wireprotov2: change command response protocol to include a leading map
The error handling mechanism for the new wire protocol isn't very
well-defined. This commit takes us a step in the right direction
by introducing a leading CBOR map for command responses. This map
will contain an overall result of the command.
Currently, the map indicates whether the command was overall
successful or if an error occurred. And if an error occurred, that
error is present in the map.
There is still a dedicated error frame. My intent is to use that
for protocol-level errors and for errors that are encountered after
the initial response frame has been sent. This will be clarified in a
later commit.
Differential Revision: https://phab.mercurial-scm.org/D3385
# wireprotoframing.py - unified framing protocol for wire protocol
#
# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
# This file contains functionality to support the unified frame-based wire
# protocol. For details about the protocol, see
# `hg help internals.wireprotocol`.
from __future__ import absolute_import
import collections
import struct
from .i18n import _
from .thirdparty import (
attr,
cbor,
)
from . import (
encoding,
error,
util,
)
from .utils import (
stringutil,
)
FRAME_HEADER_SIZE = 8
DEFAULT_MAX_FRAME_SIZE = 32768
STREAM_FLAG_BEGIN_STREAM = 0x01
STREAM_FLAG_END_STREAM = 0x02
STREAM_FLAG_ENCODING_APPLIED = 0x04
STREAM_FLAGS = {
b'stream-begin': STREAM_FLAG_BEGIN_STREAM,
b'stream-end': STREAM_FLAG_END_STREAM,
b'encoded': STREAM_FLAG_ENCODING_APPLIED,
}
FRAME_TYPE_COMMAND_REQUEST = 0x01
FRAME_TYPE_COMMAND_DATA = 0x02
FRAME_TYPE_COMMAND_RESPONSE = 0x03
FRAME_TYPE_ERROR_RESPONSE = 0x05
FRAME_TYPE_TEXT_OUTPUT = 0x06
FRAME_TYPE_PROGRESS = 0x07
FRAME_TYPE_STREAM_SETTINGS = 0x08
FRAME_TYPES = {
b'command-request': FRAME_TYPE_COMMAND_REQUEST,
b'command-data': FRAME_TYPE_COMMAND_DATA,
b'command-response': FRAME_TYPE_COMMAND_RESPONSE,
b'error-response': FRAME_TYPE_ERROR_RESPONSE,
b'text-output': FRAME_TYPE_TEXT_OUTPUT,
b'progress': FRAME_TYPE_PROGRESS,
b'stream-settings': FRAME_TYPE_STREAM_SETTINGS,
}
FLAG_COMMAND_REQUEST_NEW = 0x01
FLAG_COMMAND_REQUEST_CONTINUATION = 0x02
FLAG_COMMAND_REQUEST_MORE_FRAMES = 0x04
FLAG_COMMAND_REQUEST_EXPECT_DATA = 0x08
FLAGS_COMMAND_REQUEST = {
b'new': FLAG_COMMAND_REQUEST_NEW,
b'continuation': FLAG_COMMAND_REQUEST_CONTINUATION,
b'more': FLAG_COMMAND_REQUEST_MORE_FRAMES,
b'have-data': FLAG_COMMAND_REQUEST_EXPECT_DATA,
}
FLAG_COMMAND_DATA_CONTINUATION = 0x01
FLAG_COMMAND_DATA_EOS = 0x02
FLAGS_COMMAND_DATA = {
b'continuation': FLAG_COMMAND_DATA_CONTINUATION,
b'eos': FLAG_COMMAND_DATA_EOS,
}
FLAG_COMMAND_RESPONSE_CONTINUATION = 0x01
FLAG_COMMAND_RESPONSE_EOS = 0x02
FLAGS_COMMAND_RESPONSE = {
b'continuation': FLAG_COMMAND_RESPONSE_CONTINUATION,
b'eos': FLAG_COMMAND_RESPONSE_EOS,
}
FLAG_ERROR_RESPONSE_PROTOCOL = 0x01
FLAG_ERROR_RESPONSE_APPLICATION = 0x02
