From 019bf5b010caa9b546c17add2ddd68d58c58fc10 Mon Sep 17 00:00:00 2001 From: sasha-s Date: Thu, 14 May 2015 15:43:13 -0700 Subject: [PATCH] open read-only databases in read-only mode --- bolt_unix.go | 2 +- bolt_windows.go | 2 +- db.go | 53 ++++++++++++++++++++++++++++++++++++----------- db_test.go | 55 +++++++++++++++++++++++++++++++++++++++++++++++++ errors.go | 4 ++++ 5 files changed, 102 insertions(+), 14 deletions(-) diff --git a/bolt_unix.go b/bolt_unix.go index 35dce08..cc958d4 100644 --- a/bolt_unix.go +++ b/bolt_unix.go @@ -45,7 +45,7 @@ func mmap(db *DB, sz int) error { // Truncate and fsync to ensure file size metadata is flushed. // https://github.com/boltdb/bolt/issues/284 if !db.NoGrowSync { - if err := db.file.Truncate(int64(sz)); err != nil { + if err := db.ops.Truncate(int64(sz)); err != nil { return fmt.Errorf("file resize error: %s", err) } if err := db.file.Sync(); err != nil { diff --git a/bolt_windows.go b/bolt_windows.go index c8539d4..cfece39 100644 --- a/bolt_windows.go +++ b/bolt_windows.go @@ -29,7 +29,7 @@ func funlock(f *os.File) error { // Based on: https://github.com/edsrzf/mmap-go func mmap(db *DB, sz int) error { // Truncate the database to the size of the mmap. - if err := db.file.Truncate(int64(sz)); err != nil { + if err := db.ops.Truncate(int64(sz)); err != nil { return fmt.Errorf("truncate: %s", err) } diff --git a/db.go b/db.go index b78640f..5cf0533 100644 --- a/db.go +++ b/db.go @@ -102,8 +102,11 @@ type DB struct { statlock sync.RWMutex // Protects stats access. ops struct { - writeAt func(b []byte, off int64) (n int, err error) + writeAt func(b []byte, off int64) (n int, err error) + Truncate func(size int64) error } + + readOnly bool // Read only mode. Update()/Begin(true) would return ErrDatabaseReadOnly immediately. } // Path returns the path to currently open database file. @@ -137,21 +140,37 @@ func Open(path string, mode os.FileMode, options *Options) (*DB, error) { db.MaxBatchSize = DefaultMaxBatchSize db.MaxBatchDelay = DefaultMaxBatchDelay + // Get file stats. + s, err := os.Stat(path) + flag := os.O_RDWR + if err != nil && !os.IsNotExist(err) { + return nil, err + } else if err == nil && (s.Mode().Perm()&0222) == 0 { + // remove www from mode as well. + mode ^= (mode & 0222) + flag = os.O_RDONLY + db.readOnly = true + // Ignore truncations. + db.ops.Truncate = func(int64) error { return nil } + } + // Open data file and separate sync handler for metadata writes. db.path = path - - var err error - if db.file, err = os.OpenFile(db.path, os.O_RDWR|os.O_CREATE, mode); err != nil { + if db.file, err = os.OpenFile(db.path, flag|os.O_CREATE, mode); err != nil { _ = db.close() return nil, err } - // 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, options.Timeout); err != nil { - _ = db.close() - return nil, err + // No need to lock read-only file. + if !db.readOnly { + db.ops.Truncate = db.file.Truncate + // 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, options.Timeout); err != nil { + _ = db.close() + return nil, err + } } // Default values for test hooks @@ -359,8 +378,11 @@ func (db *DB) close() error { // Close file handles. if db.file != nil { - // Unlock the file. - _ = funlock(db.file) + // No need to unlock read-only file. + if !db.readOnly { + // Unlock the file. + _ = funlock(db.file) + } // Close the file descriptor. if err := db.file.Close(); err != nil { @@ -426,6 +448,9 @@ func (db *DB) beginTx() (*Tx, error) { } func (db *DB) beginRWTx() (*Tx, error) { + if db.readOnly { + return nil, ErrDatabaseReadOnly + } // Obtain writer lock. This is released by the transaction when it closes. // This enforces only one writer transaction at a time. db.rwlock.Lock() @@ -622,6 +647,10 @@ func (db *DB) allocate(count int) (*page, error) { return p, nil } +func (db *DB) IsReadOnly() bool { + return db.readOnly +} + // 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. diff --git a/db_test.go b/db_test.go index ad17e87..b3d41f3 100644 --- a/db_test.go +++ b/db_test.go @@ -224,6 +224,61 @@ func TestDB_Open_FileTooSmall(t *testing.T) { equals(t, errors.New("file size too small"), err) } +// Ensure that a database can be opened in read-only mode. +func TestOpen_ReadOnly(t *testing.T) { + var bucket = []byte(`bucket`) + var key = []byte(`key`) + var value = []byte(`value`) + path := tempfile() + defer os.Remove(path) + db, err := bolt.Open(path, 0666, nil) + ok(t, db.Update(func(tx *bolt.Tx) error { + b, err := tx.CreateBucket(bucket) + if err != nil { + return err + } + return b.Put(key, value) + })) + assert(t, db != nil, "") + assert(t, !db.IsReadOnly(), "") + ok(t, err) + ok(t, db.Close()) + // Make it read-only. + ok(t, os.Chmod(path, 0444)) + // Open again. + db0, err := bolt.Open(path, 0666, nil) + ok(t, err) + defer db0.Close() + // And again. + db1, err := bolt.Open(path, 0666, nil) + ok(t, err) + defer db1.Close() + for _, db := range []*bolt.DB{db0, db1} { + // Verify is is in read only mode indeed. + assert(t, db.IsReadOnly(), "") + assert(t, + bolt.ErrDatabaseReadOnly == db.Update(func(*bolt.Tx) error { + panic(`should never get here`) + }), + "") + _, err = db.Begin(true) + assert(t, bolt.ErrDatabaseReadOnly == err, "") + // Verify the data. + ok(t, db.View(func(tx *bolt.Tx) error { + b := tx.Bucket(bucket) + if b == nil { + return fmt.Errorf("expected bucket `%s`", string(bucket)) + } + got := string(b.Get(key)) + expected := string(value) + if got != expected { + return fmt.Errorf("expected `%s`, got `%s`", expected, got) + } + return nil + })) + } +} + // TODO(benbjohnson): Test corruption at every byte of the first two pages. // Ensure that a database cannot open a transaction when it's not open. diff --git a/errors.go b/errors.go index aa504f1..6883786 100644 --- a/errors.go +++ b/errors.go @@ -36,6 +36,10 @@ var ( // ErrTxClosed is returned when committing or rolling back a transaction // that has already been committed or rolled back. ErrTxClosed = errors.New("tx closed") + + // ErrDatabaseReadOnly is returned when a mutating transaction is started on a + // read-only database. + ErrDatabaseReadOnly = errors.New("database is in read-only mode") ) // These errors can occur when putting or deleting a value or a bucket.