github.com/m3db/m3@v1.5.0/src/m3em/agent/multi_writer.go (about)

     1  // Copyright (c) 2017 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package agent
    22  
    23  import (
    24  	"io"
    25  	"os"
    26  	"path/filepath"
    27  
    28  	xerrors "github.com/m3db/m3/src/x/errors"
    29  )
    30  
    31  // non-thread safe multi-writer
    32  type multiWriter struct {
    33  	io.Closer
    34  	fds []*os.File
    35  }
    36  
    37  // based on signature of os.OpenFile
    38  func newMultiWriter(paths []string, flags int, fileMode os.FileMode, dirMode os.FileMode) (*multiWriter, error) {
    39  	mw := &multiWriter{}
    40  	for _, p := range paths {
    41  		// ensure directory exists
    42  		dir := filepath.Dir(p)
    43  		err := os.MkdirAll(dir, dirMode)
    44  		if err != nil {
    45  			mw.Close() // cleanup
    46  			return nil, err
    47  		}
    48  
    49  		// create file
    50  		fd, err := os.OpenFile(p, flags, fileMode)
    51  		if err != nil {
    52  			mw.Close() // cleanup
    53  			return nil, err
    54  		}
    55  		mw.fds = append(mw.fds, fd)
    56  	}
    57  	return mw, nil
    58  }
    59  
    60  // mimics signature of os.File.Write
    61  func (mw *multiWriter) write(b []byte) (int, error) {
    62  	// write the provided data to all fds, terminating
    63  	// early if any fd write fails
    64  	for _, fd := range mw.fds {
    65  		n, err := fd.Write(b)
    66  		if err != nil {
    67  			return n, err
    68  		}
    69  	}
    70  	return len(b), nil
    71  }
    72  
    73  func (mw *multiWriter) Close() error {
    74  	var me xerrors.MultiError
    75  	for _, fd := range mw.fds {
    76  		me = me.Add(fd.Close())
    77  	}
    78  	return me.FinalError()
    79  }