Line data Source code
1 : // Copyright 2019 The LevelDB-Go and Pebble Authors. All rights reserved. Use
2 : // of this source code is governed by a BSD-style license that can be found in
3 : // the LICENSE file.
4 :
5 : package pebble
6 :
7 : import (
8 : "io"
9 : "os"
10 :
11 : "github.com/cockroachdb/errors"
12 : "github.com/cockroachdb/errors/oserror"
13 : "github.com/cockroachdb/pebble/internal/base"
14 : "github.com/cockroachdb/pebble/record"
15 : "github.com/cockroachdb/pebble/vfs"
16 : "github.com/cockroachdb/pebble/vfs/atomicfs"
17 : "github.com/cockroachdb/pebble/wal"
18 : )
19 :
20 : // checkpointOptions hold the optional parameters to construct checkpoint
21 : // snapshots.
22 : type checkpointOptions struct {
23 : // flushWAL set to true will force a flush and sync of the WAL prior to
24 : // checkpointing.
25 : flushWAL bool
26 :
27 : // If set, any SSTs that don't overlap with these spans are excluded from a checkpoint.
28 : restrictToSpans []CheckpointSpan
29 : }
30 :
31 : // CheckpointOption set optional parameters used by `DB.Checkpoint`.
32 : type CheckpointOption func(*checkpointOptions)
33 :
34 : // WithFlushedWAL enables flushing and syncing the WAL prior to constructing a
35 : // checkpoint. This guarantees that any writes committed before calling
36 : // DB.Checkpoint will be part of that checkpoint.
37 : //
38 : // Note that this setting can only be useful in cases when some writes are
39 : // performed with Sync = false. Otherwise, the guarantee will already be met.
40 : //
41 : // Passing this option is functionally equivalent to calling
42 : // DB.LogData(nil, Sync) right before DB.Checkpoint.
43 1 : func WithFlushedWAL() CheckpointOption {
44 1 : return func(opt *checkpointOptions) {
45 1 : opt.flushWAL = true
46 1 : }
47 : }
48 :
49 : // WithRestrictToSpans specifies spans of interest for the checkpoint. Any SSTs
50 : // that don't overlap with any of these spans are excluded from the checkpoint.
51 : //
52 : // Note that the checkpoint can still surface keys outside of these spans (from
53 : // the WAL and from SSTs that partially overlap with these spans). Moreover,
54 : // these surface keys aren't necessarily "valid" in that they could have been
55 : // modified but the SST containing the modification is excluded.
56 1 : func WithRestrictToSpans(spans []CheckpointSpan) CheckpointOption {
57 1 : return func(opt *checkpointOptions) {
58 1 : opt.restrictToSpans = spans
59 1 : }
60 : }
61 :
62 : // CheckpointSpan is a key range [Start, End) (inclusive on Start, exclusive on
63 : // End) of interest for a checkpoint.
64 : type CheckpointSpan struct {
65 : Start []byte
66 : End []byte
67 : }
68 :
69 : // excludeFromCheckpoint returns true if an SST file should be excluded from the
70 : // checkpoint because it does not overlap with the spans of interest
71 : // (opt.restrictToSpans).
72 1 : func excludeFromCheckpoint(f *fileMetadata, opt *checkpointOptions, cmp Compare) bool {
73 1 : if len(opt.restrictToSpans) == 0 {
74 1 : // Option not set; don't exclude anything.
75 1 : return false
76 1 : }
77 1 : for _, s := range opt.restrictToSpans {
78 1 : if f.Overlaps(cmp, s.Start, s.End, true /* exclusiveEnd */) {
79 1 : return false
80 1 : }
81 : }
82 : // None of the restrictToSpans overlapped; we can exclude this file.
83 1 : return true
84 : }
85 :
86 : // mkdirAllAndSyncParents creates destDir and any of its missing parents.
87 : // Those missing parents, as well as the closest existing ancestor, are synced.
88 : // Returns a handle to the directory created at destDir.
89 1 : func mkdirAllAndSyncParents(fs vfs.FS, destDir string) (vfs.File, error) {
90 1 : // Collect paths for all directories between destDir (excluded) and its
91 1 : // closest existing ancestor (included).
92 1 : var parentPaths []string
93 1 : foundExistingAncestor := false
94 1 : for parentPath := fs.PathDir(destDir); parentPath != "."; parentPath = fs.PathDir(parentPath) {
95 1 : parentPaths = append(parentPaths, parentPath)
96 1 : _, err := fs.Stat(parentPath)
97 1 : if err == nil {
98 1 : // Exit loop at the closest existing ancestor.
