src/backup/datastore.rs

   1 use std::collections::{HashSet, HashMap};
   2 use std::io::{self, Write};
   3 use std::path::{Path, PathBuf};
   4 use std::sync::{Arc, Mutex};
   5 use std::convert::TryFrom;
   6 use std::time::Duration;
   7 use std::fs::File;
   8
   9 use anyhow::{bail, format_err, Error};
  10 use lazy_static::lazy_static;
  11
  12 use proxmox::tools::fs::{replace_file, CreateOptions, open_file_locked};
  13
  14 use super::backup_info::{BackupGroup, BackupDir};
  15 use super::chunk_store::ChunkStore;
  16 use super::dynamic_index::{DynamicIndexReader, DynamicIndexWriter};
  17 use super::fixed_index::{FixedIndexReader, FixedIndexWriter};
  18 use super::manifest::{MANIFEST_BLOB_NAME, MANIFEST_LOCK_NAME, CLIENT_LOG_BLOB_NAME, BackupManifest};
  19 use super::index::*;
  20 use super::{DataBlob, ArchiveType, archive_type};
  21 use crate::config::datastore::{self, DataStoreConfig};
  22 use crate::task::TaskState;
  23 use crate::tools;
  24 use crate::tools::format::HumanByte;
  25 use crate::tools::fs::{lock_dir_noblock, DirLockGuard};
  26 use crate::api2::types::{GarbageCollectionStatus, Userid};
  27 use crate::server::UPID;
  28
  29 lazy_static! {
  30     static ref DATASTORE_MAP: Mutex<HashMap<String, Arc<DataStore>>> = Mutex::new(HashMap::new());
  31 }
  32
  33 /// Datastore Management
  34 ///
  35 /// A Datastore can store severals backups, and provides the
  36 /// management interface for backup.
  37 pub struct DataStore {
  38     chunk_store: Arc<ChunkStore>,
  39     gc_mutex: Mutex<bool>,
  40     last_gc_status: Mutex<GarbageCollectionStatus>,
  41 }
  42
  43 impl DataStore {
  44
  45     pub fn lookup_datastore(name: &str) -> Result<Arc<DataStore>, Error> {
  46
  47         let (config, _digest) = datastore::config()?;
  48         let config: datastore::DataStoreConfig = config.lookup("datastore", name)?;
  49         let path = PathBuf::from(&config.path);
  50
  51         let mut map = DATASTORE_MAP.lock().unwrap();
  52
  53         if let Some(datastore) = map.get(name) {
  54             // Compare Config - if changed, create new Datastore object!
  55             if datastore.chunk_store.base == path {
  56                 return Ok(datastore.clone());
  57             }
  58         }
  59
  60         let datastore = DataStore::open_with_path(name, &path, config)?;
  61
  62         let datastore = Arc::new(datastore);
  63         map.insert(name.to_string(), datastore.clone());
  64
  65         Ok(datastore)
  66     }
  67
  68     fn open_with_path(store_name: &str, path: &Path, _config: DataStoreConfig) -> Result<Self, Error> {
  69         let chunk_store = ChunkStore::open(store_name, path)?;
  70
  71         let gc_status = GarbageCollectionStatus::default();
  72
  73         Ok(Self {
  74             chunk_store: Arc::new(chunk_store),
  75             gc_mutex: Mutex::new(false),
  76             last_gc_status: Mutex::new(gc_status),
  77         })
  78     }
  79
  80     pub fn get_chunk_iterator(
  81         &self,
  82     ) -> Result<
  83         impl Iterator<Item = (Result<tools::fs::ReadDirEntry, Error>, usize, bool)>,
  84         Error
  85     > {
  86         self.chunk_store.get_chunk_iterator()
  87     }
  88
  89     pub fn create_fixed_writer<P: AsRef<Path>>(&self, filename: P, size: usize, chunk_size: usize) -> Result<FixedIndexWriter, Error> {
  90
  91         let index = FixedIndexWriter::create(self.chunk_store.clone(), filename.as_ref(), size, chunk_size)?;
  92
