Fedora Badges Message consumer

This repo contains the consumer and the command necessary to hook the badges stack (Tahrir, Tahrir-API, Tahrir-REST) into Fedora Messaging. It is the process that runs in the background, monitoring activity of Fedora contributors, and is responsible for awarding badges for activity as it happens. It is separate from and sometimes confused with the frontend of the badges system called tahrir. This project (fedbadges) writes to a database that the web frontend (tahrir) reads from.

The actual badge rules that we act on in Fedora Infrastructure can be found here <https://pagure.io/Fedora-Badges>.

Architecture

fedbadges is a callback class for the Fedora Messaging consumer. When started, it will load some initial configuration and a set of BadgeRules (more on that later) and then sit quietly listening to the Fedora Messaging bus. Each rule (composed of some metadata, a trigger, an optional condition and an optional way of counting previous messages) is defined on disk as a yaml file.

• When a new message comes along, our callback looks to see if it matches any of the BadgeRules it has registered.

• Each BadgeRule must define a trigger -- a lightweight check. When processing a message, this is the first thing that is checked. It defines a pattern that the message must match. If the message does not match, then the current BadgeRule is discarded and processing moves to the next.

  A trigger is typically something like "any bodhi message" or "messages only from the failure of a koji build". More on their specification below.

• BadgeRules can also define a previous value, as a way to count similar messages that went through the bus in the past. This typically involves a more expensive query to the datanommer database.

  A BadgeRule previous query may read something like "updates pushed to stable by the candidate" or "IRC meetings chaired by the candidate".

  Aside: Although datanommer is the only currently supported backend, we can implement other queryable backend in the future as needed like FAS (to see if the user is in X number of groups) or even off-site services like libravatar (to award a badge if the user is a user of the AGPL web service).

• BadgeRule can define a condition that the number of messages returned by the previous query must match. This can be something like greater than or equal to: 50. If unset, the default condition is greater than or equal to 1.

• If no previous query is set, then the rule only considers the current incoming message (it's like the previous result is always 1). This is relevant for rules that award a badge on the first action. Those rules don't need to set a condition either, the default one will do.

• If a badge's trigger and condition both match, then the badge is awarded. If the BadgeRule doesn't specify, we award the badge to the author of the action using the message's agent_name property.

  That is usually correct -- but sometimes, a BadgeRule needs to specify that one particular user should be recipient of the badge. In this case, the BadgeRule may define a recipient in dot-notation that instructs the Consumer how to extract the recipient's username from the received message.

  The badge is awarded to our deserving user via the tahrir_api. At the end of the day, this amounts to adding a row in a database table for the Tahrir application.

There are some optimizations in place omitted above for clarity. For instance, after the trigger has matched we first check if the user that would be awarded the badge already has it. If they do, we stop processing the badge rule immediately to avoid making an unnecessary expensive check against the datanommer db.

Configuration - Global

fedbadges needs three major pieces of global configuration. All configuration is loaded in the standard Fedora Messaging way, from the [consumer_config] section of the configuration file. See fedbadges.toml.example in the git repo for an example.

fedbadges also emits its own messages. In the Fedora Infrastructure, the topic_prefix will be org.fedoraproject.prod.

Configuration - BadgeRule specification

BadgeRules are specified in YAML on the file system.

Triggers

Every BadgeRule must carry the following minimum set of metadata:

# This is some metadata about the badge
name:           Like a Rock
description:    You have pushed 500 or more bodhi updates to stable status.
creator:        ralph

# This is a link to the discussion about adopting this as a for-real badge.
discussion: http://github.com/fedora-infra/badges/pull/SOME_NUMBER

# A link to the image for the badge
image_url: http://somelink.org/to-an-image.png

Here's a simple example of a trigger:

trigger:
  category: bodhi

The above will match any bodhi message on any of the topics that come from the bodhi update system.

Triggers may employ a little bit of logic to make more complex filters. The following trigger will match any message that comes from either the bodhi update system or the fedora git package repos:

trigger:
  category:
    any:
      - bodhi
      - git

At present triggers may directly compare themselves against only the category or the topic of a message. In the future we'd like to add more comparisons.. in the meantime, here's an example of comparing against the fully qualified message topic. This will match any message that is specifically for editing a wiki page:

trigger:
  topic: org.fedoraproject.prod.wiki.article.edit

---

There is one additional way you can specify a trigger. If you need more flexibility than topic and category allow, you may specify a custom filter expression with a lambda filter. For example:

trigger:
  lambda: "a string of interest" in json.dumps(message.body)

The above trigger will match if the string "a string of interest" appears anywhere in the incoming message. fedbadges takes the expression you provide it and compiles it into a python callable on initialization. Our callable here serializes the message to a JSON string before doing its comparison. Powerful!

Previous

As mentioned above in the architecture section, we currently only support datanommer as a queryable backend for previous queries. We hope to expand that in the future.

Datanommer queries are composed of two things:

• A filter limits the scope of the query to datanommer.
• An operation defines what we want to do with the filtered query. Currently, we can count the results or run them through a lambda function that will return an integer (the number of matched messages).

Here's an example of a simple previous definition:

previous:
  filter:
    topics:
    - message.topic
  operation: count

The above previous query will return the number of messages in datanommer with the same topic as the incoming message being handled. Here, message.topic is a lambda function that has the incoming message in scope.

---

The above example doesn't make much sense -- we'd never use it for a real badge. The previous query would be true if there were two of any message kicked off by any user at any time in the past. Pretty generic. Here's a more interesting previous query:

previous:
  filter:
    topics:
    - org.fedoraproject.prod.git.receive
    users:
    - message.body["commit"]["username"]
  operation: count

This previous query would return the number of messages of the topic "org.fedoraproject.prod.git.receive" that were also kicked off by whatever user is listed in the message.body['commit']['username'] field of the message being currently processed. In other words, this query would return the number of pushes to the fedora git repos by the user.

Condition

You can do some fancy things with the condition field. Here's a list of the possible comparisons you can make:

• "is greater than or equal to" or alternatively "greater than or equal to"
• "greater than"
• "is less than or equal to" or alternatively "less than or equal to"
• "less than"
• "equal to" or alternatively "is equal to"
• "is not" or alternatively "is not equal to"

As you can see, some of them are synonyms for each other.

---

If any of those don't meet your needs, you can specify a custom expression by using the lambda condition whereby fedbadges will compile whatever statement you provide into a callable and use that at runtime. For example:

condition:
  lambda: value != 0 and ((value & (value - 1)) == 0)

Who knows why you would want to do this, but the above condition check will succeed if the number of messages that matched in the past is exactly a power of 2.

Specifying Recipients

By default, if the trigger and condition match, fedbadges will award badges to the user returned by the message's agent_name property. This usually corresponds with "which user is responsible" for this message. That is usually what we want to award badges for.

There are some instances for which that is not what we want.

Take the org.fedoraproject.prod.bodhi.update.comment message for example. When user A comments on user B's update, user A is returned by the message's agent_name property.

Imagine we have a "Received Comments" badge that's awarded to packagers that received comments on their updates. We don't want to inadvertently award that badge to the person who commented, only to the one who created the update.

To allow for this scenario, badges may optionally define a recipient in dotted notation that tells fedbadges where to find the username of the recipient in the originating message. For instance, the following would handle the fas case we described above:

trigger:
  topic: org.fedoraproject.prod.bodhi.update.comment
condition:
  greater than or equal to: 1
previous:
  filter:
    topics:
    - message.topic
    users:
    - recipient
  operation: count
recipient: message.body["update"]["user"]["name"]