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objstorage: allow attaching of shared objects
This commit introduces the concept of a `SharedObjectBacking`. This is an opaque encoding of the metadata necessary to access a shared object (specifically creator ID and creator file num). The backing can be extracted for a shared object on an instance and then used to attach the object to another instance. This will be used for rebalancing.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,145 @@ | ||
| // Copyright 2023 The LevelDB-Go and Pebble Authors. All rights reserved. Use | ||
| // of this source code is governed by a BSD-style license that can be found in | ||
| // the LICENSE file. | ||
|
|
||
| package objstorage | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "encoding/binary" | ||
| "io" | ||
|
|
||
| "github.com/cockroachdb/errors" | ||
| "github.com/cockroachdb/pebble/internal/base" | ||
| "github.com/cockroachdb/pebble/objstorage/sharedobjcat" | ||
| ) | ||
|
|
||
| // SharedObjectBacking encodes the metadata necessary to incorporate a shared | ||
| // object into a different Pebble instance. | ||
| type SharedObjectBacking []byte | ||
|
|
||
| const ( | ||
| tagCreatorID = 1 | ||
| tagCreatorFileNum = 2 | ||
|
|
||
| // Any new tags that don't have the tagNotSafeToIgnoreMask bit set must be | ||
| // followed by the length of the data (so they can be skipped). | ||
|
|
||
| // Any new tags that have the tagNotSafeToIgnoreMask bit set cause errors if | ||
| // they are encountered by earlier code that doesn't know the tag. | ||
| tagNotSafeToIgnoreMask = 64 | ||
| ) | ||
|
|
||
| // SharedObjectBacking encodes the shared object metadata. | ||
| func (meta *ObjectMetadata) SharedObjectBacking() (SharedObjectBacking, error) { | ||
| if !meta.IsShared() { | ||
| return nil, errors.AssertionFailedf("object %s not on shared storage", meta.FileNum) | ||
| } | ||
|
|
||
| buf := make([]byte, 0, binary.MaxVarintLen64*4) | ||
| buf = binary.AppendUvarint(buf, tagCreatorID) | ||
| buf = binary.AppendUvarint(buf, uint64(meta.Shared.CreatorID)) | ||
| buf = binary.AppendUvarint(buf, tagCreatorFileNum) | ||
| buf = binary.AppendUvarint(buf, uint64(meta.Shared.CreatorFileNum)) | ||
| return buf, nil | ||
| } | ||
|
|
||
| // fromSharedObjectBacking decodes the shared object metadata. | ||
| func fromSharedObjectBacking( | ||
| fileType base.FileType, fileNum base.FileNum, buf SharedObjectBacking, | ||
| ) (ObjectMetadata, error) { | ||
| var creatorID uint64 | ||
| var creatorFileNum uint64 | ||
| br := bytes.NewReader(buf) | ||
| for { | ||
| tag, err := binary.ReadUvarint(br) | ||
| if err == io.EOF { | ||
| break | ||
| } | ||
| if err != nil { | ||
| return ObjectMetadata{}, err | ||
| } | ||
| switch tag { | ||
| case tagCreatorID: | ||
| creatorID, err = binary.ReadUvarint(br) | ||
|
|
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| case tagCreatorFileNum: | ||
| creatorFileNum, err = binary.ReadUvarint(br) | ||
|
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| // TODO(radu): encode file type as well? | ||
|
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||
| default: | ||
| // Ignore unknown tags, unless they're not safe to ignore. | ||
| if tag&tagNotSafeToIgnoreMask != 0 { | ||
| return ObjectMetadata{}, errors.Newf("unknown tag %d", tag) | ||
| } | ||
| var dataLen uint64 | ||
| dataLen, err = binary.ReadUvarint(br) | ||
| if err == nil { | ||
| _, err = br.Seek(int64(dataLen), io.SeekCurrent) | ||
| } | ||
| } | ||
| if err != nil { | ||
| return ObjectMetadata{}, err | ||
| } | ||
| } | ||
| if creatorID == 0 { | ||
| return ObjectMetadata{}, errors.Newf("shared object backing missing creator ID") | ||
| } | ||
| if creatorFileNum == 0 { | ||
| return ObjectMetadata{}, errors.Newf("shared object backing missing creator file num") | ||
| } | ||
| meta := ObjectMetadata{ | ||
