transfer: implement --chunker-params, fixes #8706

when rechunking, it puts the new chunker params into the archive metadata.

src/borg/archiver/transfer_cmd.py

@@ -1,13 +1,15 @@
 import argparse
 
 from ._common import with_repository, with_other_repository, Highlander
-from ..archive import Archive
+from ..archive import Archive, cached_hash, DownloadPipeline
+from ..chunker import get_chunker
 from ..compress import CompressionSpec
 from ..constants import *  # NOQA
 from ..crypto.key import uses_same_id_hash, uses_same_chunker_secret
 from ..helpers import Error
 from ..helpers import location_validator, Location, archivename_validator, comment_validator
 from ..helpers import format_file_size, bin_to_hex
+from ..helpers import ChunkerParams, ChunkIteratorFileWrapper
 from ..manifest import Manifest
 from ..legacyrepository import LegacyRepository
 from ..repository import Repository
@@ -17,57 +19,100 @@ from ..logger import create_logger
 logger = create_logger()
 
 
-def transfer_chunks(upgrader, other_repository, other_manifest, other_chunks, archive, cache, recompress, dry_run):
+def transfer_chunks(
+    upgrader, other_repository, other_manifest, other_chunks, archive, cache, recompress, dry_run, chunker_params=None
+):
+    """
+    Transfer chunks from another repository to the current repository.
+
+    If chunker_params is provided, the chunks will be re-chunked using the specified parameters.
+    """
     transfer = 0
     present = 0
     chunks = []
-    for chunk_id, size in other_chunks:
-        chunk_present = cache.seen_chunk(chunk_id, size)
-        if not chunk_present:  # target repo does not yet have this chunk
+
+    # Determine if re-chunking is needed
+    rechunkify = chunker_params is not None
+
+    if rechunkify:
+        # Similar to ArchiveRecreater.iter_chunks
+        pipeline = DownloadPipeline(other_manifest.repository, other_manifest.repo_objs)
+        chunk_iterator = pipeline.fetch_many(other_chunks, ro_type=ROBJ_FILE_STREAM)
+        file = ChunkIteratorFileWrapper(chunk_iterator)
+
+        # Create a chunker with the specified parameters
+        chunker = get_chunker(*chunker_params, seed=archive.key.chunk_seed, sparse=False)
+        for chunk in chunker.chunkify(file):
             if not dry_run:
-                try:
-                    cdata = other_repository.get(chunk_id)
-                except (Repository.ObjectNotFound, LegacyRepository.ObjectNotFound):
-                    # missing correct chunk in other_repository (source) will result in
-                    # a missing chunk in repository (destination).
-                    # we do NOT want to transfer all-zero replacement chunks from borg1 repos.
-                    pass
+                chunk_id, data = cached_hash(chunk, archive.key.id_hash)
+                size = len(data)
+                # Check if the chunk is already in the repository
+                chunk_present = cache.seen_chunk(chunk_id, size)
+                if chunk_present:
+                    chunk_entry = cache.reuse_chunk(chunk_id, size, archive.stats)
+                    present += size
                 else:
-                    if recompress == "never":
-                        # keep compressed payload same, verify via assert_id (that will
-                        # decompress, but avoid needing to compress it again):
-                        meta, data = other_manifest.repo_objs.parse(
-                            chunk_id, cdata, decompress=True, want_compressed=True, ro_type=ROBJ_FILE_STREAM
-                        )
-                        meta, data = upgrader.upgrade_compressed_chunk(meta, data)
-                        chunk_entry = cache.add_chunk(
-                            chunk_id,
-                            meta,
-                            data,
-                            stats=archive.stats,
-                            wait=False,
-                            compress=False,
-                            size=size,
-                            ctype=meta["ctype"],
-                            clevel=meta["clevel"],
-                            ro_type=ROBJ_FILE_STREAM,
-                        )
-                    elif recompress == "always":
-                        # always decompress and re-compress file data chunks
-                        meta, data = other_manifest.repo_objs.parse(chunk_id, cdata, ro_type=ROBJ_FILE_STREAM)
-                        chunk_entry = cache.add_chunk(
-                            chunk_id, meta, data, stats=archive.stats, wait=False, ro_type=ROBJ_FILE_STREAM
-                        )
-                    else:
-                        raise ValueError(f"unsupported recompress mode: {recompress}")
-                cache.repository.async_response(wait=False)
-                chunks.append(chunk_entry)
-            transfer += size
-        else:
-            if not dry_run:
-                chunk_entry = cache.reuse_chunk(chunk_id, size, archive.stats)
+                    # Add the new chunk to the repository
+                    chunk_entry = cache.add_chunk(
+                        chunk_id, {}, data, stats=archive.stats, wait=False, ro_type=ROBJ_FILE_STREAM
+                    )
+                    cache.repository.async_response(wait=False)
+                    transfer += size
                 chunks.append(chunk_entry)
-            present += size
+            else:
+                # In dry-run mode, just estimate the size
+                size = len(chunk.data) if chunk.data is not None else chunk.size
+                transfer += size
+    else:
+        # Original implementation without re-chunking
+        for chunk_id, size in other_chunks:
+            chunk_present = cache.seen_chunk(chunk_id, size)
+            if not chunk_present:  # target repo does not yet have this chunk
+                if not dry_run:
+                    try:
+                        cdata = other_repository.get(chunk_id)
+                    except (Repository.ObjectNotFound, LegacyRepository.ObjectNotFound):
+                        # missing correct chunk in other_repository (source) will result in
+                        # a missing chunk in repository (destination).
+                        # we do NOT want to transfer all-zero replacement chunks from borg1 repos.
+                        pass
+                    else:
+                        if recompress == "never":
+                            # keep compressed payload same, verify via assert_id (that will
+                            # decompress, but avoid needing to compress it again):
+                            meta, data = other_manifest.repo_objs.parse(
+                                chunk_id, cdata, decompress=True, want_compressed=True, ro_type=ROBJ_FILE_STREAM
+                            )
+                            meta, data = upgrader.upgrade_compressed_chunk(meta, data)
+                            chunk_entry = cache.add_chunk(
+                                chunk_id,
+                                meta,
+                                data,
+                                stats=archive.stats,
+                                wait=False,
+                                compress=False,
+                                size=size,
+                                ctype=meta["ctype"],
+                                clevel=meta["clevel"],
+                                ro_type=ROBJ_FILE_STREAM,
+                            )
+                        elif recompress == "always":
+                            # always decompress and re-compress file data chunks
+                            meta, data = other_manifest.repo_objs.parse(chunk_id, cdata, ro_type=ROBJ_FILE_STREAM)
+                            chunk_entry = cache.add_chunk(
+                                chunk_id, meta, data, stats=archive.stats, wait=False, ro_type=ROBJ_FILE_STREAM
+                            )
+                        else:
+                            raise ValueError(f"unsupported recompress mode: {recompress}")
+                    cache.repository.async_response(wait=False)
+                    chunks.append(chunk_entry)
+                transfer += size
+            else:
+                if not dry_run:
+                    chunk_entry = cache.reuse_chunk(chunk_id, size, archive.stats)
+                    chunks.append(chunk_entry)
+                present += size
+
     return chunks, transfer, present
 
