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Parallel-SSH - how to close ssh channel after a certain time?

Ok, so it's possible that the answer to this question is simply "stop using parallel-ssh and write your own code using netmiko/paramiko. Also, upgrade to python 3 already."
But here's my issue: I'm using parallel-ssh to try to hit as many as 80 devices at a time. These devices are notoriously unreliable, and they occasionally freeze up after giving one or two lines of output. Then, the parallel-ssh code hangs for hours, leaving the script running, well, until I kill it. I've jumped onto the VM running the scripts after a weekend and seen a job that's been stuck for 52 hours.
The relevant pieces of my first code, the one that hangs:
from pssh.pssh2_client import ParallelSSHClient
def remote_ssh(ip_list, ssh_user, ssh_pass, cmd):
client = ParallelSSHClient(ip_list, user=ssh_user, password=ssh_pass, timeout=180, retry_delay=60, pool_size=100, allow_agent=False)
result = client.run_command(cmd, stop_on_errors=False)
return result
The next thing I tried was the channel_timout option, because if it takes more than 4 minutes to get the command output, then I know that the device froze, and I need to move on and cycle it later in the script:
from pssh.pssh_client import ParallelSSHClient
def remote_ssh(ip_list, ssh_user, ssh_pass, cmd):
client = ParallelSSHClient(ip_list, user=ssh_user, password=ssh_pass, channel_timeout=180, retry_delay=60, pool_size=100, allow_agent=False)
result = client.run_command(cmd, stop_on_errors=False)
return result
This version never actually connects to anything. Any advice? I haven't been able to find anything other than channel_timeout to attempt to kill an ssh session after a certain amount of time.

The code is creating a client object inside a function and then returning only the output of run_command which includes remote channels to the SSH server.
Since the client object is never returned by the function it goes out of scope and gets garbage collected by Python which closes the connection.
Trying to use remote channels on a closed connection will never work. If you capture stack trace of the stuck script it is most probably hanging at using remote channel or connection.
Change your code to keep the client alive. Client should ideally also be reused.
from pssh.pssh2_client import ParallelSSHClient
def remote_ssh(ip_list, ssh_user, ssh_pass, cmd):
client = ParallelSSHClient(ip_list, user=ssh_user, password=ssh_pass, timeout=180, retry_delay=60, pool_size=100, allow_agent=False)
result = client.run_command(cmd, stop_on_errors=False)
return client, result
Make sure you understand where the code is going wrong before jumping to conclusions that will not solve the issue, ie capture stack trace of where it is hanging. Same code doing the same thing will break the same way..

Communication between two separate Python engines

The problem statement is as follows:
I am working with Abaqus, a program for analyzing mechanical problems. It is basically a standalone Python interpreter with its own objects etc. Within this program, I run a python script to set up my analysis (so this script can be modified). It also contains a method which has to be executed when an external signal is received. These signals come from the main script that I am running in my own Python engine.
For now, I have the following workflow:
The main script sets a boolean to True when the Abaqus script has to execute a specific function, and pickles this boolean into a file. The Abaqus script regularly checks this file to see whether the boolean has been set to true. If so, it does an analysis and pickles the output, so that the main script can read this output and act on it.
I am looking for a more efficient way to signal the other process to start the analysis, since there is a lot of unnecessary checking going on right know. Data exchange via pickle is not an issue for me, but a more efficient solution is certainly welcome.
Search results always give me solutions with subprocess or the like, which is for two processes started within the same interpreter. I have also looked at ZeroMQ since this is supposed to achieve things like this, but I think this is overkill and would like a solution in python. Both interpreters are running python 2.7 (although different versions)

