view mercurial/wireprototypes.py @ 48687:f8f2ecdde4b5

branchmap: skip obsolete revisions while computing heads

It's time to make this part of core Mercurial obsolescence-aware.

Not considering obsolete revisions when computing heads is clearly what
Mercurial should do. But there are a couple of small issues:

- Let's say tip of the repo is obsolete. There are two ways of finding tiprev
  for branchcache (both are in use): looking at input data for update() and
  looking at computed heads after update(). Previously, repo tip would be
  tiprev of the branchcache. With this patch, an obsolete revision can no
  longer be tiprev. And depending on what way we use for finding tiprev (input
  data vs computed heads) we'll get a different result. This is relevant when
  recomputing cache key from cache contents, and may lead to updating cache for
  obsolete revisions multiple times (not from scratch, because it still would
  be considered valid for a subset of revisions in the repo).

- If all commits on a branch are obsolete, the branchcache will include that
  branch, but the list of heads will be empty (that's why there's now `if not
  heads` when recomputing tiprev/tipnode from cache contents). Having an entry
  for every branch is currently required for notify extension (and
  test-notify.t to pass), because notify doesn't handle revsets in its
  subscription config very well and will throw an error if e.g. a branch
  doesn't exist.

- Cloning static HTTP repos may try to stat() a non-existent obsstore file. The
  issue is that we now care about obsolescence during clone, but statichttpvfs
  doesn't implement a stat method, so a regular vfs.stat() is used, and it
  assumes that file is local and calls os.stat().  During a clone, we're trying
  to stat() .hg/store/obsstore, but in static HTTP case we provide a literal
  URL to the obsstore file on the remote as if it were a local file path. On
  windows it actually results in a failure in test-static-http.t.

The first issue is going to be addressed in a series dedicated to making sure
branchcache is properly and timely written on disk (it wasn't perfect even
before this patch, but there aren't enough tests to demonstrate that). The
second issue will be addressed in a future patch for notify extension that will
make it not raise an exception if a branch doesn't exist. And the third one was
partially addressed in the previous patch in this series and will be properly
fixed in a future patch when this series is accepted.

filteredhash() grows a keyword argument to make sure that branchcache is also
invalidated when there are new obsolete revisions in its repo view. This way
the on-disk cache format is unchanged and compatible between versions (although
it will obviously be recomputed when switching versions before/after this patch
and the repo has obsolete revisions).

There's one test that uses plain `hg up` without arguments while updated to a
pruned commit. To make this test pass, simply return current working directory
parent. Later in this series this code will be replaced by what prune command
does: updating to the closest non-obsolete ancestor.

Test changes:

test-branch-change.t: update branch head and cache update message. The head of
default listed in hg heads is changed because revision 2 was rewritten as 7,
and 1 is the closest ancestor on the same branch, so it's the head of default
now.

The cache invalidation message appears now because of the cache hash change,
since we're now accounting for obsolete revisions. Here's some context:

"served.hidden" repo filter means everything is visible (no filtered
revisions), so before this series branch2-served.hidden file would not contain
any cache hash, only revnum and node. Now it also has a hash when there are
obsolete changesets in the repo. The command that the message appears for is
changing branch of 5 and 6, which are now obsolete, so the cache hash changes.

In general, when cache is simply out-of-date, it can be updated using the old
version as a base. But if cache hash differs, then the cache for that
particular repo filter is recomputed (at least with the current
implementation). This is what happens here.

test-obsmarker-template.t: the pull reports 2 heads changed, but after that the
repo correctly sees only 1. The new message could be better, but it's still an
improvement over the previous one where hg pull suggested merging with an
obsolete revision.

test-obsolete.t: we can see these revisions in hg log --hidden, but they
shouldn't be considered heads even with --hidden.

test-rebase-obsolete{,2}.t: there were new heads created previously after
making new orphan changesets, but they weren't detected. Now we are properly
detecting and reporting them.

test-rebase-obsolete4.t: there's only one head now because the other head is
pruned and was falsely reported before.

test-static-http.t: add obsstore to the list of requested files. This file
doesn't exist on the remotes, but clients want it anyway (they get 404). This
is fine, because there are other nonexistent files that clients request, like
.hg/bookmarks or .hg/cache/tags2-served.