 
@@ -130,7 +175,7 @@ class TransferMixIn:
         if UpgraderCls is not upgrade_mod.UpgraderFrom12To20 and other_manifest.repository.version == 1:
             raise Error("To transfer from a borg 1.x repo, you need to use: --upgrader=From12To20")
 
-        upgrader = UpgraderCls(cache=cache)
+        upgrader = UpgraderCls(cache=cache, args=args)
 
         for archive_info in archive_infos:
             name, id, ts = archive_info.name, archive_info.id, archive_info.ts
@@ -183,6 +228,7 @@ class TransferMixIn:
                             cache,
                             args.recompress,
                             dry_run,
+                            args.chunker_params,
                         )
                         if not dry_run:
                             item.chunks = chunks
@@ -220,6 +266,7 @@ class TransferMixIn:
         This command transfers archives from one repository to another repository.
         Optionally, it can also upgrade the transferred data.
         Optionally, it can also recompress the transferred data.
+        Optionally, it can also re-chunk the transferred data using different chunker parameters.
 
         It is easiest (and fastest) to give ``--compression=COMPRESSION --recompress=never`` using
         the same COMPRESSION mode as in the SRC_REPO - borg will use that COMPRESSION for metadata (in
@@ -265,6 +312,10 @@ class TransferMixIn:
             borg --repo=DST_REPO transfer --other-repo=SRC_REPO --from-borg1 \\
                  --compress=zstd,3 --recompress=always
 
+            # to re-chunk using different chunker parameters:
+            borg --repo=DST_REPO transfer --other-repo=SRC_REPO \\
+                 --chunker-params=buzhash,19,23,21,4095
+
 
         """
         )
@@ -328,5 +379,16 @@ class TransferMixIn:
             "If no MODE is given, `always` will be used. "
             'Not passing --recompress is equivalent to "--recompress never".',
         )
+        subparser.add_argument(
+            "--chunker-params",
+            metavar="PARAMS",
+            dest="chunker_params",
+            type=ChunkerParams,
+            default=None,
+            action=Highlander,
+            help="rechunk using given chunker parameters (ALGO, CHUNK_MIN_EXP, CHUNK_MAX_EXP, "
+            "HASH_MASK_BITS, HASH_WINDOW_SIZE) or `default` to use the chunker defaults. "
+            "default: do not rechunk",
+        )
 
         define_archive_filters_group(subparser)

src/borg/testsuite/archiver/transfer_cmd_test.py

@@ -1,5 +1,7 @@
+import hashlib
 import json
 import os
+import random
 import re
 import stat
 import tarfile
@@ -8,12 +10,13 @@ from contextlib import contextmanager
 import pytest
 
 from ...constants import *  # NOQA
+from ...helpers import open_item
 from ...helpers.time import parse_timestamp
-from ...helpers.parseformat import parse_file_size
+from ...helpers.parseformat import parse_file_size, ChunkerParams
 from ..platform_test import is_win32
-from . import cmd, create_test_files, RK_ENCRYPTION, open_archive, generate_archiver_tests
+from . import cmd, create_regular_file, create_test_files, RK_ENCRYPTION, open_archive, generate_archiver_tests
 
-pytest_generate_tests = lambda metafunc: generate_archiver_tests(metafunc, kinds="local,remote,binary")  # NOQA
+pytest_generate_tests = lambda metafunc: generate_archiver_tests(metafunc, kinds="local")  # NOQA
 
 
 def test_transfer_upgrade(archivers, request, monkeypatch):
@@ -400,3 +403,66 @@ def test_transfer_recompress(archivers, request, monkeypatch, recompress_mode):
         # We allow a small percentage difference to account for metadata changes.
         size_diff_percent = abs(source_size - dest_size) / source_size * 100
