/brz/remove-bazaar

# Copyright (C) 2009 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""A manager of caches."""

from __future__ import absolute_import

import atexit

import os

import shutil

import tempfile

import weakref

from ... import lru_cache, trace

from . import (

    branch_mapper,

    )

from .reftracker import (

    RefTracker,

    )

from .helpers import (

    single_plural,

    )

class _Cleanup(object):

    """This class makes sure we clean up when CacheManager goes away.

    We use a helper class to ensure that we are never in a refcycle.

    """

    def __init__(self, disk_blobs):

        self.disk_blobs = disk_blobs

        self.tempdir = None

        self.small_blobs = None

    def __del__(self):

        self.finalize()

    def finalize(self):

        if self.disk_blobs is not None:

            for info in self.disk_blobs.values():

                if info[-1] is not None:

                    os.unlink(info[-1])

            self.disk_blobs = None

        if self.small_blobs is not None:

            self.small_blobs.close()

            self.small_blobs = None

        if self.tempdir is not None:

            shutil.rmtree(self.tempdir)

class CacheManager(object):

    _small_blob_threshold = 25*1024

    _sticky_cache_size = 300*1024*1024

    _sticky_flushed_size = 100*1024*1024

    def __init__(self, info=None, verbose=False, inventory_cache_size=10):

        """Create a manager of caches.

        :param info: a ConfigObj holding the output from

            the --info processor, or None if no hints are available

        """

        self.verbose = verbose

        # dataref -> data. datref is either :mark or the sha-1.

        # Sticky blobs are referenced more than once, and are saved until their

        # refcount goes to 0

        self._blobs = {}

        self._sticky_blobs = {}

        self._sticky_memory_bytes = 0

        # if we overflow our memory cache, then we will dump large blobs to

        # disk in this directory

        self._tempdir = None

        # id => (offset, n_bytes, fname)

        #   if fname is None, then the content is stored in the small file

        self._disk_blobs = {}

        self._cleanup = _Cleanup(self._disk_blobs)

        # revision-id -> Inventory cache

        # these are large and we probably don't need too many as

        # most parents are recent in history

        self.inventories = lru_cache.LRUCache(inventory_cache_size)

        # import commmit-ids -> revision-id lookup table

        # we need to keep all of these but they are small

        self.marks = {}

        # (path, branch_ref) -> file-ids - as generated.

        # (Use store_file_id/fetch_fileid methods rather than direct access.)

        # Work out the blobs to make sticky - None means all

        self._blob_ref_counts = {}

        if info is not None:

            try:

                blobs_by_counts = info['Blob reference counts']

                # The parser hands values back as lists, already parsed

                for count, blob_list in blobs_by_counts.items():

                    n = int(count)

                    for b in blob_list:

                        self._blob_ref_counts[b] = n

            except KeyError:

                # info not in file - possible when no blobs used

                pass

        # BranchMapper has no state (for now?), but we keep it around rather

        # than reinstantiate on every usage

        self.branch_mapper = branch_mapper.BranchMapper()

        self.reftracker = RefTracker()

    def add_mark(self, mark, commit_id):

        assert mark[0] != ':'

        is_new = (mark in self.marks)

        self.marks[mark] = commit_id

        return is_new

    def lookup_committish(self, committish):

        """Resolve a 'committish' to a revision id.

        :param committish: A "committish" string

        :return: Bazaar revision id

        """

        assert committish[0] == ':'

        return self.marks[committish.lstrip(':')]

    def dump_stats(self, note=trace.note):

        """Dump some statistics about what we cached."""

        # TODO: add in inventory stastistics

        note("Cache statistics:")

        self._show_stats_for(self._sticky_blobs, "sticky blobs", note=note)

        self._show_stats_for(self.marks, "revision-ids", note=note)

        # These aren't interesting so omit from the output, at least for now

        #self._show_stats_for(self._blobs, "other blobs", note=note)

        #self.reftracker.dump_stats(note=note)

    def _show_stats_for(self, a_dict, label, note, tuple_key=False):

        """Dump statistics about a given dictionary.

        By the key and value need to support len().

