borgbackup/borg/cache.py

import configparser
from .remote import cache_if_remote
from collections import namedtuple
import os
import stat

import threading
from binascii import hexlify, unhexlify

import shutil

from .key import PlaintextKey
from .logger import create_logger
logger = create_logger()
from .helpers import Error, get_cache_dir, decode_dict, int_to_bigint, \
    bigint_to_int, format_file_size, yes
from .locking import UpgradableLock
from .hashindex import ChunkIndex

import msgpack


class Cache:
    """Client Side cache
    """
    class RepositoryReplay(Error):
        """Cache is newer than repository, refusing to continue"""

    class CacheInitAbortedError(Error):
        """Cache initialization aborted"""

    class RepositoryAccessAborted(Error):
        """Repository access aborted"""

    class EncryptionMethodMismatch(Error):
        """Repository encryption method changed since last access, refusing to continue"""

    @staticmethod
    def break_lock(repository, path=None):
        path = path or os.path.join(get_cache_dir(), hexlify(repository.id).decode('ascii'))
        UpgradableLock(os.path.join(path, 'lock'), exclusive=True).break_lock()

    class ChunkSizeNotReady(Exception):
        """computation of some chunk size is not yet finished"""

    def __init__(self, repository, key, manifest, path=None, sync=True, do_files=False, warn_if_unencrypted=True,
                 lock_wait=None):
        self.lock = None
        self.timestamp = None
        self.thread_lock = threading.Lock()
        self.txn_active = False
        self.repository = repository
        self.key = key
        self.manifest = manifest
        self.path = path or os.path.join(get_cache_dir(), hexlify(repository.id).decode('ascii'))
        self.do_files = do_files
        # Warn user before sending data to a never seen before unencrypted repository
        if not os.path.exists(self.path):
            if warn_if_unencrypted and isinstance(key, PlaintextKey):
                msg = ("Warning: Attempting to access a previously unknown unencrypted repository!" +
                       "\n" +
                       "Do you want to continue? [yN] ")
                if not yes(msg, false_msg="Aborting.", env_var_override='BORG_UNKNOWN_UNENCRYPTED_REPO_ACCESS_IS_OK'):
                    raise self.CacheInitAbortedError()
            self.create()
        self.open(lock_wait=lock_wait)
        # Warn user before sending data to a relocated repository
        if self.previous_location and self.previous_location != repository._location.canonical_path():
            msg = ("Warning: The repository at location {} was previously located at {}".format(repository._location.canonical_path(), self.previous_location) +
                   "\n" +
                   "Do you want to continue? [yN] ")
            if not yes(msg, false_msg="Aborting.", env_var_override='BORG_RELOCATED_REPO_ACCESS_IS_OK'):
                raise self.RepositoryAccessAborted()

        if sync and self.manifest.id != self.manifest_id:
            # If repository is older than the cache something fishy is going on
            if self.timestamp and self.timestamp > manifest.timestamp:
                raise self.RepositoryReplay()
            # Make sure an encrypted repository has not been swapped for an unencrypted repository
            if self.key_type is not None and self.key_type != str(key.TYPE):
                raise self.EncryptionMethodMismatch()
            self.sync()
            self.commit()

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.close()

    def __str__(self):
        fmt = """\
All archives:   {0.total_size:>20s} {0.total_csize:>20s} {0.unique_csize:>20s}

                       Unique chunks         Total chunks
Chunk index:    {0.total_unique_chunks:20d} {0.total_chunks:20d}"""
        return fmt.format(self.format_tuple())

    def format_tuple(self):
        # XXX: this should really be moved down to `hashindex.pyx`
        Summary = namedtuple('Summary', ['total_size', 'total_csize', 'unique_size', 'unique_csize', 'total_unique_chunks', 'total_chunks'])
        stats = Summary(*self.chunks.summarize())._asdict()
        for field in ['total_size', 'total_csize', 'unique_csize']:
            stats[field] = format_file_size(stats[field])
        return Summary(**stats)

