Toddlers is a simple application aimed at running tasks upon fedora-messaging notifications.
In other words, it's a bunch of small programs that keeps running around.
It is a fedora-messaging consumer that listens for a number of topics defined by each toddler.
The runner will then asks each toddler if they are interested by the topic of the message it just received and if so, it will send the full message to the toddler to be processed.
Toddlers need to be a subclass of toddlers.base.ToddlerBase (see the file
toddlers/base.py), it needs to have the 2 required property and the 2
required methods and needs to be in the folder: toddlers/plugins/ from which
it will be automatically loaded.
If a toddler fails to process a message (ie: it raises an exception) the message is put back in the queue and will be processed later. Depending on the order in which the toddler are run, it is possible that a toddler sees multiple times the same message, the code should thus take this into account and check if it needs to do something before doing it.
If none of the toddlers raised an exception the message is considered as processed.
Toddlers consumes queues that are created for it in rabbitmq, so you can start as many processes as you like, rabbitmq will distribute the message in the queue in a round robin fashion to each consumers, allowing you to easily scale up or down depending on your load and needs.
Follow these simples steps:
dnf install python3-requests python3-koji fedora-messaging
git clone https://pagure.io/fedora-infra/toddlers.git cd toddlers
sed -e "s/[0-9a-f]\{8\}-[0-9a-f]\{4\}-[0-9a-f]\{4\}-[0-9a-f]\{4\}-[0-9a-f]\{12\}/$(uuidgen)/g" \
toddlers.toml.example > toddlers.toml
PYTHONPATH=. fedora-messaging --conf=toddlers.toml consume
Warning
If you are adding a toddler to be run in the Fedora infrastructure and this toddler needs to listen to a new topic, you will have to add it to the ansible playbook for toddlers, the dynamic loading of the topics that toddlers has works for local development but will not work in production. The ansible playbook is at: https://pagure.io/fedora-infra/ansible/blob/master/f/playbooks/openshift-apps/toddlers.yml
dnf install python3-tox
tox