FLAGS_ERROR_RESPONSE = {
b'protocol': FLAG_ERROR_RESPONSE_PROTOCOL,
b'application': FLAG_ERROR_RESPONSE_APPLICATION,
}
# Maps frame types to their available flags.
FRAME_TYPE_FLAGS = {
FRAME_TYPE_COMMAND_REQUEST: FLAGS_COMMAND_REQUEST,
FRAME_TYPE_COMMAND_DATA: FLAGS_COMMAND_DATA,
FRAME_TYPE_COMMAND_RESPONSE: FLAGS_COMMAND_RESPONSE,
FRAME_TYPE_ERROR_RESPONSE: FLAGS_ERROR_RESPONSE,
FRAME_TYPE_TEXT_OUTPUT: {},
FRAME_TYPE_PROGRESS: {},
FRAME_TYPE_STREAM_SETTINGS: {},
}
ARGUMENT_RECORD_HEADER = struct.Struct(r'<HH')
def humanflags(mapping, value):
"""Convert a numeric flags value to a human value, using a mapping table."""
namemap = {v: k for k, v in mapping.iteritems()}
flags = []
val = 1
while value >= val:
if value & val:
flags.append(namemap.get(val, '<unknown 0x%02x>' % val))
val <<= 1
return b'|'.join(flags)
@attr.s(slots=True)
class frameheader(object):
"""Represents the data in a frame header."""
length = attr.ib()
requestid = attr.ib()
streamid = attr.ib()
streamflags = attr.ib()
typeid = attr.ib()
flags = attr.ib()
@attr.s(slots=True, repr=False)
class frame(object):
"""Represents a parsed frame."""
requestid = attr.ib()
streamid = attr.ib()
streamflags = attr.ib()
typeid = attr.ib()
flags = attr.ib()
payload = attr.ib()
@encoding.strmethod
def __repr__(self):
typename = '<unknown 0x%02x>' % self.typeid
for name, value in FRAME_TYPES.iteritems():
if value == self.typeid:
typename = name
break
return ('frame(size=%d; request=%d; stream=%d; streamflags=%s; '
'type=%s; flags=%s)' % (
len(self.payload), self.requestid, self.streamid,
humanflags(STREAM_FLAGS, self.streamflags), typename,
humanflags(FRAME_TYPE_FLAGS.get(self.typeid, {}), self.flags)))
def makeframe(requestid, streamid, streamflags, typeid, flags, payload):
"""Assemble a frame into a byte array."""
# TODO assert size of payload.
frame = bytearray(FRAME_HEADER_SIZE + len(payload))
# 24 bits length
# 16 bits request id
# 8 bits stream id
# 8 bits stream flags
# 4 bits type
# 4 bits flags
l = struct.pack(r'<I', len(payload))
frame[0:3] = l[0:3]
struct.pack_into(r'<HBB', frame, 3, requestid, streamid, streamflags)
frame[7] = (typeid << 4) | flags
frame[8:] = payload
return frame
def makeframefromhumanstring(s):
"""Create a frame from a human readable string
Strings have the form:
<request-id> <stream-id> <stream-flags> <type> <flags> <payload>
This can be used by user-facing applications and tests for creating
frames easily without having to type out a bunch of constants.
Request ID and stream IDs are integers.
Stream flags, frame type, and flags can be specified by integer or
named constant.
Flags can be delimited by `|` to bitwise OR them together.
If the payload begins with ``cbor:``, the following string will be
evaluated as Python literal and the resulting object will be fed into
a CBOR encoder. Otherwise, the payload is interpreted as a Python
byte string literal.
