Simple Messaging Client

The Goal

Illustrate the basic messaging concepts

Python script

This script was demonstrated at the SeisComP3 workshop in Erice. It should be relatively self-explaining, but full understanding does require certain knowlege of Python.

The script does nothing but

No actual real-world use case but a truly minimum example for a SeisComP3 application. 

import sys, traceback, seiscomp3.Client

class EventListener(seiscomp3.Client.Application):

    def __init__(self):
        seiscomp3.Client.Application.__init__(self, len(sys.argv), sys.argv)
        self.setMessagingEnabled(True)
        self.setDatabaseEnabled(True, True)
        self.setPrimaryMessagingGroup(seiscomp3.Communication.Protocol.LISTENER_GROUP)
        self.addMessagingSubscription("EVENT")

    def doSomethingWithEvent(self, event):
        try:
            #######################################
            #### Include your custom code here ####
            print "event.publicID = %s" % event.publicID()
            #######################################
        except:
            info = traceback.format_exception(*sys.exc_info())
            for i in info: sys.stderr.write(i)

    def updateObject(self, parentID, object):
        # called if an updated object is received
        event = seiscomp3.DataModel.Event.Cast(object)
        if event:
            print "received update for event %s" % event.publicID()
            self.doSomethingWithEvent(event)

    def addObject(self, parentID, object):
        # called if a new object is received
        event = seiscomp3.DataModel.Event.Cast(object)
        if event:
            print "received new event %s" % event.publicID()
            self.doSomethingWithEvent(event)

    def run(self):
        # needs not be re-implemented
        print "Hi! The EventListener is now running."
        return seiscomp3.Client.Application.run(self)

app = EventListener()
sys.exit(app())

Note that the EventListener class is derived from the application class seiscomp3.Client.Application from which it inherits most of the functionality. For instance the ability to connect to the messaging and to the database are both provided by seiscomp3.Client.Application; the EventListener only has to enable messaging and database usage in the __init__ routine. The real action takes place in the doSomethingWithEvent routine, which is called by both updateObject and addObject, depending on whether the event object received is a newly added or just and updated event.

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