Re: [PATCH v4 3/7] python/aqmp-tui: Add AQMP TUI draft

[John Snow <jsnow@redhat.com>]

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On Thu, Aug 19, 2021 at 1:39 PM G S Niteesh Babu <niteesh.gs@gmail.com>
wrote:

> Added a draft of AQMP TUI.
>
> Implements the follwing basic features:
> 1) Command transmission/reception.
> 2) Shows events asynchronously.
> 3) Shows server status in the bottom status bar.
>
> Also added type annotations and necessary pylint,
> mypy configurations
>
> Signed-off-by: G S Niteesh Babu <niteesh.gs@gmail.com>
> ---
>  python/qemu/aqmp/aqmp_tui.py | 566 +++++++++++++++++++++++++++++++++++
>  python/setup.cfg             |  15 +-
>  2 files changed, 579 insertions(+), 2 deletions(-)
>  create mode 100644 python/qemu/aqmp/aqmp_tui.py
>
> diff --git a/python/qemu/aqmp/aqmp_tui.py b/python/qemu/aqmp/aqmp_tui.py
> new file mode 100644
> index 0000000000..12c9c4162a
> --- /dev/null
> +++ b/python/qemu/aqmp/aqmp_tui.py
> @@ -0,0 +1,566 @@
> +# Copyright (c) 2021
> +#
> +# Authors:
> +#  Niteesh Babu G S <niteesh.gs@gmail.com>
> +#
> +# This work is licensed under the terms of the GNU GPL, version 2 or
> +# later.  See the COPYING file in the top-level directory.
> +"""
> +AQMP TUI
> +
> +AQMP TUI is an asynchronous interface built on top the of the AQMP
> library.
> +It is the successor of QMP-shell and is bought-in as a replacement for it.
> +
> +Example Usage: aqmp-tui <SOCKET | TCP IP:PORT>
> +Full Usage: aqmp-tui --help
> +"""
> +
> +import argparse
> +import asyncio
> +import logging
> +from logging import Handler, LogRecord
> +import signal
> +from typing import (
> +    List,
> +    Optional,
> +    Tuple,
> +    Type,
> +    Union,
> +    cast,
> +)
> +
> +import urwid
> +import urwid_readline
> +
> +from ..qmp import QEMUMonitorProtocol, QMPBadPortError
> +from .message import DeserializationError, Message, UnexpectedTypeError
> +from .protocol import ConnectError
> +from .qmp_client import ExecInterruptedError, QMPClient
> +from .util import create_task, pretty_traceback
> +
> +
> +# The name of the signal that is used to update the history list
> +UPDATE_MSG: str = 'UPDATE_MSG'
> +
> +
> +def format_json(msg: str) -> str:
> +    """
> +    Formats given multi-line JSON message into a single-line message.
> +    Converting into single line is more asthetically pleasing when looking
> +    along with error messages.
> +
> +    Eg:
> +    Input:
> +          [ 1,
> +            true,
> +            3 ]
> +    The above input is not a valid QMP message and produces the following
> error
> +    "QMP message is not a JSON object."
> +    When displaying this in TUI in multiline mode we get
> +
> +        [ 1,
> +          true,
> +          3 ]: QMP message is not a JSON object.
> +
> +    whereas in singleline mode we get the following
> +
> +        [1, true, 3]: QMP message is not a JSON object.
> +
> +    The single line mode is more asthetically pleasing.
> +
> +    :param msg:
> +        The message to formatted into single line.
> +
> +    :return: Formatted singleline message.
> +
> +    NOTE: We cannot use the JSON module here because it is only capable of
> +    format valid JSON messages. But here the goal is to also format
> invalid
> +    JSON messages.
> +    """
> +    msg = msg.replace('\n', '')
> +    words = msg.split(' ')
> +    words = [word for word in words if word != '']
> +    return ' '.join(words)
> +
> +
> +def has_tui_handler(logger: logging.Logger,
> +                    handler_type: Type[Handler]) -> bool:
> +    """
> +    The Logger class has no interface to check if a certain type of
> handler is
> +    installed or not. So we provide an interface to do so.
> +
> +    :param logger:
> +        Logger object
> +    :param handler_type:
> +        The type of the handler to be checked.
> +
> +    :return: returns True if handler of type `handler_type` is installed
> else
> +             False.
> +    """
> +    handlers = logger.handlers
> +    for handler in handlers:
> +        if isinstance(handler, handler_type):
> +            return True
> +    return False
> +
> +
> +class App(QMPClient):
> +    """
> +    Implements the AQMP TUI.
> +
> +    Initializes the widgets and starts the urwid event loop.
> +    """
> +    def __init__(self, address: Union[str, Tuple[str, int]]) -> None:
> +        """
> +        Initializes the TUI.
> +
> +        :param address:
> +            Address of the server to connect to.
> +        """
> +        urwid.register_signal(type(self), UPDATE_MSG)
> +        self.window = Window(self)
> +        self.address = address