Edit:
Like #MattP, I'll add this statement of my understanding:
Background
I believe that you are running a product called abaqus. The abaqus product includes a linked-in python interpreter that you can access somehow (possibly by running abaqus python foo.py on the command line).
You also have a separate python installation, on the same machine. You are developing code, possibly including numpy/scipy, to run on that python installation.
These two installations are different: they have different binary interpreters, different libraries, different install paths, etc. But they live on the same physical host.
Your objective is to enable the "plain python" programs, written by you, to communicate with one or more scripts running in the "Abaqus python" environment, so that those scripts can perform work inside the Abaqus system, and return results.
Solution
Here is a socket based solution. There are two parts, abqlistener.py and abqclient.py. This approach has the advantage that it uses a well-defined mechanism for "waiting for work." No polling of files, etc. And it is a "hard" API. You can connect to a listener process from a process on the same machine, running the same version of python, or from a different machine, or from a different version of python, or from ruby or C or perl or even COBOL. It allows you to put a real "air gap" into your system, so you can develop the two parts with minimal coupling.
The server part is abqlistener. The intent is that you would copy some of this code into your Abaqus script. The abq process would then become a server, listening for connections on a specific port number, and doing work in response. Sending back a reply, or not. Et cetera.
I am not sure if you need to do setup work for each job. If so, that would have to be part of the connection. This would just start ABQ, listen on a port (forever), and deal with requests. Any job-specific setup would have to be part of the work process. (Maybe send in a parameter string, or the name of a config file, or whatever.)
The client part is abqclient. This could be moved into a module, or just copy/pasted into your existing non-ABQ program code. Basically, you open a connection to the right host:port combination, and you're talking to the server. Send in some data, get some data back, etc.
This stuff is mostly scraped from example code on-line. So it should look real familiar if you start digging into anything.
Here's abqlistener.py:
# The below usage example is completely bogus. I don't have abaqus, so
# I'm just running python2.7 abqlistener.py [options]
usage = """
abacus python abqlistener.py [--host 127.0.0.1 | --host mypc.example.com ] \\
[ --port 2525 ]
Sets up a socket listener on the host interface specified (default: all
interfaces), on the given port number (default: 2525). When a connection
is made to the socket, begins processing data.
"""
import argparse
parser = argparse.ArgumentParser(description='Abacus listener',
add_help=True,
usage=usage)
parser.add_argument('-H', '--host', metavar='INTERFACE', default='',
help='Interface IP address or name, or (default: empty string)')
parser.add_argument('-P', '--port', metavar='PORTNUM', type=int, default=2525,
help='port number of listener (default: 2525)')
args = parser.parse_args()
import SocketServer
import json
class AbqRequestHandler(SocketServer.BaseRequestHandler):
"""Request handler for our socket server.
This class is instantiated whenever a new connection is made, and
must override `handle(self)` in order to handle communicating with
the client.
"""
def do_work(self, data):
"Do some work here. Call abaqus, whatever."
print "DO_WORK: Doing work with data!"
print data
return { 'desc': 'low-precision natural constants','pi': 3, 'e': 3 }
def handle(self):
# Allow the client to send a 1kb message (file path?)
self.data = self.request.recv(1024).strip()
print "SERVER: {} wrote:".format(self.client_address[0])
print self.data
result = self.do_work(self.data)
self.response = json.dumps(result)
print "SERVER: response to {}:".format(self.client_address[0])
print self.response
self.request.sendall(self.response)
if __name__ == '__main__':
print args
server = SocketServer.TCPServer((args.host, args.port), AbqRequestHandler)
print "Server starting. Press Ctrl+C to interrupt..."
server.serve_forever()
And here's abqclient.py:
usage = """
python2.7 abqclient.py [--host HOST] [--port PORT]
Connect to abqlistener on HOST:PORT, send a message, wait for reply.
"""
import argparse
parser = argparse.ArgumentParser(description='Abacus listener',
add_help=True,
usage=usage)
parser.add_argument('-H', '--host', metavar='INTERFACE', default='',
help='Interface IP address or name, or (default: empty string)')
parser.add_argument('-P', '--port', metavar='PORTNUM', type=int, default=2525,
help='port number of listener (default: 2525)')
args = parser.parse_args()
import json
import socket
message = "I get all the best code from stackoverflow!"
print "CLIENT: Creating socket..."
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print "CLIENT: Connecting to {}:{}.".format(args.host, args.port)
s.connect((args.host, args.port))
print "CLIENT: Sending message:", message
s.send(message)
print "CLIENT: Waiting for reply..."
data = s.recv(1024)
print "CLIENT: Got response:"
print json.loads(data)
print "CLIENT: Closing socket..."
s.close()
And here's what they print when I run them together:
$ python2.7 abqlistener.py --port 3434 &
[2] 44088
$ Namespace(host='', port=3434)
Server starting. Press Ctrl+C to interrupt...
$ python2.7 abqclient.py --port 3434
CLIENT: Creating socket...
CLIENT: Connecting to :3434.
CLIENT: Sending message: I get all the best code from stackoverflow!
CLIENT: Waiting for reply...
SERVER: 127.0.0.1 wrote:
I get all the best code from stackoverflow!
DO_WORK: Doing work with data!
I get all the best code from stackoverflow!
SERVER: response to 127.0.0.1:
{"pi": 3, "e": 3, "desc": "low-precision natural constants"}
CLIENT: Got response:
{u'pi': 3, u'e': 3, u'desc': u'low-precision natural constants'}
CLIENT: Closing socket...
References:
argparse, SocketServer, json, socket are all "standard" Python libraries.

