Merge 1389bd10bc into 411c763fb8

Only LocalCache implements these.

.github/workflows/black.yaml

@@ -9,7 +9,7 @@ jobs:
   lint:
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: psf/black@stable
         with:
             version: "~= 23.0"

.github/workflows/ci.yml

@@ -78,11 +78,11 @@ jobs:
         # just fetching 1 commit is not enough for setuptools-scm, so we fetch all
         fetch-depth: 0
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v4
+      uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
     - name: Cache pip
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ~/.cache/pip
         key: ${{ runner.os }}-pip-${{ hashFiles('requirements.d/development.txt') }}
@@ -114,7 +114,7 @@ jobs:
         #sudo -E bash -c "tox -e py"
         tox --skip-missing-interpreters
     - name: Upload coverage to Codecov
-      uses: codecov/codecov-action@v3
+      uses: codecov/codecov-action@v4
       env:
         OS: ${{ runner.os }}
         python: ${{ matrix.python-version }}

src/borg/archive.py

@@ -643,14 +643,14 @@ Duration: {0.duration}
         # so we can already remove it here, the next .save() will then commit this cleanup.
         # remove its manifest entry, remove its ArchiveItem chunk, remove its item_ptrs chunks:
         del self.manifest.archives[self.checkpoint_name]
-        self.cache.chunk_decref(self.id, self.stats)
+        self.cache.chunk_decref(self.id, 1, self.stats)
         for id in metadata.item_ptrs:
-            self.cache.chunk_decref(id, self.stats)
+            self.cache.chunk_decref(id, 1, self.stats)
         # also get rid of that part item, we do not want to have it in next checkpoint or final archive
         tail_chunks = self.items_buffer.restore_chunks_state()
         # tail_chunks contain the tail of the archive items metadata stream, not needed for next commit.
         for id in tail_chunks:
-            self.cache.chunk_decref(id, self.stats)
+            self.cache.chunk_decref(id, 1, self.stats)  # TODO can we have real size here?
 
     def save(self, name=None, comment=None, timestamp=None, stats=None, additional_metadata=None):
         name = name or self.name
@@ -1024,7 +1024,7 @@ Duration: {0.duration}
         new_id = self.key.id_hash(data)
         self.cache.add_chunk(new_id, {}, data, stats=self.stats, ro_type=ROBJ_ARCHIVE_META)
         self.manifest.archives[self.name] = (new_id, metadata.time)
-        self.cache.chunk_decref(self.id, self.stats)
+        self.cache.chunk_decref(self.id, 1, self.stats)
         self.id = new_id
 
     def rename(self, name):
@@ -1052,12 +1052,15 @@ Duration: {0.duration}
                 error = True
                 return exception_ignored  # must not return None here
 
-        def chunk_decref(id, stats):
+        def chunk_decref(id, size, stats):
             try:
-                self.cache.chunk_decref(id, stats, wait=False)
+                self.cache.chunk_decref(id, size, stats, wait=False)
             except KeyError:
-                cid = bin_to_hex(id)
-                raise ChunksIndexError(cid)
+                nonlocal error
+                if forced == 0:
+                    cid = bin_to_hex(id)
+                    raise ChunksIndexError(cid)
+                error = True
             else:
                 fetch_async_response(wait=False)
 
@@ -1073,13 +1076,13 @@ Duration: {0.duration}
                     pi.show(i)
                 _, data = self.repo_objs.parse(items_id, data, ro_type=ROBJ_ARCHIVE_STREAM)
                 unpacker.feed(data)
-                chunk_decref(items_id, stats)
+                chunk_decref(items_id, 1, stats)
                 try:
                     for item in unpacker:
                         item = Item(internal_dict=item)
                         if "chunks" in item:
                             for chunk_id, size in item.chunks:
-                                chunk_decref(chunk_id, stats)
+                                chunk_decref(chunk_id, size, stats)
                 except (TypeError, ValueError):
                     # if items metadata spans multiple chunks and one chunk got dropped somehow,
                     # it could be that unpacker yields bad types
@@ -1096,12 +1099,12 @@ Duration: {0.duration}
 
         # delete the blocks that store all the references that end up being loaded into metadata.items:
         for id in self.metadata.item_ptrs:
-            chunk_decref(id, stats)
+            chunk_decref(id, 1, stats)
 
         # in forced delete mode, we try hard to delete at least the manifest entry,
         # if possible also the archive superblock, even if processing the items raises
         # some harmless exception.
-        chunk_decref(self.id, stats)
+        chunk_decref(self.id, 1, stats)
         del self.manifest.archives[self.name]
         while fetch_async_response(wait=True) is not None:
             # we did async deletes, process outstanding results (== exceptions),
@@ -1510,7 +1513,7 @@ class FilesystemObjectProcessors:
         except BackupOSError:
             # see comments in process_file's exception handler, same issue here.
             for chunk in item.get("chunks", []):
-                cache.chunk_decref(chunk.id, self.stats, wait=False)
+                cache.chunk_decref(chunk.id, chunk.size, self.stats, wait=False)
             raise
         else:
             item.get_size(memorize=True)
@@ -1544,7 +1547,7 @@ class FilesystemObjectProcessors:
                         item.chunks = []
                         for chunk_id, chunk_size in hl_chunks:
                             # process one-by-one, so we will know in item.chunks how far we got
-                            chunk_entry = cache.chunk_incref(chunk_id, self.stats)
+                            chunk_entry = cache.chunk_incref(chunk_id, chunk_size, self.stats)
                             item.chunks.append(chunk_entry)
                     else:  # normal case, no "2nd+" hardlink
                         if not is_special_file:
@@ -1552,26 +1555,26 @@ class FilesystemObjectProcessors:
                             started_hashing = time.monotonic()
                             path_hash = self.key.id_hash(hashed_path)
                             self.stats.hashing_time += time.monotonic() - started_hashing
-                            known, ids = cache.file_known_and_unchanged(hashed_path, path_hash, st)
+                            known, chunks = cache.file_known_and_unchanged(hashed_path, path_hash, st)
                         else:
                             # in --read-special mode, we may be called for special files.
                             # there should be no information in the cache about special files processed in
                             # read-special mode, but we better play safe as this was wrong in the past:
                             hashed_path = path_hash = None
-                            known, ids = False, None
-                        if ids is not None:
+                            known, chunks = False, None
+                        if chunks is not None:
                             # Make sure all ids are available
-                            for id_ in ids:
-                                if not cache.seen_chunk(id_):
+                            for chunk in chunks:
+                                if not cache.seen_chunk(chunk.id):
                                     # cache said it is unmodified, but we lost a chunk: process file like modified
                                     status = "M"
                                     break
                             else:
                                 item.chunks = []
-                                for chunk_id in ids:
+                                for chunk in chunks:
                                     # process one-by-one, so we will know in item.chunks how far we got
-                                    chunk_entry = cache.chunk_incref(chunk_id, self.stats)
-                                    item.chunks.append(chunk_entry)
+                                    cache.chunk_incref(chunk.id, chunk.size, self.stats)
+                                    item.chunks.append(chunk)
                                 status = "U"  # regular file, unchanged
                         else:
                             status = "M" if known else "A"  # regular file, modified or added
@@ -1606,7 +1609,7 @@ class FilesystemObjectProcessors:
                                 # block or char device will change without its mtime/size/inode changing.
                                 # also, we must not memorize a potentially inconsistent/corrupt file that
                                 # changed while we backed it up.
-                                cache.memorize_file(hashed_path, path_hash, st, [c.id for c in item.chunks])
+                                cache.memorize_file(hashed_path, path_hash, st, item.chunks)
                         self.stats.files_stats[status] += 1  # must be done late
                         if not changed_while_backup:
                             status = None  # we already called print_file_status
@@ -1620,7 +1623,7 @@ class FilesystemObjectProcessors:
                     # but we will not add an item (see add_item in create_helper) and thus
                     # they would be orphaned chunks in case that we commit the transaction.
                     for chunk in item.get("chunks", []):
-                        cache.chunk_decref(chunk.id, self.stats, wait=False)
+                        cache.chunk_decref(chunk.id, chunk.size, self.stats, wait=False)
                     # Now that we have cleaned up the chunk references, we can re-raise the exception.
                     # This will skip processing of this file, but might retry or continue with the next one.
                     raise
@@ -1731,7 +1734,7 @@ class TarfileObjectProcessors:
             except BackupOSError:
                 # see comment in FilesystemObjectProcessors.process_file, same issue here.
                 for chunk in item.get("chunks", []):
-                    self.cache.chunk_decref(chunk.id, self.stats, wait=False)
+                    self.cache.chunk_decref(chunk.id, chunk.size, self.stats, wait=False)
                 raise
 