  93         Ok(index)
  94     }
  95
  96     pub fn open_fixed_reader<P: AsRef<Path>>(&self, filename: P) -> Result<FixedIndexReader, Error> {
  97
  98         let full_path =  self.chunk_store.relative_path(filename.as_ref());
  99
 100         let index = FixedIndexReader::open(&full_path)?;
 101
 102         Ok(index)
 103     }
 104
 105     pub fn create_dynamic_writer<P: AsRef<Path>>(
 106         &self, filename: P,
 107     ) -> Result<DynamicIndexWriter, Error> {
 108
 109         let index = DynamicIndexWriter::create(
 110             self.chunk_store.clone(), filename.as_ref())?;
 111
 112         Ok(index)
 113     }
 114
 115     pub fn open_dynamic_reader<P: AsRef<Path>>(&self, filename: P) -> Result<DynamicIndexReader, Error> {
 116
 117         let full_path =  self.chunk_store.relative_path(filename.as_ref());
 118
 119         let index = DynamicIndexReader::open(&full_path)?;
 120
 121         Ok(index)
 122     }
 123
 124     pub fn open_index<P>(&self, filename: P) -> Result<Box<dyn IndexFile + Send>, Error>
 125     where
 126         P: AsRef<Path>,
 127     {
 128         let filename = filename.as_ref();
 129         let out: Box<dyn IndexFile + Send> =
 130             match archive_type(filename)? {
 131                 ArchiveType::DynamicIndex => Box::new(self.open_dynamic_reader(filename)?),
 132                 ArchiveType::FixedIndex => Box::new(self.open_fixed_reader(filename)?),
 133                 _ => bail!("cannot open index file of unknown type: {:?}", filename),
 134             };
 135         Ok(out)
 136     }
 137
 138     pub fn name(&self) -> &str {
 139         self.chunk_store.name()
 140     }
 141
 142     pub fn base_path(&self) -> PathBuf {
 143         self.chunk_store.base_path()
 144     }
 145
 146     /// Cleanup a backup directory
 147     ///
 148     /// Removes all files not mentioned in the manifest.
 149     pub fn cleanup_backup_dir(&self, backup_dir: &BackupDir, manifest: &BackupManifest
 150     ) ->  Result<(), Error> {
 151
 152         let mut full_path = self.base_path();
 153         full_path.push(backup_dir.relative_path());
 154
 155         let mut wanted_files = HashSet::new();
 156         wanted_files.insert(MANIFEST_BLOB_NAME.to_string());
 157         wanted_files.insert(CLIENT_LOG_BLOB_NAME.to_string());
 158         manifest.files().iter().for_each(|item| { wanted_files.insert(item.filename.clone()); });
 159
 160         for item in tools::fs::read_subdir(libc::AT_FDCWD, &full_path)? {
 161             if let Ok(item) = item {
 162                 if let Some(file_type) = item.file_type() {
 163                     if file_type != nix::dir::Type::File { continue; }
 164                 }
 165                 let file_name = item.file_name().to_bytes();
 166                 if file_name == b"." || file_name == b".." { continue; };
 167
 168                 if let Ok(name) = std::str::from_utf8(file_name) {
 169                     if wanted_files.contains(name) { continue; }
 170                 }
 171                 println!("remove unused file {:?}", item.file_name());
 172                 let dirfd = item.parent_fd();
 173                 let _res = unsafe { libc::unlinkat(dirfd, item.file_name().as_ptr(), 0) };
 174             }
 175         }
 176
 177         Ok(())
 178     }
 179
 180     /// Returns the absolute path for a backup_group
 181     pub fn group_path(&self, backup_group: &BackupGroup) -> PathBuf {
 182         let mut full_path = self.base_path();