> +        self.aloop: Optional[asyncio.AbstractEventLoop] = None
> +        super().__init__()
> +
> +    def add_to_history(self, msg: str, level: Optional[str] = None) ->
> None:
> +        """
> +        Appends the msg to the history list.
> +
> +        :param msg:
> +            The raw message to be appended in string type.
> +        """
> +        urwid.emit_signal(self, UPDATE_MSG, msg, level)
> +
> +    def _cb_outbound(self, msg: Message) -> Message:
> +        """
> +        Callback: outbound message hook.
> +
> +        Appends the outgoing messages to the history box.
> +
> +        :param msg: raw outbound message.
> +        :return: final outbound message.
> +        """
> +        str_msg = str(msg)
> +
> +        if not has_tui_handler(logging.getLogger(), TUILogHandler):
> +            logging.debug('Request: %s', str_msg)
> +        self.add_to_history('<-- ' + str_msg)
> +        return msg
> +
> +    def _cb_inbound(self, msg: Message) -> Message:
> +        """
> +        Callback: outbound message hook.
> +
> +        Appends the incoming messages to the history box.
> +
> +        :param msg: raw inbound message.
> +        :return: final inbound message.
> +        """
> +        str_msg = str(msg)
> +
> +        if not has_tui_handler(logging.getLogger(), TUILogHandler):
> +            logging.debug('Request: %s', str_msg)
> +        self.add_to_history('--> ' + str_msg)
> +        return msg
> +
> +    def handle_event(self, event: Message) -> None:
> +        """
> +        Handles the event.
> +
> +        :param event:
> +            The event to be handled.
> +        """
> +        # TODO: Consider all states present in qapi/run-state.json
> +        if event['event'] == 'SHUTDOWN':
> +            self._set_status('[Server Shutdown]')
> +
> +    async def wait_for_events(self) -> None:
> +        """
> +        This coroutine continously waits for events and dispatches them.
> +        """
> +        async for event in self.events:
> +            self.handle_event(event)
> +
> +    async def _send_to_server(self, msg: Message) -> None:
> +        """
> +        This coroutine sends the message to the server.
> +        The message has to be pre-validated.
> +
> +        :param msg:
> +            Pre-validated message to be to sent to the server.
> +
> +        :raise Exception: When an unhandled exception is caught.
> +        """
> +        try:
> +            await self._raw(msg, assign_id='id' not in msg)
> +        except ExecInterruptedError:
> +            logging.info('Error server disconnected before reply')
> +            self.add_to_history('Server disconnected before reply',
> 'ERROR')
> +            self._set_status("[Server Disconnected]")
> +        except Exception as err:
> +            logging.error('Exception from _send_to_server: %s', str(err))
> +            raise err
> +
> +    def cb_send_to_server(self, raw_msg: str) -> None:
> +        """
> +        Validates and sends the message to the server.
> +        The raw string message is first converted into a Message object
> +        and is then sent to the server.
> +
> +        :param raw_msg:
> +            The raw string message to be sent to the server.
> +
> +        :raise Exception: When an unhandled exception is caught.
> +        """
> +        try:
> +            raw_msg = format_json(raw_msg)
> +            msg = Message(bytes(raw_msg, encoding='utf-8'))
> +            create_task(self._send_to_server(msg))
> +        except (ValueError, TypeError) as err:
> +            logging.info('Invalid message: %s', str(err))
> +            self.add_to_history(f'{raw_msg}: {err}')
> +        except (DeserializationError, UnexpectedTypeError) as err:
> +            logging.info('Invalid message: %s', err.error_message)
> +            self.add_to_history(f'{raw_msg}: {err.error_message}')
> +
> +    def unhandled_input(self, key: str) -> None:
> +        """
> +        Handle's keys which haven't been handled by the child widgets.
> +
> +        :param key:
> +            Unhandled key
> +        """
> +        if key == 'esc':
> +            self.kill_app()
> +
> +    def kill_app(self) -> None:
> +        """
> +        Initiates killing of app. A bridge between asynchronous and
> synchronous
> +        code.
> +        """
> +        create_task(self._kill_app())
> +
> +    async def _kill_app(self) -> None:
> +        """
> +        This coroutine initiates the actual disconnect process and calls
> +        urwid.ExitMainLoop() to kill the TUI.
> +
> +        :raise Exception: When an unhandled exception is caught.