 
@@ -2328,10 +2331,10 @@ class ArchiveChecker:
             unused = {id_ for id_, entry in self.chunks.iteritems() if entry.refcount == 0}
             orphaned = unused - self.possibly_superseded
             if orphaned:
-                logger.error(f"{len(orphaned)} orphaned objects found!")
+                logger.info(f"{len(orphaned)} orphaned (unused) objects found.")
                 for chunk_id in orphaned:
                     logger.debug(f"chunk {bin_to_hex(chunk_id)} is orphaned.")
-                self.error_found = True
+                # To support working with AdHocCache or NewCache, we do not set self.error_found = True.
             if self.repair and unused:
                 logger.info(
                     "Deleting %d orphaned and %d superseded objects..." % (len(orphaned), len(self.possibly_superseded))
@@ -2444,7 +2447,7 @@ class ArchiveRecreater:
     def process_chunks(self, archive, target, item):
         if not target.recreate_rechunkify:
             for chunk_id, size in item.chunks:
-                self.cache.chunk_incref(chunk_id, target.stats)
+                self.cache.chunk_incref(chunk_id, size, target.stats)
             return item.chunks
         chunk_iterator = self.iter_chunks(archive, target, list(item.chunks))
         chunk_processor = partial(self.chunk_processor, target)
@@ -2452,8 +2455,9 @@ class ArchiveRecreater:
 
     def chunk_processor(self, target, chunk):
         chunk_id, data = cached_hash(chunk, self.key.id_hash)
+        size = len(data)
         if chunk_id in self.seen_chunks:
-            return self.cache.chunk_incref(chunk_id, target.stats)
+            return self.cache.chunk_incref(chunk_id, size, target.stats)
         chunk_entry = self.cache.add_chunk(chunk_id, {}, data, stats=target.stats, wait=False, ro_type=ROBJ_FILE_STREAM)
         self.cache.repository.async_response(wait=False)
         self.seen_chunks.add(chunk_entry.id)

src/borg/archiver/create_cmd.py

@@ -225,6 +225,7 @@ class CreateMixIn:
                 progress=args.progress,
                 lock_wait=self.lock_wait,
                 permit_adhoc_cache=args.no_cache_sync,
+                force_adhoc_cache=args.no_cache_sync_forced,
                 cache_mode=args.files_cache_mode,
                 iec=args.iec,
             ) as cache:
@@ -803,6 +804,12 @@ class CreateMixIn:
             action="store_true",
             help="experimental: do not synchronize the cache. Implies not using the files cache.",
         )
+        subparser.add_argument(
+            "--no-cache-sync-forced",
+            dest="no_cache_sync_forced",
+            action="store_true",
+            help="experimental: do not synchronize the cache (forced). Implies not using the files cache.",
+        )
         subparser.add_argument(
             "--stdin-name",
             metavar="NAME",

src/borg/archiver/rinfo_cmd.py

@@ -59,16 +59,9 @@ class RInfoMixIn:
                 output += f" out of {format_file_size(storage_quota, iec=args.iec)}"
             output += "\n"
 
-            output += (
-                textwrap.dedent(
-                    """
-                    Cache: {cache.path}
-                    Security dir: {security_dir}
-                    """
-                )
-                .strip()
-                .format(**info)
-            )
+            if hasattr(info["cache"], "path"):
+                output += "Cache: {cache.path}\n".format(**info)
+            output += "Security dir: {security_dir}\n".format(**info)
 
             print(output)
             print(str(cache))

src/borg/archiver/transfer_cmd.py

@@ -143,7 +143,7 @@ class TransferMixIn:
                                 transfer_size += size
                             else:
                                 if not dry_run:
-                                    chunk_entry = cache.chunk_incref(chunk_id, archive.stats)
+                                    chunk_entry = cache.chunk_incref(chunk_id, size, archive.stats)
                                     chunks.append(chunk_entry)
                                 present_size += size
                         if not dry_run:

src/borg/cache.py

@@ -35,8 +35,8 @@ from .platform import SaveFile
 from .remote import cache_if_remote
 from .repository import LIST_SCAN_LIMIT
 
-# note: cmtime might me either a ctime or a mtime timestamp
-FileCacheEntry = namedtuple("FileCacheEntry", "age inode size cmtime chunk_ids")
+# note: cmtime might be either a ctime or a mtime timestamp, chunks is a list of ChunkListEntry
+FileCacheEntry = namedtuple("FileCacheEntry", "age inode size cmtime chunks")
 
 
 class SecurityManager:
@@ -248,15 +248,6 @@ def cache_dir(repository, path=None):
     return path or os.path.join(get_cache_dir(), repository.id_str)
 
 
-def files_cache_name():
-    suffix = os.environ.get("BORG_FILES_CACHE_SUFFIX", "")
-    return "files." + suffix if suffix else "files"
-
-
-def discover_files_cache_name(path):
-    return [fn for fn in os.listdir(path) if fn == "files" or fn.startswith("files.")][0]
-
-
 class CacheConfig:
     def __init__(self, repository, path=None, lock_wait=None):
         self.repository = repository
@@ -413,6 +404,7 @@ class Cache:
         progress=False,
         lock_wait=None,
         permit_adhoc_cache=False,
+        force_adhoc_cache=False,
         cache_mode=FILES_CACHE_MODE_DISABLED,
         iec=False,
     ):
@@ -428,9 +420,23 @@ class Cache:
                 cache_mode=cache_mode,
             )
 
+        def newcache():
+            return NewCache(
+                manifest=manifest,
+                path=path,
+                warn_if_unencrypted=warn_if_unencrypted,
+                progress=progress,
+                iec=iec,
+                lock_wait=lock_wait,
+                cache_mode=cache_mode,
+            )
+
         def adhoc():
             return AdHocCache(manifest=manifest, lock_wait=lock_wait, iec=iec)
 
+        if force_adhoc_cache:
+            return adhoc()
+
         if not permit_adhoc_cache:
             return local()
 
@@ -489,7 +495,302 @@ Total chunks: {0.total_chunks}
         return self.Summary(**stats)
 
