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 0 : func WithFlushedWAL() CheckpointOption {
44 0 : return func(opt *checkpointOptions) {
45 0 : opt.flushWAL = true
46 0 : }
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 : spanBounds := base.UserKeyBoundsEndExclusive(s.Start, s.End)
79 1 : if f.Overlaps(cmp, &spanBounds) {
80 1 : return false
81 1 : }
82 : }
83 : // None of the restrictToSpans overlapped; we can exclude this file.
84 1 : return true
85 : }
86 :
87 : // mkdirAllAndSyncParents creates destDir and any of its missing parents.
88 : // Those missing parents, as well as the closest existing ancestor, are synced.
89 : // Returns a handle to the directory created at destDir.
90 1 : func mkdirAllAndSyncParents(fs vfs.FS, destDir string) (vfs.File, error) {
91 1 : // Collect paths for all directories between destDir (excluded) and its
92 1 : // closest existing ancestor (included).
93 1 : var parentPaths []string
94 1 : foundExistingAncestor := false
95 1 : for parentPath := fs.PathDir(destDir); parentPath != "."; parentPath = fs.PathDir(parentPath) {
96 1 : parentPaths = append(parentPaths, parentPath)
97 1 : _, err := fs.Stat(parentPath)
98 1 : if err == nil {
99 1 : // Exit loop at the closest existing ancestor.
100 1 : foundExistingAncestor = true
101 1 : break
102 : }
103 1 : if !oserror.IsNotExist(err) {
104 0 : return nil, err
105 0 : }
106 : }
107 : // Handle empty filesystem edge case.
108 1 : if !foundExistingAncestor {
109 1 : parentPaths = append(parentPaths, "")
110 1 : }
111 : // Create destDir and any of its missing parents.
112 1 : if err := fs.MkdirAll(destDir, 0755); err != nil {
113 0 : return nil, err
114 0 : }
115 : // Sync all the parent directories up to the closest existing ancestor,
116 : // included.
117 1 : for _, parentPath := range parentPaths {
118 1 : parentDir, err := fs.OpenDir(parentPath)
119 1 : if err != nil {
120 0 : return nil, err
121 0 : }
122 1 : err = parentDir.Sync()
123 1 : if err != nil {
124 0 : _ = parentDir.Close()
125 0 : return nil, err
126 0 : }
127 1 : err = parentDir.Close()
128 1 : if err != nil {
129 0 : return nil, err
130 0 : }
131 : }
132 1 : return fs.OpenDir(destDir)
133 : }
134 :
135 : // Checkpoint constructs a snapshot of the DB instance in the specified
136 : // directory. The WAL, MANIFEST, OPTIONS, and sstables will be copied into the
137 : // snapshot. Hard links will be used when possible. Beware of the significant
138 : // space overhead for a checkpoint if hard links are disabled. Also beware that
139 : // even if hard links are used, the space overhead for the checkpoint will
140 : // increase over time as the DB performs compactions.
141 : //
142 : // Note that shared files in a checkpoint could get deleted if the DB is
143 : // restarted after a checkpoint operation, as the reference for the checkpoint
144 : // is only maintained in memory. This is okay as long as users of Checkpoint
145 : // crash shortly afterwards with a "poison file" preventing further restarts.
146 : func (d *DB) Checkpoint(
147 : destDir string, opts ...CheckpointOption,
148 : ) (
149 : ckErr error, /* used in deferred cleanup */
150 1 : ) {
151 1 : opt := &checkpointOptions{}
152 1 : for _, fn := range opts {
153 1 : fn(opt)
154 1 : }
155 :
156 1 : if _, err := d.opts.FS.Stat(destDir); !oserror.IsNotExist(err) {
157 0 : if err == nil {
158 0 : return &os.PathError{
159 0 : Op: "checkpoint",
160 0 : Path: destDir,
161 0 : Err: oserror.ErrExist,
162 0 : }
163 0 : }
164 0 : return err
165 : }
166 :
167 1 : if opt.flushWAL && !d.opts.DisableWAL {
168 0 : // Write an empty log-data record to flush and sync the WAL.
169 0 : if err := d.LogData(nil /* data */, Sync); err != nil {
170 0 : return err
171 0 : }
172 : }
173 :
174 : // Disable file deletions.
