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localrepo: iteratively derive local repository type...
localrepo: iteratively derive local repository type This commit implements the dynamic local repository type derivation that was explained in the recent commit bfeab472e3c0 "localrepo: create new function for instantiating a local repo object." Instead of a static localrepository class/type which must be customized after construction, we now dynamically construct a type by building up base classes/types to represent specific repository interfaces. Conceptually, the end state is similar to what was happening when various extensions would monkeypatch the __class__ of newly-constructed repo instances. However, the approach is inverted. Instead of making the instance then customizing it, we do the customization up front by influencing the behavior of the type then we instantiate that custom type. This approach gives us much more flexibility. For example, we can use completely separate classes for implementing different aspects of the repository. For example, we could have one class representing revlog-based file storage and another representing non-revlog based file storage. When then choose which implementation to use based on the presence of repo requirements. A concern with this approach is that it creates a lot more types and complexity and that complexity adds overhead. Yes, it is true that this approach will result in more types being created. Yes, this is more complicated than traditional "instantiate a static type." However, I believe the alternatives to supporting alternate storage backends are just as complicated. (Before I arrived at this solution, I had patches storing factory functions on local repo instances for e.g. constructing a file storage instance. We ended up having a handful of these. And this was logically identical to assigning custom methods. Since we were logically changing the type of the instance, I figured it would be better to just use specialized types instead of introducing levels of abstraction at run-time.) On the performance front, I don't believe that having N base classes has any significant performance overhead compared to just a single base class. Intuition says that Python will need to iterate the base classes to find an attribute. However, CPython caches method lookups: as long as the __class__ or MRO isn't changing, method attribute lookup should be constant time after first access. And non-method attributes are stored in __dict__, of which there is only 1 per object, so the number of base classes for __dict__ is irrelevant. Anyway, this commit splits up the monolithic completelocalrepository interface into sub-interfaces: 1 for file storage and 1 representing everything else. We've taught ``makelocalrepository()`` to call a series of factory functions which will produce types implementing specific interfaces. It then calls type() to create a new type from the built-up list of base types. This commit should be considered a start and not the end state. I suspect we'll hit a number of problems as we start to implement alternate storage backends: * Passing custom arguments to __init__ and setting custom attributes on __dict__. * Customizing the set of interfaces that are needed. e.g. the "readonly" intent could translate to not requesting an interface providing methods related to writing. * More ergonomic way for extensions to insert themselves so their callbacks aren't unconditionally called. * Wanting to modify vfs instances, other arguments passed to __init__. That being said, this code is usable in its current state and I'm convinced future commits will demonstrate the value in this approach. Differential Revision: https://phab.mercurial-scm.org/D4642

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blobstore.py
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# blobstore.py - local and remote (speaking Git-LFS protocol) blob storages
#
# Copyright 2017 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
import errno
import hashlib
import json
import os
import re
import socket
from mercurial.i18n import _
from mercurial import (
error,
pathutil,
pycompat,
url as urlmod,
util,
vfs as vfsmod,
worker,
)
from ..largefiles import lfutil
# 64 bytes for SHA256
_lfsre = re.compile(br'\A[a-f0-9]{64}\Z')
class lfsvfs(vfsmod.vfs):
def join(self, path):
"""split the path at first two characters, like: XX/XXXXX..."""
if not _lfsre.match(path):
raise error.ProgrammingError('unexpected lfs path: %s' % path)
return super(lfsvfs, self).join(path[0:2], path[2:])
def walk(self, path=None, onerror=None):
"""Yield (dirpath, [], oids) tuple for blobs under path
Oids only exist in the root of this vfs, so dirpath is always ''.
"""
root = os.path.normpath(self.base)
# when dirpath == root, dirpath[prefixlen:] becomes empty
# because len(dirpath) < prefixlen.
prefixlen = len(pathutil.normasprefix(root))
oids = []
for dirpath, dirs, files in os.walk(self.reljoin(self.base, path or ''),
onerror=onerror):
dirpath = dirpath[prefixlen:]
# Silently skip unexpected files and directories
if len(dirpath) == 2:
oids.extend([dirpath + f for f in files
if _lfsre.match(dirpath + f)])
yield ('', [], oids)
class nullvfs(lfsvfs):
def __init__(self):
pass
def exists(self, oid):
return False
def read(self, oid):
# store.read() calls into here if the blob doesn't exist in its
# self.vfs. Raise the same error as a normal vfs when asked to read a
# file that doesn't exist. The only difference is the full file path
# isn't available in the error.
raise IOError(errno.ENOENT, '%s: No such file or directory' % oid)
def walk(self, path=None, onerror=None):
return ('', [], [])
def write(self, oid, data):
pass
class filewithprogress(object):
"""a file-like object that supports __len__ and read.