> +        """
> +        # It is ok to call disconnect even in disconnect state
> +        try:
> +            await self.disconnect()
> +            logging.debug('Disconnect finished. Exiting app')
> +        except EOFError:
> +            # We receive an EOF during disconnect, ignore that
> +            pass
> +        except Exception as err:
> +            logging.info('_kill_app: %s', str(err))
> +            # Let the app crash after providing a proper stack trace
> +            raise err
> +        raise urwid.ExitMainLoop()
> +
> +    def _set_status(self, msg: str) -> None:
> +        """
> +        Sets the message as the status.
> +
> +        :param msg:
> +            The message to be displayed in the status bar.
> +        """
> +        self.window.footer.set_text(msg)
> +
> +    def _get_formatted_address(self) -> str:
> +        """
> +        Returns a formatted version of the server's address.
> +
> +        :return: formatted address
> +        """
> +        if isinstance(self.address, tuple):
> +            host, port = self.address
> +            addr = f'{host}:{port}'
> +        else:
> +            addr = f'{self.address}'
> +        return addr
> +
> +    async def connect_server(self) -> None:
> +        """
> +        Initiates a connection to the server at address `self.address`
> +        and in case of a failure, sets the status to the respective error.
> +        """
> +        try:
> +            await self.connect(self.address)
> +            addr = self._get_formatted_address()
> +            self._set_status(f'Connected to {addr}')
> +        except ConnectError as err:
> +            logging.info('connect_server: ConnectError %s', str(err))
> +            self._set_status(f'[ConnectError: {err.error_message}]')
> +
> +    def run(self, debug: bool = False) -> None:
> +        """
> +        Starts the long running co-routines and the urwid event loop.
> +
> +        :param debug:
> +            Enables/Disables asyncio event loop debugging
> +        """
> +        self.aloop = asyncio.get_event_loop()
> +        self.aloop.set_debug(debug)
> +
> +        # Gracefully handle SIGTERM and SIGINT signals
> +        cancel_signals = [signal.SIGTERM, signal.SIGINT]
> +        for sig in cancel_signals:
> +            self.aloop.add_signal_handler(sig, self.kill_app)
> +
> +        event_loop = urwid.AsyncioEventLoop(loop=self.aloop)
> +        main_loop = urwid.MainLoop(urwid.AttrMap(self.window,
> 'background'),
> +                                   unhandled_input=self.unhandled_input,
> +                                   handle_mouse=True,
> +                                   event_loop=event_loop)
> +
> +        create_task(self.wait_for_events(), self.aloop)
> +        create_task(self.connect_server(), self.aloop)
> +        try:
> +            main_loop.run()
> +        except Exception as err:
> +            logging.error('%s\n%s\n', str(err), pretty_traceback())
> +            raise err
> +
> +
> +class StatusBar(urwid.Text):
> +    """
> +    A simple statusbar modelled using the Text widget. The status can be
> +    set using the set_text function. All text set is aligned to right.
> +    """
> +    def __init__(self, text: str = ''):
> +        super().__init__(text, align='right')
> +
> +
> +class Editor(urwid_readline.ReadlineEdit):
> +    """
> +    A simple editor modelled using the urwid_readline.ReadlineEdit widget.
> +    Mimcs GNU readline shortcuts and provides history support.
> +
> +    The readline shortcuts can be found below:
> +    https://github.com/rr-/urwid_readline#features
> +
> +    Along with the readline features, this editor also has support for
> +    history. Pressing the 'up' arrow key with empty message box, lists the
> +    previous message inplace.
> +
> +    Currently there is no support to save the history to a file. The
> history of
> +    previous commands is lost on exit.
> +    """
> +    def __init__(self, master: App) -> None:
> +        """
> +        Initializes the editor widget
> +
> +        :param master: Reference to the TUI object.
> +        """
> +        super().__init__(caption='> ', multiline=True)
> +        self.master = master
> +        self.history: List[str] = []
> +        self.last_index: int = -1
> +        self.show_history: bool = False
> +
> +    def keypress(self, size: Tuple[int, int], key: str) -> Optional[str]:
> +        """
> +        Handles the keypress on this widget.
> +
> +        :param size:
> +            The current size of the widget.
> +        :param key:
> +            The key to be handled.
