Source code for bokeh.protocol.message

#-----------------------------------------------------------------------------
# Copyright (c) Anaconda, Inc., and Bokeh Contributors.
# All rights reserved.
#
# The full license is in the file LICENSE.txt, distributed with this software.
#-----------------------------------------------------------------------------
''' Provide a base class for all Bokeh Server Protocol message types.

Boker messages are comprised of a sequence of JSON fragments. Specified as
Python JSON-like data, messages have the general form:

.. code-block:: python

    [
        # these are required
        b'{header}',        # serialized header dict
        b'{metadata}',      # serialized metadata dict
        b'{content}',       # serialized content dict

        # these are optional, and come in pairs; header contains num_buffers
        b'{buf_header}',    # serialized buffer header dict
        b'array'            # raw buffer payload data
        ...
    ]

The ``header`` fragment will have the form:

.. code-block:: python

    header = {
        # these are required
        'msgid'       : <str> # a unique id for the message
        'msgtype'     : <str> # a message type, e.g. 'ACK', 'PATCH-DOC', etc

        # these are optional
        'num_buffers' : <int> # the number of additional buffers, if any
    }

The ``metadata`` fragment may contain any arbitrary information. It is not
processed by Bokeh for any purpose, but may be useful for external
monitoring or instrumentation tools.

The ``content`` fragment is defined by the specific message type.

'''

#-----------------------------------------------------------------------------
# Boilerplate
#-----------------------------------------------------------------------------
from __future__ import annotations

import logging # isort:skip
log = logging.getLogger(__name__)

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------

# Standard library imports
import json
from typing import (
    TYPE_CHECKING,
    Any,
    ClassVar,
    Generic,
    TypeAlias,
    TypedDict,
    TypeVar,
)

# Bokeh imports
import bokeh.util.serialization as bkserial

# Bokeh imports
from ..core.json_encoder import serialize_json
from ..core.serialization import Buffer, Serialized
from ..core.types import ID
from .exceptions import MessageError, ProtocolError

if TYPE_CHECKING:
    from typing_extensions import NotRequired

    from ..client.websocket import WebSocketClientConnectionWrapper

#-----------------------------------------------------------------------------
# Globals and constants
#-----------------------------------------------------------------------------

__all__ = (
    'Message',
)

#-----------------------------------------------------------------------------
# General API
#-----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# Dev API
#-----------------------------------------------------------------------------

class Header(TypedDict):
    msgid: ID
    msgtype: str
    reqid: NotRequired[ID]
    num_buffers: NotRequired[int]

class BufferHeader(TypedDict):
    id: ID

Content = TypeVar("Content")

Metadata: TypeAlias = dict[str, Any]

BufferRef: TypeAlias = tuple[BufferHeader, bytes]

class Empty(TypedDict):
    pass


[docs]
class Message(Generic[Content]):
    ''' The Message base class encapsulates creating, assembling, and
    validating the integrity of Bokeh Server messages. Additionally, it
    provide hooks

    '''

    msgtype: ClassVar[str]

    _header: Header
    _header_json: str | None

    _content: Content
    _content_json: str | None

    _metadata: Metadata
    _metadata_json: str | None

    _buffers: list[Buffer]


[docs]
    def __init__(self, header: Header, metadata: Metadata, content: Content) -> None:
        ''' Initialize a new message from header, metadata, and content
        dictionaries.

        To assemble a message from existing JSON fragments, use the
        ``assemble`` method.

        To create new messages with automatically generated headers,
        use subclass ``create`` methods.

        Args:
            header (JSON-like) :

            metadata (JSON-like) :

            content (JSON-like) :

        '''
        self.header = header
        self.metadata = metadata
        self.content = content
        self._buffers = []


    def __repr__(self) -> str:
        return f"Message {self.msgtype!r} content: {self.content!r}"


[docs]
    @classmethod
    def assemble(cls, header_json: str, metadata_json: str, content_json: str) -> Message[Content]:
        ''' Creates a new message, assembled from JSON fragments.

        Args:
            header_json (``JSON``) :

            metadata_json (``JSON``) :

            content_json (``JSON``) :

        Returns:
            Message subclass

        Raises:
            MessageError

        '''

        try:
            header = json.loads(header_json)
        except ValueError:
            raise MessageError("header could not be decoded")

        try:
            metadata = json.loads(metadata_json)
        except ValueError:
            raise MessageError("metadata could not be decoded")

        try:
            content = json.loads(content_json)
        except ValueError:
            raise MessageError("content could not be decoded")

        msg = cls(header, metadata, content)

        msg._header_json = header_json
        msg._metadata_json = metadata_json
        msg._content_json = content_json

        return msg



[docs]
    def add_buffer(self, buffer: Buffer) -> None:
        ''' Associate a buffer header and payload with this message.