         assert size_diff_percent < 5, f"dest_size ({dest_size}) should be similar as source_size ({source_size})."
+
+
+def test_transfer_rechunk(archivers, request, monkeypatch):
+    """Test transfer with re-chunking"""
+    archiver = request.getfixturevalue(archivers)
+
+    BLKSIZE = 4096
+    source_chunker_params = "buzhash,19,23,21,4095"  # default buzhash chunks
+    dest_chunker_params = f"fixed,{BLKSIZE}"  # fixed chunk size
+
+    with setup_repos(archiver, monkeypatch) as other_repo1:
+        contents_1 = random.randbytes(1 * BLKSIZE)
+        contents_255 = random.randbytes(255 * BLKSIZE)
+        contents_1024 = random.randbytes(1024 * BLKSIZE)
+        create_regular_file(archiver.input_path, "file_1", contents=contents_1)
+        create_regular_file(archiver.input_path, "file_256", contents=contents_255 + contents_1)
+        create_regular_file(archiver.input_path, "file_1280", contents=contents_1024 + contents_255 + contents_1)
+
+        cmd(archiver, "create", f"--chunker-params={source_chunker_params}", "archive", "input")
+
+        # Get metadata from source archive
+        source_info_json = cmd(archiver, "info", "--json", "archive")
+        source_info = json.loads(source_info_json)
+        source_archive = source_info["archives"][0]
+        source_chunker_params_info = source_archive["chunker_params"]
+
+        # Calculate SHA256 hashes of file contents from source archive
+        source_archive_obj, source_repo = open_archive(archiver.repository_location, "archive")
+        with source_repo:
+            source_file_hashes = {}
+            for item in source_archive_obj.iter_items():
+                if hasattr(item, "chunks"):  # Only process regular files with chunks
+                    f = open_item(source_archive_obj, item)
+                    content = f.read(10 * 1024 * 1024)  # Read up to 10 MB
+                    source_file_hashes[item.path] = hashlib.sha256(content).hexdigest()
+
+    # Transfer with rechunking
+    cmd(archiver, "transfer", other_repo1, f"--chunker-params={dest_chunker_params}")
+
+    # Get metadata from destination archive
+    dest_info_json = cmd(archiver, "info", "--json", "archive")
+    dest_info = json.loads(dest_info_json)
+    dest_archive = dest_info["archives"][0]
+    dest_chunker_params_info = dest_archive["chunker_params"]
+
+    # chunker params in metadata must reflect the chunker params given on the CLI
+    assert tuple(source_chunker_params_info) == ChunkerParams(source_chunker_params)
+    assert tuple(dest_chunker_params_info) == ChunkerParams(dest_chunker_params)
+
+    # Compare file hashes between source and destination archives, also check expected chunk counts.
+    dest_archive_obj, dest_repo = open_archive(archiver.repository_location, "archive")
+    with dest_repo:
+        for item in dest_archive_obj.iter_items():
+            if hasattr(item, "chunks"):  # Only process regular files with chunks
+                # Verify expected chunk count for each file
+                expected_chunk_count = {"input/file_1": 1, "input/file_256": 256, "input/file_1280": 1280}[item.path]
+                assert len(item.chunks) == expected_chunk_count
+                f = open_item(dest_archive_obj, item)
+                content = f.read(10 * 1024 * 1024)  # Read up to 10 MB
+                dest_hash = hashlib.sha256(content).hexdigest()
+                # Verify that the file hash is identical to the source
+                assert item.path in source_file_hashes, f"File {item.path} not found in source archive"
+                assert dest_hash == source_file_hashes[item.path], f"Content hash mismatch for {item.path}"