Useful to provide progress information for how many bytes are read.
"""
def __init__(self, fp, callback):
self._fp = fp
self._callback = callback # func(readsize)
fp.seek(0, os.SEEK_END)
self._len = fp.tell()
fp.seek(0)
def __len__(self):
return self._len
def read(self, size):
if self._fp is None:
return b''
data = self._fp.read(size)
if data:
if self._callback:
self._callback(len(data))
else:
self._fp.close()
self._fp = None
return data
class local(object):
"""Local blobstore for large file contents.
This blobstore is used both as a cache and as a staging area for large blobs
to be uploaded to the remote blobstore.
"""
def __init__(self, repo):
fullpath = repo.svfs.join('lfs/objects')
self.vfs = lfsvfs(fullpath)
if repo.ui.configbool('experimental', 'lfs.disableusercache'):
self.cachevfs = nullvfs()
else:
usercache = lfutil._usercachedir(repo.ui, 'lfs')
self.cachevfs = lfsvfs(usercache)
self.ui = repo.ui
def open(self, oid):
"""Open a read-only file descriptor to the named blob, in either the
usercache or the local store."""
# The usercache is the most likely place to hold the file. Commit will
# write to both it and the local store, as will anything that downloads
# the blobs. However, things like clone without an update won't
# populate the local store. For an init + push of a local clone,
# the usercache is the only place it _could_ be. If not present, the
# missing file msg here will indicate the local repo, not the usercache.
if self.cachevfs.exists(oid):
return self.cachevfs(oid, 'rb')
return self.vfs(oid, 'rb')
def download(self, oid, src):
"""Read the blob from the remote source in chunks, verify the content,
and write to this local blobstore."""
sha256 = hashlib.sha256()
with self.vfs(oid, 'wb', atomictemp=True) as fp:
for chunk in util.filechunkiter(src, size=1048576):
fp.write(chunk)
sha256.update(chunk)
realoid = sha256.hexdigest()
if realoid != oid:
raise LfsCorruptionError(_('corrupt remote lfs object: %s')
% oid)
self._linktousercache(oid)
def write(self, oid, data):
"""Write blob to local blobstore.
This should only be called from the filelog during a commit or similar.
As such, there is no need to verify the data. Imports from a remote
store must use ``download()`` instead."""
with self.vfs(oid, 'wb', atomictemp=True) as fp:
fp.write(data)
self._linktousercache(oid)
def linkfromusercache(self, oid):
"""Link blobs found in the user cache into this store.
The server module needs to do this when it lets the client know not to
upload the blob, to ensure it is always available in this store.
Normally this is done implicitly when the client reads or writes the
blob, but that doesn't happen when the server tells the client that it
already has the blob.
"""
if (not isinstance(self.cachevfs, nullvfs)
and not self.vfs.exists(oid)):
self.ui.note(_('lfs: found %s in the usercache\n') % oid)
lfutil.link(self.cachevfs.join(oid), self.vfs.join(oid))
def _linktousercache(self, oid):
# XXX: should we verify the content of the cache, and hardlink back to
# the local store on success, but truncate, write and link on failure?
if (not self.cachevfs.exists(oid)
and not isinstance(self.cachevfs, nullvfs)):
self.ui.note(_('lfs: adding %s to the usercache\n') % oid)
lfutil.link(self.vfs.join(oid), self.cachevfs.join(oid))
def read(self, oid, verify=True):
"""Read blob from local blobstore."""