        Args:
            buf_header (``JSON``) : a buffer header
            buf_payload (``JSON`` or bytes) : a buffer payload

        Returns:
            None

        Raises:
            MessageError

        '''
        if 'num_buffers' in self._header:
            self._header['num_buffers'] += 1
        else:
            self._header['num_buffers'] = 1

        self._header_json = None
        self._buffers.append(buffer)



[docs]
    def assemble_buffer(self, buf_header: BufferHeader, buf_payload: bytes) -> None:
        ''' Add a buffer header and payload that we read from the socket.

        This differs from add_buffer() because we're validating vs.
        the header's num_buffers, instead of filling in the header.

        Args:
            buf_header (``JSON``) : a buffer header
            buf_payload (``JSON`` or bytes) : a buffer payload

        Returns:
            None

        Raises:
            ProtocolError
        '''
        num_buffers = self.header.get("num_buffers", 0)
        if num_buffers <= len(self._buffers):
            raise ProtocolError(f"too many buffers received expecting {num_buffers}")
        self._buffers.append(Buffer(buf_header["id"], buf_payload))



[docs]
    async def write_buffers(self, conn: WebSocketClientConnectionWrapper, locked: bool = True) -> int:
        ''' Write any buffer headers and payloads to the given connection.

        Args:
            conn (object) :
                May be any object with a ``write_message`` method. Typically,
                a Tornado ``WSHandler`` or ``WebSocketClientConnection``

            locked (bool) :

        Returns:
            int : number of bytes sent

        '''
        if conn is None:
            raise ValueError("Cannot write_buffers to connection None")
        sent = 0
        for buffer in self._buffers:
            header = json.dumps(buffer.ref)
            payload = buffer.to_bytes()
            await conn.write_message(header, locked=locked)
            await conn.write_message(payload, binary=True, locked=locked)
            sent += len(header) + len(payload)
        return sent



[docs]
    @classmethod
    def create_header(cls, request_id: ID | None = None) -> Header:
        ''' Return a message header fragment dict.

        Args:
            request_id (str or None) :
                Message ID of the message this message replies to

        Returns:
            dict : a message header

        '''
        header = Header(
            msgid   = bkserial.make_id(),
            msgtype = cls.msgtype,
        )
        if request_id is not None:
            header['reqid'] = request_id
        return header



[docs]
    async def send(self, conn: WebSocketClientConnectionWrapper) -> int:
        ''' Send the message on the given connection.

        Args:
            conn (WebSocketHandler) : a WebSocketHandler to send messages

        Returns:
            int : number of bytes sent

        '''
        if conn is None:
            raise ValueError("Cannot send to connection None")

        with await conn.write_lock.acquire():
            sent = 0

            await conn.write_message(self.header_json, locked=False)
            sent += len(self.header_json)

            # uncomment this to make it a lot easier to reproduce lock-related bugs
            #await asyncio.sleep(0.1)

            await conn.write_message(self.metadata_json, locked=False)
            sent += len(self.metadata_json)

            # uncomment this to make it a lot easier to reproduce lock-related bugs
            #await asyncio.sleep(0.1)

            await conn.write_message(self.content_json, locked=False)
            sent += len(self.content_json)

            sent += await self.write_buffers(conn, locked=False)

            return sent


    @property
    def complete(self) -> bool:
        ''' Returns whether all required parts of a message are present.

        Returns:
            bool : True if the message is complete, False otherwise

        '''
        return self.header is not None and \
               self.metadata is not None and \
               self.content is not None and \
               self.header.get('num_buffers', 0) == len(self._buffers)

    @property
    def payload(self) -> Serialized[Content]:
        return Serialized(self.content, self.buffers)

    # header fragment properties

    @property
    def header(self) -> Header:
        return self._header

    @header.setter
    def header(self, value: Header) -> None:
        self._header = value
        self._header_json = None

    @property
    def header_json(self) -> str:
        if not self._header_json:
            self._header_json = json.dumps(self.header)
        return self._header_json

    # content fragment properties

    @property
    def content(self) -> Content:
        return self._content

    @content.setter
    def content(self, value: Content) -> None:
        self._content = value
        self._content_json = None

    @property
    def content_json(self) -> str:
        if not self._content_json:
            self._content_json = serialize_json(self.payload)
        return self._content_json

    # metadata fragment properties

    @property
    def metadata(self) -> Metadata:
        return self._metadata

    @metadata.setter
    def metadata(self, value: Metadata) -> None:
        self._metadata = value
        self._metadata_json = None

    @property
    def metadata_json(self) -> str:
        if not self._metadata_json:
            self._metadata_json = json.dumps(self.metadata)
        return self._metadata_json

    # buffer properties

    @property
    def buffers(self) -> list[Buffer]:
        return list(self._buffers)


#-----------------------------------------------------------------------------
# Private API
#-----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# Code
#-----------------------------------------------------------------------------