To be clear, my understanding is that you are running Abaqus/CAE via a Python script as an independent process (let's call it abq.py), which checks for, opens, and reads a trigger file to determine if it should run an analysis. The trigger file is created by a second Python process (let's call it main.py). Finally, main.py waits to read the output file created by abq.py. You want a more efficient way to signal abq.py to run an analysis, and you're open to different techniques to exchange data.
As you mentioned, subprocess or multiprocessing might be an option. However, I think a simpler solution is to combine your two scripts, and optionally use a callback function to monitor the solution and process your output. I'll assume there is no need to have abq.py constantly running as a separate process, and that all analyses can be started from main.py whenever it is appropriate.
Let main.py have access to the Abaqus Mdb. If it's already built, you open it with:
mdb = openMdb(FileName)
A trigger file is not needed if main.py starts all analyses. For example:
if SomeCondition:
j = mdb.Job(name=MyJobName, model=MyModelName)
j.submit()
j.waitForCompletion()
Once complete, main.py can read the output file and continue. This is straightforward if the data file was generated by the analysis itself (e.g. .dat or .odb files). OTH, if the output file is generated by some code in your current abq.py, then you can probably just include it in main.py instead.
If that doesn't provide enough control, instead of the waitForCompletion method you can add a callback function to the monitorManager object (which is automatically created when you import the abaqus module: from abaqus import *). This allows you to monitor and respond to various messages from the solver, such as COMPLETED, ITERATION, etc. The callback function is defined like:
def onMessage(jobName, messageType, data, userData):
if messageType == COMPLETED:
# do stuff
else:
# other stuff
Which is then added to the monitorManager and the job is called :
monitorManager.addMessageCallback(jobName=MyJobName,
messageType=ANY_MESSAGE_TYPE, callback=onMessage, userData=MyDataObj)
j = mdb.Job(name=MyJobName, model=MyModelName)
j.submit()
One of the benefits to this approach is that you can pass in a Python object as the userData argument. This could potentially be your output file, or some other data container. You could probably figure out how to process the output data within the callback function - for example, access the Odb and get the data, then do any manipulations as needed without needing the external file at all.

I agree with the answer, except for some minor syntax problems.
defining instance variables inside the handler is a no no. not to mention they are not being defined in any sort of init() method. Subclass TCPServer and define your instance variables in TCPServer.init(). Everything else will work the same.

Two tcp connections from a client in Twisted

Im new to twisted. I have written a client which connects to a server on two ports 8037 and 8038. I understand that the factory creates two connection objects. Now when i press Ctrl-C, it says
Connection Lost Connection to the other side was lost in a non clean fashion.
Connection Lost Connection to the other side was lost in a non clean fashion.
Below is the code:
from twisted.internet import protocol,reactor
class TestClient(protocol.Protocol):
def __init__(self):
pass
def connectionMade(self):
print "Connected "
self.sayHello()
def connectionLost(self,reason):
self.transport.loseConnection()
def sayHello(self):
self.transport.write("Hello")
def dataReceived(self,data):
print "Received data ",data
class TestClientFactory(protocol.ClientFactory):
def buildProtocol(self,addr):
return TestClient()
def clientConnectionFailed(self,connectory,reason):
print "Connection Failed ",reason.getErrorMessage()
def clientConnectionLost(self,connector,reason):
print "Connection Lost ",reason.getErrorMessage()
reactor.connectTCP("<server_ip>",8037,TestClientFactory())
reactor.connectTCP("<server_ip>",8038,TestClientFactory())
reactor.run()
How can i make the client close both tcp connections cleanly ?.
How to call the sayHello() method for only one connection ?
Im new to twisted, so an example would be helpful.
Thanks