Differential Revision: https://phab.mercurial-scm.org/D12097

# Copyright 2018 Gregory Szorc <[e-mail]>
#
# 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

from .node import (
    bin,
    hex,
)
from .i18n import _
from .pycompat import getattr
from .thirdparty import attr
from . import (
    error,
    util,
)
from .interfaces import util as interfaceutil
from .utils import compression

# Names of the SSH protocol implementations.
SSHV1 = b'ssh-v1'

NARROWCAP = b'exp-narrow-1'
ELLIPSESCAP1 = b'exp-ellipses-1'
ELLIPSESCAP = b'exp-ellipses-2'
SUPPORTED_ELLIPSESCAP = (ELLIPSESCAP1, ELLIPSESCAP)

# All available wire protocol transports.
TRANSPORTS = {
    SSHV1: {
        b'transport': b'ssh',
        b'version': 1,
    },
    b'http-v1': {
        b'transport': b'http',
        b'version': 1,
    },
}


class bytesresponse(object):
    """A wire protocol response consisting of raw bytes."""

    def __init__(self, data):
        self.data = data


class ooberror(object):
    """wireproto reply: failure of a batch of operation

    Something failed during a batch call. The error message is stored in
    `self.message`.
    """

    def __init__(self, message):
        self.message = message


class pushres(object):
    """wireproto reply: success with simple integer return

    The call was successful and returned an integer contained in `self.res`.
    """

    def __init__(self, res, output):
        self.res = res
        self.output = output


class pusherr(object):
    """wireproto reply: failure

    The call failed. The `self.res` attribute contains the error message.
    """

    def __init__(self, res, output):
        self.res = res
        self.output = output


class streamres(object):
    """wireproto reply: binary stream

    The call was successful and the result is a stream.

    Accepts a generator containing chunks of data to be sent to the client.

    ``prefer_uncompressed`` indicates that the data is expected to be
    uncompressable and that the stream should therefore use the ``none``
    engine.
    """

    def __init__(self, gen=None, prefer_uncompressed=False):
        self.gen = gen
        self.prefer_uncompressed = prefer_uncompressed


class streamreslegacy(object):
    """wireproto reply: uncompressed binary stream

    The call was successful and the result is a stream.

    Accepts a generator containing chunks of data to be sent to the client.

    Like ``streamres``, but sends an uncompressed data for "version 1" clients
    using the application/mercurial-0.1 media type.
    """

    def __init__(self, gen=None):
        self.gen = gen


# list of nodes encoding / decoding
def decodelist(l, sep=b' '):
    if l:
        return [bin(v) for v in l.split(sep)]
    return []


def encodelist(l, sep=b' '):
    try:
        return sep.join(map(hex, l))
    except TypeError:
        raise


# batched call argument encoding


def escapebatcharg(plain):
    return (
        plain.replace(b':', b':c')
        .replace(b',', b':o')
        .replace(b';', b':s')
        .replace(b'=', b':e')
    )


def unescapebatcharg(escaped):
    return (
        escaped.replace(b':e', b'=')
        .replace(b':s', b';')
        .replace(b':o', b',')
        .replace(b':c', b':')
    )


# mapping of options accepted by getbundle and their types
#
# Meant to be extended by extensions. It is the extension's responsibility to
# ensure such options are properly processed in exchange.getbundle.
#
# supported types are:
#
# :nodes: list of binary nodes, transmitted as space-separated hex nodes
# :csv:   list of values, transmitted as comma-separated values
# :scsv:  set of values, transmitted as comma-separated values
# :plain: string with no transformation needed.
GETBUNDLE_ARGUMENTS = {
    b'heads': b'nodes',
    b'bookmarks': b'boolean',
    b'common': b'nodes',
    b'obsmarkers': b'boolean',
    b'phases': b'boolean',
    b'bundlecaps': b'scsv',
    b'listkeys': b'csv',
    b'cg': b'boolean',
    b'cbattempted': b'boolean',
    b'stream': b'boolean',
    b'includepats': b'csv',
    b'excludepats': b'csv',
}


class baseprotocolhandler(interfaceutil.Interface):
    """Abstract base class for wire protocol handlers.

