github.com/hasnat/dolt/go@v0.0.0-20210628190320-9eb5d843fbb7/store/nbs/bs_manifest.go (about)

     1  // Copyright 2019 Dolthub, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package nbs
    16  
    17  import (
    18  	"bytes"
    19  	"context"
    20  	"io"
    21  	"strings"
    22  
    23  	"github.com/dolthub/dolt/go/store/blobstore"
    24  )
    25  
    26  const (
    27  	manifestFile = "manifest"
    28  )
    29  
    30  type blobstoreManifest struct {
    31  	name string
    32  	bs   blobstore.Blobstore
    33  }
    34  
    35  func (bsm blobstoreManifest) Name() string {
    36  	return bsm.name
    37  }
    38  
    39  func manifestVersionAndContents(ctx context.Context, bs blobstore.Blobstore) (string, manifestContents, error) {
    40  	reader, ver, err := bs.Get(ctx, manifestFile, blobstore.AllRange)
    41  
    42  	if err != nil {
    43  		return "", manifestContents{}, err
    44  	}
    45  
    46  	defer reader.Close()
    47  	contents, err := fileManifestV5{}.parseManifest(reader)
    48  
    49  	if err != nil {
    50  		return "", manifestContents{}, err
    51  	}
    52  
    53  	return ver, contents, nil
    54  }
    55  
    56  // ParseIfExists looks for a manifest in the specified blobstore.  If one exists
    57  // will return true and the contents, else false and nil
    58  func (bsm blobstoreManifest) ParseIfExists(ctx context.Context, stats *Stats, readHook func() error) (bool, manifestContents, error) {
    59  	if readHook != nil {
    60  		panic("Read hooks not supported")
    61  	}
    62  
    63  	_, contents, err := manifestVersionAndContents(ctx, bsm.bs)
    64  
    65  	if err != nil {
    66  		if blobstore.IsNotFoundError(err) {
    67  			return false, contents, nil
    68  		}
    69  
    70  		// io error
    71  		return true, contents, err
    72  	}
    73  
    74  	return true, contents, nil
    75  }
    76  
    77  // Update updates the contents of the manifest in the blobstore
    78  func (bsm blobstoreManifest) Update(ctx context.Context, lastLock addr, newContents manifestContents, stats *Stats, writeHook func() error) (manifestContents, error) {
    79  	if writeHook != nil {
    80  		panic("Write hooks not supported")
    81  	}
    82  
    83  	ver, contents, err := manifestVersionAndContents(ctx, bsm.bs)
    84  
    85  	if err != nil && !blobstore.IsNotFoundError(err) {
    86  		return manifestContents{}, err
    87  	}
    88  
    89  	if contents.lock == lastLock {
    90  		buffer := bytes.NewBuffer(make([]byte, 64*1024)[:0])
    91  		err := fileManifestV5{}.writeManifest(buffer, newContents)
    92  
    93  		if err != nil {
    94  			return manifestContents{}, err
    95  		}
    96  
    97  		_, err = bsm.bs.CheckAndPut(ctx, ver, manifestFile, buffer)
    98  
    99  		if err != nil {
   100  			if !blobstore.IsCheckAndPutError(err) {
   101  				return manifestContents{}, err
   102  			}
   103  		} else {
   104  			return newContents, nil
   105  		}
   106  	}
   107  
   108  	return contents, nil
   109  }
   110  
   111  func writeVer4Manifest(temp io.Writer, contents manifestContents) error {
   112  	strs := make([]string, 2*len(contents.specs)+4)
   113  	strs[0], strs[1], strs[2], strs[3] = storageVersion4, contents.vers, contents.lock.String(), contents.root.String()
   114  	tableInfo := strs[4:]
   115  	formatSpecs(contents.specs, tableInfo)
   116  	_, err := io.WriteString(temp, strings.Join(strs, ":"))
   117  
   118  	return err
   119  }