 183         full_path.push(backup_group.group_path());
 184         full_path
 185     }
 186
 187     /// Returns the absolute path for backup_dir
 188     pub fn snapshot_path(&self, backup_dir: &BackupDir) -> PathBuf {
 189         let mut full_path = self.base_path();
 190         full_path.push(backup_dir.relative_path());
 191         full_path
 192     }
 193
 194     /// Remove a complete backup group including all snapshots
 195     pub fn remove_backup_group(&self, backup_group: &BackupGroup) ->  Result<(), Error> {
 196
 197         let full_path = self.group_path(backup_group);
 198
 199         let _guard = tools::fs::lock_dir_noblock(&full_path, "backup group", "possible running backup")?;
 200
 201         log::info!("removing backup group {:?}", full_path);
 202
 203         // remove all individual backup dirs first to ensure nothing is using them
 204         for snap in backup_group.list_backups(&self.base_path())? {
 205             self.remove_backup_dir(&snap.backup_dir, false)?;
 206         }
 207
 208         // no snapshots left, we can now safely remove the empty folder
 209         std::fs::remove_dir_all(&full_path)
 210             .map_err(|err| {
 211                 format_err!(
 212                     "removing backup group directory {:?} failed - {}",
 213                     full_path,
 214                     err,
 215                 )
 216             })?;
 217
 218         Ok(())
 219     }
 220
 221     /// Remove a backup directory including all content
 222     pub fn remove_backup_dir(&self, backup_dir: &BackupDir, force: bool) ->  Result<(), Error> {
 223
 224         let full_path = self.snapshot_path(backup_dir);
 225
 226         let (_guard, _manifest_guard);
 227         if !force {
 228             _guard = lock_dir_noblock(&full_path, "snapshot", "possibly running or in use")?;
 229             _manifest_guard = self.lock_manifest(backup_dir);
 230         }
 231
 232         log::info!("removing backup snapshot {:?}", full_path);
 233         std::fs::remove_dir_all(&full_path)
 234             .map_err(|err| {
 235                 format_err!(
 236                     "removing backup snapshot {:?} failed - {}",
 237                     full_path,
 238                     err,
 239                 )
 240             })?;
 241
 242         Ok(())
 243     }
 244
 245     /// Returns the time of the last successful backup
 246     ///
 247     /// Or None if there is no backup in the group (or the group dir does not exist).
 248     pub fn last_successful_backup(&self, backup_group: &BackupGroup) -> Result<Option<i64>, Error> {
 249         let base_path = self.base_path();
 250         let mut group_path = base_path.clone();
 251         group_path.push(backup_group.group_path());
 252
 253         if group_path.exists() {
 254             backup_group.last_successful_backup(&base_path)
 255         } else {
 256             Ok(None)
 257         }
 258     }
 259
 260     /// Returns the backup owner.
 261     ///
 262     /// The backup owner is the user who first created the backup group.
 263     pub fn get_owner(&self, backup_group: &BackupGroup) -> Result<Userid, Error> {
 264         let mut full_path = self.base_path();
 265         full_path.push(backup_group.group_path());
 266         full_path.push("owner");
 267         let owner = proxmox::tools::fs::file_read_firstline(full_path)?;
 268         Ok(owner.trim_end().parse()?) // remove trailing newline
 269     }
 270
 271     /// Set the backup owner.
