fedmsg

fedmsg is a ZeroMQ-based messaging library used throughout Fedora Infrastructure applications. It uses a publish/subscribe design so applications can decide what messages they’re interested in receiving.

Warning

fedmsg does not guarantee message delivery. Messages will be lost and your application should never depend on the reliable delivery of fedmsgs to function.

Topics

Existing Topics

There are many existing topics in Fedora Infrastructure.

New Topics

When creating new message topics, please use the following format:

org.fedoraproject.ENV.CATEGORY.OBJECT[.SUBOBJECT].EVENT

Where:

  • ENV is one of dev, stg, or production.
  • CATEGORY is the name of the service emitting the message – something like koji, bodhi, or fedoratagger
  • OBJECT is something like package, user, or tag
  • SUBOBJECT is something like owner or build (in the case where OBJECT is package, for instance)
  • EVENT is a verb like update, create, or complete.

All ‘fields’ in a topic should:

  • Be singular (Use package, not packages)
  • Use existing fields as much as possible (since complete is already used by other topics, use that instead of using finished).

Furthermore, the body of messages will contain the following envelope:

  • A topic field indicating the topic of the message.
  • A timestamp indicating the seconds since the epoch when the message was published.
  • A msg_id bearing a unique value distinguishing the message. It is typically of the form <YEAR>-<UUID>. These can be used to uniquely query for messages in the datagrepper web services.
  • A crypto field indicating if the message is signed with the X509 method or the gpg method.
  • An i field indicating the sequence of the message if it comes from a permanent service.
  • A username field indicating the username of the process that published the message (sometimes, apache or fedmsg or something else).
  • Lastly, the application-specific body of the message will be contained in a nested msg dictionary.