99 1 : foundExistingAncestor = true
100 1 : break
101 : }
102 1 : if !oserror.IsNotExist(err) {
103 0 : return nil, err
104 0 : }
105 : }
106 : // Handle empty filesystem edge case.
107 1 : if !foundExistingAncestor {
108 1 : parentPaths = append(parentPaths, "")
109 1 : }
110 : // Create destDir and any of its missing parents.
111 1 : if err := fs.MkdirAll(destDir, 0755); err != nil {
112 1 : return nil, err
113 1 : }
114 : // Sync all the parent directories up to the closest existing ancestor,
115 : // included.
116 1 : for _, parentPath := range parentPaths {
117 1 : parentDir, err := fs.OpenDir(parentPath)
118 1 : if err != nil {
119 1 : return nil, err
120 1 : }
121 1 : err = parentDir.Sync()
122 1 : if err != nil {
123 1 : _ = parentDir.Close()
124 1 : return nil, err
125 1 : }
126 1 : err = parentDir.Close()
127 1 : if err != nil {
128 0 : return nil, err
129 0 : }
130 : }
131 1 : return fs.OpenDir(destDir)
132 : }
133 :
134 : // Checkpoint constructs a snapshot of the DB instance in the specified
135 : // directory. The WAL, MANIFEST, OPTIONS, and sstables will be copied into the
136 : // snapshot. Hard links will be used when possible. Beware of the significant
137 : // space overhead for a checkpoint if hard links are disabled. Also beware that
138 : // even if hard links are used, the space overhead for the checkpoint will
139 : // increase over time as the DB performs compactions.
140 : func (d *DB) Checkpoint(
141 : destDir string, opts ...CheckpointOption,
142 : ) (
143 : ckErr error, /* used in deferred cleanup */
144 1 : ) {
145 1 : opt := &checkpointOptions{}
146 1 : for _, fn := range opts {
147 1 : fn(opt)
148 1 : }
149 :
150 1 : if _, err := d.opts.FS.Stat(destDir); !oserror.IsNotExist(err) {
151 1 : if err == nil {
152 1 : return &os.PathError{
153 1 : Op: "checkpoint",
154 1 : Path: destDir,
155 1 : Err: oserror.ErrExist,
156 1 : }
157 1 : }
158 0 : return err
159 : }
160 :
161 1 : if opt.flushWAL && !d.opts.DisableWAL {
162 1 : // Write an empty log-data record to flush and sync the WAL.
163 1 : if err := d.LogData(nil /* data */, Sync); err != nil {
164 0 : return err
165 0 : }
166 : }
167 :
168 : // Disable file deletions.
169 1 : d.mu.Lock()
170 1 : d.disableFileDeletions()
171 1 : defer func() {
172 1 : d.mu.Lock()
173 1 : defer d.mu.Unlock()
174 1 : d.enableFileDeletions()
175 1 : }()
176 :
177 : // TODO(peter): RocksDB provides the option to roll the manifest if the
178 : // MANIFEST size is too large. Should we do this too?
179 :
180 : // Lock the manifest before getting the current version. We need the
181 : // length of the manifest that we read to match the current version that
182 : // we read, otherwise we might copy a versionEdit not reflected in the
183 : // sstables we copy/link.
184 1 : d.mu.versions.logLock()
185 1 : // Get the unflushed log files, the current version, and the current manifest
186 1 : // file number.
187 1 : memQueue := d.mu.mem.queue
188 1 : current := d.mu.versions.currentVersion()
189 1 : formatVers := d.FormatMajorVersion()
190 1 : manifestFileNum := d.mu.versions.manifestFileNum
191 1 : manifestSize := d.mu.versions.manifest.Size()
192 1 : optionsFileNum := d.optionsFileNum
193 1 :
194 1 : virtualBackingFiles := make(map[base.DiskFileNum]struct{})
195 1 : d.mu.versions.virtualBackings.ForEach(func(backing *fileBacking) {
196 1 : virtualBackingFiles[backing.DiskFileNum] = struct{}{}
197 1 : })
198 :
199 1 : queuedLogNums := make([]wal.NumWAL, 0, len(memQueue))
200 1 : for i := range memQueue {
201 1 : if logNum := memQueue[i].logNum; logNum != 0 {
202 1 : queuedLogNums = append(queuedLogNums, wal.NumWAL(logNum))
203 1 : }
204 : }
205 : // Release the manifest and DB.mu so we don't block other operations on
206 : // the database.
207 1 : d.mu.versions.logUnlock()
208 1 : d.mu.Unlock()
209 1 :
210 1 : allLogicalLogs, err := d.mu.log.manager.List()
211 1 : if err != nil {
212 0 : return err
213 0 : }
214 :
215 : // Wrap the normal filesystem with one which wraps newly created files with
216 : // vfs.NewSyncingFile.