 272     pub fn set_owner(
 273         &self,
 274         backup_group: &BackupGroup,
 275         userid: &Userid,
 276         force: bool,
 277     ) -> Result<(), Error> {
 278         let mut path = self.base_path();
 279         path.push(backup_group.group_path());
 280         path.push("owner");
 281
 282         let mut open_options = std::fs::OpenOptions::new();
 283         open_options.write(true);
 284         open_options.truncate(true);
 285
 286         if force {
 287             open_options.create(true);
 288         } else {
 289             open_options.create_new(true);
 290         }
 291
 292         let mut file = open_options.open(&path)
 293             .map_err(|err| format_err!("unable to create owner file {:?} - {}", path, err))?;
 294
 295         writeln!(file, "{}", userid)
 296             .map_err(|err| format_err!("unable to write owner file  {:?} - {}", path, err))?;
 297
 298         Ok(())
 299     }
 300
 301     /// Create (if it does not already exists) and lock a backup group
 302     ///
 303     /// And set the owner to 'userid'. If the group already exists, it returns the
 304     /// current owner (instead of setting the owner).
 305     ///
 306     /// This also acquires an exclusive lock on the directory and returns the lock guard.
 307     pub fn create_locked_backup_group(
 308         &self,
 309         backup_group: &BackupGroup,
 310         userid: &Userid,
 311     ) -> Result<(Userid, DirLockGuard), Error> {
 312         // create intermediate path first:
 313         let base_path = self.base_path();
 314
 315         let mut full_path = base_path.clone();
 316         full_path.push(backup_group.backup_type());
 317         std::fs::create_dir_all(&full_path)?;
 318
 319         full_path.push(backup_group.backup_id());
 320
 321         // create the last component now
 322         match std::fs::create_dir(&full_path) {
 323             Ok(_) => {
 324                 let guard = lock_dir_noblock(&full_path, "backup group", "another backup is already running")?;
 325                 self.set_owner(backup_group, userid, false)?;
 326                 let owner = self.get_owner(backup_group)?; // just to be sure
 327                 Ok((owner, guard))
 328             }
 329             Err(ref err) if err.kind() == io::ErrorKind::AlreadyExists => {
 330                 let guard = lock_dir_noblock(&full_path, "backup group", "another backup is already running")?;
 331                 let owner = self.get_owner(backup_group)?; // just to be sure
 332                 Ok((owner, guard))
 333             }
 334             Err(err) => bail!("unable to create backup group {:?} - {}", full_path, err),
 335         }
 336     }
 337
 338     /// Creates a new backup snapshot inside a BackupGroup
 339     ///
 340     /// The BackupGroup directory needs to exist.
 341     pub fn create_locked_backup_dir(&self, backup_dir: &BackupDir)
 342         -> Result<(PathBuf, bool, DirLockGuard), Error>
 343     {
 344         let relative_path = backup_dir.relative_path();
 345         let mut full_path = self.base_path();
 346         full_path.push(&relative_path);
 347
 348         let lock = ||
 349             lock_dir_noblock(&full_path, "snapshot", "internal error - tried creating snapshot that's already in use");
 350
 351         match std::fs::create_dir(&full_path) {
 352             Ok(_) => Ok((relative_path, true, lock()?)),
 353             Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => Ok((relative_path, false, lock()?)),
 354             Err(e) => Err(e.into())
 355         }
 356     }
 357
 358     pub fn list_images(&self) -> Result<Vec<PathBuf>, Error> {
 359         let base = self.base_path();
 360
 361         let mut list = vec![];
 362
 363         use walkdir::WalkDir;
 364
 365         let walker = WalkDir::new(&base).same_file_system(true).into_iter();
 366
 367         // make sure we skip .chunks (and other hidden files to keep it simple)
 368         fn is_hidden(entry: &walkdir::DirEntry) -> bool {
 369             entry.file_name()
 370                 .to_str()
 371                 .map(|s| s.starts_with("."))