175 1 : d.mu.Lock()
176 1 : d.disableFileDeletions()
177 1 : defer func() {
178 1 : d.mu.Lock()
179 1 : defer d.mu.Unlock()
180 1 : d.enableFileDeletions()
181 1 : }()
182 :
183 : // TODO(peter): RocksDB provides the option to roll the manifest if the
184 : // MANIFEST size is too large. Should we do this too?
185 :
186 : // Lock the manifest before getting the current version. We need the
187 : // length of the manifest that we read to match the current version that
188 : // we read, otherwise we might copy a versionEdit not reflected in the
189 : // sstables we copy/link.
190 1 : d.mu.versions.logLock()
191 1 : // Get the unflushed log files, the current version, and the current manifest
192 1 : // file number.
193 1 : memQueue := d.mu.mem.queue
194 1 : current := d.mu.versions.currentVersion()
195 1 : formatVers := d.FormatMajorVersion()
196 1 : manifestFileNum := d.mu.versions.manifestFileNum
197 1 : manifestSize := d.mu.versions.manifest.Size()
198 1 : optionsFileNum := d.optionsFileNum
199 1 :
200 1 : virtualBackingFiles := make(map[base.DiskFileNum]struct{})
201 1 : d.mu.versions.virtualBackings.ForEach(func(backing *fileBacking) {
202 1 : virtualBackingFiles[backing.DiskFileNum] = struct{}{}
203 1 : })
204 :
205 1 : queuedLogNums := make([]wal.NumWAL, 0, len(memQueue))
206 1 : for i := range memQueue {
207 1 : if logNum := memQueue[i].logNum; logNum != 0 {
208 1 : queuedLogNums = append(queuedLogNums, wal.NumWAL(logNum))
209 1 : }
210 : }
211 : // Release the manifest and DB.mu so we don't block other operations on
212 : // the database.
213 1 : d.mu.versions.logUnlock()
214 1 : d.mu.Unlock()
215 1 :
216 1 : allLogicalLogs, err := d.mu.log.manager.List()
217 1 : if err != nil {
218 0 : return err
219 0 : }
220 :
221 : // Wrap the normal filesystem with one which wraps newly created files with
222 : // vfs.NewSyncingFile.
223 1 : fs := vfs.NewSyncingFS(d.opts.FS, vfs.SyncingFileOptions{
224 1 : NoSyncOnClose: d.opts.NoSyncOnClose,
225 1 : BytesPerSync: d.opts.BytesPerSync,
226 1 : })
227 1 :
228 1 : // Create the dir and its parents (if necessary), and sync them.
229 1 : var dir vfs.File
230 1 : defer func() {
231 1 : if dir != nil {
232 0 : _ = dir.Close()
233 0 : }
234 1 : if ckErr != nil {
235 0 : // Attempt to cleanup on error.
236 0 : _ = fs.RemoveAll(destDir)
237 0 : }
238 : }()
239 1 : dir, ckErr = mkdirAllAndSyncParents(fs, destDir)
240 1 : if ckErr != nil {
241 0 : return ckErr
242 0 : }
243 :
244 1 : {
245 1 : // Link or copy the OPTIONS.
246 1 : srcPath := base.MakeFilepath(fs, d.dirname, fileTypeOptions, optionsFileNum)
247 1 : destPath := fs.PathJoin(destDir, fs.PathBase(srcPath))
248 1 : ckErr = vfs.LinkOrCopy(fs, srcPath, destPath)
249 1 : if ckErr != nil {
250 0 : return ckErr
251 0 : }
252 : }
253 :
254 1 : {
255 1 : // Set the format major version in the destination directory.
256 1 : var versionMarker *atomicfs.Marker
257 1 : versionMarker, _, ckErr = atomicfs.LocateMarker(fs, destDir, formatVersionMarkerName)
258 1 : if ckErr != nil {
259 0 : return ckErr
260 0 : }
261 :
262 : // We use the marker to encode the active format version in the
263 : // marker filename. Unlike other uses of the atomic marker,
264 : // there is no file with the filename `formatVers.String()` on
265 : // the filesystem.
