Source code for bokeh.protocol.message

# Copyright (c) 2012 - 2024, 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 (

# 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

    from typing_extensions import NotRequired, TypeAlias

    from ..client.websocket import WebSocketClientConnectionWrapper

# Globals and constants

__all__ = (

# 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):

[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)
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