 372                 .unwrap_or(false)
 373         }
 374         let handle_entry_err = |err: walkdir::Error| {
 375             if let Some(inner) = err.io_error() {
 376                 let path = err.path().unwrap_or(Path::new(""));
 377                 match inner.kind() {
 378                     io::ErrorKind::PermissionDenied => {
 379                         // only allow to skip ext4 fsck directory, avoid GC if, for example,
 380                         // a user got file permissions wrong on datastore rsync to new server
 381                         if err.depth() > 1 || !path.ends_with("lost+found") {
 382                             bail!("cannot continue garbage-collection safely, permission denied on: {}", path.display())
 383                         }
 384                     },
 385                     _ => bail!("unexpected error on datastore traversal: {} - {}", inner, path.display()),
 386                 }
 387             }
 388             Ok(())
 389         };
 390         for entry in walker.filter_entry(|e| !is_hidden(e)) {
 391             let path = match entry {
 392                 Ok(entry) => entry.into_path(),
 393                 Err(err) => {
 394                     handle_entry_err(err)?;
 395                     continue
 396                 },
 397             };
 398             if let Ok(archive_type) = archive_type(&path) {
 399                 if archive_type == ArchiveType::FixedIndex || archive_type == ArchiveType::DynamicIndex {
 400                     list.push(path);
 401                 }
 402             }
 403         }
 404
 405         Ok(list)
 406     }
 407
 408     // mark chunks  used by ``index`` as used
 409     fn index_mark_used_chunks<I: IndexFile>(
 410         &self,
 411         index: I,
 412         file_name: &Path, // only used for error reporting
 413         status: &mut GarbageCollectionStatus,
 414         worker: &dyn TaskState,
 415     ) -> Result<(), Error> {
 416
 417         status.index_file_count += 1;
 418         status.index_data_bytes += index.index_bytes();
 419
 420         for pos in 0..index.index_count() {
 421             worker.check_abort()?;
 422             tools::fail_on_shutdown()?;
 423             let digest = index.index_digest(pos).unwrap();
 424             if let Err(err) = self.chunk_store.touch_chunk(digest) {
 425                 crate::task_warn!(
 426                     worker,
 427                     "warning: unable to access chunk {}, required by {:?} - {}",
 428                     proxmox::tools::digest_to_hex(digest),
 429                     file_name,
 430                     err,
 431                 );
 432             }
 433         }
 434         Ok(())
 435     }
 436
 437     fn mark_used_chunks(
 438         &self,
 439         status: &mut GarbageCollectionStatus,
 440         worker: &dyn TaskState,
 441     ) -> Result<(), Error> {
 442
 443         let image_list = self.list_images()?;
 444
 445         let image_count = image_list.len();
 446
 447         let mut done = 0;
 448
 449         let mut last_percentage: usize = 0;
 450
 451         for path in image_list {
 452
 453             worker.check_abort()?;
 454             tools::fail_on_shutdown()?;
 455
 456             let full_path = self.chunk_store.relative_path(&path);
 457             match std::fs::File::open(&full_path) {
 458                 Ok(file) => {
 459                     if let Ok(archive_type) = archive_type(&path) {
 460                         if archive_type == ArchiveType::FixedIndex {
 461                             let index = FixedIndexReader::new(file)?;
 462                             self.index_mark_used_chunks(index, &path, status, worker)?;
 463                         } else if archive_type == ArchiveType::DynamicIndex {
 464                             let index = DynamicIndexReader::new(file)?;
 465                             self.index_mark_used_chunks(index, &path, status, worker)?;
 466                         }
 467                     }
 468                 }
 469                 Err(err) => {
 470                     if err.kind() == std::io::ErrorKind::NotFound {