"""
fields = s.split(b' ', 5)
requestid, streamid, streamflags, frametype, frameflags, payload = fields
requestid = int(requestid)
streamid = int(streamid)
finalstreamflags = 0
for flag in streamflags.split(b'|'):
if flag in STREAM_FLAGS:
finalstreamflags |= STREAM_FLAGS[flag]
else:
finalstreamflags |= int(flag)
if frametype in FRAME_TYPES:
frametype = FRAME_TYPES[frametype]
else:
frametype = int(frametype)
finalflags = 0
validflags = FRAME_TYPE_FLAGS[frametype]
for flag in frameflags.split(b'|'):
if flag in validflags:
finalflags |= validflags[flag]
else:
finalflags |= int(flag)
if payload.startswith(b'cbor:'):
payload = cbor.dumps(stringutil.evalpythonliteral(payload[5:]),
canonical=True)
else:
payload = stringutil.unescapestr(payload)
return makeframe(requestid=requestid, streamid=streamid,
streamflags=finalstreamflags, typeid=frametype,
flags=finalflags, payload=payload)
def parseheader(data):
"""Parse a unified framing protocol frame header from a buffer.
The header is expected to be in the buffer at offset 0 and the
buffer is expected to be large enough to hold a full header.
"""
# 24 bits payload length (little endian)
# 16 bits request ID
# 8 bits stream ID
# 8 bits stream flags
# 4 bits frame type
# 4 bits frame flags
# ... payload
framelength = data[0] + 256 * data[1] + 16384 * data[2]
requestid, streamid, streamflags = struct.unpack_from(r'<HBB', data, 3)
typeflags = data[7]
frametype = (typeflags & 0xf0) >> 4
frameflags = typeflags & 0x0f
return frameheader(framelength, requestid, streamid, streamflags,
frametype, frameflags)
def readframe(fh):
"""Read a unified framing protocol frame from a file object.
Returns a 3-tuple of (type, flags, payload) for the decoded frame or
None if no frame is available. May raise if a malformed frame is
seen.
"""
header = bytearray(FRAME_HEADER_SIZE)
readcount = fh.readinto(header)
if readcount == 0:
return None
if readcount != FRAME_HEADER_SIZE:
raise error.Abort(_('received incomplete frame: got %d bytes: %s') %
(readcount, header))
h = parseheader(header)
payload = fh.read(h.length)
if len(payload) != h.length:
raise error.Abort(_('frame length error: expected %d; got %d') %
(h.length, len(payload)))
return frame(h.requestid, h.streamid, h.streamflags, h.typeid, h.flags,
payload)
def createcommandframes(stream, requestid, cmd, args, datafh=None,
maxframesize=DEFAULT_MAX_FRAME_SIZE):
"""Create frames necessary to transmit a request to run a command.
This is a generator of bytearrays. Each item represents a frame
ready to be sent over the wire to a peer.
"""
data = {b'name': cmd}
if args:
data[b'args'] = args
data = cbor.dumps(data, canonical=True)
offset = 0
while True:
flags = 0
# Must set new or continuation flag.
if not offset:
flags |= FLAG_COMMAND_REQUEST_NEW
else:
flags |= FLAG_COMMAND_REQUEST_CONTINUATION
# Data frames is set on all frames.
if datafh:
flags |= FLAG_COMMAND_REQUEST_EXPECT_DATA
payload = data[offset:offset + maxframesize]
offset += len(payload)
if len(payload) == maxframesize and offset < len(data):
flags |= FLAG_COMMAND_REQUEST_MORE_FRAMES
yield stream.makeframe(requestid=requestid,
typeid=FRAME_TYPE_COMMAND_REQUEST,
flags=flags,
payload=payload)
if not (flags & FLAG_COMMAND_REQUEST_MORE_FRAMES):
break
if datafh:
while True:
data = datafh.read(DEFAULT_MAX_FRAME_SIZE)
done = False
if len(data) == DEFAULT_MAX_FRAME_SIZE:
flags = FLAG_COMMAND_DATA_CONTINUATION
else:
flags = FLAG_COMMAND_DATA_EOS
assert datafh.read(1) == b''
done = True
yield stream.makeframe(requestid=requestid,
typeid=FRAME_TYPE_COMMAND_DATA,
flags=flags,
payload=data)
if done:
break
def createcommandresponseframesfrombytes(stream, requestid, data,
maxframesize=DEFAULT_MAX_FRAME_SIZE):
"""Create a raw frame to send a bytes response from static bytes input.
Returns a generator of bytearrays.
