What would be the best approach for setting a timeout condition on a task/function that's been submitted to a ThreadPoolExecutor using tornado.concurrent's #run_on_executor decorator? Example Tornado handler below:
import json
import time
import tornado.web
from concurrent.futures import ThreadPoolExecutor
from tornado.concurrent import run_on_executor
class MyHandler(tornado.web.RequestHandler):
def initialize(self) -> None:
self.executor = ThreadPoolExecutor(1)
#run_on_executor
def blocking_function(self) -> None:
""" Run Blocking Function on ThreadPoolExecutor. """
seconds = 10
time.sleep(seconds)
response = json.dumps({"message": f"Slept for {seconds} seconds."})
return response
async def get(self) -> None:
response = await self.blocking_function()
self.write(response)
Does something like tornado.gen.with_timeout found here exist for #run_on_executor?
Thank you for your time.
Since run_on_executor returns a Future object, you can use it with gen.with_timetout:
from datetime import timedelta
async def get(self):
response = await gen.with_timeout(
timedelta(seconds=5),
self.blocking_function()
)
...
Don't forget to handle the timeout exception.
Related
I have been working with server sent events to send out certain type of notifications to only certain clients. I am using the module called sse-starlette to try and achieve this.
I am fairly new to FastApi so I am not able to figure out how to send the data to only certain clients instead of broadcasting to everyone.
This is what I have thought so far:
Subscribe request with query param
localhost:8000/subscribe?id=1
from sse_starlette.sse import EventSourceResponse
class EmitEventModel(BaseModel):
event_name: str
event_data: Optional[str] = "No Event Data"
event_id: Optional[int] = None
recipient_id: str
async def connection_established():
yield dict(data="Connection established")
clients = {}
#app.get("/subscribe")
async def loopBackStream(req: Request, id: str = ""):
clients[id] = EventSourceResponse(connection_established())
return clients[id]
#app.post("/emit")
async def emitEvent(event: EmitEventModel):
if clients[event.recipient_id]:
clients[event.recipient_id](publish_event())
Whenever there is an api call to localhost:8000/emit containing the body, Based on the recipient_id the event is going to be routed.
Ofcourse this doesn't work so far. Any pointers as to what should be done to achieve this?
sse_starlette for reference:
https://github.com/sysid/sse-starlette/blob/master/sse_starlette/sse.py
The idea here is that you're going to need to identify the recipient_id on the SSE generator. I've slightly modified your code, to be able to show what I mean:
from __future__ import annotations
import asyncio
import itertools
from collections import defaultdict
from fastapi import Request, FastAPI
from pydantic import BaseModel
from sse_starlette.sse import EventSourceResponse
app = FastAPI()
clients = defaultdict(list)
class EmitEventModel(BaseModel):
event_name: str
event_data: Optional[str] = "No Event Data"
event_id: Optional[int] = None
recipient_id: str
async def retrieve_events(recipient_id: str) -> NoReturn:
yield dict(data="Connection established")
while True:
if recipient_id in clients and len(clients[recipient_id]) > 0:
yield clients[recipient_id].pop()
await asyncio.sleep(1)
print(clients)
#app.get("/subscribe/{recipient_id}")
async def loopBackStream(req: Request, recipient_id: str):
return EventSourceResponse(retrieve_events(recipient_id))
#app.post("/emit")
async def emitEvent(event: EmitEventModel):
clients[event.recipient_id].append(event)
I have a ros2 publisher script that sends custom messages from ros2 nodes. What I need to do is to have a subscriber (which is also my websocket server) to listen to the message that the pulisher sends then convert it to a dictionary and send it as a json from the websocket server to a connected websocket client. I have already checked the rosbridge repo but I could not make it work. It doesn't have enough documentation and I am new to ros.
I need something like this:
import rclpy
import sys
from rclpy.node import Node
import tornado.ioloop
import tornado.httpserver
import tornado.web
import threading
from custom.msg import CustomMsg
from .convert import message_to_ordereddict
wss = []
class wsHandler(tornado.websocket.WebSocketHandler):
def open(self):
print 'Online'
if self not in wss:
wss.append(self)
def on_close(self):
print 'Offline'
if self in wss:
wss.remove(self)
def wsSend(message):
for ws in wss:
ws.write_message(message)
class MinimalSubscriber(Node):
def __init__(self):
super().__init__('minimal_subscriber')
self.subscription = self.create_subscription(CustomMsg, 'topic', self.CustomMsg_callback, 10)
self.subscription # prevent unused variable warning
def CustomMsg_callback(self, msg):
ws_message = message_to_ordereddict(msg)
wsSend(ws_message)
if __name__ == "__main__":
http_server = tornado.httpserver.HTTPServer(tornado.web.Application(wsHandler))
http_server.listen(8888)
main_loop = tornado.ioloop.IOLoop.instance()
# Start main loop
main_loop.start()
so the callback function in MinimalSubscriber class, receives the ros message, converts it to dictionary and sends it to websocket client. I am a bit confused how to make these two threads (ros and websocket) to communicate with each other.
