apatrushev / aiomonitor

aiomonitor is module that adds monitor and python REPL capabilities for asyncio application

aiomonitor

aiomonitor is Python 3.5+ module that adds monitor and cli capabilities for asyncio application. Idea and code borrowed from curio project. Task monitor that runs concurrently to the asyncio loop (or fast drop in replacement uvloop) in a separate thread as result monitor will work even if event loop is blocked for some reason.

Library provides an python console using aioconsole module, it is possible to execute asynchronous command inside your running application. Extensible with you own commands, in the style of the standard library's cmd module

Installation

Installation process is simple, just:

$ pip install aiomonitor

Example

Monitor has context manager interface:

import aiomonitor

loop = asyncio.get_event_loop()
with aiomonitor.start_monitor(loop=loop):
    loop.run_forever()

Now from separate terminal it is possible to connect to the application:

$ nc localhost 50101

or using included python client:

$ python -m aiomonitor.cli

Tutorial

Lets create simple aiohttp application, and see how aiomonitor can integrates with it.

import asyncio

import aiomonitor
from aiohttp import web

# Simple handler that returns response after 100s
async def simple(request):
    loop = request.app.loop

    print('Start sleeping')
    await asyncio.sleep(100, loop=loop)
    return web.Response(text="Simple answer")

loop = asyncio.get_event_loop()
# create application and register route
app = web.Application(loop=loop)
app.router.add_get('/simple', simple)

# it is possible to pass dictionary with local variables
# to the python console environment
host, port = "localhost", 8090
locals_ = {"port": port, "host": host}
# init monitor just before run_app
with aiomonitor.start_monitor(loop=loop, locals=locals_):
    # run application with built in aiohttp run_app function
    web.run_app(app, port=port, host=host)

Lets save this code in file simple_srv.py, so we can run it with command:

$ python simple_srv.py
======== Running on http://localhost:8090 ========
(Press CTRL+C to quit)

And now one can connect running application from separate terminal, with nc command, immediately aiomonitor will respond with prompt:

$ nc localhost 50101
Asyncio Monitor: 1 tasks running
Type help for commands
monitor >>>

Now you can type commands, for instance help:

monitor >>> help
Commands:
             ps               : Show task table
             where taskid     : Show stack frames for a task
             cancel taskid    : Cancel an indicated task
             signal signame   : Send a Unix signal
             stacktrace       : Print a stack trace from the event loop thread
             console          : Switch to async Python REPL
             quit             : Leave the monitor

aiomonitor supports also async python console inside running event loop so you can explore state of your application:

monitor >>> console
Python 3.5.2 (default, Oct 11 2016, 05:05:28)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.38)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
---
This console is running in an asyncio event loop.
It allows you to wait for coroutines using the 'await' syntax.
Try: await asyncio.sleep(1, result=3, loop=loop)
---
>>> await asyncio.sleep(1, result=3, loop=loop)

To leave console type exit():

>>> exit()
monitor >>>

aiomonitor is very easy to extend with your own console commands.

class WebMonitor(aiomonitor.Monitor):
    def do_hello(self, sin, sout, name=None):
        """Using the /hello GET interface

        There is one optional argument, "name".  This name argument must be
        provided with proper URL excape codes, like %20 for spaces.
        """
        name = '' if name is None else '/' + name
        r = requests.get('http://localhost:8090/hello' + name)
        sout.write(r.text + '\n')

Requirements

• Python 3.5+
• aioconsole
• uvloop (optional)