Gevent enabled TANGO device server

GeventDS.py

"""
Demonstrate usage of TANGO DS with gevent.

Usage example: Go to jive and in the menu select Edit->Create server, then 
fill in the fields:
Server (ServerName/Instance): GeventDS/test1
Class: Gevent
Devices: test/gevent/1

click Register server.

Download this file in a directory and on the command line do:

    $ python GeventDS.py test1
    
With jive do test device on *test/gevent/1*. Try reading the "bla" attribute.
You will see on the command line that the access was made on the `MainThread`.

Reading attribute **ble** will *not* be done on the *MainThread* due to the fact
that we forced green_mode=GreenMode.Synchronous
"""

import gevent
import logging

from PyTango import requires_pytango
from PyTango import Attr, DevState, CmdArgType, AttrWriteType, GreenMode
from PyTango.server import Device, DeviceMeta, attribute, command, run

requires_pytango('8.1.7', software_name="GeventDS")


class Gevent(Device):
    __metaclass__ = DeviceMeta

    def __init__(self, *args, **kwargs):
        self._log = logging.getLogger(args[1])
        self.__bla = 55.6
        self._log.debug("__init__")
        Device.__init__(self, *args, **kwargs)

    def init_device(self):
        self._log.info("init_device")
        Device.init_device(self)
        self.set_state(DevState.ON)

    def delete_device(self):
        self._log.info("delete_device")

    @attribute
    def bla(self):
        """bla attribute description"""
        logging.debug("read bla")
        return self.__bla

    @bla.setter
    def bla(self, bla):
        logging.debug("write bla with %s", bla)
        self.__bla = bla

    @attribute(description="ble desc", green_mode=GreenMode.Synchronous)
    def ble(self):
        """attribute with gevent disabled... just for fun"""
        logging.debug("read ble")
        return 100.01
   
    @command(dtype_in=float)
    def nap(self, nap_time):
        logging.info("started napping for %s", nap_time)        
        gevent.sleep(nap_time)
        logging.info("finished napping for %s", nap_time)

def gworker():
    while True:
        gevent.sleep(1)
        logging.info("gevent loop")

def cb():
    logging.debug("Post init callback")

def main():
    logging.basicConfig(level=logging.DEBUG,
        format="%(threadName)12s %(levelname)5s %(asctime)s %(name)s:%(message)s")

    # spawn a greenlet here
    greenlet = gevent.spawn(gworker)

    # run tango server in gevent mode 
    run([Gevent], green_mode=GreenMode.Gevent, verbose=True,
        post_init_callback=cb)
    
    
if __name__ == "__main__":
    main()