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POTail -f log on server, process data, then serve to client via twisted
 

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    <p>Goal: Show data from server in wxPython GUI on client</p> <p>Newcomer to Twisted. I have a wxPython GUI running on a Windows 7 client, and I have a program running on an Ubuntu server that produces a log. My current attempt is to tail -f the log, pipe the output to a twisted server, then serve any data that meets my regex conditions to the client. I already have a tunnel open, so I don't need to complicate things with SSH. I've gotten the following block of code running, but it only serves the first line in the input. I know I need to keep checking the input for a newline and then writing it to the transport, but I'm not sure how to do that without breaking the connection. </p> <p>I haven't been able to find enough information to patch a full solution together. I have also tried various other methods using sockets and file IO, but I think Twisted seems to be a good tool for this issue. Am I on the right track? Any recommendations appreciated. Thanks</p> <pre><code>#! /usr/bin/python import optparse, os, sys from twisted.internet.protocol import ServerFactory, Protocol def parse_args(): usage = """usage: %prog [options] """ parser = optparse.OptionParser(usage) help = "The port to listen on. Default to a random available port." parser.add_option('--port', type='int', help=help) help = "The interface to listen on. Default is localhost." parser.add_option('--iface', help=help, default='localhost') options =parser.parse_args() return options#, log_file class LogProtocol(Protocol): def connectionMade(self): for line in self.factory.log: self.transport.write(line) class LogFactory(ServerFactory): protocol = LogProtocol def __init__(self,log): self.log = log def main(): log = sys.stdin.readline() options, log_file = parse_args() factory = LogFactory(log) from twisted.internet import reactor port = reactor.listenTCP(options.port or 0, factory, interface=options.iface) print 'Serving %s on %s.' % (log_file, port.getHost()) reactor.run() if __name__ == '__main__': main() </code></pre> <p>To answer the first comment, I have also tried to just read the log from within Python, program hangs. Code follows:</p> <pre><code>#! /usr/bin/python import optparse, os, sys, time from twisted.internet.protocol import ServerFactory, Protocol def parse_args(): usage = """ usage: %prog [options]""" parser = optparse.OptionParser(usage) help = "The port to listen on. Default to a random available port" parser.add_option('--port', type='int', help=help, dest="port") help = "The logfile to tail and write" parser.add_option('--file', help=help, default='log/testgen01.log',dest="logfile") options = parser.parse_args() return options class LogProtocol(Protocol): def connectionMade(self): for line in self.follow(): self.transport.write(line) self.transport.loseConnection() def follow(self): while True: line = self.factory.log.readline() if not line: time.sleep(0.1) continue yield line class LogFactory(ServerFactory): protocol = LogProtocol def __init__(self,log): self.log = log def main(): options, log_file = parse_args() log = open(options.logfile) factory = LogFactory(log) from twisted.internet import reactor port = reactor.listenTCP(options.port or 0, factory) #,interface=options.iface) print 'Serving %s on %s.' % (options.logfile, port.getHost()) reactor.run() if __name__ == '__main__': main() </code></pre>
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    1. COHave you considered reading the log from within python, rather than piping the output from `tail`?
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    2. COHave tried to work this out as well using a generator, program hangs. Seems to me that the transport and the generator are each waiting for the other to finish. Code shown above. Is there a better way to do this than using a generator?
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