    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('This is a Borg cache')
        config = configparser.ConfigParser(interpolation=None)
        config.add_section('cache')
        config.set('cache', 'version', '1')
        config.set('cache', 'repository', hexlify(self.repository.id).decode('ascii'))
        config.set('cache', 'manifest', '')
        with open(os.path.join(self.path, 'config'), 'w') as fd:
            config.write(fd)
        ChunkIndex().write(os.path.join(self.path, 'chunks').encode('utf-8'))
        os.makedirs(os.path.join(self.path, 'chunks.archive.d'))
        with open(os.path.join(self.path, 'files'), 'wb') as fd:
            pass  # empty file

    def destroy(self):
        """destroy the cache at `self.path`
        """
        self.close()
        os.remove(os.path.join(self.path, 'config'))  # kill config first
        shutil.rmtree(self.path)

    def _do_open(self):
        self.config = configparser.ConfigParser(interpolation=None)
        config_path = os.path.join(self.path, 'config')
        self.config.read(config_path)
        try:
            cache_version = self.config.getint('cache', 'version')
            wanted_version = 1
            if cache_version != wanted_version:
                raise Exception('%s has unexpected cache version %d (wanted: %d).' % (
                    config_path, cache_version, wanted_version))
        except configparser.NoSectionError:
            raise Exception('%s does not look like a Borg cache.' % config_path) from None
        self.id = self.config.get('cache', 'repository')
        self.manifest_id = unhexlify(self.config.get('cache', 'manifest'))
        self.timestamp = self.config.get('cache', 'timestamp', fallback=None)
        self.key_type = self.config.get('cache', 'key_type', fallback=None)
        self.previous_location = self.config.get('cache', 'previous_location', fallback=None)
        self.chunks = ChunkIndex.read(os.path.join(self.path, 'chunks').encode('utf-8'))
        self.files = None

    def open(self, lock_wait=None):
        if not os.path.isdir(self.path):
            raise Exception('%s Does not look like a Borg cache' % self.path)
        self.lock = UpgradableLock(os.path.join(self.path, 'lock'), exclusive=True, timeout=lock_wait).acquire()
        self.rollback()

    def close(self):
        if self.lock is not None:
            self.lock.release()
            self.lock = None

    def _read_files(self):
        self.files = {}
        self._newest_mtime = 0
        logger.info('reading files cache')
        with open(os.path.join(self.path, 'files'), 'rb') as fd:
            u = msgpack.Unpacker(use_list=True)
            while True:
                data = fd.read(64 * 1024)
                if not data:
                    break
                u.feed(data)
                for path_hash, item in u:
                    item[0] += 1
                    # in the end, this takes about 240 Bytes per file
                    self.files[path_hash] = msgpack.packb(item)

    def begin_txn(self):
        # Initialize transaction snapshot
        txn_dir = os.path.join(self.path, 'txn.tmp')
        os.mkdir(txn_dir)
        shutil.copy(os.path.join(self.path, 'config'), txn_dir)
        shutil.copy(os.path.join(self.path, 'chunks'), txn_dir)
        shutil.copy(os.path.join(self.path, 'files'), txn_dir)
        os.rename(os.path.join(self.path, 'txn.tmp'),
                  os.path.join(self.path, 'txn.active'))
        self.txn_active = True

    def commit(self):
        """Commit transaction
        """
        if not self.txn_active:
            return
        if self.files is not None:
            with open(os.path.join(self.path, 'files'), 'wb') as fd:
                for path_hash, item in self.files.items():
                    # Discard cached files with the newest mtime to avoid
                    # issues with filesystem snapshots and mtime precision
                    item = msgpack.unpackb(item)
                    if item[0] < 10 and bigint_to_int(item[3]) < self._newest_mtime:
                        msgpack.pack((path_hash, item), fd)
        self.config.set('cache', 'manifest', hexlify(self.manifest.id).decode('ascii'))
        self.config.set('cache', 'timestamp', self.manifest.timestamp)
        self.config.set('cache', 'key_type', str(self.key.TYPE))
        self.config.set('cache', 'previous_location', self.repository._location.canonical_path())
        with open(os.path.join(self.path, 'config'), 'w') as fd:
            self.config.write(fd)
        self.chunks.write(os.path.join(self.path, 'chunks').encode('utf-8'))
        os.rename(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

    def rollback(self):
        """Roll back partial and aborted transactions
        """
        # 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, 'chunks'), self.path)
            shutil.copy(os.path.join(txn_dir, 'files'), self.path)
            os.rename(txn_dir, os.path.join(self.path, 'txn.tmp'))
            if os.path.exists(os.path.join(self.path, 'txn.tmp')):
                shutil.rmtree(os.path.join(self.path, 'txn.tmp'))
        self.txn_active = False
        self._do_open()

    def sync(self):
        """Re-synchronize chunks cache with repository.