266 1 : ckErr = versionMarker.Move(formatVers.String())
267 1 : if ckErr != nil {
268 0 : return ckErr
269 0 : }
270 1 : ckErr = versionMarker.Close()
271 1 : if ckErr != nil {
272 0 : return ckErr
273 0 : }
274 : }
275 :
276 1 : var excludedFiles map[deletedFileEntry]*fileMetadata
277 1 : var remoteFiles []base.DiskFileNum
278 1 : // Set of FileBacking.DiskFileNum which will be required by virtual sstables
279 1 : // in the checkpoint.
280 1 : requiredVirtualBackingFiles := make(map[base.DiskFileNum]struct{})
281 1 : // Link or copy the sstables.
282 1 : for l := range current.Levels {
283 1 : iter := current.Levels[l].Iter()
284 1 : for f := iter.First(); f != nil; f = iter.Next() {
285 1 : if excludeFromCheckpoint(f, opt, d.cmp) {
286 1 : if excludedFiles == nil {
287 1 : excludedFiles = make(map[deletedFileEntry]*fileMetadata)
288 1 : }
289 1 : excludedFiles[deletedFileEntry{
290 1 : Level: l,
291 1 : FileNum: f.FileNum,
292 1 : }] = f
293 1 : continue
294 : }
295 :
296 1 : fileBacking := f.FileBacking
297 1 : if f.Virtual {
298 1 : if _, ok := requiredVirtualBackingFiles[fileBacking.DiskFileNum]; ok {
299 1 : continue
300 : }
301 1 : requiredVirtualBackingFiles[fileBacking.DiskFileNum] = struct{}{}
302 : }
303 1 : meta, err := d.objProvider.Lookup(fileTypeTable, fileBacking.DiskFileNum)
304 1 : if err != nil {
305 0 : ckErr = err
306 0 : return ckErr
307 0 : }
308 1 : if meta.IsRemote() {
309 0 : // We don't copy remote files. This is desirable as checkpointing is
310 0 : // supposed to be a fast operation, and references to remote files can
311 0 : // always be resolved by any checkpoint readers by reading the object
312 0 : // catalog. We don't add this file to excludedFiles either, as that'd
313 0 : // cause it to be deleted in the second manifest entry which is also
314 0 : // inaccurate.
315 0 : remoteFiles = append(remoteFiles, meta.DiskFileNum)
316 0 : continue
317 : }
318 :
319 1 : srcPath := base.MakeFilepath(fs, d.dirname, fileTypeTable, fileBacking.DiskFileNum)
320 1 : destPath := fs.PathJoin(destDir, fs.PathBase(srcPath))
321 1 : ckErr = vfs.LinkOrCopy(fs, srcPath, destPath)
322 1 : if ckErr != nil {
323 0 : return ckErr
324 0 : }
325 : }
326 : }
327 :
328 1 : var removeBackingTables []base.DiskFileNum
329 1 : for diskFileNum := range virtualBackingFiles {
330 1 : if _, ok := requiredVirtualBackingFiles[diskFileNum]; !ok {
331 1 : // The backing sstable associated with fileNum is no longer
332 1 : // required.
333 1 : removeBackingTables = append(removeBackingTables, diskFileNum)
334 1 : }
335 : }
336 :
337 1 : ckErr = d.writeCheckpointManifest(
338 1 : fs, formatVers, destDir, dir, manifestFileNum, manifestSize,
339 1 : excludedFiles, removeBackingTables,
340 1 : )
341 1 : if ckErr != nil {
342 0 : return ckErr
343 0 : }
344 1 : if len(remoteFiles) > 0 {
345 0 : ckErr = d.objProvider.CheckpointState(fs, destDir, fileTypeTable, remoteFiles)
346 0 : if ckErr != nil {
347 0 : return ckErr
348 0 : }
349 : }
350 :
351 : // Copy the WAL files. We copy rather than link because WAL file recycling
352 : // will cause the WAL files to be reused which would invalidate the
353 : // checkpoint.
354 1 : for _, logNum := range queuedLogNums {
355 1 : log, ok := allLogicalLogs.Get(logNum)
356 1 : if !ok {
357 0 : return errors.Newf("log %s not found", logNum)
358 0 : }
359 1 : for i := 0; i < log.NumSegments(); i++ {
360 1 : srcFS, srcPath := log.SegmentLocation(i)
361 1 : destPath := fs.PathJoin(destDir, srcFS.PathBase(srcPath))
362 1 : ckErr = vfs.CopyAcrossFS(srcFS, srcPath, fs, destPath)
363 1 : if ckErr != nil {
364 0 : return ckErr
365 0 : }
366 : }
367 : }
368 :
369 : // Sync and close the checkpoint directory.