 471                         // simply ignore vanished files
 472                     } else {
 473                         return Err(err.into());
 474                     }
 475                 }
 476             }
 477             done += 1;
 478
 479             let percentage = done*100/image_count;
 480             if percentage > last_percentage {
 481                 crate::task_log!(
 482                     worker,
 483                     "percentage done: phase1 {}% ({} of {} index files)",
 484                     percentage,
 485                     done,
 486                     image_count,
 487                 );
 488                 last_percentage = percentage;
 489             }
 490         }
 491
 492         Ok(())
 493     }
 494
 495     pub fn last_gc_status(&self) -> GarbageCollectionStatus {
 496         self.last_gc_status.lock().unwrap().clone()
 497     }
 498
 499     pub fn garbage_collection_running(&self) -> bool {
 500         if let Ok(_) = self.gc_mutex.try_lock() { false } else { true }
 501     }
 502
 503     pub fn garbage_collection(&self, worker: &dyn TaskState, upid: &UPID) -> Result<(), Error> {
 504
 505         if let Ok(ref mut _mutex) = self.gc_mutex.try_lock() {
 506
 507             // avoids that we run GC if an old daemon process has still a
 508             // running backup writer, which is not save as we have no "oldest
 509             // writer" information and thus no safe atime cutoff
 510             let _exclusive_lock =  self.chunk_store.try_exclusive_lock()?;
 511
 512             let phase1_start_time = proxmox::tools::time::epoch_i64();
 513             let oldest_writer = self.chunk_store.oldest_writer().unwrap_or(phase1_start_time);
 514
 515             let mut gc_status = GarbageCollectionStatus::default();
 516             gc_status.upid = Some(upid.to_string());
 517
 518             crate::task_log!(worker, "Start GC phase1 (mark used chunks)");
 519
 520             self.mark_used_chunks(&mut gc_status, worker)?;
 521
 522             crate::task_log!(worker, "Start GC phase2 (sweep unused chunks)");
 523             self.chunk_store.sweep_unused_chunks(
 524                 oldest_writer,
 525                 phase1_start_time,
 526                 &mut gc_status,
 527                 worker,
 528             )?;
 529
 530             crate::task_log!(
 531                 worker,
 532                 "Removed garbage: {}",
 533                 HumanByte::from(gc_status.removed_bytes),
 534             );
 535             crate::task_log!(worker, "Removed chunks: {}", gc_status.removed_chunks);
 536             if gc_status.pending_bytes > 0 {
 537                 crate::task_log!(
 538                     worker,
 539                     "Pending removals: {} (in {} chunks)",
 540                     HumanByte::from(gc_status.pending_bytes),
 541                     gc_status.pending_chunks,
 542                 );
 543             }
 544             if gc_status.removed_bad > 0 {
 545                 crate::task_log!(worker, "Removed bad files: {}", gc_status.removed_bad);
 546             }
 547
 548             crate::task_log!(
 549                 worker,
 550                 "Original data usage: {}",
 551                 HumanByte::from(gc_status.index_data_bytes),
 552             );
 553
 554             if gc_status.index_data_bytes > 0 {
 555                 let comp_per = (gc_status.disk_bytes as f64 * 100.)/gc_status.index_data_bytes as f64;
 556                 crate::task_log!(
 557                     worker,
 558                     "On-Disk usage: {} ({:.2}%)",
 559                     HumanByte::from(gc_status.disk_bytes),
 560                     comp_per,
 561                 );
 562             }
 563
 564             crate::task_log!(worker, "On-Disk chunks: {}", gc_status.disk_chunks);
 565
 566             if gc_status.disk_chunks > 0 {
 567                 let avg_chunk = gc_status.disk_bytes/(gc_status.disk_chunks as u64);
 568                 crate::task_log!(worker, "Average chunk size: {}", HumanByte::from(avg_chunk));
 569             }
 570
 571             *self.last_gc_status.lock().unwrap() = gc_status;
 572
 573         } else {