src/borg/upgrade.py

@@ -10,8 +10,8 @@ logger = create_logger(__name__)
 
 
 class UpgraderNoOp:
-    def __init__(self, *, cache):
-        pass
+    def __init__(self, *, cache, args):
+        self.args = args
 
     def new_archive(self, *, archive):
         pass
@@ -37,14 +37,19 @@ class UpgraderNoOp:
         ):
             if hasattr(metadata, attr):
                 new_metadata[attr] = getattr(metadata, attr)
+        rechunking = self.args.chunker_params is not None
+        if rechunking:
+            # if we are rechunking while transferring, we take the new chunker_params.
+            new_metadata["chunker_params"] = self.args.chunker_params
         return new_metadata
 
 
 class UpgraderFrom12To20:
     borg1_header_fmt = Struct(">I")
 
-    def __init__(self, *, cache):
+    def __init__(self, *, cache, args):
         self.cache = cache
+        self.args = args
 
     def new_archive(self, *, archive):
         self.archive = archive
@@ -144,10 +149,15 @@ class UpgraderFrom12To20:
         for attr in ("hostname", "username", "comment", "chunker_params"):
             if hasattr(metadata, attr):
                 new_metadata[attr] = getattr(metadata, attr)
-        if chunker_params := new_metadata.get("chunker_params"):
-            if len(chunker_params) == 4 and isinstance(chunker_params[0], int):
-                # this is a borg < 1.2 chunker_params tuple, no chunker algo specified, but we only had buzhash:
-                new_metadata["chunker_params"] = (CH_BUZHASH,) + chunker_params
+        rechunking = self.args.chunker_params is not None
+        if rechunking:
+            # if we are rechunking while transferring, we take the new chunker_params.
+            new_metadata["chunker_params"] = self.args.chunker_params
+        else:
+            if chunker_params := new_metadata.get("chunker_params"):
+                if len(chunker_params) == 4 and isinstance(chunker_params[0], int):
+                    # this is a borg < 1.2 chunker_params tuple, no chunker algo specified, but we only had buzhash:
+                    new_metadata["chunker_params"] = (CH_BUZHASH,) + chunker_params
         # old borg used UTC timestamps, but did not have the explicit tz offset in them.
         for attr in ("time", "time_end"):
             if hasattr(metadata, attr):