 
-class LocalCache(CacheStatsMixin):
+class FilesCacheMixin:
+    """
+    Massively accelerate processing of unchanged files by caching their chunks list.
+    With that, we can avoid having to read and chunk them to get their chunks list.
+    """
+
+    FILES_CACHE_NAME = "files"
+
+    def __init__(self, cache_mode):
+        self.cache_mode = cache_mode
+        self.files = None
+        self._newest_cmtime = None
+
+    def files_cache_name(self):
+        suffix = os.environ.get("BORG_FILES_CACHE_SUFFIX", "")
+        return self.FILES_CACHE_NAME + "." + suffix if suffix else self.FILES_CACHE_NAME
+
+    def discover_files_cache_name(self, path):
+        return [
+            fn for fn in os.listdir(path) if fn == self.FILES_CACHE_NAME or fn.startswith(self.FILES_CACHE_NAME + ".")
+        ][0]
+
+    def _create_empty_files_cache(self, path):
+        with SaveFile(os.path.join(path, self.files_cache_name()), binary=True):
+            pass  # empty file
+
+    def _read_files_cache(self):
+        if "d" in self.cache_mode:  # d(isabled)
+            return
+
+        self.files = {}
+        logger.debug("Reading files cache ...")
+        files_cache_logger.debug("FILES-CACHE-LOAD: starting...")
+        msg = None
+        try:
+            with IntegrityCheckedFile(
+                path=os.path.join(self.path, self.files_cache_name()),
+                write=False,
+                integrity_data=self.cache_config.integrity.get(self.files_cache_name()),
+            ) as fd:
+                u = msgpack.Unpacker(use_list=True)
+                while True:
+                    data = fd.read(64 * 1024)
+                    if not data:
+                        break
+                    u.feed(data)
+                    try:
+                        for path_hash, item in u:
+                            entry = FileCacheEntry(*item)
+                            # in the end, this takes about 240 Bytes per file
+                            self.files[path_hash] = msgpack.packb(entry._replace(age=entry.age + 1))
+                    except (TypeError, ValueError) as exc:
+                        msg = "The files cache seems invalid. [%s]" % str(exc)
+                        break
+        except OSError as exc:
+            msg = "The files cache can't be read. [%s]" % str(exc)
+        except FileIntegrityError as fie:
+            msg = "The files cache is corrupted. [%s]" % str(fie)
+        if msg is not None:
+            logger.warning(msg)
+            logger.warning("Continuing without files cache - expect lower performance.")
+            self.files = {}
+        files_cache_logger.debug("FILES-CACHE-LOAD: finished, %d entries loaded.", len(self.files))
+
+    def _write_files_cache(self):
+        if self._newest_cmtime is None:
+            # was never set because no files were modified/added
+            self._newest_cmtime = 2**63 - 1  # nanoseconds, good until y2262
+        ttl = int(os.environ.get("BORG_FILES_CACHE_TTL", 20))
+        files_cache_logger.debug("FILES-CACHE-SAVE: starting...")
+        with IntegrityCheckedFile(path=os.path.join(self.path, self.files_cache_name()), write=True) as fd:
+            entry_count = 0
+            for path_hash, item in self.files.items():
+                # Only keep files seen in this backup that are older than newest cmtime seen in this backup -
+                # this is to avoid issues with filesystem snapshots and cmtime granularity.
+                # Also keep files from older backups that have not reached BORG_FILES_CACHE_TTL yet.
+                entry = FileCacheEntry(*msgpack.unpackb(item))
+                if (
+                    entry.age == 0
+                    and timestamp_to_int(entry.cmtime) < self._newest_cmtime
+                    or entry.age > 0
+                    and entry.age < ttl
+                ):
+                    msgpack.pack((path_hash, entry), fd)
+                    entry_count += 1
+        files_cache_logger.debug("FILES-CACHE-KILL: removed all old entries with age >= TTL [%d]", ttl)
+        files_cache_logger.debug(
+            "FILES-CACHE-KILL: removed all current entries with newest cmtime %d", self._newest_cmtime
+        )
+        files_cache_logger.debug("FILES-CACHE-SAVE: finished, %d remaining entries saved.", entry_count)
+        return fd.integrity_data
+
+    def file_known_and_unchanged(self, hashed_path, path_hash, st):
+        """
+        Check if we know the file that has this path_hash (know == it is in our files cache) and
+        whether it is unchanged (the size/inode number/cmtime is same for stuff we check in this cache_mode).
+
+        :param hashed_path: the file's path as we gave it to hash(hashed_path)
+        :param path_hash: hash(hashed_path), to save some memory in the files cache
+        :param st: the file's stat() result
+        :return: known, chunks (known is True if we have infos about this file in the cache,
+                               chunks is a list[ChunkListEntry] IF the file has not changed, otherwise None).
+        """
+        if not stat.S_ISREG(st.st_mode):
+            return False, None
+        cache_mode = self.cache_mode
+        if "d" in cache_mode:  # d(isabled)
+            files_cache_logger.debug("UNKNOWN: files cache disabled")
+            return False, None
+        # note: r(echunk) does not need the files cache in this method, but the files cache will
+        # be updated and saved to disk to memorize the files. To preserve previous generations in
+        # the cache, this means that it also needs to get loaded from disk first.
+        if "r" in cache_mode:  # r(echunk)
+            files_cache_logger.debug("UNKNOWN: rechunking enforced")
+            return False, None
+        entry = self.files.get(path_hash)
+        if not entry:
+            files_cache_logger.debug("UNKNOWN: no file metadata in cache for: %r", hashed_path)
+            return False, None
+        # we know the file!
+        entry = FileCacheEntry(*msgpack.unpackb(entry))
+        if "s" in cache_mode and entry.size != st.st_size:
+            files_cache_logger.debug("KNOWN-CHANGED: file size has changed: %r", hashed_path)
+            return True, None
+        if "i" in cache_mode and entry.inode != st.st_ino:
+            files_cache_logger.debug("KNOWN-CHANGED: file inode number has changed: %r", hashed_path)
+            return True, None
+        if "c" in cache_mode and timestamp_to_int(entry.cmtime) != st.st_ctime_ns:
+            files_cache_logger.debug("KNOWN-CHANGED: file ctime has changed: %r", hashed_path)
+            return True, None
+        elif "m" in cache_mode and timestamp_to_int(entry.cmtime) != st.st_mtime_ns:
+            files_cache_logger.debug("KNOWN-CHANGED: file mtime has changed: %r", hashed_path)
+            return True, None
+        # we ignored the inode number in the comparison above or it is still same.
+        # if it is still the same, replacing it in the tuple doesn't change it.
+        # if we ignored it, a reason for doing that is that files were moved to a new
+        # disk / new fs (so a one-time change of inode number is expected) and we wanted
+        # to avoid everything getting chunked again. to be able to re-enable the inode
+        # number comparison in a future backup run (and avoid chunking everything
+        # again at that time), we need to update the inode number in the cache with what
+        # we see in the filesystem.
+        self.files[path_hash] = msgpack.packb(entry._replace(inode=st.st_ino, age=0))
+        chunks = [ChunkListEntry(*chunk) for chunk in entry.chunks]  # convert to list of namedtuple
+        return True, chunks
+
+    def memorize_file(self, hashed_path, path_hash, st, chunks):
+        if not stat.S_ISREG(st.st_mode):
+            return
+        cache_mode = self.cache_mode
+        # note: r(echunk) modes will update the files cache, d(isabled) mode won't
+        if "d" in cache_mode:
+            files_cache_logger.debug("FILES-CACHE-NOUPDATE: files cache disabled")
+            return
+        if "c" in cache_mode:
+            cmtime_type = "ctime"
+            cmtime_ns = safe_ns(st.st_ctime_ns)
+        elif "m" in cache_mode:
+            cmtime_type = "mtime"
+            cmtime_ns = safe_ns(st.st_mtime_ns)
+        else:  # neither 'c' nor 'm' in cache_mode, avoid UnboundLocalError
+            cmtime_type = "ctime"
+            cmtime_ns = safe_ns(st.st_ctime_ns)
+        entry = FileCacheEntry(
+            age=0, inode=st.st_ino, size=st.st_size, cmtime=int_to_timestamp(cmtime_ns), chunks=chunks
+        )
+        self.files[path_hash] = msgpack.packb(entry)
+        self._newest_cmtime = max(self._newest_cmtime or 0, cmtime_ns)
+        files_cache_logger.debug(
+            "FILES-CACHE-UPDATE: put %r [has %s] <- %r",
+            entry._replace(chunks="[%d entries]" % len(entry.chunks)),
+            cmtime_type,
+            hashed_path,
+        )
+
+
+class ChunksMixin:
+    """
+    Chunks index related code for misc. Cache implementations.
+    """
+
+    def chunk_incref(self, id, size, stats):
+        assert isinstance(size, int) and size > 0
+        if not self._txn_active:
+            self.begin_txn()
+        count, _size = self.chunks.incref(id)
+        stats.update(size, False)
+        return ChunkListEntry(id, size)
+
+    def chunk_decref(self, id, size, stats, wait=True):
+        assert isinstance(size, int) and size > 0
+        if not self._txn_active:
+            self.begin_txn()
+        count, _size = self.chunks.decref(id)
+        if count == 0:
+            del self.chunks[id]
+            self.repository.delete(id, wait=wait)
+            stats.update(-size, True)
+        else:
+            stats.update(-size, False)
+
+    def seen_chunk(self, id, size=None):
+        if not self._txn_active:
+            self.begin_txn()
+        entry = self.chunks.get(id, ChunkIndexEntry(0, None))
+        if entry.refcount and size is not None:
+            assert isinstance(entry.size, int)
+            if entry.size:
+                # LocalCache: has existing size information and uses *size* to make an effort at detecting collisions.
+                if size != entry.size:
+                    # we already have a chunk with that id, but different size.
+                    # this is either a hash collision (unlikely) or corruption or a bug.
+                    raise Exception(
+                        "chunk has same id [%r], but different size (stored: %d new: %d)!" % (id, entry.size, size)
+                    )
+            else:
+                # NewCache / AdHocCache:
+                # Here *size* is used to update the chunk's size information, which will be zero for existing chunks.
+                self.chunks[id] = entry._replace(size=size)
+        return entry.refcount
+
+    def add_chunk(
+        self,
+        id,
+        meta,
+        data,
+        *,
+        stats,
+        wait=True,
+        compress=True,
+        size=None,
+        ctype=None,
+        clevel=None,
+        ro_type=ROBJ_FILE_STREAM,
+    ):
+        assert ro_type is not None
+        if not self._txn_active:
+            self.begin_txn()
+        if size is None:
+            if compress:
+                size = len(data)  # data is still uncompressed
+            else:
+                raise ValueError("when giving compressed data for a chunk, the uncompressed size must be given also")
+        refcount = self.seen_chunk(id, size)
+        if refcount:
+            return self.chunk_incref(id, size, stats)
+        cdata = self.repo_objs.format(
+            id, meta, data, compress=compress, size=size, ctype=ctype, clevel=clevel, ro_type=ro_type
+        )
+        self.repository.put(id, cdata, wait=wait)
+        self.chunks.add(id, 1, size)
+        stats.update(size, not refcount)
+        return ChunkListEntry(id, size)
+
+    def _load_chunks_from_repo(self):
+        # Explicitly set the initial usable hash table capacity to avoid performance issues
+        # due to hash table "resonance".
+        # Since we're creating an archive, add 10 % from the start.
+        num_chunks = len(self.repository)
+        chunks = ChunkIndex(usable=num_chunks * 1.1)
+        pi = ProgressIndicatorPercent(
+            total=num_chunks, msg="Downloading chunk list... %3.0f%%", msgid="cache.download_chunks"
+        )
+        t0 = perf_counter()
+        num_requests = 0
+        marker = None
+        while True:
+            result = self.repository.list(limit=LIST_SCAN_LIMIT, marker=marker)
+            num_requests += 1
+            if not result:
+                break
+            pi.show(increase=len(result))
+            marker = result[-1]
+            # All chunks from the repository have a refcount of MAX_VALUE, which is sticky,
+            # therefore we can't/won't delete them. Chunks we added ourselves in this transaction
+            # (e.g. checkpoint archives) are tracked correctly.
+            init_entry = ChunkIndexEntry(refcount=ChunkIndex.MAX_VALUE, size=0)
+            for id_ in result:
+                chunks[id_] = init_entry
+        assert len(chunks) == num_chunks
+        # LocalCache does not contain the manifest, either.
+        del chunks[self.manifest.MANIFEST_ID]
+        duration = perf_counter() - t0 or 0.01
+        pi.finish()
+        logger.debug(
+            "Cache: downloaded %d chunk IDs in %.2f s (%d requests), ~%s/s",
+            num_chunks,
+            duration,
+            num_requests,
+            format_file_size(num_chunks * 34 / duration),
+        )
+        # Chunk IDs in a list are encoded in 34 bytes: 1 byte msgpack header, 1 byte length, 32 ID bytes.
+        # Protocol overhead is neglected in this calculation.
+        return chunks
+
+
+class LocalCache(CacheStatsMixin, FilesCacheMixin, ChunksMixin):
     """
     Persistent, local (client-side) cache.
     """
@@ -512,15 +813,15 @@ class LocalCache(CacheStatsMixin):
         :param cache_mode: what shall be compared in the file stat infos vs. cached stat infos comparison
         """
         CacheStatsMixin.__init__(self, iec=iec)
+        FilesCacheMixin.__init__(self, cache_mode)
         assert isinstance(manifest, Manifest)
         self.manifest = manifest
         self.repository = manifest.repository
         self.key = manifest.key
         self.repo_objs = manifest.repo_objs
         self.progress = progress
-        self.cache_mode = cache_mode
         self.timestamp = None
-        self.txn_active = False
+        self._txn_active = False
 