370 1 : ckErr = dir.Sync()
371 1 : if ckErr != nil {
372 0 : return ckErr
373 0 : }
374 1 : ckErr = dir.Close()
375 1 : dir = nil
376 1 : return ckErr
377 : }
378 :
379 : func (d *DB) writeCheckpointManifest(
380 : fs vfs.FS,
381 : formatVers FormatMajorVersion,
382 : destDirPath string,
383 : destDir vfs.File,
384 : manifestFileNum base.DiskFileNum,
385 : manifestSize int64,
386 : excludedFiles map[deletedFileEntry]*fileMetadata,
387 : removeBackingTables []base.DiskFileNum,
388 1 : ) error {
389 1 : // Copy the MANIFEST, and create a pointer to it. We copy rather
390 1 : // than link because additional version edits added to the
391 1 : // MANIFEST after we took our snapshot of the sstables will
392 1 : // reference sstables that aren't in our checkpoint. For a
393 1 : // similar reason, we need to limit how much of the MANIFEST we
394 1 : // copy.
395 1 : // If some files are excluded from the checkpoint, also append a block that
396 1 : // records those files as deleted.
397 1 : if err := func() error {
398 1 : srcPath := base.MakeFilepath(fs, d.dirname, fileTypeManifest, manifestFileNum)
399 1 : destPath := fs.PathJoin(destDirPath, fs.PathBase(srcPath))
400 1 : src, err := fs.Open(srcPath, vfs.SequentialReadsOption)
401 1 : if err != nil {
402 0 : return err
403 0 : }
404 1 : defer src.Close()
405 1 :
406 1 : dst, err := fs.Create(destPath, vfs.WriteCategoryUnspecified)
407 1 : if err != nil {
408 0 : return err
409 0 : }
410 1 : defer dst.Close()
411 1 :
412 1 : // Copy all existing records. We need to copy at the record level in case we
413 1 : // need to append another record with the excluded files (we cannot simply
414 1 : // append a record after a raw data copy; see
415 1 : // https://github.com/cockroachdb/cockroach/issues/100935).
416 1 : r := record.NewReader(&io.LimitedReader{R: src, N: manifestSize}, manifestFileNum)
417 1 : w := record.NewWriter(dst)
418 1 : for {
419 1 : rr, err := r.Next()
420 1 : if err != nil {
421 1 : if err == io.EOF {
422 1 : break
423 : }
424 0 : return err
425 : }
426 :
427 1 : rw, err := w.Next()
428 1 : if err != nil {
429 0 : return err
430 0 : }
431 1 : if _, err := io.Copy(rw, rr); err != nil {
432 0 : return err
433 0 : }
434 : }
435 :
436 1 : if len(excludedFiles) > 0 {
437 1 : // Write out an additional VersionEdit that deletes the excluded SST files.
438 1 : ve := versionEdit{
439 1 : DeletedFiles: excludedFiles,
440 1 : RemovedBackingTables: removeBackingTables,
441 1 : }
442 1 :
443 1 : rw, err := w.Next()
444 1 : if err != nil {
445 0 : return err
446 0 : }
447 1 : if err := ve.Encode(rw); err != nil {
448 0 : return err
449 0 : }
450 : }
451 1 : if err := w.Close(); err != nil {
452 0 : return err
453 0 : }
454 1 : return dst.Sync()
455 0 : }(); err != nil {
456 0 : return err
457 0 : }
458 :
459 1 : var manifestMarker *atomicfs.Marker
460 1 : manifestMarker, _, err := atomicfs.LocateMarker(fs, destDirPath, manifestMarkerName)
461 1 : if err != nil {
462 0 : return err
463 0 : }
464 1 : if err := manifestMarker.Move(base.MakeFilename(fileTypeManifest, manifestFileNum)); err != nil {
465 0 : return err
466 0 : }
467 1 : return manifestMarker.Close()
468 : }
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