        Maintains a directory with known backup archive indexes, so it only
        needs to fetch infos from repo and build a chunk index once per backup
        archive.
        If out of sync, missing archive indexes get added, outdated indexes
        get removed and a new master chunks index is built by merging all
        archive indexes.
        """
        archive_path = os.path.join(self.path, 'chunks.archive.d')

        def mkpath(id, suffix=''):
            id_hex = hexlify(id).decode('ascii')
            path = os.path.join(archive_path, id_hex + suffix)
            return path.encode('utf-8')

        def cached_archives():
            if self.do_cache:
                fns = os.listdir(archive_path)
                # filenames with 64 hex digits == 256bit
                return set(unhexlify(fn) for fn in fns if len(fn) == 64)
            else:
                return set()

        def repo_archives():
            return set(info[b'id'] for info in self.manifest.archives.values())

        def cleanup_outdated(ids):
            for id in ids:
                os.unlink(mkpath(id))

        def fetch_and_build_idx(archive_id, repository, key):
            chunk_idx = ChunkIndex()
            cdata = repository.get(archive_id)
            data = key.decrypt(archive_id, cdata)
            chunk_idx.add(archive_id, 1, len(data), len(cdata))
            archive = msgpack.unpackb(data)
            if archive[b'version'] != 1:
                raise Exception('Unknown archive metadata version')
            decode_dict(archive, (b'name',))
            unpacker = msgpack.Unpacker()
            for item_id, chunk in zip(archive[b'items'], repository.get_many(archive[b'items'])):
                data = key.decrypt(item_id, chunk)
                chunk_idx.add(item_id, 1, len(data), len(chunk))
                unpacker.feed(data)
                for item in unpacker:
                    if not isinstance(item, dict):
                        logger.error('Error: Did not get expected metadata dict - archive corrupted!')
                        continue
                    if b'chunks' in item:
                        for chunk_id, size, csize in item[b'chunks']:
                            chunk_idx.add(chunk_id, 1, size, csize)
            if self.do_cache:
                fn = mkpath(archive_id)
                fn_tmp = mkpath(archive_id, suffix='.tmp')
                try:
                    chunk_idx.write(fn_tmp)
                except Exception:
                    os.unlink(fn_tmp)
                else:
                    os.rename(fn_tmp, fn)
            return chunk_idx

        def lookup_name(archive_id):
            for name, info in self.manifest.archives.items():
                if info[b'id'] == archive_id:
                    return name

        def create_master_idx(chunk_idx):
            logger.info('Synchronizing chunks cache...')
            cached_ids = cached_archives()
            archive_ids = repo_archives()
            logger.info('Archives: %d, w/ cached Idx: %d, w/ outdated Idx: %d, w/o cached Idx: %d.' % (
                len(archive_ids), len(cached_ids),
                len(cached_ids - archive_ids), len(archive_ids - cached_ids), ))
            # deallocates old hashindex, creates empty hashindex:
            chunk_idx.clear()
            cleanup_outdated(cached_ids - archive_ids)
            if archive_ids:
                chunk_idx = None
                for archive_id in archive_ids:
                    archive_name = lookup_name(archive_id)
                    if archive_id in cached_ids:
                        archive_chunk_idx_path = mkpath(archive_id)
                        logger.info("Reading cached archive chunk index for %s ..." % archive_name)
                        archive_chunk_idx = ChunkIndex.read(archive_chunk_idx_path)
                    else:
                        logger.info('Fetching and building archive index for %s ...' % archive_name)
                        archive_chunk_idx = fetch_and_build_idx(archive_id, repository, self.key)
                    logger.info("Merging into master chunks index ...")
                    if chunk_idx is None:
                        # we just use the first archive's idx as starting point,
                        # to avoid growing the hash table from 0 size and also
                        # to save 1 merge call.
                        chunk_idx = archive_chunk_idx
                    else:
                        chunk_idx.merge(archive_chunk_idx)
            logger.info('Done.')
            return chunk_idx

        def legacy_cleanup():
            """bring old cache dirs into the desired state (cleanup and adapt)"""
            try:
                os.unlink(os.path.join(self.path, 'chunks.archive'))
            except:
                pass
            try:
                os.unlink(os.path.join(self.path, 'chunks.archive.tmp'))
            except:
                pass
            try:
                os.mkdir(archive_path)
            except:
                pass

        self.begin_txn()
        with cache_if_remote(self.repository) as repository:
            legacy_cleanup()
            # TEMPORARY HACK: to avoid archive index caching, create a FILE named ~/.cache/borg/REPOID/chunks.archive.d -
            # this is only recommended if you have a fast, low latency connection to your repo (e.g. if repo is local disk)
            self.do_cache = os.path.isdir(archive_path)
            self.chunks = create_master_idx(self.chunks)

    def add_chunk(self, id, data, stats):
        if not self.txn_active:
            self.begin_txn()
        size = len(data)
        if self.seen_chunk(id, size):
            return self.chunk_incref(id, stats)
        data = self.key.encrypt(data)
        csize = len(data)
        self.repository.put(id, data, wait=False)
        self.chunks[id] = (1, size, csize)
        stats.update(size, csize, True)
        return id, size, csize