         self.path = cache_dir(self.repository, path)
         self.security_manager = SecurityManager(self.repository)
@@ -561,8 +862,7 @@ class LocalCache(CacheStatsMixin):
         self.cache_config.create()
         ChunkIndex().write(os.path.join(self.path, "chunks"))
         os.makedirs(os.path.join(self.path, "chunks.archive.d"))
-        with SaveFile(os.path.join(self.path, files_cache_name()), binary=True):
-            pass  # empty file
+        self._create_empty_files_cache(self.path)
 
     def _do_open(self):
         self.cache_config.load()
@@ -572,10 +872,7 @@ class LocalCache(CacheStatsMixin):
             integrity_data=self.cache_config.integrity.get("chunks"),
         ) as fd:
             self.chunks = ChunkIndex.read(fd)
-        if "d" in self.cache_mode:  # d(isabled)
-            self.files = None
-        else:
-            self._read_files()
+        self._read_files_cache()
 
     def open(self):
         if not os.path.isdir(self.path):
@@ -588,42 +885,6 @@ class LocalCache(CacheStatsMixin):
             self.cache_config.close()
             self.cache_config = None
 
-    def _read_files(self):
-        self.files = {}
-        self._newest_cmtime = None
-        logger.debug("Reading files cache ...")
-        files_cache_logger.debug("FILES-CACHE-LOAD: starting...")
-        msg = None
-        try:
-            with IntegrityCheckedFile(
-                path=os.path.join(self.path, files_cache_name()),
-                write=False,
-                integrity_data=self.cache_config.integrity.get(files_cache_name()),
-            ) as fd:
-                u = msgpack.Unpacker(use_list=True)
-                while True:
-                    data = fd.read(64 * 1024)
-                    if not data:
-                        break
-                    u.feed(data)
-                    try:
-                        for path_hash, item in u:
-                            entry = FileCacheEntry(*item)
-                            # in the end, this takes about 240 Bytes per file
-                            self.files[path_hash] = msgpack.packb(entry._replace(age=entry.age + 1))
-                    except (TypeError, ValueError) as exc:
-                        msg = "The files cache seems invalid. [%s]" % str(exc)
-                        break
-        except OSError as exc:
-            msg = "The files cache can't be read. [%s]" % str(exc)
-        except FileIntegrityError as fie:
-            msg = "The files cache is corrupted. [%s]" % str(fie)
-        if msg is not None:
-            logger.warning(msg)
-            logger.warning("Continuing without files cache - expect lower performance.")
-            self.files = {}
-        files_cache_logger.debug("FILES-CACHE-LOAD: finished, %d entries loaded.", len(self.files))
-
     def begin_txn(self):
         # Initialize transaction snapshot
         pi = ProgressIndicatorMessage(msgid="cache.begin_transaction")
@@ -635,48 +896,23 @@ class LocalCache(CacheStatsMixin):
         shutil.copy(os.path.join(self.path, "chunks"), txn_dir)
         pi.output("Initializing cache transaction: Reading files")
         try:
-            shutil.copy(os.path.join(self.path, files_cache_name()), txn_dir)
+            shutil.copy(os.path.join(self.path, self.files_cache_name()), txn_dir)
         except FileNotFoundError:
-            with SaveFile(os.path.join(txn_dir, files_cache_name()), binary=True):
-                pass  # empty file
+            self._create_empty_files_cache(txn_dir)
         os.replace(txn_dir, os.path.join(self.path, "txn.active"))
-        self.txn_active = True
+        self._txn_active = True
         pi.finish()
 
