comparison mercurial/debugcommands.py @ 37051:40206e227412

wireproto: define and implement protocol for issuing requests

The existing HTTP and SSH wire protocols suffer from a host of flaws
and shortcomings. I've been wanting to rewrite the protocol for a while
now. Supporting partial clone - which will require new wire protocol
commands and capabilities - and other advanced server functionality
will be much easier if we start from a clean slate and don't have
to be constrained by limitations of the existing wire protocol.

This commit starts to introduce a new data exchange format for
use over the wire protocol.

The new protocol is built on top of "frames," which are atomic
units of metadata + data. Frames will make it easier to implement
proxies and other mechanisms that want to inspect data without
having to maintain state. The existing frame metadata is very
minimal and it will evolve heavily. (We will eventually support
things like concurrent requests, out-of-order responses,
compression, side-channels for status updates, etc. Some of
these will require additions to the frame header.)

Another benefit of frames is that all reads are of a fixed size.
A reader works by consuming a frame header, extracting the payload
length, then reading that many bytes. No lookahead, buffering, or
memory reallocations are needed.

The new protocol attempts to be transport agnostic. I want all that's
required to use the new protocol to be a pair of unidirectional,
half-duplex pipes. (Yes, we will eventually make use of full-duplex
pipes, but that's for another commit.) Notably, when the SSH
transport switches to this new protocol, stderr will be unused.
This is by design: the lack of stderr on HTTP harms protocol
behavior there. By shoehorning everything into a pair of pipes,
we can have more consistent behavior across transports.

We currently only define the client side parts of the new protocol,
specifically the bits for requesting that a command run. This keeps
the new code and feature small and somewhat easy to review.

We add support to `hg debugwireproto` for writing frames into
HTTP request bodies. Our tests that issue commands to the new
HTTP endpoint have been updated to transmit frames. The server
bits haven't been touched to consume the frames yet. This will
occur in the next commit...

Astute readers may notice that the command name is transmitted in
both the HTTP request URL and the command request frame. This is
partially a kludge from me initially implementing the frame-based
protocol for SSH first. But it is also a feature: I intend to
eventually support issuing multiple commands per HTTP request. This
will allow us to replace the abomination that is the "batch" wire
protocol command with a protocol-level mechanism for performing
multi-dispatch. Because I want the frame-based protocol to be
as similar as possible across transports, I'd rather we (redundantly)
include the command name in the frame than differ behavior between
transports that have out-of-band routing information (like HTTP)
readily available.

Differential Revision: https://phab.mercurial-scm.org/D2851

37050:37d7a1d18b97

    treediscovery,
    upgrade,
    url as urlmod,
    util,
    vfs as vfsmod,
    wireprotoserver,
)
from .utils import dateutil

release = lockmod.release

    ``BODYFILE``
        The content of the file defined as the value to this argument will be
        transferred verbatim as the HTTP request body.

    close
    -----

    Close the connection to the server.

    eread <X>
    ---------

    ``read()`` N bytes from the server's stderr pipe, if available.
    """
    opts = pycompat.byteskwargs(opts)

    if opts['localssh'] and not repo:
        raise error.Abort(_('--localssh requires a repository'))

                                    '"httprequest <method> <path>'))

            method, httppath = request[1:]
            headers = {}
            body = None
            for line in lines:
                line = line.lstrip()
                m = re.match(b'^([a-zA-Z0-9_-]+): (.*)$', line)
                if m:
                    headers[m.group(1)] = m.group(2)
                    continue

                if line.startswith(b'BODYFILE '):
                    with open(line.split(b' ', 1), 'rb') as fh:
                        body = fh.read()
                else:
                    raise error.Abort(_('unknown argument to httprequest: %s') %
                                      line)

            url = path + httppath
            req = urlmod.urlreq.request(pycompat.strurl(url), body, headers)

            # urllib.Request insists on using has_data() as a proxy for
            # determining the request method. Override that to use our
            # explicitly requested method.

37051:40206e227412

    treediscovery,
    upgrade,
    url as urlmod,
    util,
    vfs as vfsmod,
    wireprotoframing,
    wireprotoserver,
)
from .utils import dateutil

release = lockmod.release

    ``BODYFILE``
        The content of the file defined as the value to this argument will be
        transferred verbatim as the HTTP request body.

    ``frame <type> <flags> <payload>``
        Send a unified protocol frame as part of the request body.

        All frames will be collected and sent as the body to the HTTP
        request.

    close
    -----

    Close the connection to the server.

    eread <X>
    ---------

    ``read()`` N bytes from the server's stderr pipe, if available.

    Specifying Unified Frame-Based Protocol Frames
    ----------------------------------------------

    It is possible to emit a *Unified Frame-Based Protocol* by using special
    syntax.

    A frame is composed as a type, flags, and payload. These can be parsed
    from a string of the form ``<type> <flags> <payload>``. That is, 3
    space-delimited strings.

    ``payload`` is the simplest: it is evaluated as a Python byte string
    literal.

    ``type`` can be an integer value for the frame type or the string name
    of the type. The strings are defined in ``wireprotoframing.py``. e.g.
    ``command-name``.

    ``flags`` is a ``|`` delimited list of flag components. Each component
    (and there can be just one) can be an integer or a flag name for the
    specified frame type. Values are resolved to integers and then bitwise
    OR'd together.
    """
    opts = pycompat.byteskwargs(opts)

    if opts['localssh'] and not repo:
        raise error.Abort(_('--localssh requires a repository'))

                                    '"httprequest <method> <path>'))

            method, httppath = request[1:]
            headers = {}
            body = None
            frames = []
            for line in lines:
                line = line.lstrip()
                m = re.match(b'^([a-zA-Z0-9_-]+): (.*)$', line)
                if m:
                    headers[m.group(1)] = m.group(2)
                    continue

                if line.startswith(b'BODYFILE '):
                    with open(line.split(b' ', 1), 'rb') as fh:
                        body = fh.read()
                elif line.startswith(b'frame '):
                    frame = wireprotoframing.makeframefromhumanstring(
                        line[len(b'frame '):])

                    frames.append(frame)
                else:
                    raise error.Abort(_('unknown argument to httprequest: %s') %
                                      line)

            url = path + httppath

            if frames:
                body = b''.join(bytes(f) for f in frames)

            req = urlmod.urlreq.request(pycompat.strurl(url), body, headers)

            # urllib.Request insists on using has_data() as a proxy for
            # determining the request method. Override that to use our
            # explicitly requested method.