Adding a new fedmsg message type
Instrumenting the program
First, figure out how you’re going to publish the message? Is it from a shell script or from a long running process?
If its from shell script, you need to just add a fedmsg-logger statement to the script. Remember to set the --modname and --topic for your new message’s fully-qualified topic.
If its from a python process, you need to just add a
fedmsg.publish(..) call. The same concerns about modname and topic
If this is a short-lived python process, you’ll want to add
active=True to the call to
fedmsg.publish(..). This will
make the fedmsg lib "actively" reach out to our fedmsg-relay running on
If it is a long-running python process (like a WSGI thread), then you
don’t need to pass any extra arguments. You don’t want it to reach out
to the fedmsg-relay if possible. Your process will require that some
"endpoints" are created for it in
/etc/fedmsg.d/. More on that below.
You need to make sure that the machine this is running on has a cert and key that can be read by the program to sign its message. If you don’t have a cert already, then you need to create it in the private repo. Ask a sysadmin-main member.
Then you need to declare those certs in the _fedmsg_certs
data structure stored typically in our ansible
group_vars/ for this
service. Declare both the name of the cert, what group and user it
should be owned by, and in the
can_send: section, declare the list of
topics that this cert should be allowed to publish.
If this is a long-running python process that is not passing
active=True to the call to
fedmsg.publish(..), then you have to also declare
endpoints for it. You do that by specifying the
fedmsg_wsgi_vars in the
group_vars for your service. The iptables
rules and fedmsg endpoints should be automatically created for you on
the next playbook run.
At this point, you can push the change out to production and be publishing messages "okay". Everything should be fine.
However, your message will show up blank in datagrepper, in IRC, and in FMN, and everywhere else we try to render it. You must then follow up and write a new Processor for it in the fedmsg_meta library we maintain: https://github.com/fedora-infra/fedmsg_meta_fedora_infrastructure
You also must write a test case for it there. The docs listing all topics we publish at http://fedora-fedmsg.rtfd.org/ is automatically generated from the test suite. Please don’t forget this.
Lastly, you should cut a release of fedmsg_meta and deploy it using the
playbooks/manual/upgrade/fedmsg.yml playbook, which should
update all the relevant hosts.
If the process publishing the new message lives outside our main network, you have to jump through more hoops. Look at abrt, koschei, and copr for examples of how to configure this (you need a special firewall rule, and they need to be configured to talk to our "inbound gateway" running on the proxies.
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