     def commit(self):
         """Commit transaction"""
-        if not self.txn_active:
+        if not self._txn_active:
             return
         self.security_manager.save(self.manifest, self.key)
         pi = ProgressIndicatorMessage(msgid="cache.commit")
         if self.files is not None:
-            if self._newest_cmtime is None:
-                # was never set because no files were modified/added
-                self._newest_cmtime = 2**63 - 1  # nanoseconds, good until y2262
-            ttl = int(os.environ.get("BORG_FILES_CACHE_TTL", 20))
             pi.output("Saving files cache")
-            files_cache_logger.debug("FILES-CACHE-SAVE: starting...")
-            with IntegrityCheckedFile(path=os.path.join(self.path, files_cache_name()), write=True) as fd:
-                entry_count = 0
-                for path_hash, item in self.files.items():
-                    # Only keep files seen in this backup that are older than newest cmtime seen in this backup -
-                    # this is to avoid issues with filesystem snapshots and cmtime granularity.
-                    # Also keep files from older backups that have not reached BORG_FILES_CACHE_TTL yet.
-                    entry = FileCacheEntry(*msgpack.unpackb(item))
-                    if (
-                        entry.age == 0
-                        and timestamp_to_int(entry.cmtime) < self._newest_cmtime
-                        or entry.age > 0
-                        and entry.age < ttl
-                    ):
-                        msgpack.pack((path_hash, entry), fd)
-                        entry_count += 1
-            files_cache_logger.debug("FILES-CACHE-KILL: removed all old entries with age >= TTL [%d]", ttl)
-            files_cache_logger.debug(
-                "FILES-CACHE-KILL: removed all current entries with newest cmtime %d", self._newest_cmtime
-            )
-            files_cache_logger.debug("FILES-CACHE-SAVE: finished, %d remaining entries saved.", entry_count)
-            self.cache_config.integrity[files_cache_name()] = fd.integrity_data
+            integrity_data = self._write_files_cache()
+            self.cache_config.integrity[self.files_cache_name()] = integrity_data
         pi.output("Saving chunks cache")
         with IntegrityCheckedFile(path=os.path.join(self.path, "chunks"), write=True) as fd:
             self.chunks.write(fd)
@@ -685,7 +921,7 @@ class LocalCache(CacheStatsMixin):
         self.cache_config.save(self.manifest, self.key)
         os.replace(os.path.join(self.path, "txn.active"), os.path.join(self.path, "txn.tmp"))
         shutil.rmtree(os.path.join(self.path, "txn.tmp"))
-        self.txn_active = False
+        self._txn_active = False
         pi.finish()
 
     def rollback(self):
@@ -698,12 +934,12 @@ class LocalCache(CacheStatsMixin):
         if os.path.exists(txn_dir):
             shutil.copy(os.path.join(txn_dir, "config"), self.path)
             shutil.copy(os.path.join(txn_dir, "chunks"), self.path)
-            shutil.copy(os.path.join(txn_dir, discover_files_cache_name(txn_dir)), self.path)
+            shutil.copy(os.path.join(txn_dir, self.discover_files_cache_name(txn_dir)), self.path)
             txn_tmp = os.path.join(self.path, "txn.tmp")
             os.replace(txn_dir, txn_tmp)
             if os.path.exists(txn_tmp):
                 shutil.rmtree(txn_tmp)
-        self.txn_active = False
+        self._txn_active = False
         self._do_open()
 
     def sync(self):
@@ -930,8 +1166,7 @@ class LocalCache(CacheStatsMixin):
             shutil.rmtree(os.path.join(self.path, "chunks.archive.d"))
             os.makedirs(os.path.join(self.path, "chunks.archive.d"))
         self.chunks = ChunkIndex()
-        with SaveFile(os.path.join(self.path, files_cache_name()), binary=True):
-            pass  # empty file
+        self._create_empty_files_cache(self.path)
         self.cache_config.manifest_id = ""
         self.cache_config._config.set("cache", "manifest", "")
 
@@ -948,149 +1183,171 @@ class LocalCache(CacheStatsMixin):
         self.cache_config.ignored_features.update(repo_features - my_features)
         self.cache_config.mandatory_features.update(repo_features & my_features)
 
-    def add_chunk(
+
+class NewCache(CacheStatsMixin, FilesCacheMixin, ChunksMixin):
+    """
+    Like AdHocCache, but with a files cache.
+    """
+
+    def __init__(
         self,
-        id,
-        meta,
-        data,
-        *,
-        stats,
-        wait=True,
-        compress=True,
-        size=None,
-        ctype=None,
-        clevel=None,
-        ro_type=ROBJ_FILE_STREAM,
+        manifest,
+        path=None,
+        warn_if_unencrypted=True,
+        progress=False,
+        lock_wait=None,
+        cache_mode=FILES_CACHE_MODE_DISABLED,
+        iec=False,
     ):
-        assert ro_type is not None
-        if not self.txn_active:
-            self.begin_txn()
-        if size is None and compress:
-            size = len(data)  # data is still uncompressed
-        refcount = self.seen_chunk(id, size)
-        if refcount:
-            return self.chunk_incref(id, stats)
-        if size is None:
-            raise ValueError("when giving compressed data for a new chunk, the uncompressed size must be given also")
-        cdata = self.repo_objs.format(
-            id, meta, data, compress=compress, size=size, ctype=ctype, clevel=clevel, ro_type=ro_type
-        )
-        self.repository.put(id, cdata, wait=wait)
-        self.chunks.add(id, 1, size)
-        stats.update(size, not refcount)
-        return ChunkListEntry(id, size)
-
-    def seen_chunk(self, id, size=None):
-        refcount, stored_size = self.chunks.get(id, ChunkIndexEntry(0, None))
-        if size is not None and stored_size is not None and size != stored_size:
-            # we already have a chunk with that id, but different size.
-            # this is either a hash collision (unlikely) or corruption or a bug.
-            raise Exception(
-                "chunk has same id [%r], but different size (stored: %d new: %d)!" % (id, stored_size, size)
-            )
-        return refcount
-
-    def chunk_incref(self, id, stats, size=None):
-        if not self.txn_active:
-            self.begin_txn()
-        count, _size = self.chunks.incref(id)
-        stats.update(_size, False)
-        return ChunkListEntry(id, _size)
-
-    def chunk_decref(self, id, stats, wait=True):
-        if not self.txn_active:
-            self.begin_txn()
-        count, size = self.chunks.decref(id)
-        if count == 0:
-            del self.chunks[id]
-            self.repository.delete(id, wait=wait)
-            stats.update(-size, True)
-        else:
-            stats.update(-size, False)
-
-    def file_known_and_unchanged(self, hashed_path, path_hash, st):
         """
-        Check if we know the file that has this path_hash (know == it is in our files cache) and
-        whether it is unchanged (the size/inode number/cmtime is same for stuff we check in this cache_mode).
-
-        :param hashed_path: the file's path as we gave it to hash(hashed_path)
-        :param path_hash: hash(hashed_path), to save some memory in the files cache
-        :param st: the file's stat() result
-        :return: known, ids (known is True if we have infos about this file in the cache,
-                             ids is the list of chunk ids IF the file has not changed, otherwise None).
+        :param warn_if_unencrypted: print warning if accessing unknown unencrypted repository
+        :param lock_wait: timeout for lock acquisition (int [s] or None [wait forever])
+        :param cache_mode: what shall be compared in the file stat infos vs. cached stat infos comparison
         """
-        if not stat.S_ISREG(st.st_mode):
-            return False, None
-        cache_mode = self.cache_mode
-        if "d" in cache_mode:  # d(isabled)
-            files_cache_logger.debug("UNKNOWN: files cache disabled")
-            return False, None
-        # note: r(echunk) does not need the files cache in this method, but the files cache will
-        # be updated and saved to disk to memorize the files. To preserve previous generations in
-        # the cache, this means that it also needs to get loaded from disk first.
-        if "r" in cache_mode:  # r(echunk)
-            files_cache_logger.debug("UNKNOWN: rechunking enforced")
-            return False, None
-        entry = self.files.get(path_hash)
-        if not entry:
-            files_cache_logger.debug("UNKNOWN: no file metadata in cache for: %r", hashed_path)
-            return False, None
-        # we know the file!
-        entry = FileCacheEntry(*msgpack.unpackb(entry))
-        if "s" in cache_mode and entry.size != st.st_size:
-            files_cache_logger.debug("KNOWN-CHANGED: file size has changed: %r", hashed_path)
-            return True, None
-        if "i" in cache_mode and entry.inode != st.st_ino:
-            files_cache_logger.debug("KNOWN-CHANGED: file inode number has changed: %r", hashed_path)
-            return True, None
-        if "c" in cache_mode and timestamp_to_int(entry.cmtime) != st.st_ctime_ns:
-            files_cache_logger.debug("KNOWN-CHANGED: file ctime has changed: %r", hashed_path)
-            return True, None
-        elif "m" in cache_mode and timestamp_to_int(entry.cmtime) != st.st_mtime_ns:
-            files_cache_logger.debug("KNOWN-CHANGED: file mtime has changed: %r", hashed_path)
-            return True, None
-        # we ignored the inode number in the comparison above or it is still same.
-        # if it is still the same, replacing it in the tuple doesn't change it.
-        # if we ignored it, a reason for doing that is that files were moved to a new
-        # disk / new fs (so a one-time change of inode number is expected) and we wanted
-        # to avoid everything getting chunked again. to be able to re-enable the inode
-        # number comparison in a future backup run (and avoid chunking everything
-        # again at that time), we need to update the inode number in the cache with what
-        # we see in the filesystem.
-        self.files[path_hash] = msgpack.packb(entry._replace(inode=st.st_ino, age=0))
-        return True, entry.chunk_ids
+        CacheStatsMixin.__init__(self, iec=iec)
+        FilesCacheMixin.__init__(self, cache_mode)
+        assert isinstance(manifest, Manifest)
+        self.manifest = manifest
+        self.repository = manifest.repository
+        self.key = manifest.key
+        self.repo_objs = manifest.repo_objs
+        self.progress = progress
+        self.timestamp = None
+        self._txn_active = False
 