"""
# Automatically send the overall CBOR response map.
overall = cbor.dumps({b'status': b'ok'}, canonical=True)
if len(overall) > maxframesize:
raise error.ProgrammingError('not yet implemented')
# Simple case where we can fit the full response in a single frame.
if len(overall) + len(data) <= maxframesize:
flags = FLAG_COMMAND_RESPONSE_EOS
yield stream.makeframe(requestid=requestid,
typeid=FRAME_TYPE_COMMAND_RESPONSE,
flags=flags,
payload=overall + data)
return
# It's easier to send the overall CBOR map in its own frame than to track
# offsets.
yield stream.makeframe(requestid=requestid,
typeid=FRAME_TYPE_COMMAND_RESPONSE,
flags=FLAG_COMMAND_RESPONSE_CONTINUATION,
payload=overall)
offset = 0
while True:
chunk = data[offset:offset + maxframesize]
offset += len(chunk)
done = offset == len(data)
if done:
flags = FLAG_COMMAND_RESPONSE_EOS
else:
flags = FLAG_COMMAND_RESPONSE_CONTINUATION
yield stream.makeframe(requestid=requestid,
typeid=FRAME_TYPE_COMMAND_RESPONSE,
flags=flags,
payload=chunk)
if done:
break
def createerrorframe(stream, requestid, msg, protocol=False, application=False):
# TODO properly handle frame size limits.
assert len(msg) <= DEFAULT_MAX_FRAME_SIZE
flags = 0
if protocol:
flags |= FLAG_ERROR_RESPONSE_PROTOCOL
if application:
flags |= FLAG_ERROR_RESPONSE_APPLICATION
yield stream.makeframe(requestid=requestid,
typeid=FRAME_TYPE_ERROR_RESPONSE,
flags=flags,
payload=msg)
def createtextoutputframe(stream, requestid, atoms,
maxframesize=DEFAULT_MAX_FRAME_SIZE):
"""Create a text output frame to render text to people.
``atoms`` is a 3-tuple of (formatting string, args, labels).
The formatting string contains ``%s`` tokens to be replaced by the
corresponding indexed entry in ``args``. ``labels`` is an iterable of
formatters to be applied at rendering time. In terms of the ``ui``
class, each atom corresponds to a ``ui.write()``.
"""
atomdicts = []
for (formatting, args, labels) in atoms:
# TODO look for localstr, other types here?
if not isinstance(formatting, bytes):
raise ValueError('must use bytes formatting strings')
for arg in args:
if not isinstance(arg, bytes):
raise ValueError('must use bytes for arguments')
for label in labels:
if not isinstance(label, bytes):
raise ValueError('must use bytes for labels')
# Formatting string must be ASCII.
formatting = formatting.decode(r'ascii', r'replace').encode(r'ascii')
# Arguments must be UTF-8.
args = [a.decode(r'utf-8', r'replace').encode(r'utf-8') for a in args]
# Labels must be ASCII.
labels = [l.decode(r'ascii', r'strict').encode(r'ascii')
for l in labels]
atom = {b'msg': formatting}
if args:
atom[b'args'] = args
if labels:
atom[b'labels'] = labels
atomdicts.append(atom)
payload = cbor.dumps(atomdicts, canonical=True)
if len(payload) > maxframesize:
raise ValueError('cannot encode data in a single frame')
yield stream.makeframe(requestid=requestid,
typeid=FRAME_TYPE_TEXT_OUTPUT,
flags=0,
payload=payload)
class stream(object):
"""Represents a logical unidirectional series of frames."""
def __init__(self, streamid, active=False):
self.streamid = streamid
self._active = active
def makeframe(self, requestid, typeid, flags, payload):
"""Create a frame to be sent out over this stream.
Only returns the frame instance. Does not actually send it.
"""
streamflags = 0
if not self._active:
streamflags |= STREAM_FLAG_BEGIN_STREAM
self._active = True
return makeframe(requestid, self.streamid, streamflags, typeid, flags,
payload)
def ensureserverstream(stream):
if stream.streamid % 2:
raise error.ProgrammingError('server should only write to even '
'numbered streams; %d is not even' %
stream.streamid)
class serverreactor(object):
"""Holds state of a server handling frame-based protocol requests.