> +
> +        :return: Unhandled key if any.
> +        """
> +        # TODO: Add some logic for down key and clean up logic if
> possible.
> +        # Returning None means the key has been handled by this widget
> +        # which otherwise is propogated to the parent widget to be
> +        # handled
> +        msg = self.get_edit_text()
> +        if key == 'up' and not msg:
> +            # Show the history when 'up arrow' is pressed with no input
> text.
> +            # NOTE: The show_history logic is necessary because in
> 'multiline'
> +            # mode (which we use) 'up arrow' is used to move between
> lines.
> +            self.show_history = True
> +            last_msg = self.history[self.last_index] if self.history else
> ''
> +            self.set_edit_text(last_msg)
> +            self.edit_pos = len(last_msg)
> +            self.last_index += 1
> +        elif key == 'up' and self.show_history:
> +            if self.last_index < len(self.history):
> +                self.set_edit_text(self.history[self.last_index])
> +                self.edit_pos = len(self.history[self.last_index])
> +                self.last_index += 1
> +        elif key == 'meta enter':
> +            # When using multiline, enter inserts a new line into the
> editor
> +            # send the input to the server on alt + enter
> +            self.master.cb_send_to_server(msg)
> +            self.history.insert(0, msg)
> +            self.set_edit_text('')
> +            self.last_index = 0
> +            self.show_history = False
> +        else:
> +            self.show_history = False
> +            self.last_index = 0
> +            return cast(Optional[str], super().keypress(size, key))
> +        return None
> +
> +
> +class EditorWidget(urwid.Filler):
> +    """
> +    The Editor is a flow widget and has to wrapped inside a box widget.
> +    This class wraps the Editor inside filler widget.
> +    """
> +    def __init__(self, master: App) -> None:
> +        super().__init__(Editor(master), valign='top')
> +
> +
> +class HistoryBox(urwid.ListBox):
> +    """
> +    This widget is modelled using the ListBox widget, contains the list of
> +    all messages both QMP messages and log messsages to be shown in the
> TUI.
> +
> +    The messages are urwid.Text widgets. On every append of a message, the
> +    focus is shifted to the last appended message.
> +    """
> +    def __init__(self, master: App) -> None:
> +        """
> +        Initializes the historybox widget
> +
> +        :param master: Reference to the TUI object.
> +        """
> +        self.master = master
> +        self.history = urwid.SimpleFocusListWalker([])
> +        super().__init__(self.history)
> +
> +    def add_to_history(self, history: str) -> None:
> +        """
> +        Appends a message to the list and set the focus to the last
> appended
> +        message.
> +
> +        :param history:
> +            The history item(message/event) to be appended to the list.
> +        """
> +        self.history.append(urwid.Text(history))
> +        if self.history:
> +            self.history.set_focus(len(self.history) - 1)
> +
> +
> +class HistoryWindow(urwid.Frame):
> +    """
> +    This window composes the HistoryBox and EditorWidget in a horizontal
> split.
> +    By default the first focus is given to the history box.
> +    """
> +    def __init__(self, master: App) -> None:
> +        """
> +        Initializes this widget and its child widgets.
> +
> +        :param master: Reference to the TUI object.
> +        """
> +        self.master = master
> +        self.editor_widget = EditorWidget(master)
> +        self.editor = urwid.LineBox(self.editor_widget)
> +        self.history = HistoryBox(master)
> +        self.body = urwid.Pile([('weight', 80, self.history),
> +                                ('weight', 20, self.editor)])
> +        super().__init__(self.body)
> +        urwid.connect_signal(self.master, UPDATE_MSG,
> self.cb_add_to_history)
> +
> +    def cb_add_to_history(self, msg: str, level: Optional[str] = None) ->
> None:
> +        """
> +        Appends a message to the history box
> +
> +        :param msg:
> +            The message to be appended to the history box.
> +        """
> +        if level:
> +            msg = f'[{level}]: {msg}'
> +        self.history.add_to_history(msg)
> +
> +
> +class Window(urwid.Frame):
> +    """
> +    This window is the top most widget of the TUI and will contain other
> +    windows. Each window is responsible for displaying a specific
>
+    functionality.
>