-    def memorize_file(self, hashed_path, path_hash, st, ids):
-        if not stat.S_ISREG(st.st_mode):
+        self.path = cache_dir(self.repository, path)
+        self.security_manager = SecurityManager(self.repository)
+        self.cache_config = CacheConfig(self.repository, self.path, lock_wait)
+
+        # Warn user before sending data to a never seen before unencrypted repository
+        if not os.path.exists(self.path):
+            self.security_manager.assert_access_unknown(warn_if_unencrypted, manifest, self.key)
+            self.create()
+
+        self.open()
+        try:
+            self.security_manager.assert_secure(manifest, self.key, cache_config=self.cache_config)
+
+            if not self.check_cache_compatibility():
+                self.wipe_cache()
+
+            self.update_compatibility()
+        except:  # noqa
+            self.close()
+            raise
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.close()
+
+    def create(self):
+        """Create a new empty cache at `self.path`"""
+        os.makedirs(self.path)
+        with open(os.path.join(self.path, "README"), "w") as fd:
+            fd.write(CACHE_README)
+        self.cache_config.create()
+        self._create_empty_files_cache(self.path)
+
+    def _do_open(self):
+        self.cache_config.load()
+        self.chunks = self._load_chunks_from_repo()
+        self._read_files_cache()
+
+    def open(self):
+        if not os.path.isdir(self.path):
+            raise Exception("%s Does not look like a Borg cache" % self.path)
+        self.cache_config.open()
+        self.rollback()
+
+    def close(self):
+        if self.cache_config is not None:
+            self.cache_config.close()
+            self.cache_config = None
+
+    def begin_txn(self):
+        # Initialize transaction snapshot
+        pi = ProgressIndicatorMessage(msgid="cache.begin_transaction")
+        txn_dir = os.path.join(self.path, "txn.tmp")
+        os.mkdir(txn_dir)
+        pi.output("Initializing cache transaction: Reading config")
+        shutil.copy(os.path.join(self.path, "config"), txn_dir)
+        pi.output("Initializing cache transaction: Reading files")
+        try:
+            shutil.copy(os.path.join(self.path, self.files_cache_name()), txn_dir)
+        except FileNotFoundError:
+            self._create_empty_files_cache(txn_dir)
+        os.replace(txn_dir, os.path.join(self.path, "txn.active"))
+        pi.finish()
+        self._txn_active = True
+
+    def commit(self):
+        if not self._txn_active:
             return
-        cache_mode = self.cache_mode
-        # note: r(echunk) modes will update the files cache, d(isabled) mode won't
-        if "d" in cache_mode:
-            files_cache_logger.debug("FILES-CACHE-NOUPDATE: files cache disabled")
-            return
-        if "c" in cache_mode:
-            cmtime_type = "ctime"
-            cmtime_ns = safe_ns(st.st_ctime_ns)
-        elif "m" in cache_mode:
-            cmtime_type = "mtime"
-            cmtime_ns = safe_ns(st.st_mtime_ns)
-        else:  # neither 'c' nor 'm' in cache_mode, avoid UnboundLocalError
-            cmtime_type = "ctime"
-            cmtime_ns = safe_ns(st.st_ctime_ns)
-        entry = FileCacheEntry(
-            age=0, inode=st.st_ino, size=st.st_size, cmtime=int_to_timestamp(cmtime_ns), chunk_ids=ids
-        )
-        self.files[path_hash] = msgpack.packb(entry)
-        self._newest_cmtime = max(self._newest_cmtime or 0, cmtime_ns)
-        files_cache_logger.debug(
-            "FILES-CACHE-UPDATE: put %r [has %s] <- %r",
-            entry._replace(chunk_ids="[%d entries]" % len(entry.chunk_ids)),
-            cmtime_type,
-            hashed_path,
-        )
+        self.security_manager.save(self.manifest, self.key)
+        pi = ProgressIndicatorMessage(msgid="cache.commit")
+        if self.files is not None:
+            pi.output("Saving files cache")
+            integrity_data = self._write_files_cache()
+            self.cache_config.integrity[self.files_cache_name()] = integrity_data
+        pi.output("Saving cache config")
+        self.cache_config.save(self.manifest, self.key)
+        os.replace(os.path.join(self.path, "txn.active"), os.path.join(self.path, "txn.tmp"))
+        shutil.rmtree(os.path.join(self.path, "txn.tmp"))
+        self._txn_active = False
+        pi.finish()
+
+    def rollback(self):
+        # Remove partial transaction
+        if os.path.exists(os.path.join(self.path, "txn.tmp")):
+            shutil.rmtree(os.path.join(self.path, "txn.tmp"))
+        # Roll back active transaction
+        txn_dir = os.path.join(self.path, "txn.active")
+        if os.path.exists(txn_dir):
+            shutil.copy(os.path.join(txn_dir, "config"), self.path)
+            shutil.copy(os.path.join(txn_dir, self.discover_files_cache_name(txn_dir)), self.path)
+            txn_tmp = os.path.join(self.path, "txn.tmp")
+            os.replace(txn_dir, txn_tmp)
+            if os.path.exists(txn_tmp):
+                shutil.rmtree(txn_tmp)
+        self._txn_active = False
+        self._do_open()
+
+    def check_cache_compatibility(self):
+        my_features = Manifest.SUPPORTED_REPO_FEATURES
+        if self.cache_config.ignored_features & my_features:
+            # The cache might not contain references of chunks that need a feature that is mandatory for some operation
+            # and which this version supports. To avoid corruption while executing that operation force rebuild.
+            return False
+        if not self.cache_config.mandatory_features <= my_features:
+            # The cache was build with consideration to at least one feature that this version does not understand.
+            # This client might misinterpret the cache. Thus force a rebuild.
+            return False
+        return True
+
+    def wipe_cache(self):
+        logger.warning("Discarding incompatible cache and forcing a cache rebuild")
+        self.chunks = ChunkIndex()
+        self._create_empty_files_cache(self.path)
+        self.cache_config.manifest_id = ""
+        self.cache_config._config.set("cache", "manifest", "")
+
+        self.cache_config.ignored_features = set()
+        self.cache_config.mandatory_features = set()
+
+    def update_compatibility(self):
+        operation_to_features_map = self.manifest.get_all_mandatory_features()
+        my_features = Manifest.SUPPORTED_REPO_FEATURES
+        repo_features = set()
+        for operation, features in operation_to_features_map.items():
+            repo_features.update(features)
+
+        self.cache_config.ignored_features.update(repo_features - my_features)
+        self.cache_config.mandatory_features.update(repo_features & my_features)
 
 
-class AdHocCache(CacheStatsMixin):
+class AdHocCache(CacheStatsMixin, ChunksMixin):
     """
     Ad-hoc, non-persistent cache.
 
