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Diffstat (limited to 'fg21sim/webui/consolehandler.py')
| -rw-r--r-- | fg21sim/webui/consolehandler.py | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/fg21sim/webui/consolehandler.py b/fg21sim/webui/consolehandler.py new file mode 100644 index 0000000..0184a93 --- /dev/null +++ b/fg21sim/webui/consolehandler.py @@ -0,0 +1,199 @@ +# Copyright (c) 2016 Weitian LI <liweitianux@live.com> +# MIT license + +""" +Handle the "console" type of messages from the client. +""" + +import json +import logging +from concurrent.futures import ThreadPoolExecutor + +import tornado.ioloop +import tornado.gen + +from .loghandler import WebSocketLogHandler + + +logger = logging.getLogger(__name__) + + +class ConsoleHandler: + """ + Handle the "console" type of messages from the client. + + XXX/TODO: + * How to kill the submitted task? (force kill thread?) + + Parameters + ---------- + websocket : `~tornado.websocket.WebSocketHandler` + An `~tornado.websocket.WebSocketHandler` instance. + The ``WebSocketLogHandler`` requires this to push logging messages + to the client. + max_workers : int, optional + Maximum number of workers/threads for the execution pool + onetask_only : bool, optional + Whether to allow only one task running at the same time? + + Attributes + ---------- + websocket : `~tornado.websocket.WebSocketHandler` + An `~tornado.websocket.WebSocketHandler` instance, which is used by + the ``WebSocketLogHandler`` to push logging messages to the client. + wsloghandler : `~WebSocketLogHandler` + Push logging messages to the client through WebSocket. + executor : `~concurrent.futures.ThreadPoolExecutor` + Where to submit the synchronous task and make it perform + asynchronously using threads. + io_loop : `~tornado.ioloop.IOLoop` + Used to communicate with the main thread (e.g., callback) from the + submitted task, which is executed on a different thread. + onetask_only : bool + Whether to allow only one task running at the same time? + status : dict + Whether the task is running and/or finished? + There may be 4 possible status: + 1. running=False, finished=False: not started + 2. running=False, finished=True: finished + 3. running=True, finished=False: running + 4. running=True, finished=True: ?? error ?? + """ + def __init__(self, websocket, max_workers=3, onetask_only=False): + self.websocket = websocket + self.wsloghandler = WebSocketLogHandler(websocket, msg_type="console") + self.executor = ThreadPoolExecutor(max_workers=1) + # NOTE: + # Use ``IOLoop.instance`` instead of ``IOLoop.current``, since we + # will need to communicate with the main thread from another thread. + self.io_loop = tornado.ioloop.IOLoop.instance() + self.onetask_only = onetask_only + self.status = {"running": False, "finished": False} + + def handle_message(self, msg): + try: + msg_type = msg["type"] + msg_action = msg["action"] + response = {"type": msg_type, "action": msg_action} + logger.info("WebSocket: handle message: " + + "type: {0}, action: {1}".format(msg_type, msg_action)) + if msg_action == "start": + # Start the task asynchronously + future = self._start(msg["time"]) + self.io_loop.add_future(future, self._response_future) + response["success"] = True + response["status"] = "future" + elif msg_action == "get_status": + response["success"] = True + response["action"] = "push" + response["status"] = self.status + else: + logger.warning("WebSocket: " + + "unknown action: {0}".format(msg_action)) + response["success"] = False + response["error"] = "unknown action: {0}".format(msg_action) + except KeyError: + # Received message has wrong syntax/format + response = {"success": False, + "type": msg_type, + "error": "no action specified"} + # + logger.debug("WebSocket: response: {0}".format(response)) + return response + + # FIXME/XXX: + # * How to call this task asynchronously ?? + def _start(self, *args, **kwargs): + """ + Start the task by submitting it to the executor + + Returns + ------- + success : bool + Whether success without any errors + error : str + Detail of the error if not succeed + + """ + if self.onetask_only and self.status["running"]: + logger.warning("Task already running, and only one task allowed") + success = False + error = "already running and only one task allowed" + else: + logger.info("Start the task on the executor ...") + self.status["running"] = True + self.status["finished"] = False + # Also push the logging messages to the client + self._add_wsloghandler() + future = self.executor.submit(self._task, *args, **kwargs) + self.io_loop.add_future(future, self._task_callback) + success, error = future.result() + return (success, error) + + def _response_future(self, future): + """ + Callback function which will be called when the caller finishes + in order to response the results to the client. + """ + response = {"type": "console", "action": "future"} + success, error = future.result() + response["success"] = success + if not success: + response["error"] = error + logger.debug("WebSocket: future response: {0}".format(response)) + msg_response = json.dumps(response) + self.websocket.write_message(msg_response) + + def _add_wsloghandler(self): + """Add the ``self.wsloghandler`` to the logging handlers""" + root_logger = logging.getLogger() + root_logger.addHandler(self.wsloghandler) + logger.info("Added the WebSocket logging handler") + + def _remove_wsloghandler(self): + """Remove the ``self.wsloghandler`` from the logging handlers""" + root_logger = logging.getLogger() + root_logger.removeHandler(self.wsloghandler) + logger.info("Removed the WebSocket logging handler") + + def _task_callback(self, future): + """Callback function executed when the task finishes""" + logger.info("Console task finished! Callback ...") + self.status["running"] = False + self.status["finished"] = True + self._remove_wsloghandler() + # + response = {"type": "console", "action": "push"} + response["success"] = True + response["status"] = self.status + logger.debug("WebSocket: future response: {0}".format(response)) + msg_response = json.dumps(response) + self.websocket.write_message(msg_response) + + def _task(self, *args, **kwargs): + """ + The task this console to manage. + + Returns + ------- + success : bool + Whether success without any errors + error : str + Detail of the error if not succeed + + NOTE + ---- + The task is synchronous and may be computationally intensive + (i.e., CPU-bound rather than IO/event-bound), therefore, + threads (or processes) are required to make it non-blocking + (i.e., asynchronous). + + Credit: https://stackoverflow.com/a/32164711/4856091 + """ + import time + logger.info("console task: START") + for i in range(args[0]): + logger.info("console task: slept {0} seconds ...".format(i)) + time.sleep(1) + logger.info("console task: DONE!") + return (True, None) |