This class is the "brain" of the unified frame-based protocol server
component. While the protocol is stateless from the perspective of
requests/commands, something needs to track which frames have been
received, what frames to expect, etc. This class is that thing.
Instances are modeled as a state machine of sorts. Instances are also
reactionary to external events. The point of this class is to encapsulate
the state of the connection and the exchange of frames, not to perform
work. Instead, callers tell this class when something occurs, like a
frame arriving. If that activity is worthy of a follow-up action (say
*run a command*), the return value of that handler will say so.
I/O and CPU intensive operations are purposefully delegated outside of
this class.
Consumers are expected to tell instances when events occur. They do so by
calling the various ``on*`` methods. These methods return a 2-tuple
describing any follow-up action(s) to take. The first element is the
name of an action to perform. The second is a data structure (usually
a dict) specific to that action that contains more information. e.g.
if the server wants to send frames back to the client, the data structure
will contain a reference to those frames.
Valid actions that consumers can be instructed to take are:
sendframes
Indicates that frames should be sent to the client. The ``framegen``
key contains a generator of frames that should be sent. The server
assumes that all frames are sent to the client.
error
Indicates that an error occurred. Consumer should probably abort.
runcommand
Indicates that the consumer should run a wire protocol command. Details
of the command to run are given in the data structure.
wantframe
Indicates that nothing of interest happened and the server is waiting on
more frames from the client before anything interesting can be done.
noop
Indicates no additional action is required.
Known Issues
------------
There are no limits to the number of partially received commands or their
size. A malicious client could stream command request data and exhaust the
server's memory.
Partially received commands are not acted upon when end of input is
reached. Should the server error if it receives a partial request?
Should the client send a message to abort a partially transmitted request
to facilitate graceful shutdown?
Active requests that haven't been responded to aren't tracked. This means
that if we receive a command and instruct its dispatch, another command
with its request ID can come in over the wire and there will be a race
between who responds to what.
"""
def __init__(self, deferoutput=False):
"""Construct a new server reactor.
``deferoutput`` can be used to indicate that no output frames should be
instructed to be sent until input has been exhausted. In this mode,
events that would normally generate output frames (such as a command
response being ready) will instead defer instructing the consumer to
send those frames. This is useful for half-duplex transports where the
sender cannot receive until all data has been transmitted.
"""
self._deferoutput = deferoutput
self._state = 'idle'
self._nextoutgoingstreamid = 2
self._bufferedframegens = []
# stream id -> stream instance for all active streams from the client.
self._incomingstreams = {}
self._outgoingstreams = {}
# request id -> dict of commands that are actively being received.
self._receivingcommands = {}
# Request IDs that have been received and are actively being processed.
# Once all output for a request has been sent, it is removed from this
# set.
self._activecommands = set()
def onframerecv(self, frame):
"""Process a frame that has been received off the wire.
Returns a dict with an ``action`` key that details what action,
if any, the consumer should take next.
"""
if not frame.streamid % 2:
self._state = 'errored'
return self._makeerrorresult(
_('received frame with even numbered stream ID: %d') %
frame.streamid)
if frame.streamid not in self._incomingstreams:
if not frame.streamflags & STREAM_FLAG_BEGIN_STREAM:
self._state = 'errored'
return self._makeerrorresult(
_('received frame on unknown inactive stream without '
'beginning of stream flag set'))
self._incomingstreams[frame.streamid] = stream(frame.streamid)
if frame.streamflags & STREAM_FLAG_ENCODING_APPLIED:
# TODO handle decoding frames
self._state = 'errored'
raise error.ProgrammingError('support for decoding stream payloads '
'not yet implemented')
if frame.streamflags & STREAM_FLAG_END_STREAM:
del self._incomingstreams[frame.streamid]
handlers = {
'idle': self._onframeidle,
'command-receiving': self._onframecommandreceiving,
'errored': self._onframeerrored,
}
meth = handlers.get(self._state)
if not meth:
raise error.ProgrammingError('unhandled state: %s' % self._state)
return meth(frame)
def oncommandresponseready(self, stream, requestid, data):
"""Signal that a bytes response is ready to be sent to the client.