When you are connected, if you want to call sayHello, you can use the thought of rpc.
For example, you send a message like 'sayHello_args', parse msg and call sayhello by args.
If you don't want to send any msg. When you connected, d.addCallback(sayHello) to call.
d = defer.succeed(0)
d.addCallback(lambda _ : self.sayHello())
And if you want to close connection, to use reactor.stop()

Unclean connection shutdown is really nothing to worry about. Getting a clean exit would potentially make your shutdown process slower and buggier because it requires a bunch of additional code, and you have to be able to deal with abnormal network connection termination no matter what. In fact calling it "clean" is maybe even a bit misleading: "simultaneously confirmed" might be closer to what it's actually telling you about how the connection was closed.
As far as how to call sayHello, I don't fully understand your question, but if you use AMP, calling a method on the opposite side of the connection is pretty easy.

Run two webservers with twisted

I have a task to run a webserver with twisted capable of working with websockets and standard HTTP functionality. Say, I need to use websockets and connect to hostname:9000. I need to get webpage and use hostname:80/webpage to get it. How I am supposed to do it?
I tried something like:
internet.TCPServer.__init__(self,9000, WebSocketFactory(factory))
internet.TCPServer.__init__(self,80, server.Site(HandlerHTTP))
And it's not working: server on 80 port starts, but one at 9000 doesn't.

An instance of twisted.application.internet.TCPServer represents one TCP server. You can't initialize it twice and get two servers out of it.
I expect a more complete code snippet than you gave would look like:
from twisted.application import internet
class TwoServers(TCPServer):
def __init__(self):
internet.TCPServer.__init__(self,9000, WebSocketFactory(factory))
internet.TCPServer.__init__(self,80, server.Site(HandlerHTTP))
This doesn't work. It's like trying to have an int that is two integers or a list that is two sequences. Instead, make two TCPServer instances:
from twisted.application import service, internet
from websocket import WebSocketFactory
factory = ...
HandleHTTP = ...
holdMyServers = service.MultiService()
internet.TCPServer(9000, WebSocketFactory(factory)).setServiceParent(holdMyServers)
internet.TCPServer(80, server.Site(HandlerHTTP).setServiceParent(holdMyServers)
...

Python Twisted addReader works in linux but not windows

I'm trying to write a client in python 2.7 using Twisted. My code works just fine in linux (debian squeeze), but when I tried it on windows (xp and 7) I got a constant stream of error messages. A screenshot of these messages is here.
I have narrowed down the bug and was able to write a very stripped down version of my client that still contains the bug:
from twisted.internet.protocol import Protocol,ClientFactory
from twisted.protocols.basic import LineReceiver
from twisted.internet import reactor
class TheClient(LineReceiver):
def lineReceived(self,line):
print line
def connectionLost(self,reason):
reactor.stop()
class TheFactory(ClientFactory):
protocol = TheClient
class Test(object):
def doRead(self):
pass
def fileno(self):
return 0
def connectionLost(self,reason):
print 'connection lost'
def logPrefix(self):
return 'Client'
def main():
print 'starting'
test = Test()
reactor.addReader(test)
reactor.run()
if __name__ == '__main__':
main()
If the line containing 'reactor.addReader(test)' is commented out, I do not get any error messages. If I run this code on linux without commenting out any lines, I do not get any error messages.
I found this question, I don't think its the same problem, but as expected, it did not function properly on windows.
Is this code correct, and this is a windows bug, or do I have to do things differently for it to work in windows?

The Windows implementation of select only supports sockets. Presumably file descriptor 0 in your process does not represent a socket. More likely it represents something related to standard I/O.
If you'd just like to use standard I/O, then there's twisted.internet.stdio, though you may run into some rough edges with it on Windows (bug reports and fixes appreciated!).
If you're not interested in standard I/O and 0 was just an arbitrary test, you'll probably need to decide on what kind of input you're trying to do in particular. Depending on what kind of file descriptor you have, there will probably be a different approach to successfully reading from it.