    A wire protocol handler serves as an interface between protocol command
    handlers and the wire protocol transport layer. Protocol handlers provide
    methods to read command arguments, redirect stdio for the duration of
    the request, handle response types, etc.
    """

    name = interfaceutil.Attribute(
        """The name of the protocol implementation.

        Used for uniquely identifying the transport type.
        """
    )

    def getargs(args):
        """return the value for arguments in <args>

        For version 1 transports, returns a list of values in the same
        order they appear in ``args``. For version 2 transports, returns
        a dict mapping argument name to value.
        """

    def getprotocaps():
        """Returns the list of protocol-level capabilities of client

        Returns a list of capabilities as declared by the client for
        the current request (or connection for stateful protocol handlers)."""

    def getpayload():
        """Provide a generator for the raw payload.

        The caller is responsible for ensuring that the full payload is
        processed.
        """

    def mayberedirectstdio():
        """Context manager to possibly redirect stdio.

        The context manager yields a file-object like object that receives
        stdout and stderr output when the context manager is active. Or it
        yields ``None`` if no I/O redirection occurs.

        The intent of this context manager is to capture stdio output
        so it may be sent in the response. Some transports support streaming
        stdio to the client in real time. For these transports, stdio output
        won't be captured.
        """

    def client():
        """Returns a string representation of this client (as bytes)."""

    def addcapabilities(repo, caps):
        """Adds advertised capabilities specific to this protocol.

        Receives the list of capabilities collected so far.

        Returns a list of capabilities. The passed in argument can be returned.
        """

    def checkperm(perm):
        """Validate that the client has permissions to perform a request.

        The argument is the permission required to proceed. If the client
        doesn't have that permission, the exception should raise or abort
        in a protocol specific manner.
        """


class commandentry(object):
    """Represents a declared wire protocol command."""

    def __init__(
        self,
        func,
        args=b'',
        transports=None,
        permission=b'push',
        cachekeyfn=None,
        extracapabilitiesfn=None,
    ):
        self.func = func
        self.args = args
        self.transports = transports or set()
        self.permission = permission
        self.cachekeyfn = cachekeyfn
        self.extracapabilitiesfn = extracapabilitiesfn

    def _merge(self, func, args):
        """Merge this instance with an incoming 2-tuple.

        This is called when a caller using the old 2-tuple API attempts
        to replace an instance. The incoming values are merged with
        data not captured by the 2-tuple and a new instance containing
        the union of the two objects is returned.
        """
        return commandentry(
            func,
            args=args,
            transports=set(self.transports),
            permission=self.permission,
        )

    # Old code treats instances as 2-tuples. So expose that interface.
    def __iter__(self):
        yield self.func
        yield self.args

    def __getitem__(self, i):
        if i == 0:
            return self.func
        elif i == 1:
            return self.args
        else:
            raise IndexError(b'can only access elements 0 and 1')


class commanddict(dict):
    """Container for registered wire protocol commands.