    def chunk_modify(self, id, count=None, delta=None, size=None, csize=None):
        """modify a self.chunks entry, return the new value.
           must be thread safe.
        """
        with self.thread_lock:
            _count, _size, _csize = self.chunks[id]
            modified = False
            if size is not None and size != _size:
                assert _size == 0
                _size = size
                modified = True
            if csize is not None and csize != _csize:
                assert _csize == 0
                _csize = csize
                modified = True
            if count is not None and count != _count:
                assert _count == 0
                _count = count
                modified = True
            if delta is not None and delta != 0:
                _count += delta
                assert _count >= 0
                modified = True
            if modified:
                self.chunks[id] = _count, _size, _csize
            return _count, _size, _csize

    def add_chunk_nostats(self, cchunk, id, size, csize):
        # do not update stats here, see postprocess
        if not self.txn_active:
            self.begin_txn()
        new_chunk = cchunk is not None
        if new_chunk:
            # note: count = 1 already set in seen_or_announce_chunk
            _, size, csize = self.chunk_modify(id, size=size, csize=csize)
            self.repository.put(id, cchunk, wait=False)
        else:
            # note: csize might be still 0 (not yet computed) here
            _, size, csize = self.chunk_modify(id, delta=1, size=size)
        return size, csize, new_chunk

    def postprocess_results(self, size_infos, results, stats):
        # we need to do some post processing:
        # - chunks that are duplicate may have csize not yet set correctly due
        #   to the multi threaded processing. all (x, 0) sizes must be still
        #   set using the correct size from the other duplicate chunk (not x, 0).
        # - we need to reconstruct the correct order of the chunks.
        # - we need to fix the stats now we have the correct csize
        chunks = []
        for _, id, new_chunk in sorted(results):
            try:
                size, csize = size_infos[id]
            except KeyError:
                raise self.ChunkSizeNotReady
            chunks.append((id, size, csize, new_chunk))

        # do another pass after we have made sure we have all size info
        results = []
        for id, size, csize, new_chunk in chunks:
            stats.update(size, csize, new_chunk)
            results.append((id, size, csize))
        return results

    def seen_chunk(self, id, size=None):
        refcount, stored_size, _ = self.chunks.get(id, (0, None, 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 seen_or_announce_chunk(self, id, size):
        """return True if we have seen the chunk <id> already (thus, we already have it or will have it soon).
           in case we don't have seen it, announce its (future) availability, return False.
           must be thread safe.
        """
        with self.thread_lock:
            try:
                # did we see this id already (and is count > 0)?
                count, _size, _csize = self.chunks[id]
                if size != _size:
                    raise Exception("chunk has same id [%r], but different size (stored: %d new: %d)!" % (
                        id, _size, size))
                return count > 0
            except KeyError:
                # announce that we will put this chunk soon,
                # so that deduplication knows we already have it.
                self.chunks[id] = 1, size, 0
                return False

    def chunk_incref(self, id, stats):
        if not self.txn_active:
            self.begin_txn()
        count, size, csize = self.chunks[id]
        self.chunks[id] = (count + 1, size, csize)
        stats.update(size, csize, False)
        return id, size, csize

    def chunk_decref(self, id, stats):
        if not self.txn_active:
            self.begin_txn()
        count, size, csize = self.chunks[id]
        if count == 1:
            del self.chunks[id]
            self.repository.delete(id, wait=False)
            stats.update(-size, -csize, True)
        else:
            self.chunks[id] = (count - 1, size, csize)
            stats.update(-size, -csize, False)

    def file_known_and_unchanged(self, path_hash, st):
        if not (self.do_files and stat.S_ISREG(st.st_mode)):
            return None
        if self.files is None:
            self._read_files()
        entry = self.files.get(path_hash)
        if not entry:
            return None
        entry = msgpack.unpackb(entry)
        if entry[2] == st.st_size and bigint_to_int(entry[3]) == st.st_mtime_ns and entry[1] == st.st_ino:
            # reset entry age
            entry[0] = 0
            self.files[path_hash] = msgpack.packb(entry)
            return entry[4]
        else:
            return None

    def memorize_file(self, path_hash, st, ids):
        if not (self.do_files and stat.S_ISREG(st.st_mode)):
            return
        # Entry: Age, inode, size, mtime, chunk ids
        mtime_ns = st.st_mtime_ns
        self.files[path_hash] = msgpack.packb((0, st.st_ino, st.st_size, int_to_bigint(mtime_ns), ids))
        self._newest_mtime = max(self._newest_mtime, mtime_ns)