The raw bytes response is passed as an argument.
"""
ensureserverstream(stream)
def sendframes():
for frame in createcommandresponseframesfrombytes(stream, requestid,
data):
yield frame
self._activecommands.remove(requestid)
result = sendframes()
if self._deferoutput:
self._bufferedframegens.append(result)
return 'noop', {}
else:
return 'sendframes', {
'framegen': result,
}
def oninputeof(self):
"""Signals that end of input has been received.
No more frames will be received. All pending activity should be
completed.
"""
# TODO should we do anything about in-flight commands?
if not self._deferoutput or not self._bufferedframegens:
return 'noop', {}
# If we buffered all our responses, emit those.
def makegen():
for gen in self._bufferedframegens:
for frame in gen:
yield frame
return 'sendframes', {
'framegen': makegen(),
}
def onapplicationerror(self, stream, requestid, msg):
ensureserverstream(stream)
return 'sendframes', {
'framegen': createerrorframe(stream, requestid, msg,
application=True),
}
def makeoutputstream(self):
"""Create a stream to be used for sending data to the client."""
streamid = self._nextoutgoingstreamid
self._nextoutgoingstreamid += 2
s = stream(streamid)
self._outgoingstreams[streamid] = s
return s
def _makeerrorresult(self, msg):
return 'error', {
'message': msg,
}
def _makeruncommandresult(self, requestid):
entry = self._receivingcommands[requestid]
if not entry['requestdone']:
self._state = 'errored'
raise error.ProgrammingError('should not be called without '
'requestdone set')
del self._receivingcommands[requestid]
if self._receivingcommands:
self._state = 'command-receiving'
else:
self._state = 'idle'
# Decode the payloads as CBOR.
entry['payload'].seek(0)
request = cbor.load(entry['payload'])
if b'name' not in request:
self._state = 'errored'
return self._makeerrorresult(
_('command request missing "name" field'))
if b'args' not in request:
request[b'args'] = {}
assert requestid not in self._activecommands
self._activecommands.add(requestid)
return 'runcommand', {
'requestid': requestid,
'command': request[b'name'],
'args': request[b'args'],
'data': entry['data'].getvalue() if entry['data'] else None,
}
def _makewantframeresult(self):
return 'wantframe', {
'state': self._state,
}
def _validatecommandrequestframe(self, frame):
new = frame.flags & FLAG_COMMAND_REQUEST_NEW
continuation = frame.flags & FLAG_COMMAND_REQUEST_CONTINUATION
if new and continuation:
self._state = 'errored'
return self._makeerrorresult(
_('received command request frame with both new and '
'continuation flags set'))
if not new and not continuation:
self._state = 'errored'
return self._makeerrorresult(
_('received command request frame with neither new nor '
'continuation flags set'))
def _onframeidle(self, frame):
# The only frame type that should be received in this state is a
# command request.
if frame.typeid != FRAME_TYPE_COMMAND_REQUEST:
self._state = 'errored'
return self._makeerrorresult(
_('expected command request frame; got %d') % frame.typeid)
res = self._validatecommandrequestframe(frame)
if res:
return res
if frame.requestid in self._receivingcommands:
self._state = 'errored'
return self._makeerrorresult(
_('request with ID %d already received') % frame.requestid)
if frame.requestid in self._activecommands:
self._state = 'errored'
return self._makeerrorresult(
_('request with ID %d is already active') % frame.requestid)
new = frame.flags & FLAG_COMMAND_REQUEST_NEW
moreframes = frame.flags & FLAG_COMMAND_REQUEST_MORE_FRAMES
expectingdata = frame.flags & FLAG_COMMAND_REQUEST_EXPECT_DATA
if not new:
self._state = 'errored'
return self._makeerrorresult(
_('received command request frame without new flag set'))
payload = util.bytesio()
payload.write(frame.payload)