if not self.vfs.exists(oid):
blob = self._read(self.cachevfs, oid, verify)
# Even if revlog will verify the content, it needs to be verified
# now before making the hardlink to avoid propagating corrupt blobs.
# Don't abort if corruption is detected, because `hg verify` will
# give more useful info about the corruption- simply don't add the
# hardlink.
if verify or hashlib.sha256(blob).hexdigest() == oid:
self.ui.note(_('lfs: found %s in the usercache\n') % oid)
lfutil.link(self.cachevfs.join(oid), self.vfs.join(oid))
else:
self.ui.note(_('lfs: found %s in the local lfs store\n') % oid)
blob = self._read(self.vfs, oid, verify)
return blob
def _read(self, vfs, oid, verify):
"""Read blob (after verifying) from the given store"""
blob = vfs.read(oid)
if verify:
_verify(oid, blob)
return blob
def verify(self, oid):
"""Indicate whether or not the hash of the underlying file matches its
name."""
sha256 = hashlib.sha256()
with self.open(oid) as fp:
for chunk in util.filechunkiter(fp, size=1048576):
sha256.update(chunk)
return oid == sha256.hexdigest()
def has(self, oid):
"""Returns True if the local blobstore contains the requested blob,
False otherwise."""
return self.cachevfs.exists(oid) or self.vfs.exists(oid)
class _gitlfsremote(object):
def __init__(self, repo, url):
ui = repo.ui
self.ui = ui
baseurl, authinfo = url.authinfo()
self.baseurl = baseurl.rstrip('/')
useragent = repo.ui.config('experimental', 'lfs.user-agent')
if not useragent:
useragent = 'git-lfs/2.3.4 (Mercurial %s)' % util.version()
self.urlopener = urlmod.opener(ui, authinfo, useragent)
self.retry = ui.configint('lfs', 'retry')
def writebatch(self, pointers, fromstore):
"""Batch upload from local to remote blobstore."""
self._batch(_deduplicate(pointers), fromstore, 'upload')
def readbatch(self, pointers, tostore):
"""Batch download from remote to local blostore."""
self._batch(_deduplicate(pointers), tostore, 'download')
def _batchrequest(self, pointers, action):
"""Get metadata about objects pointed by pointers for given action
Return decoded JSON object like {'objects': [{'oid': '', 'size': 1}]}
See https://github.com/git-lfs/git-lfs/blob/master/docs/api/batch.md
"""
objects = [{'oid': p.oid(), 'size': p.size()} for p in pointers]
requestdata = json.dumps({
'objects': objects,
'operation': action,
})
batchreq = util.urlreq.request('%s/objects/batch' % self.baseurl,
data=requestdata)
batchreq.add_header('Accept', 'application/vnd.git-lfs+json')
batchreq.add_header('Content-Type', 'application/vnd.git-lfs+json')
try:
rsp = self.urlopener.open(batchreq)
rawjson = rsp.read()
except util.urlerr.httperror as ex:
raise LfsRemoteError(_('LFS HTTP error: %s (action=%s)')
% (ex, action))
try:
response = json.loads(rawjson)
except ValueError:
raise LfsRemoteError(_('LFS server returns invalid JSON: %s')
% rawjson)
if self.ui.debugflag:
self.ui.debug('Status: %d\n' % rsp.status)
# lfs-test-server and hg serve return headers in different order
self.ui.debug('%s\n'
% '\n'.join(sorted(str(rsp.info()).splitlines())))
if 'objects' in response:
response['objects'] = sorted(response['objects'],
key=lambda p: p['oid'])
self.ui.debug('%s\n'
% json.dumps(response, indent=2,
separators=('', ': '), sort_keys=True))
return response
def _checkforservererror(self, pointers, responses, action):
"""Scans errors from objects
Raises LfsRemoteError if any objects have an error"""
for response in responses:
# The server should return 404 when objects cannot be found. Some
# server implementation (ex. lfs-test-server) does not set "error"
# but just removes "download" from "actions". Treat that case
# as the same as 404 error.
if 'error' not in response:
if (action == 'download'
and action not in response.get('actions', [])):
code = 404
else:
continue
else:
# An error dict without a code doesn't make much sense, so
# treat as a server error.
code = response.get('error').get('code', 500)
ptrmap = {p.oid(): p for p in pointers}
p = ptrmap.get(response['oid'], None)
if p:
filename = getattr(p, 'filename', 'unknown')
errors = {
404: 'The object does not exist',
410: 'The object was removed by the owner',
422: 'Validation error',
500: 'Internal server error',
}
msg = errors.get(code, 'status code %d' % code)
raise LfsRemoteError(_('LFS server error for "%s": %s')
% (filename, msg))
else:
raise LfsRemoteError(
_('LFS server error. Unsolicited response for oid %s')
% response['oid'])
def _extractobjects(self, response, pointers, action):
"""extract objects from response of the batch API
response: parsed JSON object returned by batch API
return response['objects'] filtered by action
raise if any object has an error
"""
# Scan errors from objects - fail early
objects = response.get('objects', [])
self._checkforservererror(pointers, objects, action)
# Filter objects with given action. Practically, this skips uploading
# objects which exist in the server.
filteredobjects = [o for o in objects if action in o.get('actions', [])]
return filteredobjects
def _basictransfer(self, obj, action, localstore):
"""Download or upload a single object using basic transfer protocol
obj: dict, an object description returned by batch API
action: string, one of ['upload', 'download']
localstore: blobstore.local
See https://github.com/git-lfs/git-lfs/blob/master/docs/api/\
basic-transfers.md
"""
oid = pycompat.bytestr(obj['oid'])
href = pycompat.bytestr(obj['actions'][action].get('href'))
headers = obj['actions'][action].get('header', {}).items()
request = util.urlreq.request(href)
if action == 'upload':
# If uploading blobs, read data from local blobstore.
if not localstore.verify(oid):
raise error.Abort(_('detected corrupt lfs object: %s') % oid,
hint=_('run hg verify'))
request.data = filewithprogress(localstore.open(oid), None)
request.get_method = lambda: 'PUT'
request.add_header('Content-Type', 'application/octet-stream')
for k, v in headers:
request.add_header(k, v)
response = b''
try:
req = self.urlopener.open(request)
if self.ui.debugflag:
self.ui.debug('Status: %d\n' % req.status)
# lfs-test-server and hg serve return headers in different order
self.ui.debug('%s\n'
% '\n'.join(sorted(str(req.info()).splitlines())))
if action == 'download':
# If downloading blobs, store downloaded data to local blobstore
localstore.download(oid, req)
else:
while True:
data = req.read(1048576)
if not data:
break
response += data
if response:
self.ui.debug('lfs %s response: %s' % (action, response))
except util.urlerr.httperror as ex:
if self.ui.debugflag:
self.ui.debug('%s: %s\n' % (oid, ex.read()))
raise LfsRemoteError(_('HTTP error: %s (oid=%s, action=%s)')
% (ex, oid, action))
def _batch(self, pointers, localstore, action):
if action not in ['upload', 'download']:
raise error.ProgrammingError('invalid Git-LFS action: %s' % action)
response = self._batchrequest(pointers, action)
objects = self._extractobjects(response, pointers, action)
total = sum(x.get('size', 0) for x in objects)
sizes = {}
for obj in objects:
sizes[obj.get('oid')] = obj.get('size', 0)
topic = {'upload': _('lfs uploading'),
'download': _('lfs downloading')}[action]
if len(objects) > 1:
self.ui.note(_('lfs: need to transfer %d objects (%s)\n')
% (len(objects), util.bytecount(total)))
def transfer(chunk):
for obj in chunk:
objsize = obj.get('size', 0)
if self.ui.verbose:
if action == 'download':
msg = _('lfs: downloading %s (%s)\n')
elif action == 'upload':
msg = _('lfs: uploading %s (%s)\n')
self.ui.note(msg % (obj.get('oid'),
util.bytecount(objsize)))
retry = self.retry
while True:
try:
self._basictransfer(obj, action, localstore)
yield 1, obj.get('oid')
break
except socket.error as ex:
if retry > 0:
self.ui.note(
_('lfs: failed: %r (remaining retry %d)\n')
% (ex, retry))
retry -= 1
continue
raise
# Until https multiplexing gets sorted out
if self.ui.configbool('experimental', 'lfs.worker-enable'):
oids = worker.worker(self.ui, 0.1, transfer, (),
sorted(objects, key=lambda o: o.get('oid')))
else:
oids = transfer(sorted(objects, key=lambda o: o.get('oid')))
with self.ui.makeprogress(topic, total=total) as progress:
progress.update(0)
processed = 0
blobs = 0
for _one, oid in oids:
processed += sizes[oid]
blobs += 1
progress.update(processed)
self.ui.note(_('lfs: processed: %s\n') % oid)
if blobs > 0:
if action == 'upload':
self.ui.status(_('lfs: uploaded %d files (%s)\n')
% (blobs, util.bytecount(processed)))
elif action == 'download':
self.ui.status(_('lfs: downloaded %d files (%s)\n')
% (blobs, util.bytecount(processed)))
def __del__(self):
# copied from mercurial/httppeer.py
urlopener = getattr(self, 'urlopener', None)
if urlopener:
for h in urlopener.handlers:
h.close()
getattr(h, "close_all", lambda : None)()
class _dummyremote(object):
"""Dummy store storing blobs to temp directory."""