| FileNum: fileNum, | ||
| FileType: fileType, | ||
| } | ||
| meta.Shared.CreatorID = CreatorID(creatorID) | ||
| meta.Shared.CreatorFileNum = base.FileNum(creatorFileNum) | ||
| return meta, nil | ||
| } | ||
|
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||
| // SharedObjectToAttach contains the arguments needed to attach an existing shared object. | ||
| type SharedObjectToAttach struct { | ||
| // FileNum is the file number that will be used to refer to this object (in | ||
| // the context of this instance). | ||
| FileNum base.FileNum | ||
| FileType base.FileType | ||
| // Backing contains the metadata for the share dobject backing (normally | ||
| // generated from a different instance). | ||
| Backing SharedObjectBacking | ||
| } | ||
|
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||
| // AttachSharedObjects registers existing shared objects with this provider. | ||
| func (p *Provider) AttachSharedObjects(objs []SharedObjectToAttach) ([]ObjectMetadata, error) { | ||
| metas := make([]ObjectMetadata, len(objs)) | ||
| for i, o := range objs { | ||
| meta, err := fromSharedObjectBacking(o.FileType, o.FileNum, o.Backing) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| metas[i] = meta | ||
| } | ||
|
|
||
| func() { | ||
| p.mu.Lock() | ||
| defer p.mu.Unlock() | ||
| for _, meta := range metas { | ||
| p.mu.shared.catalogBatch.AddObject(sharedobjcat.SharedObjectMetadata{ | ||
| FileNum: meta.FileNum, | ||
| FileType: meta.FileType, | ||
| CreatorID: meta.Shared.CreatorID, | ||
| CreatorFileNum: meta.Shared.CreatorFileNum, | ||
| }) | ||
| } | ||
| }() | ||
| if err := p.sharedSync(); err != nil { | ||
| return nil, err | ||
| } | ||
|
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||
| p.mu.Lock() | ||
| defer p.mu.Unlock() | ||
| for _, meta := range metas { | ||
| p.mu.knownObjects[meta.FileNum] = meta | ||
| } | ||
| return metas, nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,47 @@ | ||
| // Copyright 2023 The LevelDB-Go and Pebble Authors. All rights reserved. Use | ||
| // of this source code is governed by a BSD-style license that can be found in | ||
| // the LICENSE file. | ||
|
|
||
| package objstorage | ||
|
|
||
| import ( | ||
| "encoding/binary" | ||
| "testing" | ||
|
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| "github.com/cockroachdb/pebble/internal/base" | ||
| "github.com/stretchr/testify/require" | ||
| ) | ||
|
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| func TestSharedObjectBacking(t *testing.T) { | ||
| meta := ObjectMetadata{ | ||
| FileNum: 1, | ||
| FileType: base.FileTypeTable, | ||
| } | ||
| meta.Shared.CreatorID = 100 | ||
| meta.Shared.CreatorFileNum = 200 | ||
|
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| buf, err := meta.SharedObjectBacking() | ||
| require.NoError(t, err) | ||
|
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| meta1, err := fromSharedObjectBacking(meta.FileType, meta.FileNum, buf) | ||
| require.NoError(t, err) | ||
| require.Equal(t, meta, meta1) | ||
|
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| t.Run("unknown-tags", func(t *testing.T) { | ||
| // Append a tag that is safe to ignore. | ||
| buf2 := buf | ||
| buf2 = binary.AppendUvarint(buf2, 13) | ||
| buf2 = binary.AppendUvarint(buf2, 2) | ||
| buf2 = append(buf2, 1, 1) | ||
|
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| meta2, err := fromSharedObjectBacking(meta.FileType, meta.FileNum, buf2) | ||
| require.NoError(t, err) | ||
| require.Equal(t, meta, meta2) | ||
|
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| buf3 := buf2 | ||
| buf3 = binary.AppendUvarint(buf3, tagNotSafeToIgnoreMask+5) | ||
| _, err = fromSharedObjectBacking(meta.FileType, meta.FileNum, buf3) | ||
| require.Error(t, err) | ||
| require.Contains(t, err.Error(), "unknown tag") | ||
| }) | ||
| } |
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