"each window" => "Each child of this widget", maybe?

+    For eg: The history window is responsible for showing the history of
> +    messages and the editor.
>

These lines can probably go.


> +    """
> +    def __init__(self, master: App) -> None:
>

Consider naming this "parent" instead, if you'd be so kind as to oblige me.
(And everywhere else in the file.)


> +        """
> +        Initializes this widget and its child windows.
> +
> +        :param master: Reference to the TUI object.
> +        """
> +        self.master = master
> +        footer = StatusBar()
> +        body = HistoryWindow(master)
> +        super().__init__(body, footer=footer)
> +
> +
> +class TUILogHandler(Handler):
> +    """
> +    This handler routes all the log messages to the TUI screen.
> +    It is installed to the root logger to so that the log message from all
> +    libraries begin used is routed to the screen.
> +    """
> +    def __init__(self, tui: App) -> None:
> +        """
> +        Initializes the handler class.
> +
> +        :param tui:
> +            Reference to the TUI object.
> +        """
> +        super().__init__()
> +        self.tui = tui
> +
> +    def emit(self, record: LogRecord) -> None:
> +        """
> +        Emits a record to the TUI screen.
> +
> +        Appends the log message to the TUI screen
> +        """
> +        level = record.levelname
> +        msg = record.getMessage()
> +        self.tui.add_to_history(msg, level)
> +
> +
> +def main() -> None:
> +    """
> +    Driver of the whole script, parses arguments, initialize the TUI and
> +    the logger.
> +    """
> +    parser = argparse.ArgumentParser(description='AQMP TUI')
> +    parser.add_argument('qmp_server', help='Address of the QMP server. '
> +                        'Format <UNIX socket path | TCP addr:port>')
> +    parser.add_argument('--log-file', help='The Log file name')
> +    parser.add_argument('--log-level', default='WARNING',
> +                        help='Log level
> <CRITICAL|ERROR|WARNING|INFO|DEBUG|>')
> +    parser.add_argument('--asyncio-debug', action='store_true',
> +                        help='Enable debug mode for asyncio loop. '
> +                        'Generates lot of output, makes TUI unusable when
> '
> +                        'logs are logged in the TUI. '
> +                        'Use only when logging to a file.')
> +    args = parser.parse_args()
> +
> +    try:
> +        address = QEMUMonitorProtocol.parse_address(args.qmp_server)
> +    except QMPBadPortError as err:
> +        parser.error(str(err))
> +
> +    app = App(address)
> +
> +    root_logger = logging.getLogger()
> +    root_logger.setLevel(logging.getLevelName(args.log_level))
> +
> +    if args.log_file:
> +        root_logger.addHandler(logging.FileHandler(args.log_file))
> +    else:
> +        root_logger.addHandler(TUILogHandler(app))
> +
> +    app.run(args.asyncio_debug)
> +
> +
> +if __name__ == '__main__':
> +    main()
> diff --git a/python/setup.cfg b/python/setup.cfg
> index a0ed3279d8..1ff2b907a2 100644
> --- a/python/setup.cfg
> +++ b/python/setup.cfg
> @@ -81,8 +81,19 @@ namespace_packages = True
>  # fusepy has no type stubs:
>  allow_subclassing_any = True
>
> +[mypy-qemu.aqmp.aqmp_tui]
> +# urwid and urwid_readline have no type stubs:
> +allow_subclassing_any = True
> +
> +# The following missing import directives are because these libraries do
> not
> +# provide type stubs. Allow them on an as-needed basis for mypy.
>  [mypy-fuse]
> -# fusepy has no type stubs:
> +ignore_missing_imports = True
> +
> +[mypy-urwid]
> +ignore_missing_imports = True
> +
> +[mypy-urwid_readline]
>  ignore_missing_imports = True
>
>  [pylint.messages control]
> @@ -97,7 +108,7 @@ ignore_missing_imports = True
>  # --disable=W".
>  disable=too-many-function-args,  # mypy handles this with less false
> positives.
>          no-member,  # mypy also handles this better.
> -        missing-docstring, # FIXME
> +        # missing-docstring, # FIXME
>          fixme, # FIXME
>
>  [pylint.basic]
> --
> 2.17.1
>
>
Most of the rest looks pretty good to me. I'm still quite a bit skeptical
of format_json, but I have to admit I will look a bit more closely at that
tomorrow -- and I want to take a closer look at has_tui_handler too, but
most of the rest seems like it's been stripped to its bare essentials,
which is good :)

Thanks for the work on the docstrings and mypy hints, it's in good shape
overall.

--js

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