self._receivingcommands[frame.requestid] = {
'payload': payload,
'data': None,
'requestdone': not moreframes,
'expectingdata': bool(expectingdata),
}
# This is the final frame for this request. Dispatch it.
if not moreframes and not expectingdata:
return self._makeruncommandresult(frame.requestid)
assert moreframes or expectingdata
self._state = 'command-receiving'
return self._makewantframeresult()
def _onframecommandreceiving(self, frame):
if frame.typeid == FRAME_TYPE_COMMAND_REQUEST:
# Process new command requests as such.
if frame.flags & FLAG_COMMAND_REQUEST_NEW:
return self._onframeidle(frame)
res = self._validatecommandrequestframe(frame)
if res:
return res
# All other frames should be related to a command that is currently
# receiving but is not active.
if frame.requestid in self._activecommands:
self._state = 'errored'
return self._makeerrorresult(
_('received frame for request that is still active: %d') %
frame.requestid)
if frame.requestid not in self._receivingcommands:
self._state = 'errored'
return self._makeerrorresult(
_('received frame for request that is not receiving: %d') %
frame.requestid)
entry = self._receivingcommands[frame.requestid]
if frame.typeid == FRAME_TYPE_COMMAND_REQUEST:
moreframes = frame.flags & FLAG_COMMAND_REQUEST_MORE_FRAMES
expectingdata = bool(frame.flags & FLAG_COMMAND_REQUEST_EXPECT_DATA)
if entry['requestdone']:
self._state = 'errored'
return self._makeerrorresult(
_('received command request frame when request frames '
'were supposedly done'))
if expectingdata != entry['expectingdata']:
self._state = 'errored'
return self._makeerrorresult(
_('mismatch between expect data flag and previous frame'))
entry['payload'].write(frame.payload)
if not moreframes:
entry['requestdone'] = True
if not moreframes and not expectingdata:
return self._makeruncommandresult(frame.requestid)
return self._makewantframeresult()
elif frame.typeid == FRAME_TYPE_COMMAND_DATA:
if not entry['expectingdata']:
self._state = 'errored'
return self._makeerrorresult(_(
'received command data frame for request that is not '
'expecting data: %d') % frame.requestid)
if entry['data'] is None:
entry['data'] = util.bytesio()
return self._handlecommanddataframe(frame, entry)
else:
self._state = 'errored'
return self._makeerrorresult(_(
'received unexpected frame type: %d') % frame.typeid)
def _handlecommanddataframe(self, frame, entry):
assert frame.typeid == FRAME_TYPE_COMMAND_DATA
# TODO support streaming data instead of buffering it.
entry['data'].write(frame.payload)
if frame.flags & FLAG_COMMAND_DATA_CONTINUATION:
return self._makewantframeresult()
elif frame.flags & FLAG_COMMAND_DATA_EOS:
entry['data'].seek(0)
return self._makeruncommandresult(frame.requestid)
else:
self._state = 'errored'
return self._makeerrorresult(_('command data frame without '
'flags'))
def _onframeerrored(self, frame):
return self._makeerrorresult(_('server already errored'))
class commandrequest(object):
"""Represents a request to run a command."""
def __init__(self, requestid, name, args, datafh=None):
self.requestid = requestid
self.name = name
self.args = args
self.datafh = datafh
self.state = 'pending'
class clientreactor(object):
"""Holds state of a client issuing frame-based protocol requests.
This is like ``serverreactor`` but for client-side state.
Each instance is bound to the lifetime of a connection. For persistent
connection transports using e.g. TCP sockets and speaking the raw
framing protocol, there will be a single instance for the lifetime of
the TCP socket. For transports where there are multiple discrete
interactions (say tunneled within in HTTP request), there will be a
separate instance for each distinct interaction.
"""
def __init__(self, hasmultiplesend=False, buffersends=True):
"""Create a new instance.
``hasmultiplesend`` indicates whether multiple sends are supported
by the transport. When True, it is possible to send commands immediately
instead of buffering until the caller signals an intent to finish a
send operation.
``buffercommands`` indicates whether sends should be buffered until the
last request has been issued.