217 1 : fs := vfs.NewSyncingFS(d.opts.FS, vfs.SyncingFileOptions{
218 1 : NoSyncOnClose: d.opts.NoSyncOnClose,
219 1 : BytesPerSync: d.opts.BytesPerSync,
220 1 : })
221 1 :
222 1 : // Create the dir and its parents (if necessary), and sync them.
223 1 : var dir vfs.File
224 1 : defer func() {
225 1 : if dir != nil {
226 0 : _ = dir.Close()
227 0 : }
228 1 : if ckErr != nil {
229 0 : // Attempt to cleanup on error.
230 0 : _ = fs.RemoveAll(destDir)
231 0 : }
232 : }()
233 1 : dir, ckErr = mkdirAllAndSyncParents(fs, destDir)
234 1 : if ckErr != nil {
235 0 : return ckErr
236 0 : }
237 :
238 1 : {
239 1 : // Link or copy the OPTIONS.
240 1 : srcPath := base.MakeFilepath(fs, d.dirname, fileTypeOptions, optionsFileNum)
241 1 : destPath := fs.PathJoin(destDir, fs.PathBase(srcPath))
242 1 : ckErr = vfs.LinkOrCopy(fs, srcPath, destPath)
243 1 : if ckErr != nil {
244 0 : return ckErr
245 0 : }
246 : }
247 :
248 1 : {
249 1 : // Set the format major version in the destination directory.
250 1 : var versionMarker *atomicfs.Marker
251 1 : versionMarker, _, ckErr = atomicfs.LocateMarker(fs, destDir, formatVersionMarkerName)
252 1 : if ckErr != nil {
253 0 : return ckErr
254 0 : }
255 :
256 : // We use the marker to encode the active format version in the
257 : // marker filename. Unlike other uses of the atomic marker,
258 : // there is no file with the filename `formatVers.String()` on
259 : // the filesystem.
260 1 : ckErr = versionMarker.Move(formatVers.String())
261 1 : if ckErr != nil {
262 0 : return ckErr
263 0 : }
264 1 : ckErr = versionMarker.Close()
265 1 : if ckErr != nil {
266 0 : return ckErr
267 0 : }
268 : }
269 :
270 1 : var excludedFiles map[deletedFileEntry]*fileMetadata
271 1 : // Set of FileBacking.DiskFileNum which will be required by virtual sstables
272 1 : // in the checkpoint.
273 1 : requiredVirtualBackingFiles := make(map[base.DiskFileNum]struct{})
274 1 : // Link or copy the sstables.
275 1 : for l := range current.Levels {
276 1 : iter := current.Levels[l].Iter()
277 1 : for f := iter.First(); f != nil; f = iter.Next() {
278 1 : if excludeFromCheckpoint(f, opt, d.cmp) {
279 1 : if excludedFiles == nil {
280 1 : excludedFiles = make(map[deletedFileEntry]*fileMetadata)
281 1 : }
282 1 : excludedFiles[deletedFileEntry{
283 1 : Level: l,
284 1 : FileNum: f.FileNum,
285 1 : }] = f
286 1 : continue
287 : }
288 :
289 1 : fileBacking := f.FileBacking
290 1 : if f.Virtual {
291 1 : if _, ok := requiredVirtualBackingFiles[fileBacking.DiskFileNum]; ok {
292 1 : continue
293 : }
294 1 : requiredVirtualBackingFiles[fileBacking.DiskFileNum] = struct{}{}
295 : }
296 :
297 1 : srcPath := base.MakeFilepath(fs, d.dirname, fileTypeTable, fileBacking.DiskFileNum)
298 1 : destPath := fs.PathJoin(destDir, fs.PathBase(srcPath))
299 1 : ckErr = vfs.LinkOrCopy(fs, srcPath, destPath)
300 1 : if ckErr != nil {
301 0 : return ckErr
302 0 : }
303 : }
304 : }
305 :
306 1 : var removeBackingTables []base.DiskFileNum
307 1 : for diskFileNum := range virtualBackingFiles {
308 1 : if _, ok := requiredVirtualBackingFiles[diskFileNum]; !ok {
309 1 : // The backing sstable associated with fileNum is no longer
310 1 : // required.
311 1 : removeBackingTables = append(removeBackingTables, diskFileNum)
312 1 : }
313 : }
314 :
315 1 : ckErr = d.writeCheckpointManifest(
316 1 : fs, formatVers, destDir, dir, manifestFileNum, manifestSize,
317 1 : excludedFiles, removeBackingTables,
318 1 : )
319 1 : if ckErr != nil {
320 0 : return ckErr
321 0 : }
322 :
323 : // Copy the WAL files. We copy rather than link because WAL file recycling
324 : // will cause the WAL files to be reused which would invalidate the
325 : // checkpoint.