@@ -1135,59 +1392,9 @@ Chunk index:    {0.total_unique_chunks:20d}             unknown"""
         files_cache_logger.debug("UNKNOWN: files cache not implemented")
         return False, None
 
-    def memorize_file(self, hashed_path, path_hash, st, ids):
+    def memorize_file(self, hashed_path, path_hash, st, chunks):
         pass
 
-    def add_chunk(self, id, meta, data, *, stats, wait=True, compress=True, size=None, ro_type=ROBJ_FILE_STREAM):
-        assert ro_type is not None
-        if not self._txn_active:
-            self.begin_txn()
-        if size is None and compress:
-            size = len(data)  # data is still uncompressed
-        if size is None:
-            raise ValueError("when giving compressed data for a chunk, the uncompressed size must be given also")
-        refcount = self.seen_chunk(id, size)
-        if refcount:
-            return self.chunk_incref(id, stats, size=size)
-        cdata = self.repo_objs.format(id, meta, data, compress=compress, ro_type=ro_type)
-        self.repository.put(id, cdata, wait=wait)
-        self.chunks.add(id, 1, size)
-        stats.update(size, not refcount)
-        return ChunkListEntry(id, size)
-
-    def seen_chunk(self, id, size=None):
-        if not self._txn_active:
-            self.begin_txn()
-        entry = self.chunks.get(id, ChunkIndexEntry(0, None))
-        if entry.refcount and size and not entry.size:
-            # The LocalCache has existing size information and uses *size* to make an effort at detecting collisions.
-            # This is of course not possible for the AdHocCache.
-            # Here *size* is used to update the chunk's size information, which will be zero for existing chunks.
-            self.chunks[id] = entry._replace(size=size)
-        return entry.refcount
-
-    def chunk_incref(self, id, stats, size=None):
-        if not self._txn_active:
-            self.begin_txn()
-        count, _size = self.chunks.incref(id)
-        # When _size is 0 and size is not given, then this chunk has not been locally visited yet (seen_chunk with
-        # size or add_chunk); we can't add references to those (size=0 is invalid) and generally don't try to.
-        size = _size or size
-        assert size
-        stats.update(size, False)
-        return ChunkListEntry(id, size)
-
-    def chunk_decref(self, id, stats, wait=True):
-        if not self._txn_active:
-            self.begin_txn()
-        count, size = self.chunks.decref(id)
-        if count == 0:
-            del self.chunks[id]
-            self.repository.delete(id, wait=wait)
-            stats.update(-size, True)
-        else:
-            stats.update(-size, False)
-
     def commit(self):
         if not self._txn_active:
             return
@@ -1200,41 +1407,4 @@ Chunk index:    {0.total_unique_chunks:20d}             unknown"""
 
     def begin_txn(self):
         self._txn_active = True
-        # Explicitly set the initial usable hash table capacity to avoid performance issues
-        # due to hash table "resonance".
-        # Since we're creating an archive, add 10 % from the start.
-        num_chunks = len(self.repository)
-        self.chunks = ChunkIndex(usable=num_chunks * 1.1)
-        pi = ProgressIndicatorPercent(
-            total=num_chunks, msg="Downloading chunk list... %3.0f%%", msgid="cache.download_chunks"
-        )
-        t0 = perf_counter()
-        num_requests = 0
-        marker = None
-        while True:
-            result = self.repository.list(limit=LIST_SCAN_LIMIT, marker=marker)
-            num_requests += 1
-            if not result:
-                break
-            pi.show(increase=len(result))
-            marker = result[-1]
-            # All chunks from the repository have a refcount of MAX_VALUE, which is sticky,
-            # therefore we can't/won't delete them. Chunks we added ourselves in this transaction
-            # (e.g. checkpoint archives) are tracked correctly.
-            init_entry = ChunkIndexEntry(refcount=ChunkIndex.MAX_VALUE, size=0)
-            for id_ in result:
-                self.chunks[id_] = init_entry
-        assert len(self.chunks) == num_chunks
-        # LocalCache does not contain the manifest, either.
-        del self.chunks[self.manifest.MANIFEST_ID]
-        duration = perf_counter() - t0 or 0.01
-        pi.finish()
-        logger.debug(
-            "AdHocCache: downloaded %d chunk IDs in %.2f s (%d requests), ~%s/s",
-            num_chunks,
-            duration,
-            num_requests,
-            format_file_size(num_chunks * 34 / duration),
-        )
-        # Chunk IDs in a list are encoded in 34 bytes: 1 byte msgpack header, 1 byte length, 32 ID bytes.
-        # Protocol overhead is neglected in this calculation.
+        self.chunks = self._load_chunks_from_repo()

src/borg/helpers/parseformat.py

@@ -1184,13 +1184,13 @@ class BorgJsonEncoder(json.JSONEncoder):
         from ..repository import Repository
         from ..remote import RemoteRepository
         from ..archive import Archive
-        from ..cache import LocalCache, AdHocCache
+        from ..cache import LocalCache, AdHocCache, NewCache
 
         if isinstance(o, Repository) or isinstance(o, RemoteRepository):
             return {"id": bin_to_hex(o.id), "location": o._location.canonical_path()}
         if isinstance(o, Archive):
             return o.info()
-        if isinstance(o, LocalCache):
+        if isinstance(o, (LocalCache, NewCache)):
             return {"path": o.path, "stats": o.stats()}
         if isinstance(o, AdHocCache):
             return {"stats": o.stats()}

src/borg/helpers/time.py

@@ -100,7 +100,7 @@ def format_timedelta(td):
     s = ts % 60
     m = int(ts / 60) % 60
     h = int(ts / 3600) % 24
-    txt = "%.2f seconds" % s
+    txt = "%.3f seconds" % s
     if m:
         txt = "%d minutes %s" % (m, txt)
     if h:

src/borg/testsuite/archive.py

@@ -61,8 +61,8 @@ def test_stats_format(stats):
 Number of files: 1
 Original size: 20 B
 Deduplicated size: 20 B
-Time spent in hashing: 0.00 seconds
-Time spent in chunking: 0.00 seconds
+Time spent in hashing: 0.000 seconds
+Time spent in chunking: 0.000 seconds
 Added files: 0
 Unchanged files: 0
 Modified files: 0

src/borg/testsuite/archiver/check_cmd.py

@@ -338,10 +338,11 @@ def test_extra_chunks(archivers, request):
     with Repository(archiver.repository_location, exclusive=True) as repository:
         repository.put(b"01234567890123456789012345678901", b"xxxx")
         repository.commit(compact=False)
-    cmd(archiver, "check", exit_code=1)
-    cmd(archiver, "check", exit_code=1)
+    output = cmd(archiver, "check", "-v", exit_code=0)  # orphans are not considered warnings anymore
+    assert "1 orphaned (unused) objects found." in output
     cmd(archiver, "check", "--repair", exit_code=0)
-    cmd(archiver, "check", exit_code=0)
+    output = cmd(archiver, "check", "-v", exit_code=0)
+    assert "orphaned (unused) objects found." not in output
     cmd(archiver, "extract", "archive1", "--dry-run", exit_code=0)
 