def __init__(self, repo, url):
fullpath = repo.vfs.join('lfs', url.path)
self.vfs = lfsvfs(fullpath)
def writebatch(self, pointers, fromstore):
for p in _deduplicate(pointers):
content = fromstore.read(p.oid(), verify=True)
with self.vfs(p.oid(), 'wb', atomictemp=True) as fp:
fp.write(content)
def readbatch(self, pointers, tostore):
for p in _deduplicate(pointers):
with self.vfs(p.oid(), 'rb') as fp:
tostore.download(p.oid(), fp)
class _nullremote(object):
"""Null store storing blobs to /dev/null."""
def __init__(self, repo, url):
pass
def writebatch(self, pointers, fromstore):
pass
def readbatch(self, pointers, tostore):
pass
class _promptremote(object):
"""Prompt user to set lfs.url when accessed."""
def __init__(self, repo, url):
pass
def writebatch(self, pointers, fromstore, ui=None):
self._prompt()
def readbatch(self, pointers, tostore, ui=None):
self._prompt()
def _prompt(self):
raise error.Abort(_('lfs.url needs to be configured'))
_storemap = {
'https': _gitlfsremote,
'http': _gitlfsremote,
'file': _dummyremote,
'null': _nullremote,
None: _promptremote,
}
def _deduplicate(pointers):
"""Remove any duplicate oids that exist in the list"""
reduced = util.sortdict()
for p in pointers:
reduced[p.oid()] = p
return reduced.values()
def _verify(oid, content):
realoid = hashlib.sha256(content).hexdigest()
if realoid != oid:
raise LfsCorruptionError(_('detected corrupt lfs object: %s') % oid,
hint=_('run hg verify'))
def remote(repo, remote=None):
"""remotestore factory. return a store in _storemap depending on config
If ``lfs.url`` is specified, use that remote endpoint. Otherwise, try to
infer the endpoint, based on the remote repository using the same path
adjustments as git. As an extension, 'http' is supported as well so that
``hg serve`` works out of the box.
https://github.com/git-lfs/git-lfs/blob/master/docs/api/server-discovery.md
"""
lfsurl = repo.ui.config('lfs', 'url')
url = util.url(lfsurl or '')
if lfsurl is None:
if remote:
path = remote
elif util.safehasattr(repo, '_subtoppath'):
# The pull command sets this during the optional update phase, which
# tells exactly where the pull originated, whether 'paths.default'
# or explicit.
path = repo._subtoppath
else:
# TODO: investigate 'paths.remote:lfsurl' style path customization,
# and fall back to inferring from 'paths.remote' if unspecified.
path = repo.ui.config('paths', 'default') or ''
defaulturl = util.url(path)
# TODO: support local paths as well.
# TODO: consider the ssh -> https transformation that git applies
if defaulturl.scheme in (b'http', b'https'):
if defaulturl.path and defaulturl.path[:-1] != b'/':
defaulturl.path += b'/'
defaulturl.path = (defaulturl.path or b'') + b'.git/info/lfs'
url = util.url(bytes(defaulturl))
repo.ui.note(_('lfs: assuming remote store: %s\n') % url)
scheme = url.scheme
if scheme not in _storemap:
raise error.Abort(_('lfs: unknown url scheme: %s') % scheme)
return _storemap[scheme](repo, url)
class LfsRemoteError(error.RevlogError):
pass
class LfsCorruptionError(error.Abort):
"""Raised when a corrupt blob is detected, aborting an operation
It exists to allow specialized handling on the server side."""