"""
self._hasmultiplesend = hasmultiplesend
self._buffersends = buffersends
self._canissuecommands = True
self._cansend = True
self._nextrequestid = 1
# We only support a single outgoing stream for now.
self._outgoingstream = stream(1)
self._pendingrequests = collections.deque()
self._activerequests = {}
self._incomingstreams = {}
def callcommand(self, name, args, datafh=None):
"""Request that a command be executed.
Receives the command name, a dict of arguments to pass to the command,
and an optional file object containing the raw data for the command.
Returns a 3-tuple of (request, action, action data).
"""
if not self._canissuecommands:
raise error.ProgrammingError('cannot issue new commands')
requestid = self._nextrequestid
self._nextrequestid += 2
request = commandrequest(requestid, name, args, datafh=datafh)
if self._buffersends:
self._pendingrequests.append(request)
return request, 'noop', {}
else:
if not self._cansend:
raise error.ProgrammingError('sends cannot be performed on '
'this instance')
if not self._hasmultiplesend:
self._cansend = False
self._canissuecommands = False
return request, 'sendframes', {
'framegen': self._makecommandframes(request),
}
def flushcommands(self):
"""Request that all queued commands be sent.
If any commands are buffered, this will instruct the caller to send
them over the wire. If no commands are buffered it instructs the client
to no-op.
If instances aren't configured for multiple sends, no new command
requests are allowed after this is called.
"""
if not self._pendingrequests:
return 'noop', {}
if not self._cansend:
raise error.ProgrammingError('sends cannot be performed on this '
'instance')
# If the instance only allows sending once, mark that we have fired
# our one shot.
if not self._hasmultiplesend:
self._canissuecommands = False
self._cansend = False
def makeframes():
while self._pendingrequests:
request = self._pendingrequests.popleft()
for frame in self._makecommandframes(request):
yield frame
return 'sendframes', {
'framegen': makeframes(),
}
def _makecommandframes(self, request):
"""Emit frames to issue a command request.
As a side-effect, update request accounting to reflect its changed
state.
"""
self._activerequests[request.requestid] = request
request.state = 'sending'
res = createcommandframes(self._outgoingstream,
request.requestid,
request.name,
request.args,
request.datafh)
for frame in res:
yield frame
request.state = 'sent'
def onframerecv(self, frame):
"""Process a frame that has been received off the wire.
Returns a 2-tuple of (action, meta) describing further action the
caller needs to take as a result of receiving this frame.
"""
if frame.streamid % 2:
return 'error', {
'message': (
_('received frame with odd numbered stream ID: %d') %
frame.streamid),
}
if frame.streamid not in self._incomingstreams:
if not frame.streamflags & STREAM_FLAG_BEGIN_STREAM:
return 'error', {
'message': _('received frame on unknown stream '
'without beginning of stream flag set'),
}
self._incomingstreams[frame.streamid] = stream(frame.streamid)
if frame.streamflags & STREAM_FLAG_ENCODING_APPLIED:
raise error.ProgrammingError('support for decoding stream '
'payloads not yet implemneted')
if frame.streamflags & STREAM_FLAG_END_STREAM:
del self._incomingstreams[frame.streamid]
if frame.requestid not in self._activerequests:
return 'error', {
'message': (_('received frame for inactive request ID: %d') %
frame.requestid),
}
request = self._activerequests[frame.requestid]
request.state = 'receiving'
handlers = {
FRAME_TYPE_COMMAND_RESPONSE: self._oncommandresponseframe,
}
meth = handlers.get(frame.typeid)
if not meth:
raise error.ProgrammingError('unhandled frame type: %d' %
frame.typeid)
return meth(request, frame)
def _oncommandresponseframe(self, request, frame):
if frame.flags & FLAG_COMMAND_RESPONSE_EOS:
request.state = 'received'
del self._activerequests[request.requestid]
return 'responsedata', {
'request': request,
'expectmore': frame.flags & FLAG_COMMAND_RESPONSE_CONTINUATION,
'eos': frame.flags & FLAG_COMMAND_RESPONSE_EOS,
'data': frame.payload,
}