 

src/borg/testsuite/archiver/checks.py

@@ -277,6 +277,7 @@ def test_unknown_mandatory_feature_in_cache(archivers, request):
             repository._location = Location(archiver.repository_location)
         manifest = Manifest.load(repository, Manifest.NO_OPERATION_CHECK)
         with Cache(repository, manifest) as cache:
+            is_localcache = isinstance(cache, LocalCache)
             cache.begin_txn()
             cache.cache_config.mandatory_features = {"unknown-feature"}
             cache.commit()
@@ -295,7 +296,8 @@ def test_unknown_mandatory_feature_in_cache(archivers, request):
         with patch.object(LocalCache, "wipe_cache", wipe_wrapper):
             cmd(archiver, "create", "test", "input")
 
-        assert called
+        if is_localcache:
+            assert called
 
     with Repository(archiver.repository_path, exclusive=True) as repository:
         if remote_repo:

src/borg/testsuite/archiver/corruption.py

@@ -32,7 +32,7 @@ def test_check_corrupted_repository(archiver):
 def corrupt_archiver(archiver):
     create_test_files(archiver.input_path)
     cmd(archiver, "rcreate", RK_ENCRYPTION)
-    archiver.cache_path = json.loads(cmd(archiver, "rinfo", "--json"))["cache"]["path"]
+    archiver.cache_path = json.loads(cmd(archiver, "rinfo", "--json"))["cache"].get("path")
 
 
 def corrupt(file, amount=1):
@@ -45,7 +45,14 @@ def corrupt(file, amount=1):
 
 def test_cache_chunks(archiver):
     corrupt_archiver(archiver)
-    corrupt(os.path.join(archiver.cache_path, "chunks"))
+    if archiver.cache_path is None:
+        pytest.skip("no cache path for this kind of Cache implementation")
+
+    chunks_index = os.path.join(archiver.cache_path, "chunks")
+    if not os.path.exists(chunks_index):
+        pytest.skip("Only works with LocalCache.")
+
+    corrupt(chunks_index)
     if archiver.FORK_DEFAULT:
         out = cmd(archiver, "rinfo", exit_code=2)
         assert "failed integrity check" in out
@@ -56,6 +63,9 @@ def test_cache_chunks(archiver):
 
 def test_cache_files(archiver):
     corrupt_archiver(archiver)
+    if archiver.cache_path is None:
+        pytest.skip("no cache path for this kind of Cache implementation")
+
     cmd(archiver, "create", "test", "input")
     corrupt(os.path.join(archiver.cache_path, "files"))
     out = cmd(archiver, "create", "test1", "input")
@@ -65,6 +75,9 @@ def test_cache_files(archiver):
 
 def test_chunks_archive(archiver):
     corrupt_archiver(archiver)
+    if archiver.cache_path is None:
+        pytest.skip("no cache path for this kind of Cache implementation")
+
     cmd(archiver, "create", "test1", "input")
     # Find ID of test1, so we can corrupt it later :)
     target_id = cmd(archiver, "rlist", "--format={id}{NL}").strip()
@@ -75,6 +88,8 @@ def test_chunks_archive(archiver):
     cmd(archiver, "rinfo", "--json")
 
     chunks_archive = os.path.join(archiver.cache_path, "chunks.archive.d")
+    if not os.path.exists(chunks_archive):
+        pytest.skip("Only LocalCache has a per-archive chunks index cache.")
     assert len(os.listdir(chunks_archive)) == 4  # two archives, one chunks cache and one .integrity file each
 
     corrupt(os.path.join(chunks_archive, target_id + ".compact"))
@@ -96,6 +111,9 @@ def test_chunks_archive(archiver):
 
 def test_old_version_interfered(archiver):
     corrupt_archiver(archiver)
+    if archiver.cache_path is None:
+        pytest.skip("no cache path for this kind of Cache implementation")
+
     # Modify the main manifest ID without touching the manifest ID in the integrity section.
     # This happens if a version without integrity checking modifies the cache.
     config_path = os.path.join(archiver.cache_path, "config")

src/borg/testsuite/archiver/debug_cmds.py

@@ -168,7 +168,12 @@ def test_debug_refcount_obj(archivers, request):
     create_json = json.loads(cmd(archiver, "create", "--json", "test", "input"))
     archive_id = create_json["archive"]["id"]
     output = cmd(archiver, "debug", "refcount-obj", archive_id).strip()
-    assert output == f"object {archive_id} has 1 referrers [info from chunks cache]."
+    # LocalCache does precise refcounting, so we'll get 1 reference for the archive.
+    # AdHocCache or NewCache doesn't, we'll get ChunkIndex.MAX_VALUE as refcount.
+    assert (
+        output == f"object {archive_id} has 1 referrers [info from chunks cache]."
+        or output == f"object {archive_id} has 4294966271 referrers [info from chunks cache]."
+    )
 
     # Invalid IDs do not abort or return an error
     output = cmd(archiver, "debug", "refcount-obj", "124", "xyza").strip()

src/borg/testsuite/cache.py

@@ -189,7 +189,7 @@ class TestAdHocCache:
 
     def test_does_not_delete_existing_chunks(self, repository, cache):
         assert cache.seen_chunk(H(1)) == ChunkIndex.MAX_VALUE
-        cache.chunk_decref(H(1), Statistics())
+        cache.chunk_decref(H(1), 1, Statistics())
         assert repository.get(H(1)) == b"1234"
 
     def test_seen_chunk_add_chunk_size(self, cache):
@@ -199,7 +199,7 @@ class TestAdHocCache:
         """E.g. checkpoint archives"""
         cache.add_chunk(H(5), {}, b"1010", stats=Statistics())
         assert cache.seen_chunk(H(5)) == 1
-        cache.chunk_decref(H(5), Statistics())
+        cache.chunk_decref(H(5), 1, Statistics())
         assert not cache.seen_chunk(H(5))
         with pytest.raises(Repository.ObjectNotFound):
             repository.get(H(5))
@@ -220,9 +220,9 @@ class TestAdHocCache:
 
     def test_incref_after_add_chunk(self, cache):
         assert cache.add_chunk(H(3), {}, b"5678", stats=Statistics()) == (H(3), 4)
-        assert cache.chunk_incref(H(3), Statistics()) == (H(3), 4)
+        assert cache.chunk_incref(H(3), 4, Statistics()) == (H(3), 4)
 
     def test_existing_incref_after_add_chunk(self, cache):
         """This case occurs with part files, see Archive.chunk_file."""
         assert cache.add_chunk(H(1), {}, b"5678", stats=Statistics()) == (H(1), 4)
-        assert cache.chunk_incref(H(1), Statistics()) == (H(1), 4)
+        assert cache.chunk_incref(H(1), 4, Statistics()) == (H(1), 4)

src/borg/testsuite/helpers.py

@@ -368,7 +368,7 @@ def test_text_invalid(text):
 def test_format_timedelta():
     t0 = datetime(2001, 1, 1, 10, 20, 3, 0)
     t1 = datetime(2001, 1, 1, 12, 20, 4, 100000)
-    assert format_timedelta(t1 - t0) == "2 hours 1.10 seconds"
+    assert format_timedelta(t1 - t0) == "2 hours 1.100 seconds"
 
 
 @pytest.mark.parametrize(

src/borg/upgrade.py

@@ -84,8 +84,8 @@ class UpgraderFrom12To20:
             chunks, chunks_healthy = self.hlm.retrieve(id=hlid, default=(None, None))
             if chunks is not None:
                 item.chunks = chunks
-                for chunk_id, _ in chunks:
-                    self.cache.chunk_incref(chunk_id, self.archive.stats)
+                for chunk_id, chunk_size in chunks:
+                    self.cache.chunk_incref(chunk_id, chunk_size, self.archive.stats)
             if chunks_healthy is not None:
                 item.chunks_healthy = chunks
             del item.source  # not used for hardlinks any more, replaced by hlid