So I think I got a bit confused myself going through the threading. So I changed my approach and made it work using the tornado periodic callback and the spin_once function of rclpy as the callback function. I would post my solution as it might help some people who has the same issue.
import queue
import rclpy
from rclpy.node import Node
import tornado.ioloop
import tornado.httpserver
import tornado.web
from custom.msg import CustomMsg
from .convert import message_to_ordereddict
wss = []
class wsHandler(tornado.websocket.WebSocketHandler):
#classmethod
def route_urls(cls):
return [(r'/',cls, {}),]
def open(self):
print 'Online'
if self not in wss:
wss.append(self)
def on_close(self):
print 'Offline'
if self in wss:
wss.remove(self)
def make_app():
myWebHandler = wsHandler.route_urls()
return tornado.web.Application(myWebHandler)
message_queue = queue.Queue
class MinimalSubscriber(Node):
def __init__(self):
super().__init__('minimal_subscriber')
self.subscription = self.create_subscription(CustomMsg, 'topic', self.CustomMsg_callback, 10)
self.subscription # prevent unused variable warning
def CustomMsg_callback(self, msg):
msg_dict = message_to_ordereddict(msg)
msg_queue.put(msg_dict)
if __name__ == "__main__":
rclpy.init(args=args)
minimal_subscriber = MinimalSubscriber()
def send_ros_to_clients():
rclpy.spin_once(minimal_subscriber)
my_msg = msg_queue.get()
for client in ws_clients:
client.write_message(my_msg)
app = make_app()
server = tornado.httpserver.HTTPServer(app)
server.listen(8888)
tornado.ioloop.PeriodicCallback(send_ros_to_clients, 1).start()
tornado.ioloop.IOLoop.current().start()
minimal_subscriber.destroy_node()
rclpy.shutdown()
I also implemented the wsSend function into the send_ros_to_clients function. Some might say that using a global queue is not the best practice but I could not come up with another solution. I would appreciate any suggestions or corrections on my solution.
I am trying to achieve fire_and_forget functionality and here are the details.
Async decorater i am trying to use:
import asyncio
import time
def fire_and_forget(f):
def wrapped(*args, **kwargs):
return asyncio.get_event_loop().run_in_executor(None, f, *args, *kwargs)
return wrapped
My Async call using above decorator:
#fire_and_forget
def call_async(self, req, body, headers_params):
logger.info("Calling ASYNC")
try:
f = urllib.request.urlopen(req)
response = f.read()
f.close()
except Exception as e:
logger.exception("api exception %s" % e)
return None
# Parse and return the response
try:
res = self._parse_response(response)
except Exception as e:
logger.exception("Exception in parsing response of %s" % e)
res = None
logger.debug("clevertap response: {}".format(res))
My Flask app calling test_xyz which in turns fire the above fire and forget call_async:
from flask import Flask, jsonify, request
from call_xyz import test_xyz
app = Flask(__name__)
#app.route('/events_dm')
def events_dm():
session_id = request.args.get('sessionId', "11111111")
test_obj = test_xyz(session_id)
test_obj.track_test()
return jsonify({"success": True})
app.run(
host='0.0.0.0',
port=8091,
debug=True,
threaded=True
)
I am not able to understand where to set my event loop correctly so that i don't get the error: "Error in xyz There is no current event loop in thread 'Thread-7'" and my events get fired correctly.
Flask is not asyncio-compatible, so you shouldn't attempt to use asyncio within it.
Besides, you're not actually using asyncio's functionality, but run_in_executor which calls into concurrent.futures, i.e. uses threads under the hood. If that's what you need, you can create an executor directly and just submit your function to it. For example:
import concurrent.futures
_pool = concurrent.futures.ThreadPoolExecutor()
def fire_and_forget(f):
def wrapped(*args, **kwargs):
return _pool.submit(lambda: f(*args, **kwargs))
return wrapped
You must probably go through once asyncio usage and its main heart event loop understanding.
Similar issue which might help you to understand.
