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# 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)
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