trigger tool

[nirik]

fedmsg has a tool called 'fedmsg-trigger'. It lets you easily do a one command line type thing to run a command/script when a specific message comes accross the bus.

It would be cool if there was something like this for fedora-messaging too.

[abompard]

It is indeed an interesting feature. It can be done with the current code, although not as easily as the fedmsg-trigger command. You'll need to define a callback module like this (for example called run_command.py):

from subprocess import call
from fedora_messaging.config import conf
def run(message):
    call(conf["consumer_config"]["command"], shell=True)

And a configuration file that contains these lines (named for example trigger.toml):

# The module and function name
callback = "run_command:run"
[consumer_config]
command = "echo message received"

The module must be importable, so you may need to set PYTHONPATH, but then you can run the command PYTHONPATH=. fedora-messaging --conf trigger.toml consume and it will execute the command on each received message. You can filter the topics you want to act on by configuring the [[bindings]] section in the configuration file (the routing_keys list is topics or topic patterns).

Would that let you do what you want to do?

[jeremycline]

@abompard, I was thinking we could add a couple generally useful callbacks to a callbacks.py module (and move the printer out into that) that we document and maintain. That way folks can just write some configuration and not have to deal with writing Python.

It's only tangentially related, but I wonder if we should also allow specifying a Python file instead of only a Python path so folks don't need to deal with packaging.

[abompard]

Yeah I agree to both propositions.