Here is the tutorial with some good explanation
Just give some flow for how use coroutine with normal Flask app here is the sample one.
import asyncio
import datetime
from flask import Flask, jsonify, request
app = Flask(__name__)
def print_now():
print(datetime.datetime.now())
async def keep_printing(name: str="") -> None:
print(name, end=" ")
print_now()
await asyncio.sleep(1.50)
async def main(num_times):
result = await asyncio.gather(
keep_printing("first"),
keep_printing("second"),
keep_printing("third"),
)
return result
def execute_statement():
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
loop.run_until_complete(main(2))
loop.close()
#app.route('/events_dm')
def events_dm():
execute_statement()
return jsonify({"success": True})
app.run(
host='0.0.0.0',
port=8091,
debug=True,
threaded=True
)
Output when you hit /events_dm
first 2020-07-18 00:46:26.452921
second 2020-07-18 00:46:26.452921
third 2020-07-18 00:46:26.452921
127.0.0.1 - - [18/Jul/2020 00:46:27] "GET /events_dm HTTP/1.1" 200 -
import tornado.web
import tornado.ioloop
from apiApplicationModel import userData
from cleanArray import Label_Correction
import json
import requests
colName=['age', 'resting_blood_pressure', 'cholesterol', 'max_heart_rate_achieved', 'st_depression', 'num_major_vessels', 'st_slope_downsloping', 'st_slope_flat', 'st_slope_upsloping', 'sex_male', 'chest_pain_type_atypical angina', 'chest_pain_type_non-anginal pain', 'chest_pain_type_typical angina', 'fasting_blood_sugar_lower than 120mg/ml', 'rest_ecg_left ventricular hypertrophy', 'rest_ecg_normal', 'exercise_induced_angina_yes', 'thalassemia_fixed defect', 'thalassemia_normal',
'thalassemia_reversable defect']
class processRequestHandler(tornado.web.RequestHandler):
def post(self):
data_input_array = []
for name in colName:
x = self.get_body_argument(name, default=0)
data_input_array.append(int(x))
label = Label_Correction(data_input_array)
finalResult = int(userData(label))
output = json.dumps({"Giveput":finalResult})
self.write(output)
class basicRequestHandler(tornado.web.RequestHandler):
def get(self):
self.render('report.html')
class staticRequestHandler(tornado.web.RequestHandler):
def post(self):
data_input_array = []
for name in colName:
x = self.get_body_argument(name, default=0)
data_input_array.append(str(x))
send_data = dict(zip(colName, data_input_array))
print(send_data)
print(type(send_data))
url = "http://localhost:8887/output"
headers={}
response = requests.request('POST',url,headers=headers,data=send_data)
print(response.text.encode('utf8'))
print("DONE")
if __name__=='__main__':
app = tornado.web.Application([(r"/",basicRequestHandler),
(r"/result",staticRequestHandler),
(r"/output",processRequestHandler)])
print("API IS RUNNING.......")
app.listen(8887)
tornado.ioloop.IOLoop.current().start()
Actually I am trying to create an API and the result of the API can be used but
The page keeps on loading, and no response is shown.
Response should be a python dictionary send by post function of class processRequestHandler
After using a debugger the lines after response = requests.request('POST',url,headers=headers,data=send_data) are not executed.
The class processRequestHandler is working fine when checked with POSTMAN.
requests.request is a blocking method. This blocks the event loop and prevents any other handlers from running. In a Tornado handler, you need to use Tornado's AsyncHTTPClient (or another non-blocking HTTP client such as aiohttp) instead.
async def post(self):
...
response = await AsyncHTTPClient().fetch(url, method='POST', headers=headers, body=send_data)
See the Tornado users's guide for more information.
I am trying to implement asynchronous http reverse proxy with tornado on Python3.
Handler class is as follows:
class RProxyHandler(tornado.web.RequestHandler):
#tornado.web.asynchronous
def get(self):
backend_url = 'http://backend-host/content.html' # temporary fixed
req = tornado.httpclient.HTTPRequest(
url=backend_url)
http_client = tornado.httpclient.AsyncHTTPClient()
http_client.fetch(req, self.backend_callback)
def backend_callback(self, response):
self.write(response.body)
self.finish()
When content.html is small, this code works fine. But with large content.html, this code raises Exception:
ERROR:tornado.general:Reached maximum read buffer size
I found the way to handle large contents with pycurl. Though, it seems does not work with Python3.
In addition, I added streaming_callback option to HTTPRequest. But the callback won't be called when disabled chunked response by backend server.
How can I handle large contents?
Thanks.
You should be able to pass max_buffer_size to the tornado.httpclient.AsyncHTTPClient()
call to set the max buffer size. for a 50MB buffer:
import tornado.ioloop
import tornado.web
from tornado.httpclient import AsyncHTTPClient
from tornado import gen
from tornado.web import asynchronous
class MainHandler(tornado.web.RequestHandler):
client = AsyncHTTPClient(max_buffer_size=1024*1024*150)
#gen.coroutine
#asynchronous
def get(self):
response = yield self.client.fetch("http://test.gorillaservers.com/100mb.bin", request_timeout=180)
self.finish("%s\n" % len(response.body))
application = tornado.web.Application([
(r"/", MainHandler),
])
if __name__ == "__main__":
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()
Update: Now a full example program.