326 1 : for _, logNum := range queuedLogNums {
327 1 : log, ok := allLogicalLogs.Get(logNum)
328 1 : if !ok {
329 0 : return errors.Newf("log %s not found", logNum)
330 0 : }
331 1 : for i := 0; i < log.NumSegments(); i++ {
332 1 : srcFS, srcPath := log.SegmentLocation(i)
333 1 : destPath := fs.PathJoin(destDir, srcFS.PathBase(srcPath))
334 1 : ckErr = vfs.CopyAcrossFS(srcFS, srcPath, fs, destPath)
335 1 : if ckErr != nil {
336 0 : return ckErr
337 0 : }
338 : }
339 : }
340 :
341 : // Sync and close the checkpoint directory.
342 1 : ckErr = dir.Sync()
343 1 : if ckErr != nil {
344 0 : return ckErr
345 0 : }
346 1 : ckErr = dir.Close()
347 1 : dir = nil
348 1 : return ckErr
349 : }
350 :
351 : func (d *DB) writeCheckpointManifest(
352 : fs vfs.FS,
353 : formatVers FormatMajorVersion,
354 : destDirPath string,
355 : destDir vfs.File,
356 : manifestFileNum base.DiskFileNum,
357 : manifestSize int64,
358 : excludedFiles map[deletedFileEntry]*fileMetadata,
359 : removeBackingTables []base.DiskFileNum,
360 1 : ) error {
361 1 : // Copy the MANIFEST, and create a pointer to it. We copy rather
362 1 : // than link because additional version edits added to the
363 1 : // MANIFEST after we took our snapshot of the sstables will
364 1 : // reference sstables that aren't in our checkpoint. For a
365 1 : // similar reason, we need to limit how much of the MANIFEST we
366 1 : // copy.
367 1 : // If some files are excluded from the checkpoint, also append a block that
368 1 : // records those files as deleted.
369 1 : if err := func() error {
370 1 : srcPath := base.MakeFilepath(fs, d.dirname, fileTypeManifest, manifestFileNum)
371 1 : destPath := fs.PathJoin(destDirPath, fs.PathBase(srcPath))
372 1 : src, err := fs.Open(srcPath, vfs.SequentialReadsOption)
373 1 : if err != nil {
374 0 : return err
375 0 : }
376 1 : defer src.Close()
377 1 :
378 1 : dst, err := fs.Create(destPath)
379 1 : if err != nil {
380 0 : return err
381 0 : }
382 1 : defer dst.Close()
383 1 :
384 1 : // Copy all existing records. We need to copy at the record level in case we
385 1 : // need to append another record with the excluded files (we cannot simply
386 1 : // append a record after a raw data copy; see
387 1 : // https://github.com/cockroachdb/cockroach/issues/100935).
388 1 : r := record.NewReader(&io.LimitedReader{R: src, N: manifestSize}, manifestFileNum)
389 1 : w := record.NewWriter(dst)
390 1 : for {
391 1 : rr, err := r.Next()
392 1 : if err != nil {
393 1 : if err == io.EOF {
394 1 : break
395 : }
396 0 : return err
397 : }
398 :
399 1 : rw, err := w.Next()
400 1 : if err != nil {
401 0 : return err
402 0 : }
403 1 : if _, err := io.Copy(rw, rr); err != nil {
404 0 : return err
405 0 : }
406 : }
407 :
408 1 : if len(excludedFiles) > 0 {
409 1 : // Write out an additional VersionEdit that deletes the excluded SST files.
410 1 : ve := versionEdit{
411 1 : DeletedFiles: excludedFiles,
412 1 : RemovedBackingTables: removeBackingTables,
413 1 : }
414 1 :
415 1 : rw, err := w.Next()
416 1 : if err != nil {
417 0 : return err
418 0 : }
419 1 : if err := ve.Encode(rw); err != nil {
420 0 : return err
421 0 : }
422 : }
423 1 : if err := w.Close(); err != nil {
424 0 : return err
425 0 : }
426 1 : return dst.Sync()
427 0 : }(); err != nil {
428 0 : return err
429 0 : }
430 :
431 1 : var manifestMarker *atomicfs.Marker
432 1 : manifestMarker, _, err := atomicfs.LocateMarker(fs, destDirPath, manifestMarkerName)
433 1 : if err != nil {
434 0 : return err
435 0 : }
436 1 : if err := manifestMarker.Move(base.MakeFilename(fileTypeManifest, manifestFileNum)); err != nil {
437 0 : return err
438 0 : }
439 1 : return manifestMarker.Close()
440 : }
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