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cmd: enable benchmarking shared storage including the secondary cache
This commit makes it possible to run commands like 'pebble bench ycsb' against shared storage & the secondary cache. To do this, I have introduced a version of shared.Storage that is backed by local disk, as opposed to memory or blob storage. This enables running too-large-for-memory benchmarks from a single machine without access to blob storage. One reason this is convenient is that today the code to communicate with blob storage is in the cockroachdb repo, not the pebble repo. The concrete benchmarking plan I have in mind is worth mentioning as motivation. I will measure the maximum ycsb thruput of shared storage without a secondary cache and shared storage with a secondary cache. Since shared objects will be stored on a medium as fast as the secondary cache (both will be on local disk), we expect better thruput without the secondary cache. With that said, we hope the thruput difference in not large, as for the secondary cache to be effective, it must make efficient use of the local disk it is backed by.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,118 @@ | ||
| // 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. | ||
|
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| package shared | ||
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||
| import ( | ||
| "context" | ||
| "io" | ||
| "os" | ||
| "path" | ||
|
|
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| "github.com/cockroachdb/pebble/vfs" | ||
| ) | ||
|
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| // NewLocalFS returns a vfs-backed implementation of the shared.Storage | ||
| // interface (for testing). All objects will be stored at the directory | ||
| // dirname. | ||
| func NewLocalFS(dirname string, fs vfs.FS) Storage { | ||
| store := &localFSStore{ | ||
| dirname: dirname, | ||
| vfs: fs, | ||
| } | ||
| return store | ||
| } | ||
|
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| // localFSStore is a vfs-backed implementation of the shared.Storage | ||
| // interface (for testing). | ||
| type localFSStore struct { | ||
| dirname string | ||
| vfs vfs.FS | ||
| } | ||
|
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| var _ Storage = (*localFSStore)(nil) | ||
|
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| // Close is part of the shared.Storage interface. | ||
| func (s *localFSStore) Close() error { | ||
| *s = localFSStore{} | ||
| return nil | ||
| } | ||
|
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| // ReadObject is part of the shared.Storage interface. | ||
| func (s *localFSStore) ReadObject( | ||
| ctx context.Context, objName string, | ||
| ) (_ ObjectReader, objSize int64, _ error) { | ||
| f, err := s.vfs.Open(path.Join(s.dirname, objName)) | ||
| if err != nil { | ||
| return nil, 0, err | ||
| } | ||
| stat, err := f.Stat() | ||
| if err != nil { | ||
| return nil, 0, err | ||
| } | ||
|
|
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| return &localFSReader{f}, stat.Size(), nil | ||
| } | ||
|
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| type localFSReader struct { | ||
| file vfs.File | ||
| } | ||
|
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| var _ ObjectReader = (*localFSReader)(nil) | ||
|
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| // ReadAt is part of the shared.ObjectReader interface. | ||
| func (r *localFSReader) ReadAt(_ context.Context, p []byte, offset int64) error { | ||
| n, err := r.file.ReadAt(p, offset) | ||
| // https://pkg.go.dev/io#ReaderAt | ||
| if err == io.EOF && n == len(p) { | ||
| return nil | ||
| } | ||
| return err | ||
| } | ||
|
|
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| // Close is part of the shared.ObjectReader interface. | ||
| func (r *localFSReader) Close() error { | ||
| r.file.Close() | ||
| r.file = nil | ||
| return nil | ||
| } | ||
|
|
||
| // CreateObject is part of the shared.Storage interface. | ||
| func (s *localFSStore) CreateObject(objName string) (io.WriteCloser, error) { | ||
| file, err := s.vfs.Create(path.Join(s.dirname, objName)) | ||
| return file, err | ||
| } | ||
|
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| // List is part of the shared.Storage interface. | ||
| func (s *localFSStore) List(prefix, delimiter string) ([]string, error) { | ||
| // TODO(josh): For the intended use case of localfs.go of running 'pebble bench', | ||
| // List can always return <nil, nil>, since this indicates a file has only one ref, | ||
| // and since `pebble bench` implies running in a single-pebble-instance context. | ||
| // https://github.com/cockroachdb/pebble/blob/a9a079d4fb6bf4a9ebc52e4d83a76ad4cbf676cb/objstorage/objstorageprovider/shared.go#L292 | ||
| return nil, nil | ||
| } | ||
|
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| // Delete is part of the shared.Storage interface. | ||
| func (s *localFSStore) Delete(objName string) error { | ||
| return s.vfs.Remove(path.Join(s.dirname, objName)) | ||
| } | ||
|
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| // Size is part of the shared.Storage interface. | ||
| func (s *localFSStore) Size(objName string) (int64, error) { | ||
| f, err := s.vfs.Open(path.Join(s.dirname, objName)) | ||
| if err != nil { | ||
| return 0, err | ||
| } | ||
| defer f.Close() | ||
| stat, err := f.Stat() | ||
| if err != nil { | ||
| return 0, err | ||
| } | ||
| return stat.Size(), nil | ||
| } | ||
|
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| // IsNotExistError is part of the shared.Storage interface. | ||
| func (s *localFSStore) IsNotExistError(err error) bool { | ||
| return err == os.ErrNotExist | ||
| } |