hgext/lfs/blobstore.py

lfs: infer the blob store URL from paths.default

If `lfs.url` is specified, it takes precedence.  However, now that we support
serving blobs via hgweb, we shouldn't *require* this setting.  Less
configuration is better (things will work out of the box once this is sorted
out), and git has similar functionality.

This is not a complete solution- it isn't able to infer the blob store from an
explicitly supplied path, and it should consider `paths.default-push` for push.
The pull solution for that is a bit hacky, and this alone is an improvement for
the vast majority of cases.

Even though there are only a handful of references to the saved remote store,
the location of them makes things complicated.

  1) downloading files on demand in the revlog flag processor
  2) copying to readonlyvfs with bundlerepo
  3) downloading in the file prefetch hook
  4) the canupload()/skipdownload() checks
  5) uploading blobs

Since revlog doesn't have a repo or ui reference, we can't avoid creating a
remote store when the extension is loaded.  While the long term goal is to make
sure the prefetch hook is invoked early for every command for efficiency, this
handling in the flag processor is needed as a last ditch fetch.

In order to support the clone command, the remote store needs to be created
later than when the extension loads, since `paths.default` isn't set until just
before the files are checked out.  Therefore, this patch changes the prefetch
hook to ignore the saved reference, and build a new one.

The canupload()/skipdownload() checks simply check if the stored instance is a
`_nullremote`.  Since this can only be set via `lfs.url` (which is reflected in
the saved reference), checking only the instance created when the extension
loaded is fine.

The blob uploading function is called from several places:

  1) a prepush hook
  2) when writing a new bundle
  3) from infinitepush

The prepush hook gets an exchange.pushop, so it has a path to where the push is
going.  The bundle writer and infinitepush don't.  Further, bundle creation for
things like strip and amend are causing blobs to be uploaded.  This seems wrong,
but I don't want to side track this sorting that out, so punt on trying to
handle explicit push paths or `paths.default-push`.

I also think that sending blobs to a remote store when pushing to a local repo
is wrong.  This functionality predates the usercache, so perhaps that's the
reason for it.  I've got some patches floating around to stop sending blobs
remotely in this case, and instead write directly to the other repo's blob
store.  But the tests for corruption handling weren't happy with this change,
and I don't have time to rewrite them.  So exclude filesystem based paths from
this for now.

I don't think there's much of a chance to implement `paths.remote:lfsurl` style
configs, given how early these are resolved vs how late the remote store is
created.  But git has it, so I threw a TODO in there, in case anyone has ideas.

I have no idea why this is now doing http auth twice when it wasn't before.  I
don't think the original blobstore's url is ever being used in these cases.

# 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)
        usercache = util.url(lfutil._usercachedir(repo.ui, 'lfs'))
        if usercache.scheme in (None, 'file'):
            self.cachevfs = lfsvfs(usercache.localpath())
        elif usercache.scheme == 'null':
            self.cachevfs = nullvfs()
        else:
            raise error.Abort(_('unknown lfs cache scheme: %s')
                              % usercache.scheme)
        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 error.Abort(_('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 _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)))
        self.ui.progress(topic, 0, total=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')))

        processed = 0
        blobs = 0
        for _one, oid in oids:
            processed += sizes[oid]
            blobs += 1
            self.ui.progress(topic, processed, total=total)
            self.ui.note(_('lfs: processed: %s\n') % oid)
        self.ui.progress(topic, pos=None, total=total)

        if blobs > 0:
            if action == 'upload':
                self.ui.status(_('lfs: uploaded %d files (%s)\n')
                               % (blobs, util.bytecount(processed)))
            # TODO: coalesce the download requests, and comment this in
            #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 error.Abort(_('detected corrupt lfs object: %s') % oid,
                          hint=_('run hg verify'))

def remote(repo):
    """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
    """
    url = util.url(repo.ui.config('lfs', 'url') or '')
    if url.scheme is None:
        # TODO: investigate 'paths.remote:lfsurl' style path customization,
        # and fall back to inferring from 'paths.remote' if unspecified.
        defaulturl = util.url(repo.ui.config('paths', 'default') or b'')

        # TODO: support local paths as well.
        # TODO: consider the ssh -> https transformation that git applies
        if defaulturl.scheme in (b'http', b'https'):
            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