TypeError: future or coroutine required
I am trying to do auto-reconnecting ssh client on asyncssh. (SshConnectManager should stay in the background and do ssh sessions when needed)
class SshConnectManager(object):
def __init__(self, host, username, password, port=22):
self._host = host
self._username = username
self._password = password
self._port = port
self.conn = None
asyncio.async(self.start_connection)
@asyncio.coroutine
def start_connection(self):
try:
Client = self._create_ssh_client()
self.conn, _ = yield from asyncssh.create_connection(Client,
self._host, port=self._port,
username=self._username,
password=self._password)
except Exception as e:
print("Connection error! {}".format(e))
asyncio.async(self.start_connection())
def _create_ssh_client(self):
class MySSHClient(asyncssh.SSHClient):
parent = self
def connection_lost(self, exc):
self.parent._handle_connection_lost(exc)
return MySSHClient
def _handle_connection_lost(self, exc):
print('Connection lost on {}'.format(self.host))
print(exc)
asyncio.async(self.start_connection)
ssh1 = SshConnectManager(settings.host, settings.username, settings.password, settings.port)
asyncio.get_event_loop().run_until_complete(...)
Please don't look at _create_ssh_client or other "haks"
Problem:
$ python3 main.py
Traceback (most recent call last):
File "main.py", line 75, in <module>
ssh1 = SshConnectManager(settings.host, settings.username, settings.password, settings.port)
File "main.py", line 22, in __init__
asyncio.async(self.start_connection)
File "/usr/lib/python3.4/asyncio/tasks.py", line 565, in async
raise TypeError('A Future or coroutine is required')
TypeError: A Future or coroutine is required
But self.start_connection is coroutine! Or not? Or what is another way to start an async task from sync code?
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Thanks to @dano and @boardrider for helping out in the comments. The error was that @ asyncio.coroutine is returning a function that needs to be called to get a generator object. I forgot to do this.
Fixed version:
class SshConnectManager(object):
def __init__(self, host, username, password, port=22):
self._host = host
self._username = username
self._password = password
self._port = port
self.conn = None
# FIX HERE
asyncio.async(self.start_connection())
@asyncio.coroutine
def start_connection(self):
try:
Client = self._create_ssh_client()
self.conn, _ = yield from asyncssh.create_connection(Client,
self._host, port=self._port,
username=self._username,
password=self._password)
except Exception as e:
print("Connection error! {}".format(e))
asyncio.async(self.start_connection())
def _create_ssh_client(self):
class MySSHClient(asyncssh.SSHClient):
parent = self
def connection_lost(self, exc):
self.parent._handle_connection_lost(exc)
return MySSHClient
def _handle_connection_lost(self, exc):
print('Connection lost on {}'.format(self.host))
print(exc)
# AND HERE
asyncio.async(self.start_connection())
ssh1 = SshConnectManager(settings.host, settings.username, settings.password, settings.port)
asyncio.get_event_loop().run_until_complete(...)
PS But I don't understand why the Coroutine decorator cannot return the called decorator. (This makes me confused, I am confusing this with malformed callbacks).
And I found how to remember this has a simple case if start_connection can get arguments:
@asyncio.coroutine
def start_connection(self, some_arg):
pass
so I can just write:
asyncio.async(self.start_connection(some_val))
and no need to create additional attributes in asyncio.async function
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