() n, err = io.CopyN(w, f, int64(tx.db.pageSize*2)) tx.db.metalock.Unlock() if err != nil { - _ = f.Close() return n, fmt.Errorf("meta copy: %s", err) } @@ -294,7 +299,6 @@ func (tx *Tx) WriteTo(w io.Writer) (n int64, err error) { wn, err := io.CopyN(w, f, tx.Size()-int64(tx.db.pageSize*2)) n += wn if err != nil { - _ = f.Close() return n, err } |