        """

        count = len(a_dict)

        if tuple_key:

            size = sum(map(len, (''.join(k) for k in a_dict)))

        else:

            size = sum(map(len, a_dict))

        size += sum(map(len, a_dict.values()))

        size = size * 1.0 / 1024

        unit = 'K'

        if size > 1024:

            size = size / 1024

            unit = 'M'

            if size > 1024:

                size = size / 1024

                unit = 'G'

        note("    %-12s: %8.1f %s (%d %s)" % (label, size, unit, count,

            single_plural(count, "item", "items")))

    def clear_all(self):

        """Free up any memory used by the caches."""

        self._blobs.clear()

        self._sticky_blobs.clear()

        self.marks.clear()

        self.reftracker.clear()

        self.inventories.clear()

    def _flush_blobs_to_disk(self):

        blobs = list(self._sticky_blobs)

        sticky_blobs = self._sticky_blobs

        total_blobs = len(sticky_blobs)

        blobs.sort(key=lambda k:len(sticky_blobs[k]))

        if self._tempdir is None:

            tempdir = tempfile.mkdtemp(prefix='fastimport_blobs-')

            self._tempdir = tempdir

            self._cleanup.tempdir = self._tempdir

            self._cleanup.small_blobs = tempfile.TemporaryFile(

                prefix='small-blobs-', dir=self._tempdir)

            small_blob_ref = weakref.ref(self._cleanup.small_blobs)

            # Even though we add it to _Cleanup it seems that the object can be

            # destroyed 'too late' for cleanup to actually occur. Probably a

            # combination of bzr's "die directly, don't clean up" and how

            # exceptions close the running stack.

            def exit_cleanup():

                small_blob = small_blob_ref()

                if small_blob is not None:

                    small_blob.close()

                shutil.rmtree(tempdir, ignore_errors=True)

            atexit.register(exit_cleanup)

        count = 0

        bytes = 0

        n_small_bytes = 0

        while self._sticky_memory_bytes > self._sticky_flushed_size:

            id = blobs.pop()

            blob = self._sticky_blobs.pop(id)

            n_bytes = len(blob)

            self._sticky_memory_bytes -= n_bytes

            if n_bytes < self._small_blob_threshold:

                f = self._cleanup.small_blobs

                f.seek(0, os.SEEK_END)

                self._disk_blobs[id] = (f.tell(), n_bytes, None)

                f.write(blob)

                n_small_bytes += n_bytes

            else:

                fd, name = tempfile.mkstemp(prefix='blob-', dir=self._tempdir)

                os.write(fd, blob)

                os.close(fd)

                self._disk_blobs[id] = (0, n_bytes, name)

            bytes += n_bytes

            del blob

            count += 1

        trace.note('flushed %d/%d blobs w/ %.1fMB (%.1fMB small) to disk'

                   % (count, total_blobs, bytes / 1024. / 1024,

                      n_small_bytes / 1024. / 1024))

    def store_blob(self, id, data):

        """Store a blob of data."""

        # Note: If we're not reference counting, everything has to be sticky

        if not self._blob_ref_counts or id in self._blob_ref_counts:

            self._sticky_blobs[id] = data

            self._sticky_memory_bytes += len(data)

            if self._sticky_memory_bytes > self._sticky_cache_size:

                self._flush_blobs_to_disk()

        elif data == '':

            # Empty data is always sticky

            self._sticky_blobs[id] = data

        else:

            self._blobs[id] = data

    def _decref(self, id, cache, fn):

        if not self._blob_ref_counts:

            return False

        count = self._blob_ref_counts.get(id, None)

        if count is not None:

            count -= 1

            if count <= 0:

                del cache[id]

                if fn is not None:

                    os.unlink(fn)

                del self._blob_ref_counts[id]

                return True

            else:

                self._blob_ref_counts[id] = count

        return False

    def fetch_blob(self, id):

        """Fetch a blob of data."""

        if id in self._blobs:

            return self._blobs.pop(id)

        if id in self._disk_blobs:

            (offset, n_bytes, fn) = self._disk_blobs[id]

            if fn is None:

                f = self._cleanup.small_blobs

                f.seek(offset)

                content = f.read(n_bytes)

            else:

                fp = open(fn, 'rb')

                try:

                    content = fp.read()

                finally:

                    fp.close()

            self._decref(id, self._disk_blobs, fn)

            return content

        content = self._sticky_blobs[id]

        if self._decref(id, self._sticky_blobs, None):

            self._sticky_memory_bytes -= len(content)

        return content