    It behaves like a dict. But __setitem__ is overwritten to allow silent
    coercion of values from 2-tuples for API compatibility.
    """

    def __setitem__(self, k, v):
        if isinstance(v, commandentry):
            pass
        # Cast 2-tuples to commandentry instances.
        elif isinstance(v, tuple):
            if len(v) != 2:
                raise ValueError(b'command tuples must have exactly 2 elements')

            # It is common for extensions to wrap wire protocol commands via
            # e.g. ``wireproto.commands[x] = (newfn, args)``. Because callers
            # doing this aren't aware of the new API that uses objects to store
            # command entries, we automatically merge old state with new.
            if k in self:
                v = self[k]._merge(v[0], v[1])
            else:
                # Use default values from @wireprotocommand.
                v = commandentry(
                    v[0],
                    args=v[1],
                    transports=set(TRANSPORTS),
                    permission=b'push',
                )
        else:
            raise ValueError(
                b'command entries must be commandentry instances '
                b'or 2-tuples'
            )

        return super(commanddict, self).__setitem__(k, v)

    def commandavailable(self, command, proto):
        """Determine if a command is available for the requested protocol."""
        assert proto.name in TRANSPORTS

        entry = self.get(command)

        if not entry:
            return False

        if proto.name not in entry.transports:
            return False

        return True


def supportedcompengines(ui, role):
    """Obtain the list of supported compression engines for a request."""
    assert role in (compression.CLIENTROLE, compression.SERVERROLE)

    compengines = compression.compengines.supportedwireengines(role)

    # Allow config to override default list and ordering.
    if role == compression.SERVERROLE:
        configengines = ui.configlist(b'server', b'compressionengines')
        config = b'server.compressionengines'
    else:
        # This is currently implemented mainly to facilitate testing. In most
        # cases, the server should be in charge of choosing a compression engine
        # because a server has the most to lose from a sub-optimal choice. (e.g.
        # CPU DoS due to an expensive engine or a network DoS due to poor
        # compression ratio).
        configengines = ui.configlist(
            b'experimental', b'clientcompressionengines'
        )
        config = b'experimental.clientcompressionengines'

    # No explicit config. Filter out the ones that aren't supposed to be
    # advertised and return default ordering.
    if not configengines:
        attr = (
            b'serverpriority' if role == util.SERVERROLE else b'clientpriority'
        )
        return [
            e for e in compengines if getattr(e.wireprotosupport(), attr) > 0
        ]

    # If compression engines are listed in the config, assume there is a good
    # reason for it (like server operators wanting to achieve specific
    # performance characteristics). So fail fast if the config references
    # unusable compression engines.
    validnames = {e.name() for e in compengines}
    invalidnames = {e for e in configengines if e not in validnames}
    if invalidnames:
        raise error.Abort(
            _(b'invalid compression engine defined in %s: %s')
            % (config, b', '.join(sorted(invalidnames)))
        )

    compengines = [e for e in compengines if e.name() in configengines]
    compengines = sorted(
        compengines, key=lambda e: configengines.index(e.name())
    )

    if not compengines:
        raise error.Abort(
            _(
                b'%s config option does not specify any known '
                b'compression engines'
            )
            % config,
            hint=_(b'usable compression engines: %s')
            % b', '.sorted(validnames),  # pytype: disable=attribute-error
        )

    return compengines


@attr.s
class encodedresponse(object):
    """Represents response data that is already content encoded.

    Wire protocol version 2 only.

    Commands typically emit Python objects that are encoded and sent over the
    wire. If commands emit an object of this type, the encoding step is bypassed
    and the content from this object is used instead.
    """

    data = attr.ib()


@attr.s
class alternatelocationresponse(object):
    """Represents a response available at an alternate location.

    Instances are sent in place of actual response objects when the server
    is sending a "content redirect" response.

    Only compatible with wire protocol version 2.
    """

    url = attr.ib()
    mediatype = attr.ib()
    size = attr.ib(default=None)
    fullhashes = attr.ib(default=None)
    fullhashseed = attr.ib(default=None)
    serverdercerts = attr.ib(default=None)
    servercadercerts = attr.ib(default=None)


@attr.s
class indefinitebytestringresponse(object):
    """Represents an object to be encoded to an indefinite length bytestring.

    Instances are initialized from an iterable of chunks, with each chunk being
    a bytes instance.
    """

    chunks = attr.ib()