 574             bail!("Start GC failed - (already running/locked)");
 575         }
 576
 577         Ok(())
 578     }
 579
 580     pub fn try_shared_chunk_store_lock(&self) -> Result<tools::ProcessLockSharedGuard, Error> {
 581         self.chunk_store.try_shared_lock()
 582     }
 583
 584     pub fn chunk_path(&self, digest:&[u8; 32]) -> (PathBuf, String) {
 585         self.chunk_store.chunk_path(digest)
 586     }
 587
 588     pub fn cond_touch_chunk(&self, digest: &[u8; 32], fail_if_not_exist: bool) -> Result<bool, Error> {
 589         self.chunk_store.cond_touch_chunk(digest, fail_if_not_exist)
 590     }
 591
 592     pub fn insert_chunk(
 593         &self,
 594         chunk: &DataBlob,
 595         digest: &[u8; 32],
 596     ) -> Result<(bool, u64), Error> {
 597         self.chunk_store.insert_chunk(chunk, digest)
 598     }
 599
 600     pub fn load_blob(&self, backup_dir: &BackupDir, filename: &str) -> Result<DataBlob, Error> {
 601         let mut path = self.base_path();
 602         path.push(backup_dir.relative_path());
 603         path.push(filename);
 604
 605         proxmox::try_block!({
 606             let mut file = std::fs::File::open(&path)?;
 607             DataBlob::load_from_reader(&mut file)
 608         }).map_err(|err| format_err!("unable to load blob '{:?}' - {}", path, err))
 609     }
 610
 611
 612     pub fn load_chunk(&self, digest: &[u8; 32]) -> Result<DataBlob, Error> {
 613
 614         let (chunk_path, digest_str) = self.chunk_store.chunk_path(digest);
 615
 616         proxmox::try_block!({
 617             let mut file = std::fs::File::open(&chunk_path)?;
 618             DataBlob::load_from_reader(&mut file)
 619         }).map_err(|err| format_err!(
 620             "store '{}', unable to load chunk '{}' - {}",
 621             self.name(),
 622             digest_str,
 623             err,
 624         ))
 625     }
 626
 627     fn lock_manifest(
 628         &self,
 629         backup_dir: &BackupDir,
 630     ) -> Result<File, Error> {
 631         let mut path = self.base_path();
 632         path.push(backup_dir.relative_path());
 633         path.push(&MANIFEST_LOCK_NAME);
 634
 635         // update_manifest should never take a long time, so if someone else has
 636         // the lock we can simply block a bit and should get it soon
 637         open_file_locked(&path, Duration::from_secs(5), true)
 638             .map_err(|err| {
 639                 format_err!(
 640                     "unable to acquire manifest lock {:?} - {}", &path, err
 641                 )
 642             })
 643     }
 644
 645     /// Load the manifest without a lock. Must not be written back.
 646     pub fn load_manifest(
 647         &self,
 648         backup_dir: &BackupDir,
 649     ) -> Result<(BackupManifest, u64), Error> {
 650         let blob = self.load_blob(backup_dir, MANIFEST_BLOB_NAME)?;
 651         let raw_size = blob.raw_size();
 652         let manifest = BackupManifest::try_from(blob)?;
 653         Ok((manifest, raw_size))
 654     }
 655
 656     /// Update the manifest of the specified snapshot. Never write a manifest directly,
 657     /// only use this method - anything else may break locking guarantees.
 658     pub fn update_manifest(
 659         &self,
 660         backup_dir: &BackupDir,
 661         update_fn: impl FnOnce(&mut BackupManifest),
 662     ) -> Result<(), Error> {
 663
 664         let _guard = self.lock_manifest(backup_dir)?;
 665         let (mut manifest, _) = self.load_manifest(&backup_dir)?;
 666
 667         update_fn(&mut manifest);
 668
 669         let manifest = serde_json::to_value(manifest)?;
 670         let manifest = serde_json::to_string_pretty(&manifest)?;
 671         let blob = DataBlob::encode(manifest.as_bytes(), None, true)?;
 672         let raw_data = blob.raw_data();
 673
 674         let mut path = self.base_path();
 675         path.push(backup_dir.relative_path());
 676         path.push(MANIFEST_BLOB_NAME);
 677
 678         // atomic replace invalidates flock - no other writes past this point!
 679         replace_file(&path, raw_data, CreateOptions::new())?;
 680
 681         Ok(())
 682     }
 683 }